[EE] Electric Blanket catastrophic failure

[Art]

I had a catastrophic failure of my electric blanket, and the autopsy of
the damage leaves more questions than answers.

I lost bedding and my mattress, while there were no open flames, it
scared the living crap outta me. I woke up to amazing heat in my bed, in
a very localized area very close to my body. All the damage was from
melted synthetic bedding and mattress materials. The house was filled
with smoke and fortunately I woke up quickly enough to escape without
injury.

I was able to remove the cable from the blanket, and it looks like it
failed only in one location. The wire in the area of the failure was
black and melted. In the area where the damage was the worst, there were
2 of the conductors melted together with almost no insulation left on
the wires-it had apparently caught fire and burned totally away.

I can only guess that the blanket wasn't laying flat and that the wires
crossed, which created more heat in a small area. So, the insulation
began to melt, eventually failing, which allowed the conductors to short
together as the wires insulation became molten.

I've used this brand of electric blanket for years, this is the third
catastrophic failure I've had in the last 20 years. Although none of the
previous failures were nearly as damaging as the latest one.

The electric blankets are high end Biddeford brand products, were all
the same model, the TC12BO controller, see:

https://biddefordblankets.com/products/controller-digital-tc12bo

All of the previous failures were quickly and briefly autopsied, but I'm
feeling compelled to dig deeper after this last failure.

All the blankets used heavy duty 600 volt rating on each of the 4 pins
on the connector that runs from the controller into the blanket, a photo
of the connector is here:

Loading Image...

Inside the controller is a PIC chip, triac switching and a mylar cap
based line voltage to low voltage power supply. There is a thermistor
mounted on the PCB, which is used to compensate for the ambient
temperature change in the room. There are 2 output wires and the heating
element is a single conductor (actually 2 parallel conductors) within
the blanket itself. Although there are 4 terminals on the controller
connector, only 2 of them are used. There are no connections to the
other remaining pins on the blanket.

Here's where it gets interesting............

The heating element wire is actually made up of 2 conductors, each very
very small. One is copper (or it appears to be). The other is some sort
of silver color, likely tungsten or nichrome, or a combination of both.

The silver colored wire, which I assume is the heating element is at the
center of the heating cable, it is spiral wrapped with some sort of very
small diameter multi stranded synthetic cord, with fibers so fine, I
can't see the individual fiber strands. Around the core is a layer of
what appears to be insulation. On the outside of that, the copper wire
is spiral wound around the insulation, at about 6 turns per inch. Over
that, is the outer sheath of the wire.

The company has a PR type version of the controllers function, which
sounds like crap to me....claiming that the insulation and the copper
conductor signal the controller to shut down if a fault occurs. However,
there is no signal path to the controller, even if the plastic
insulating material was indeed some sort of temperature sensitive
sensor. THE COPPER AND THE SILVER COLORED WIRES RUN IN PARALLEL WITH
EACH OTHER, THERE IS NO SENSOR OR FEEDBACK METHOD FOR A SENSOR.

In other words, there is no possible way for the controller to know that
the 'sensor' is detecting a hot spot, there are only 2 active terminals
in the blanket and in the controller output.

The company's explanation is here:

https://biddefordblankets.com/pages/our-technology

The verbiage of the company makes it sound like there is an active
sensor, but the heating element is 2 parallel conductors. There is no
way to for the controller to know there is a hot spot in the blanket.

At best, I think they can only detect a change in current flowing
through the heating element, which can only occur after the electrical
failure and is not reusable....a one shot deal. I know it's possible to
make temperature sensitive self regulating heating elements, but the
company strongly implies there is an actual 'sensor'.

By the way, my smoke detector never went off!!!! I discovered that every
single smoke detector in my house, including some pricey AC powered
units is the ionization type, which are nearly worthless. I count myself
as lucky to have learned this lesson without getting seriously injured
or worse. I have 2 temporary smoke detectors (photoelectric) bought at
the local hardware store and will do a more proper photoelectric
detector buy and install soon. I urge all to weed out the ionization
smoke detectors and to replace them with more proper photoelectric
types. Any search engine, or youtube search will yield info regarding
why the ionization detectors are being outlawed lately-to many people
have died needlessly.

Regards,

Art

[James Cameron]

Ouch!

[RussellMc]

Peripheral:



On Tue, 27 Nov 2018 at 19:15, Art <***@myfairpoint.net> wrote:

... I urge all to weed out the ionization

Post by Art
smoke detectors and to replace them with more proper photoelectric
types. Any search engine, or youtube search will yield info regarding
why the ionization detectors are being outlawed lately-to many people
have died needlessly.

Interesting.
I've had good results over decades with ionisation type detectors and have
found photoelectric ones less sensitive than I'd like.

I had intended to do an informal test of various detectors and locations
"sometime" / manana (manana manana?) .

Post by Art
Regards,
Art
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[Harold Hallikainen]

Post by RussellMc
Interesting.
I've had good results over decades with ionisation type detectors and have
found photoelectric ones less sensitive than I'd like.
I had intended to do an informal test of various detectors and locations
"sometime" / manana (manana manana?) .

I don't know what kind of smoke detectors we have. but they definitely
work since they trip pretty often when cooking. That's our "periodic
test."

Harold

[David Van Horn]

I don't know what kind of smoke detectors we have. but they definitely work since they trip pretty often when cooking. That's our "periodic test."
Harold

But was that a CALIBRATED grilled cheese test sandwich? 😊

[Chris McSweeny]

On Tue, Nov 27, 2018 at 5:42 PM Harold Hallikainen <

Post by Harold Hallikainen
I don't know what kind of smoke detectors we have. but they definitely
work since they trip pretty often when cooking. That's our "periodic
test."
I'm not sure if lots of false alarms from cooking is the best test! I've

recently moved onto a narrowboat (for those from other countries you'll
have to google as I think it's a peculiarly English thing, but it's a long
thin boat with living accommodation) and unlike in the typical house I
don't have a door between my kitchen and where the smoke alarm is (right
outside the bedroom door - don't really want to put it the other side of
that). The original smoke alarm was an ionisation type and pretty much any
cooking, even just boiling the kettle set it off. I've replaced it with
https://www.amazon.co.uk/gp/product/B013T9W2AE/ref=ox_sc_act_title_1?smid=A2MTK2J2TB084L&psc=1
which is combined thermal and optical and no longer set off by my cooking,
but then it's not supposed to be as what it should be detecting is
something different. I presume yours is an ionisation type if your cooking
is setting it off.

Chris

[Sean Breheny]

I've seen ionization ones go off from cooking. I've also seen a
photoelectric one that would go off if you just swept the area with a broom
and kicked fine dust into the air.

I've also seen an ionization one go off if you just spray a canned
compressed gas duster into it. I assume that the fluorocarbon gas is harder
to ionize (or maybe it is just the fact that there is such a high flow rate
that it blows ions out of the way).

Post by Chris McSweeny
On Tue, Nov 27, 2018 at 5:42 PM Harold Hallikainen <

Post by Harold Hallikainen
I don't know what kind of smoke detectors we have. but they definitely
work since they trip pretty often when cooking. That's our "periodic
test."
I'm not sure if lots of false alarms from cooking is the best test! I've

recently moved onto a narrowboat (for those from other countries you'll
have to google as I think it's a peculiarly English thing, but it's a long
thin boat with living accommodation) and unlike in the typical house I
don't have a door between my kitchen and where the smoke alarm is (right
outside the bedroom door - don't really want to put it the other side of
that). The original smoke alarm was an ionisation type and pretty much any
cooking, even just boiling the kettle set it off. I've replaced it with
https://www.amazon.co.uk/gp/product/B013T9W2AE/ref=ox_sc_act_title_1?smid=A2MTK2J2TB084L&psc=1
which is combined thermal and optical and no longer set off by my cooking,
but then it's not supposed to be as what it should be detecting is
something different. I presume yours is an ionisation type if your cooking
is setting it off.
Chris
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[Martin McCormick]

Post by Sean Breheny
I've seen ionization ones go off from cooking. I've also seen a
photoelectric one that would go off if you just swept the area with a broom
and kicked fine dust into the air.
I've also seen an ionization one go off if you just spray a canned
compressed gas duster into it. I assume that the fluorocarbon gas is harder
to ionize (or maybe it is just the fact that there is such a high flow rate
that it blows ions out of the way).

I have also heard the suggestion that you need both types
of detectors.

I live near the campus of Oklahoma State University which
has, of course, lots of buildings, about 25,000 students on
campus and mostly photo-electric smoke detectors tied to alarm
panels in each building. They also have a training program in
fire service technology due to a rather big conflagration around
the turn of the last century in which several buildings burned
around Halloween one year so they take fire safety seriously
around here.

The smoke detectors in student living quarters do go off
for all the usual reasons such as candles and cooking accidents
plus a few false triggers due to shower steam, hair spray, hair
straightening irons and, recently, vaping.

In the public buildings such as labs, offices and
classrooms, they have false alarms from construction dust and
vigorous custodial activities such as sweeping and vacuuming and
a few odd ones such as the time that a building was the seen of a
false fire alarm several days in a row until somebody noticed that
once each day, photons from our nearest star had a clean path
from the Sun through ninety-three-million miles of space, through
a window in that building and finally to the smoke detector in
question.

I don't know if this was a new installation or what but
it all lined up twice a year so I don't know what they did to fix
the problem.

We have also had false alarms that were due to fog
machines which are used for special effects during public events.
The photo-electric smoke alarms flash a light in to a black
chamber and, if something like a cloud of fog or dust is there,
it reflects.

I would think the ionization type detectors might also
get mixed up over particulates in the air since that would
probably unbalance the comparison between the sealed air sample
and the ambient air sample.

One year, the city of Tulsa was experiencing ozone alerts
during a stretch of Summer weather and a news reporter from one
of the television stations did a story on the ozone detectors and
interviewed the technician who ran them. They used an ionization
source and appeared to me to be much like an ionization smoke
alarm. I believe the report was that ozone caused a different
amount of ionization to show up at the detector.

Martin WB5AGZ

[Sean Breheny]

About ten years ago I had a situation where the company I was working for
was considering adding smoke detectors to automated robot battery charging
stations. I was given the task of testing their effectiveness at detecting
the beginning of an ABS plastic fire and to compare ionization and
photoelectric types. I had very interesting results although my memory is a
bit hazy, I think what I found was that neither type was better than the
other overall. If I recall correctly, the photoelectric one was usually
much faster to trip but sometimes never tripped, depending on how smoky the
fire was (Some of my tests had a hot piece of metal in contact with the
plastic, causing it to char but not visibly burn. Others had visible flames
coming from the plastic). The ionization one almost always tripped but it
sometimes took much longer to do so.

My conclusion is that you really want both types in your house. This seems
to be vindicated by the advice I've seen given to the public recently, as
well as the prevalence of dual-action (photo/ionization) types for sale now.

Sean

Post by RussellMc
Interesting.
I've had good results over decades with ionisation type detectors and have
found photoelectric ones less sensitive than I'd like.
I had intended to do an informal test of various detectors and locations
"sometime" / manana (manana manana?) .

[RussellMc]

On Tue, 27 Nov 2018 at 19:15, Art <***@myfairpoint.net> wrote:

...

The silver colored wire, which I assume is the heating element is at the
center of the heating cable, it is spiral wrapped with some sort of very
small diameter multi stranded synthetic cord, with fibers so fine, I
can't see the individual fiber strands. Around the core is a layer of
what appears to be insulation. On the outside of that, the copper wire
is spiral wound around the insulation, at about 6 turns per inch. Over
that, is the outer sheath of the wire.

The outer wire cannot be copper as it would short the heating element. Odds

are it is of higher resistance than the heating element and with
temperature variable resistance, so that you get SOME resistance change
with temperature.

You can measure the resistance of a section of core and outer "wires' to
see what actual resistances are - and of an end to end element section if
you have a "good" blanket.


Russell

[Justin Richards]

That is quite and ordeal.

Some time ago we found if you were standing on the floor and touched
someone lying in the bed you would get that hard to describe buzzing/furry
sensation on the finger tips. Kids thought it was great fun.

From memory I measured 80v A/C from person to ground.

That was the last time we used an electric blanket.

...
The silver colored wire, which I assume is the heating element is at the
center of the heating cable, it is spiral wrapped with some sort of very
small diameter multi stranded synthetic cord, with fibers so fine, I
can't see the individual fiber strands. Around the core is a layer of
what appears to be insulation. On the outside of that, the copper wire
is spiral wound around the insulation, at about 6 turns per inch. Over
that, is the outer sheath of the wire.
The outer wire cannot be copper as it would short the heating element. Odds

are it is of higher resistance than the heating element and with
temperature variable resistance, so that you get SOME resistance change
with temperature.

You can measure the resistance of a section of core and outer "wires' to
see what actual resistances are - and of an end to end element section if
you have a "good" blanket.
Russell
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[RussellMc]

Post by Justin Richards
That is quite and ordeal.
Some time ago we found if you were standing on the floor and touched
someone lying in the bed you would get that hard to describe buzzing/furry
sensation on the finger tips. Kids thought it was great fun.

From memory I measured 80v A/C from person to ground.

Yes. And/but this is safe/harmless for most values of safe/harmless.

The affect is caused by capacitive coupling from element to recumbent
target and from there via body contact to ground.
The magnitude of the tingle depends on the coupling capacitance.
When measuring with a meter the meter forms the lower leg of an impedance
divider from element via Ccoupling to body and then via meter to ground.
A higher impedance meter will give a value closer to mains voltage than a
lower impedance meter.

Blanket instructions (which most ignore) say not to have blanket powered on
when a person is in bed.

Leaving a blanket on high while sleeping will convince you that you NEVER
want to do it again. HOT!!!.

Russell

[David C Brown]

Quite apart from the heating effect of sleeping on an energised blanket
you will be subjecting yourself to the dangers of the EM field.
To quote from "WeeksMD"

*My parents compromise by turning it on 10 minutes before getting into the
classic freezing New England bedsheets and then they turn the electric
blanket off before actually intoxicating themselves. However, we now know
that the blanket itself, while on and heating up the bed, creates dirty
electricity and also that the wires in the blanket serve as potent antena
which focuses toxic electricity on your body all night long while you
sleep. So now, they take one additional step for safety: they UNPLUG the
blanket from the wall before they climb into they warm bed. *

(Disclaimer: I am being ironic)



__________________________________________
David C Brown
43 Bings Road
Whaley Bridge
High Peak Phone: [phone]
Derbyshire eMail: ***@gmail.com
SK23 7ND web: www.bings-knowle.co.uk/dcb
<http://www.jb.man.ac.uk/~dcb>



*Sent from my etch-a-sketch*

Post by Justin Richards

Post by Justin Richards
That is quite and ordeal.
Some time ago we found if you were standing on the floor and touched
someone lying in the bed you would get that hard to describe

buzzing/furry

Post by Justin Richards
sensation on the finger tips. Kids thought it was great fun.

From memory I measured 80v A/C from person to ground.

Yes. And/but this is safe/harmless for most values of safe/harmless.
The affect is caused by capacitive coupling from element to recumbent
target and from there via body contact to ground.
The magnitude of the tingle depends on the coupling capacitance.
When measuring with a meter the meter forms the lower leg of an impedance
divider from element via Ccoupling to body and then via meter to ground.
A higher impedance meter will give a value closer to mains voltage than a
lower impedance meter.
Blanket instructions (which most ignore) say not to have blanket powered on
when a person is in bed.
Leaving a blanket on high while sleeping will convince you that you NEVER
want to do it again. HOT!!!.
Russell
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[David Van Horn]

* So now, they take one additional step for safety: they UNPLUG the blanket from the wall before they climb into they warm bed. *

(Disclaimer: I am being ironic)


Tragically hilarious, though I would agree they are in fact safer that way, just not from the hazard they were expecting.

[AB Pearce - UKRI STFC]

All the blankets used heavy duty 600 volt rating on each of the 4 pins on the connector

...

Inside the controller is a PIC chip, triac switching and a mylar cap based line voltage to low
voltage power supply. There is a thermistor mounted on the PCB, which is used to compensate
for the ambient temperature change in the room. There are 2 output wires and the heating
element is a single conductor (actually 2 parallel conductors) within the blanket itself. Although
there are 4 terminals on the controller connector, only 2 of them are used. There are no
connections to the other remaining pins on the blanket.

Does the controller itself have 4 connections to the connector? It sounds to me like the element end has been mis-wired, hence why the failures on the reports that someone else posted.

[David Van Horn]

Arc Fault interrupters are supposed to prevent this by detecting the electrical noise from the failing connection.

If you were in the US, I'd suggest the Consumer Products Safety Commission. They have big pointy teeth and aren't afraid to use them.

Glad you're ok though, and it certainly could have been much worse.

As to the double wire thing, they might have been intending to detect a short between the silver and copper wires? Just guessing.

[Brooke Clarke]

Hi:

This might explain it (uses a 16F72):
https://patents.google.com/patent/US20120004788A1/en
--
Have Fun,

Brooke Clarke
https://www.PRC68.com
https://www.end2partygovernment.com/2012Issues.html
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.

[Art]

Hi All,

I heard back from Biddeford today, although the person wasn't very
knowledgeable (technically).

He was elusive and well versed on the writings at:

https://biddefordblankets.com/pages/our-technology

He told me that the blanket does indeed have 4 pins on the connector,
two for the heating element itself and the other 2 are for the 'sensor'.
He said the sensor was temperature sensitive type. But, after a lot of
cross examination, he finally admitted the sensor is not a sensor, it's
a one time use fail safe and that all their products will fail if they
are bunched up. I asked him if 'bunched up' meant just rolling over on
top of the blanket, and he said YES!!! I'm not sure how any manufacturer
can make a bedding product that is susceptible to fire if the owner
rolls over onto the blanket, which forces the wires together and makes a
hot spot...that will later fail at the point where the wires crossed.
Expecting the blanket to remain perfectly flat while the owner sleeps
seems inappropriate.

And, the rep also admitted they use very low melting temp insulation, so
that the blanket will fail on purpose. In other words, it is designed to
fail!

I'm not sure how UL considers this safe.

My blanket however had no connections to the spiral wrapped sensor
wire-which is why the controller didn't shut the blanket down!! The rep
didn't believe me, but the 2 connector pins designed to allow the
connector to pass the sensor signal to the microprocessor had no wires
connected to them, the 'sensor' was never hooked up!

I wish I had saved all the parts and taken some pictures!!!
Unfortunately, I didn't.

TY all who commented, I'm now looking for dual detector smoke alarms for
my house. With the amount of smoke in my house, I was very lucky to
escape from the fire.

Regards,

Art

Post by Art
I had a catastrophic failure of my electric blanket, and the autopsy of
the damage leaves more questions than answers.
I lost bedding and my mattress, while there were no open flames, it
scared the living crap outta me. I woke up to amazing heat in my bed, in
a very localized area very close to my body. All the damage was from
melted synthetic bedding and mattress materials. The house was filled
with smoke and fortunately I woke up quickly enough to escape without
injury.
I was able to remove the cable from the blanket, and it looks like it
failed only in one location. The wire in the area of the failure was
black and melted. In the area where the damage was the worst, there were
2 of the conductors melted together with almost no insulation left on
the wires-it had apparently caught fire and burned totally away.
I can only guess that the blanket wasn't laying flat and that the wires
crossed, which created more heat in a small area. So, the insulation
began to melt, eventually failing, which allowed the conductors to short
together as the wires insulation became molten.
I've used this brand of electric blanket for years, this is the third
catastrophic failure I've had in the last 20 years. Although none of the
previous failures were nearly as damaging as the latest one.
The electric blankets are high end Biddeford brand products, were all
https://biddefordblankets.com/products/controller-digital-tc12bo
All of the previous failures were quickly and briefly autopsied, but I'm
feeling compelled to dig deeper after this last failure.
All the blankets used heavy duty 600 volt rating on each of the 4 pins
on the connector that runs from the controller into the blanket, a photo
https://duckduckgo.com/?q=biddeford+elecrtric+blanket+failures&t=brave&iax=images&ia=images&iai=https%3A%2F%2Fimages.bonanzastatic.com%2Fafu%2Fimages%2F7714%2F7783%2FBiddeford__76PA_1.jpg
Inside the controller is a PIC chip, triac switching and a mylar cap
based line voltage to low voltage power supply. There is a thermistor
mounted on the PCB, which is used to compensate for the ambient
temperature change in the room. There are 2 output wires and the heating
element is a single conductor (actually 2 parallel conductors) within
the blanket itself. Although there are 4 terminals on the controller
connector, only 2 of them are used. There are no connections to the
other remaining pins on the blanket.
Here's where it gets interesting............
The heating element wire is actually made up of 2 conductors, each very
very small. One is copper (or it appears to be). The other is some sort
of silver color, likely tungsten or nichrome, or a combination of both.
The silver colored wire, which I assume is the heating element is at the
center of the heating cable, it is spiral wrapped with some sort of very
small diameter multi stranded synthetic cord, with fibers so fine, I
can't see the individual fiber strands. Around the core is a layer of
what appears to be insulation. On the outside of that, the copper wire
is spiral wound around the insulation, at about 6 turns per inch. Over
that, is the outer sheath of the wire.
The company has a PR type version of the controllers function, which
sounds like crap to me....claiming that the insulation and the copper
conductor signal the controller to shut down if a fault occurs. However,
there is no signal path to the controller, even if the plastic
insulating material was indeed some sort of temperature sensitive
sensor. THE COPPER AND THE SILVER COLORED WIRES RUN IN PARALLEL WITH
EACH OTHER, THERE IS NO SENSOR OR FEEDBACK METHOD FOR A SENSOR.
In other words, there is no possible way for the controller to know that
the 'sensor' is detecting a hot spot, there are only 2 active terminals
in the blanket and in the controller output.
https://biddefordblankets.com/pages/our-technology
The verbiage of the company makes it sound like there is an active
sensor, but the heating element is 2 parallel conductors. There is no
way to for the controller to know there is a hot spot in the blanket.
At best, I think they can only detect a change in current flowing
through the heating element, which can only occur after the electrical
failure and is not reusable....a one shot deal. I know it's possible to
make temperature sensitive self regulating heating elements, but the
company strongly implies there is an actual 'sensor'.
By the way, my smoke detector never went off!!!! I discovered that every
single smoke detector in my house, including some pricey AC powered
units is the ionization type, which are nearly worthless. I count myself
as lucky to have learned this lesson without getting seriously injured
or worse. I have 2 temporary smoke detectors (photoelectric) bought at
the local hardware store and will do a more proper photoelectric
detector buy and install soon. I urge all to weed out the ionization
smoke detectors and to replace them with more proper photoelectric
types. Any search engine, or youtube search will yield info regarding
why the ionization detectors are being outlawed lately-to many people
have died needlessly.
Regards,
Art

[Jason White]

Art, I suppose you could buy another blanket and test it - taking pictures
along the way.

IMHO the manufacturer should not be permitted to sell an unsafe design
(with non-functioning safety features) - it could harm others.

-Jason White

[David C Brown]

In Europe they are not so permitted.
The obligatory CE mark indicates conformity with health, safety, and
environmental protection standards for products sold within the European
Economic Area <https://en.wikipedia.org/wiki/European_Economic_Area> (EEA).


Mind you: that didn't stop a faulty washing machine from starting the
tragic fire in Grenfell Towers.
__________________________________________
David C Brown
43 Bings Road
Whaley Bridge
High Peak Phone: [phone]
Derbyshire eMail: ***@gmail.com
SK23 7ND web: www.bings-knowle.co.uk/dcb
<http://www.jb.man.ac.uk/~dcb>



*Sent from my etch-a-sketch*

Post by Jason White
Art, I suppose you could buy another blanket and test it - taking pictures
along the way.
IMHO the manufacturer should not be permitted to sell an unsafe design
(with non-functioning safety features) - it could harm others.
-Jason White
--
Jason White
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[AB Pearce - UKRI STFC]

Mind you: that didn't stop a faulty washing machine from starting the tragic fire in Grenfell Towers.

And the ongoing evidence seems to suggest that the cost cutting of appliance manufacturers is causing rather too many fires in homes, sadly.

[David C Brown]

And the problem with Chinese goods that show a very similar CE mark which
they say stands for Chinese export rather then Conformitee European :-)
__________________________________________
David C Brown
43 Bings Road
Whaley Bridge
High Peak Phone: [phone]
Derbyshire eMail: ***@gmail.com
SK23 7ND web: www.bings-knowle.co.uk/dcb
<http://www.jb.man.ac.uk/~dcb>



*Sent from my etch-a-sketch*


On Thu, 29 Nov 2018 at 14:40, AB Pearce - UKRI STFC <

Post by David C Brown

Post by David C Brown
Mind you: that didn't stop a faulty washing machine from starting the

tragic fire in Grenfell Towers.
And the ongoing evidence seems to suggest that the cost cutting of
appliance manufacturers is causing rather too many fires in homes, sadly.
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[David Van Horn]

I'm fairly well convinced that "China Export" occurred AFTER the first complaints started coming in about products with that marking.

[Art]

I think you're so right Alan,

The blanket has 3 loops of wire over the entire surface of the queen
size version, so there is about one wire every foot or so. If there were
more feet of wire per each blanket, the power density would be much
improved and the surface temperature of the insulation would be lower.
So, for the same amount of power from the outlet, any wires pressed
against each other from 'bunching' would be much less prone to failure
by melting.

Now, add in teflon or similar higher melting point insulation, and the
problem would probably be nonexistent and there would be no need for any
failsafe spiral copper wire wrap.

I am very upset to hear that low temperature melting insulation was used
INTENTIONALLY!

BTW, the company rep had no idea why the copper spiral winding was not
connected inside the blanket. I'm wondering now if it was a Chinese
fake??? It was purchased through JC Penny however.

I wish I wasn't so anxious to throw the remains in the trash!!! It was
trash day however, the bedding had burned and there was no need to keep
it. So, after the autopsy, everything went into the trash! Damn, I wish
I had kept the remains::>

In fairness to Biddeford, their rep offered to replace my mattress and
the damaged bedding, even though this was a 5 to 7 year old blanket. I
declined his offer, but I did accept the replacement blanket he offered.

=================

Just between you and me, I'm tempted to dissect the blanket Biddeford
sends and then rebuild it with some larger gauge teflon insulated
stranded copper wire...using more wire loops, but running it on 3 to 12
volts (or even lower). There would be no failsafe protection, but it
probably isn't needed anyway IF the blanket has more feet of wire within
the blanket itself. To demonstrate that no failsafe protection is
needed, I'd roll the thing into a ball and leave it operating. I think
it would be much safer.

I think I'd have a PIC monitoring the current draw constantly, so any
shorting out of the conductors within the blanket would be detected
immediately. There would be no need for the failsafe spiral wrap winding.

I'm not sure if a heating element can be made from copper however. Today
we can make highly efficient power supplies at low voltage, *so maybe
copper wire can be used as a heating element. Comments on the heating
wire heating element would be appreciated.*

Regards,

Art


....meaning the insulation  On 11/29/18 9:40 AM, AB Pearce - UKRI STFC

Post by AB Pearce - UKRI STFC

Mind you: that didn't stop a faulty washing machine from starting the tragic fire in Grenfell Towers.

And the ongoing evidence seems to suggest that the cost cutting of appliance manufacturers is causing rather too many fires in homes, sadly.

[John Gardner]

According to Boodle, Biddeford products are "now made in China".

What a surprise.

Perhaps factory "value re-engineering" is a factor in the failure?

...

Post by Art
I think you're so right Alan,
The blanket has 3 loops of wire over the entire surface of the queen
size version, so there is about one wire every foot or so. If there were
more feet of wire per each blanket, the power density would be much
improved and the surface temperature of the insulation would be lower.
So, for the same amount of power from the outlet, any wires pressed
against each other from 'bunching' would be much less prone to failure
by melting.
Now, add in teflon or similar higher melting point insulation, and the
problem would probably be nonexistent and there would be no need for any
failsafe spiral copper wire wrap.
I am very upset to hear that low temperature melting insulation was used
INTENTIONALLY!
BTW, the company rep had no idea why the copper spiral winding was not
connected inside the blanket. I'm wondering now if it was a Chinese
fake??? It was purchased through JC Penny however.
I wish I wasn't so anxious to throw the remains in the trash!!! It was
trash day however, the bedding had burned and there was no need to keep
it. So, after the autopsy, everything went into the trash! Damn, I wish
I had kept the remains::>
In fairness to Biddeford, their rep offered to replace my mattress and
the damaged bedding, even though this was a 5 to 7 year old blanket. I
declined his offer, but I did accept the replacement blanket he offered.
=================
Just between you and me, I'm tempted to dissect the blanket Biddeford
sends and then rebuild it with some larger gauge teflon insulated
stranded copper wire...using more wire loops, but running it on 3 to 12
volts (or even lower). There would be no failsafe protection, but it
probably isn't needed anyway IF the blanket has more feet of wire within
the blanket itself. To demonstrate that no failsafe protection is
needed, I'd roll the thing into a ball and leave it operating. I think
it would be much safer.
I think I'd have a PIC monitoring the current draw constantly, so any
shorting out of the conductors within the blanket would be detected
immediately. There would be no need for the failsafe spiral wrap winding.
I'm not sure if a heating element can be made from copper however. Today
we can make highly efficient power supplies at low voltage, *so maybe
copper wire can be used as a heating element. Comments on the heating
wire heating element would be appreciated.*
Regards,
Art
....meaning the insulation  On 11/29/18 9:40 AM, AB Pearce - UKRI STFC

Post by AB Pearce - UKRI STFC

Post by David C Brown
Mind you: that didn't stop a faulty washing machine from starting the
tragic fire in Grenfell Towers.

And the ongoing evidence seems to suggest that the cost cutting of
appliance manufacturers is causing rather too many fires in homes, sadly.

--
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View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

[John Gardner]

The "Electric Blanket Institute" also reports that other

brands made by Beddeford include Sealey, Cannon,

and Delightful Nights...

Post by John Gardner
According to Boodle, Biddeford products are "now made in China".
What a surprise.
Perhaps factory "value re-engineering" is a factor in the failure?
...

Post by Art
I think you're so right Alan,
The blanket has 3 loops of wire over the entire surface of the queen
size version, so there is about one wire every foot or so. If there were
more feet of wire per each blanket, the power density would be much
improved and the surface temperature of the insulation would be lower.
So, for the same amount of power from the outlet, any wires pressed
against each other from 'bunching' would be much less prone to failure
by melting.
Now, add in teflon or similar higher melting point insulation, and the
problem would probably be nonexistent and there would be no need for any
failsafe spiral copper wire wrap.
I am very upset to hear that low temperature melting insulation was used
INTENTIONALLY!
BTW, the company rep had no idea why the copper spiral winding was not
connected inside the blanket. I'm wondering now if it was a Chinese
fake??? It was purchased through JC Penny however.
I wish I wasn't so anxious to throw the remains in the trash!!! It was
trash day however, the bedding had burned and there was no need to keep
it. So, after the autopsy, everything went into the trash! Damn, I wish
I had kept the remains::>
In fairness to Biddeford, their rep offered to replace my mattress and
the damaged bedding, even though this was a 5 to 7 year old blanket. I
declined his offer, but I did accept the replacement blanket he offered.
=================
Just between you and me, I'm tempted to dissect the blanket Biddeford
sends and then rebuild it with some larger gauge teflon insulated
stranded copper wire...using more wire loops, but running it on 3 to 12
volts (or even lower). There would be no failsafe protection, but it
probably isn't needed anyway IF the blanket has more feet of wire within
the blanket itself. To demonstrate that no failsafe protection is
needed, I'd roll the thing into a ball and leave it operating. I think
it would be much safer.
I think I'd have a PIC monitoring the current draw constantly, so any
shorting out of the conductors within the blanket would be detected
immediately. There would be no need for the failsafe spiral wrap winding.
I'm not sure if a heating element can be made from copper however. Today
we can make highly efficient power supplies at low voltage, *so maybe
copper wire can be used as a heating element. Comments on the heating
wire heating element would be appreciated.*
Regards,
Art
....meaning the insulation  On 11/29/18 9:40 AM, AB Pearce - UKRI STFC

Post by AB Pearce - UKRI STFC

Post by David C Brown
Mind you: that didn't stop a faulty washing machine from starting the
tragic fire in Grenfell Towers.

And the ongoing evidence seems to suggest that the cost cutting of
appliance manufacturers is causing rather too many fires in homes, sadly.

--
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View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

[Richard Prosser]

Just to hijack things slightly, regarding the 'Designed to Fail' aspect.

We have had a number of electric blankets over the years and they all seem
to last about 3 years and then die. In all cases it has been the controller
that dies although the problem is presented as a blanket failure. We swap
the controllers side-side and all is well again (I don't use mine, my wife
uses her side only). Then next time we buy a replacement controller set.
Except that after 5-6 years replacement controllers are no longer available
anywhere.

I've taken a number of the controllers apart but been unable to figure out
the faulty part. The more expensive ones appear to have 2 PICs or similar
in them, one driving the display. The cheaper units have just one. The
firmware in the PICs appears to be protected against downloading &
examination. It's quite possible that there's a count-down timer involved
in the firmware.

The only other component that is possibly involved is the neon indicator
lamp. it seems to be being used as a voltage reference of some sort. As
they age they get dimmer and may be it's having an effect. Manufacturers
data is useless and the patents involved are so tangled the actual detail
is hidden and may refer to a different idea / product anyway. Even the most
expensive, all singing/dancing LCD display units have a neon indicator that
has a line going to a voltage divider and then to the micro.

IIRC last time we had two controllers replaced under warranty as they were
still just inside the period, then bought 2 more for about $120 each. Then,
next time they were just not to be found.

So far I think we've had about 8 controllers 'fail' - including the
cheaper ones (same brand) on my daughters bed. All after about 3-4 years of
use, and all with no problem / difference to be found in the blanket itself.

We now have a heat pump in the bedroom & my daughter has moved out so the
blankets get a lot less use and I'm not as worried about it. But it seems a
complete waste to have to throw out a completely 'good' blanket because of
designed-in failure & irreplaceable parts.
If I had my way we wouldn't buy that brand (Sunbeam) again but the
selection is limited by the 'requirements' and I get little say in that
part of the process.

Oh yes, last time it happened, about a year ago, we couldn't find a blanket
with all the features we wanted anyway - timed switchon being the main
requirement. Apparently UL have decided that that mode is unsafe unless you
use an external timer.

rant over (for now).

RP

Post by John Gardner
The "Electric Blanket Institute" also reports that other
brands made by Beddeford include Sealey, Cannon,
and Delightful Nights...

Post by John Gardner
According to Boodle, Biddeford products are "now made in China".
What a surprise.
Perhaps factory "value re-engineering" is a factor in the failure?
...

Post by Art
I think you're so right Alan,
The blanket has 3 loops of wire over the entire surface of the queen
size version, so there is about one wire every foot or so. If there were
more feet of wire per each blanket, the power density would be much
improved and the surface temperature of the insulation would be lower.
So, for the same amount of power from the outlet, any wires pressed
against each other from 'bunching' would be much less prone to failure
by melting.
Now, add in teflon or similar higher melting point insulation, and the
problem would probably be nonexistent and there would be no need for any
failsafe spiral copper wire wrap.
I am very upset to hear that low temperature melting insulation was used
INTENTIONALLY!
BTW, the company rep had no idea why the copper spiral winding was not
connected inside the blanket. I'm wondering now if it was a Chinese
fake??? It was purchased through JC Penny however.
I wish I wasn't so anxious to throw the remains in the trash!!! It was
trash day however, the bedding had burned and there was no need to keep
it. So, after the autopsy, everything went into the trash! Damn, I wish
I had kept the remains::>
In fairness to Biddeford, their rep offered to replace my mattress and
the damaged bedding, even though this was a 5 to 7 year old blanket. I
declined his offer, but I did accept the replacement blanket he offered.
=================
Just between you and me, I'm tempted to dissect the blanket Biddeford
sends and then rebuild it with some larger gauge teflon insulated
stranded copper wire...using more wire loops, but running it on 3 to 12
volts (or even lower). There would be no failsafe protection, but it
probably isn't needed anyway IF the blanket has more feet of wire within
the blanket itself. To demonstrate that no failsafe protection is
needed, I'd roll the thing into a ball and leave it operating. I think
it would be much safer.
I think I'd have a PIC monitoring the current draw constantly, so any
shorting out of the conductors within the blanket would be detected
immediately. There would be no need for the failsafe spiral wrap

winding.

Post by John Gardner

Post by Art
I'm not sure if a heating element can be made from copper however. Today
we can make highly efficient power supplies at low voltage, *so maybe
copper wire can be used as a heating element. Comments on the heating
wire heating element would be appreciated.*
Regards,
Art
....meaning the insulation On 11/29/18 9:40 AM, AB Pearce - UKRI STFC

Post by AB Pearce - UKRI STFC

Post by David C Brown
Mind you: that didn't stop a faulty washing machine from starting the
tragic fire in Grenfell Towers.

And the ongoing evidence seems to suggest that the cost cutting of
appliance manufacturers is causing rather too many fires in homes, sadly.

--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

[Art]

Hi Richard et al,

My expereince with the controllers is identical to yours, despite the
fact that I do not use Sunbeam products. All my experience is with
Biddeford products and their high end flagship product (using the TC12B0
controller).

They self destruct, producing an 'E' error code and they will not tell
me why this happens, only that I need to buy a new controller. The
blankets themselves still work, only the controllers fail at a high rate.

I am disgusted by their use of low temperature insulation and the
problems it creates with melting plastic when the owner rolls over onto
the blanket, pushing the conductors together-which makes a hot spot,
which leads to a fire if the controller fails to shut down the power to
the blanket.

In reading the complaints in detail, many have had fires and received
burns, despite the claim by the company that the blanket will shut down
safely. Even so though......LOW TEMP INSULATION?? WT FRACK!! It's
designed to fail and UL (apparently) condones this practice.

I've long suspected that Biddeford programs the PIC to shut down
purposely, just to make more money.  Corporate greed is strong (in
America especially).

This spiral wrapped heating element with the copper wire winding puts
117v on the sensor terminals, which destroys the controller. I do not
oppose this practice as it is a failsafe for safety. But, low
temperature plastic insulation practically guarantees the blanket will
self destruct if the blanket is bunched together. The extremely low
temperature plastic is the problem.

For the purposes of safety, a much higher melting point plastic would
stop or prevent failures from bunching and the spiral wrap failsafe
would be just as effective if a blanket did melt down or the insulation
failed due to abrasion.

However, why allow the blanket to melt down at all??? If we monitor the
current through the heating element when the blanket is turned on, the
blanket could be turned off and an alarm could sound.....long before the
spiral wrap failsafe had a chance to kick in.

I'm wondering if there is opportunity here for a new electric blanket
manufacturer. The public wants lower EMF protection, better safety and
controllers that don't need to be replaced every 2 or 3 years.

I'm already thinking about designing my own direct replacement PCB for
my existing Biddeford TC12BO controller because I know it will fail
soon! Or, a 'repair' kit for dead TC12BO controllers that will restore
them to proper operation without the need to buy a completely new
controller.

Aloha....and, please feel free to hijack the thread anytime-the input
from the PIC group is outstanding and much appreciated by me.

Art

Post by Richard Prosser
Just to hijack things slightly, regarding the 'Designed to Fail' aspect.
We have had a number of electric blankets over the years and they all seem
to last about 3 years and then die. In all cases it has been the controller
that dies although the problem is presented as a blanket failure. We swap
the controllers side-side and all is well again (I don't use mine, my wife
uses her side only). Then next time we buy a replacement controller set.
Except that after 5-6 years replacement controllers are no longer available
anywhere.
I've taken a number of the controllers apart but been unable to figure out
the faulty part. The more expensive ones appear to have 2 PICs or similar
in them, one driving the display. The cheaper units have just one. The
firmware in the PICs appears to be protected against downloading &
examination. It's quite possible that there's a count-down timer involved
in the firmware.
The only other component that is possibly involved is the neon indicator
lamp. it seems to be being used as a voltage reference of some sort. As
they age they get dimmer and may be it's having an effect. Manufacturers
data is useless and the patents involved are so tangled the actual detail
is hidden and may refer to a different idea / product anyway. Even the most
expensive, all singing/dancing LCD display units have a neon indicator that
has a line going to a voltage divider and then to the micro.
IIRC last time we had two controllers replaced under warranty as they were
still just inside the period, then bought 2 more for about $120 each. Then,
next time they were just not to be found.
So far I think we've had about 8 controllers 'fail' - including the
cheaper ones (same brand) on my daughters bed. All after about 3-4 years of
use, and all with no problem / difference to be found in the blanket itself.
We now have a heat pump in the bedroom & my daughter has moved out so the
blankets get a lot less use and I'm not as worried about it. But it seems a
complete waste to have to throw out a completely 'good' blanket because of
designed-in failure & irreplaceable parts.
If I had my way we wouldn't buy that brand (Sunbeam) again but the
selection is limited by the 'requirements' and I get little say in that
part of the process.
Oh yes, last time it happened, about a year ago, we couldn't find a blanket
with all the features we wanted anyway - timed switchon being the main
requirement. Apparently UL have decided that that mode is unsafe unless you
use an external timer.
rant over (for now).
RP

Post by John Gardner
The "Electric Blanket Institute" also reports that other
brands made by Beddeford include Sealey, Cannon,
and Delightful Nights...

Post by John Gardner
According to Boodle, Biddeford products are "now made in China".
What a surprise.
Perhaps factory "value re-engineering" is a factor in the failure?
...

[Harold Hallikainen]

Since an insulation failure SHOULD result in a safe shutdown, I wonder if
the low temperature insulation is actually a safety feature. Excessive
temperature, for whatever reason, shuts the system down. UL has required
us to have electronics in a "fire enclosure" if more than 15 watts is
available. A fire enclosure for an electric blanket seems difficult, and
limiting power to 15 watts seems a bit low (I think a person at rest
dissipates about 100 watts, so a person would warm the bed a lot more than
a 15W blanket).

I think it would be difficult to design a safe electric blanket.

Harold

[Art]

I talked to UL today.

They can't do much without a complaint and I'm not sure I should get
involved to that extent. I would however like the public to know about
the issue and that the company designs their products to fail.

They did give me the 2 relevant standards for this class of product, I
haven't had a chance to look at them yet. The actual standard is a
commercial product, however they provide a free summary document that is
public and can be distributed without permission.

The issue is so called 'bunching'. If the blanket is doubled over and
wires intersect (physically), a hot spot is created, which eventually
melts the insulation IF the user rolls over onto the blanket, which
pushes the conductors together with some force. The company rep told me
I need to be sure I didn't roll over onto the bunched blanket in my
sleep!!! Which I think is unrealistic. A higher melting point plastic in
the heating element however would nip this problem in the bud however
and I believe the failsafe protection would still be functional with the
higher melting point plastic insulation.

It is unknown why my unit didn't shut down, the controller must have failed.

I just wrote a letter to the company today. I suggested that they should
use the PIC to monitor the current in the heating element, and that it
should shut down the drive current if the current varies by more than a
few percent, especially if the current increases. And, that the PIC
protection should be the primary protection method.

I was able to confirm that they DO NOT measure the current in the
heating element at the present time.

I further suggested that higher temperature plastic would still provide
the same failsafe function, albiet the response would be a little slower.

Yes, it is difficult to design a safe electric blanket. The primary
danger is overheating/fires. Electrocution being a safety issue as well.

But, today we have mature power conversion technology and I think the
blanket should be run on low voltage with full galvanic insulation from
both line voltage power leads. And that the electronics should monitor
the heating element current as the primary safety feature.

If Biddeford does not respond, it might be time for a new company to
take the reins and build something safer::>

Regards,

Art


 

Post by Harold Hallikainen
Since an insulation failure SHOULD result in a safe shutdown, I wonder if
the low temperature insulation is actually a safety feature. Excessive
temperature, for whatever reason, shuts the system down. UL has required
us to have electronics in a "fire enclosure" if more than 15 watts is
available. A fire enclosure for an electric blanket seems difficult, and
limiting power to 15 watts seems a bit low (I think a person at rest
dissipates about 100 watts, so a person would warm the bed a lot more than
a 15W blanket).
I think it would be difficult to design a safe electric blanket.
Harold

[John Gardner]

...today we have mature power conversion technology and I think the
blanket should be run on low voltage with full galvanic insulation from
both line voltage power leads...

Hear hear... Low voltage (12VAC with PWM?), temp sensors,

AND power monitoring... But its not really a technical problem.

It does'nt do any good to design a better product which your

Chinese factory will ignore, in favor of the lowest possible manu-

facturing cost that'll move product, while the important-looking

white guys in $5K suits in Westchester pretend they're oblivious...

...

Post by Art
I talked to UL today.
They can't do much without a complaint and I'm not sure I should get
involved to that extent. I would however like the public to know about
the issue and that the company designs their products to fail.
They did give me the 2 relevant standards for this class of product, I
haven't had a chance to look at them yet. The actual standard is a
commercial product, however they provide a free summary document that is
public and can be distributed without permission.
The issue is so called 'bunching'. If the blanket is doubled over and
wires intersect (physically), a hot spot is created, which eventually
melts the insulation IF the user rolls over onto the blanket, which
pushes the conductors together with some force. The company rep told me
I need to be sure I didn't roll over onto the bunched blanket in my
sleep!!! Which I think is unrealistic. A higher melting point plastic in
the heating element however would nip this problem in the bud however
and I believe the failsafe protection would still be functional with the
higher melting point plastic insulation.
It is unknown why my unit didn't shut down, the controller must have failed.
I just wrote a letter to the company today. I suggested that they should
use the PIC to monitor the current in the heating element, and that it
should shut down the drive current if the current varies by more than a
few percent, especially if the current increases. And, that the PIC
protection should be the primary protection method.
I was able to confirm that they DO NOT measure the current in the
heating element at the present time.
I further suggested that higher temperature plastic would still provide
the same failsafe function, albiet the response would be a little slower.
Yes, it is difficult to design a safe electric blanket. The primary
danger is overheating/fires. Electrocution being a safety issue as well.
But, today we have mature power conversion technology and I think the
blanket should be run on low voltage with full galvanic insulation from
both line voltage power leads. And that the electronics should monitor
the heating element current as the primary safety feature.
If Biddeford does not respond, it might be time for a new company to
take the reins and build something safer::>
Regards,
Art

Post by Harold Hallikainen
Since an insulation failure SHOULD result in a safe shutdown, I wonder if
the low temperature insulation is actually a safety feature. Excessive
temperature, for whatever reason, shuts the system down. UL has required
us to have electronics in a "fire enclosure" if more than 15 watts is
available. A fire enclosure for an electric blanket seems difficult, and
limiting power to 15 watts seems a bit low (I think a person at rest
dissipates about 100 watts, so a person would warm the bed a lot more than
a 15W blanket).
I think it would be difficult to design a safe electric blanket.
Harold

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http://mailman.mit.edu/mailman/listinfo/piclist

[RussellMc]

Post by John Gardner
It does'nt do any good to design a better product which your
Chinese factory will ignore, in favor of the lowest possible manu-
facturing cost that'll move product, while the important-looking
white guys in $5K suits in Westchester pretend they're oblivious...
Point understood.

And/but the quality of Chinese goods sold on foreign markets is largely the
"fault" of the buyers. As you indicate.

It's not enough to design a better product. You need to do so for a
customer who wants the better results AND is willing to do what it takes to
ensure these are achieved.
It's doable.

But - only with a will. I think that every or nearly every new design or
major change in anything I designed that was built in China needed recall
or remediation of the first batch despite the most strenuous efforts on my
part to ensure the factory and the customer did not make it otherwise. This
not due to any design issues (another matter :-) ) but due to manufacturing
funnies of various sorts. Even when we had an excellent in factory
inspection company operating at one stage a 'first batch sneak through'
occurred.
I was in the factory on that occasion and tried desperately to have a
trucked load of product recalled when it became evident what had happened.
Alas, they managed to get delivered into customs store and thus took weeks
to recover :-) :-(.

Russell

[RussellMc]

Post by John Gardner
According to Boodle, Biddeford products are "now made in China".
What a surprise.
Perhaps factory "value re-engineering" is a factor in the failure?
Russell's laws of manufacturing in China.

1. You have to be there*.

followed by the later

0. Don't**.

* ie you or a competent authorised representative loyal to you and with
full authority has to be on site and involved enough to be able to
guarantee that what is done is what is meant to be done.

** If you can't comply with 1. , don't even try.

You MAY be lucky, and some are, but odds are ... .

Russell

Post by John Gardner
...

Post by Art
I think you're so right Alan,
The blanket has 3 loops of wire over the entire surface of the queen
size version, so there is about one wire every foot or so. If there were
more feet of wire per each blanket, the power density would be much
improved and the surface temperature of the insulation would be lower.
So, for the same amount of power from the outlet, any wires pressed
against each other from 'bunching' would be much less prone to failure
by melting.
Now, add in teflon or similar higher melting point insulation, and the
problem would probably be nonexistent and there would be no need for any
failsafe spiral copper wire wrap.
I am very upset to hear that low temperature melting insulation was used
INTENTIONALLY!
BTW, the company rep had no idea why the copper spiral winding was not
connected inside the blanket. I'm wondering now if it was a Chinese
fake??? It was purchased through JC Penny however.
I wish I wasn't so anxious to throw the remains in the trash!!! It was
trash day however, the bedding had burned and there was no need to keep
it. So, after the autopsy, everything went into the trash! Damn, I wish
I had kept the remains::>
In fairness to Biddeford, their rep offered to replace my mattress and
the damaged bedding, even though this was a 5 to 7 year old blanket. I
declined his offer, but I did accept the replacement blanket he offered.
=================
Just between you and me, I'm tempted to dissect the blanket Biddeford
sends and then rebuild it with some larger gauge teflon insulated
stranded copper wire...using more wire loops, but running it on 3 to 12
volts (or even lower). There would be no failsafe protection, but it
probably isn't needed anyway IF the blanket has more feet of wire within
the blanket itself. To demonstrate that no failsafe protection is
needed, I'd roll the thing into a ball and leave it operating. I think
it would be much safer.
I think I'd have a PIC monitoring the current draw constantly, so any
shorting out of the conductors within the blanket would be detected
immediately. There would be no need for the failsafe spiral wrap winding.
I'm not sure if a heating element can be made from copper however. Today
we can make highly efficient power supplies at low voltage, *so maybe
copper wire can be used as a heating element. Comments on the heating
wire heating element would be appreciated.*
Regards,
Art
....meaning the insulation On 11/29/18 9:40 AM, AB Pearce - UKRI STFC

Post by AB Pearce - UKRI STFC

Post by David C Brown
Mind you: that didn't stop a faulty washing machine from starting the
tragic fire in Grenfell Towers.

And the ongoing evidence seems to suggest that the cost cutting of
appliance manufacturers is causing rather too many fires in homes,

sadly.

Post by Art
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