Ceramic heater safety cutout switch temperatures?

[Mike Tomlinson]

Fixing a ceramic heater for a family member. Started blowing cold air.
It's very similar to this one:

https://en.wikipedia.org/wiki/File:Goldair_GCH200_ceramic_heater.jpg

It has a NC safety temperature switch fitted, this has failed open. One of
the spade lugs has clearly overheated. The switch is shown at the bottom
of this pic:

http://www.zuglet.com/ev/saturn/images/ceramicElement.jpg

It's marked KSD301 250V 10A. But there is no temperature marking :(

There is also a thermal fuse, this is OK.

This ebay auction:

http://www.ebay.co.uk/itm/262117559259

shows replacements with temperature values ranging from 40C to 160C. Can
anyone suggest what value I should choose?

The heater works OK with the wires to the switch shorted, but I would like
to replace it.

Thanks.

--
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(='.'=) Bunny says: Windows 10? Nein danke!
(")_(")

[N_Cook]

I've never known the bimetal dome to fail on these, always the contacts
or the little ceramic trigger out of position.
First with a soldering iron barrel , confirm by listening for a click
over, then repeat with a thermometer, glass or pyro.

[Mike Tomlinson]

En el artículo <napt3g$1id$1...@dont-email.me>, N_Cook <div...@tcp.co.uk>
escribió:

>I've never known the bimetal dome to fail on these, always the contacts
>or the little ceramic trigger out of position.
>First with a soldering iron barrel , confirm by listening for a click
>over, then repeat with a thermometer, glass or pyro.

It's open circuit, with a burnt spade terminal. Trust me, it's u/s.

[N_Cook]

On 26/02/2016 16:16, Mike Tomlinson wrote:
> En el artículo <napt3g$1id$1...@dont-email.me>, N_Cook <div...@tcp.co.uk>
> escribió:
>
>> I've never known the bimetal dome to fail on these, always the contacts
>> or the little ceramic trigger out of position.
>> First with a soldering iron barrel , confirm by listening for a click
>> over, then repeat with a thermometer, glass or pyro.
>
> It's open circuit, with a burnt spade terminal. Trust me, it's u/s.
>

But not the dome, hack into it and extract the dome.
Now not constrained, you need to make sure it does not fly off , when
it flips to the opposite state.

[mrob...@att.net]

In sci.electronics.repair Mike Tomlinson <mi...@jasper.org.uk> wrote:
> https://en.wikipedia.org/wiki/File:Goldair_GCH200_ceramic_heater.jpg

I have a similar heater that I bought here in the US, branded Holmes,
made in China. It is rated at 1500 W, 120 V, 60 Hz. As a first cut,
their product support page

http://www.holmesproducts.com/service-and-support/product-support/product-faqs/heaters/general-information/heaters-general-faq.html

says the "overheat shutoff temperature" varies from 149 to 265 F, or
about 65 to 130 C. Note that this covers both ceramic and non-ceramic
heaters.

Taking mine apart, the ceramic core is about 3.25 x 3.5 x 0.5 inches,
or about 83 x 89 x 13 mm. If yours is very different than this, then it
may need a different temperature rating!

The safety switch is an "open frame" design, like the one seen in the
picture you linked -

> http://www.zuglet.com/ev/saturn/images/ceramicElement.jpg

- and not an enclosed one like the KSD301 Ebay link you gave. When
installed, the bimetal with contacts is about 0.125" or 3 mm away
from the top edge of the ceramic core.

It is marked AUONE, AUT95P, and has VDE and USA-Canada UL component
marking ("backwards RU").

Google leads me to http://www.auone.com/showproduct13.asp?ProID=1849 .
The part I have looks like their "AUT-P" series (with the white plastic
tab), which lets me *guess* that the "95" in the part number means
95 C (or 203 F). Again, this is _just a guess_.

Please proceed with caution. The house you don't burn down may be
your own.

Matt Roberds

[Mike Tomlinson]

En el artículo <naqubs$uaf$1...@dont-email.me>, mrob...@att.net escribió:

>says the "overheat shutoff temperature" varies from 149 to 265 F, or
>about 65 to 130 C. Note that this covers both ceramic and non-ceramic
>heaters.

A useful data point, thanks.

>Taking mine apart,

You didn't have to go to that much trouble, but thank you.

> the ceramic core is about 3.25 x 3.5 x 0.5 inches,
>or about 83 x 89 x 13 mm. If yours is very different than this, then it
>may need a different temperature rating!

3.5" x 3.25", so very similar. There's 4 ceramic cores with two heat
levels selected by a switch (heat level 1 = 2 cores operating, heat
level 2 = 4 cores operating)

Ceramic elements are PTC so self-regulating to an extent.

>Google leads me to http://www.auone.com/showproduct13.asp?ProID=1849 .
>The part I have looks like their "AUT-P" series (with the white plastic
>tab)

That sounds like a resettable one.

>, which lets me *guess* that the "95" in the part number means
>95 C (or 203 F). Again, this is _just a guess_.

It's also right in the middle of the "65 to 130C" shutoff temperature
you quote above.

Many thanks.

>Please proceed with caution. The house you don't burn down may be
>your own.

Obviously, I need to choose a sensible temperature for the cutoff - too
low, and it'll trip on and off all the time. There is also a thermal
fuse as a belt-and-braces measure at the top of the ceramic frame. I
haven't looked to see what temperature rating it is. Obviously, if that
fails, it will fail open permanently.

The ceramic element is held in place in a hard plastic frame, so isn't
going to be allowed to get very hot.

I'll try a 95C switch with a temporary neon indicator on the feed to the
element to see if it's cycling excessively, and go from there.

It's a nice little heater, very quiet and efficient, so worth a bit of
time.

Thanks again.

[mrob...@att.net]

Mike Tomlinson <mi...@jasper.org.uk> wrote:
> En el artículo <naqubs$uaf$1...@dont-email.me>, mrob...@att.net escribió:

>> Taking mine apart,
>
> You didn't have to go to that much trouble, but thank you.

I use it a lot in fan-only mode, so it was about ready for its annual
dusting anyway. :)

> There's 4 ceramic cores with two heat levels selected by a switch
> (heat level 1 = 2 cores operating, heat level 2 = 4 cores operating)

Same here.

>> The part I have looks like their "AUT-P" series (with the white
>> plastic tab)
>
> That sounds like a resettable one.

It is. There is no user-resettable button; you just have to unplug
the heater and let it cool off.

> The ceramic element is held in place in a hard plastic frame, so isn't
> going to be allowed to get very hot.

Same here. On mine, the frame also extends back towards the intake to
hold the fan motor and make a venturi/shroud for the fan blade.

Matt Roberds

[Mike Tomlinson]

En el artículo <naso0k$jrm$1...@dont-email.me>, mrob...@att.net escribió:

>On mine, the frame also extends back towards the intake to
>hold the fan motor and make a venturi/shroud for the fan blade.

Yes, same here. It's all one piece. The section holding the ceramic
element is square, then there's a short cylinder to the fan housing
which is square. The lot fixes to the back half of the enclosure with 4
screws.

I suspect this is pretty much a commodity part made in China and badged
with OEM logos as required.

I've ordered the 95C switch, pretty sure that'll do the trick. Thanks
again for your help, have a virtual pint on me :)

[et...@whidbey.com]

Nice as it is the efficiency is same as any other electric heater. All
the power going into it becames heat in the room it's in.
ERS