Thermocouples????

[Dougal]

Anyone know if there's such a thing as a 'generic thermocouple' for a very old 3way fridge?

I have a 'Groenland' T725 made by Camping Gaz. I think the thermocouple is gone, but cannot find one anywhere;-(

Anyone know a way round this? (apart from a new fridge)

 

[JumbleDuck]

Anyone know if there's such a thing as a 'generic thermocouple' for a very old 3way fridge?

I have a 'Groenland' T725 made by Camping Gaz. I think the thermocouple is gone, but cannot find one anywhere;-(

Anyone know a way round this? (apart from a new fridge)

As far as I know, they characteristics of a thermocouple depend solely on the two metals used, so any device using the same two metals should behave the same way (we used to make 'em for cryogenic work by twisting copper and nichrome wire together). If I'm right, which has happened occasionally, the physical package is probably the thing to match,

 

[VicMallows]

Best thing is to post a pic and someone might identify a suitable direct replacement. Otherwise, as Jumbleduck says, electrically they will all be just about the same so it essentially comes down to finding something which physically fits.

 

[Iliade]

Yes, go to PTS or even Screwfix. Take the old one for a length check. All else is standard(ish)

 

[Jcorstorphine]

I am not sure I agree about this. I think some systems use a flame failure device which (I think) is an expansion capillary to a mechanical valve which is held open by the capillary so long as the end is heated.

See this link. http://www.ybw.com/forums/showthrea...e-Gas-Shut-Off-Devices-On-Marine-Cookers-Work

I am not convinced that a thermocouple could produce enough "oomf" to hold a valve open directly as a Type K at 750 C only produces about 30 mV.

 

[VicS]

I am not sure I agree about this. I think some systems use a flame failure device which (I think) is an expansion capillary to a mechanical valve which is held open by the capillary so long as the end is heated.

See this link. http://www.ybw.com/forums/showthrea...e-Gas-Shut-Off-Devices-On-Marine-Cookers-Work

I am not convinced that a thermocouple could produce enough "oomf" to hold a valve open directly as a Type K at 750 C only produces about 30 mV.

I thought that for a long time ..... but they are thermocouples

 

[Dougal]

Sadly, I can't get at it. The boat is in France, and I'm hoping to take something out in a few weeks that might fit. Am I even talking about the right part i wonder....? Nesting in the cooling fins inside the fridge, is the start of it (a small dia flexible rod). It disappears into the back, where I'm guessing it connects to the shut-off device?

 

[VicMallows]

Nesting in the cooling fins inside the fridge, is the start of it (a small dia flexible rod). It disappears into the back, where I'm guessing it connects to the shut-off device?

No! ... That's the thermostat which controls the fridge temperature ..... but only when working on mains electricity (not on 12v or gas).

If your fridge doesn't work when on mains, then it could be the thermostat, but more likely the electric heating element has failed. (easy to check which with a meter).

 

[VicS]

No! ... That's the thermostat which controls the fridge temperature ..... but only when working on mains electricity (not on 12v or gas).

and that will almost certainly be a bulb and a capillary and an integral part of the thermostat

 

[Dougal]

It's bizarre.... The freezer section works on gas and 12v (not mains), but the cooling fins in the main fridge won't work. Looks like they each have separate thermostats.

 

[daveyw]

http://www.gasproducts.co.uk/acatalog/Super_Universal_Gas_Thermocouple_1200mm.html

 

[Dougal]

That's awesome thanks Dave!!!
Thinking on though, it's got to be the thermostat hasn't it, as gas stays lit for the freezer section. It's that the fins won't cool.

 

[William_H]

http://www.gasproducts.co.uk/acatalog/Super_Universal_Gas_Thermocouple_1200mm.html

That is interesting that they call that a "thermocouple". A thermo couple with the exception of some that drive a moving coil meter always need electronics to convert the tiny voltage to something useful. It is possible that the "thermocouple" pictured has a centre electric conductor. On the other hand it may be a fluid thermostat and they have hijacked the "thermocouple" name.
A thermostat using tiny tube of expanding fulid is more like a thermometer the fluid presure operating contacts. Is most common in refrigerators.
A thermostat can be tested by attaching an ohm meter to the contacts. If you put some ice on the proble and select warmest setting on the dial you should get a change of the contacts. Usually open with cold.
A different thermostat might be fitted for the gas side as it will need to operate a valve to cut gas back. good luck olewill

 

[VicMallows]

It is possible that the "thermocouple" pictured has a centre electric conductor. On the other hand it may be a fluid thermostat and they have hijacked the "thermocouple" name.

Will, I can assure you that the item in question (and pictured in the link) is an electrical thermocouple. Yes, it is essentially mineral insulated coax. These have been standard in all domestic boilers (furnaces) with pilot lights for at least 50 years. Surely you have the same in Aus?.

It is better to think of them as current generators. They create just enough to keep a gas solenoid open once you have opened it manually. Many gas fridges now have a simple meter to indicate that the flame is alight. This is IN SERIES with the thermocouple which keeps the gas valve open.