Thermocouple trigger

[Ringhilescu]

Hello,

Hello! I am Ciprian from Romania and I own an Abbey Vogue GTS 214 caravan, from 1998, with a Carver heating system. I am facing the following problem. When I connect the heating to 220V, and from the control panel it is set to minimum, and the speed is on auto, my resettable thermocouple is triggered. I mention that I measured the trigger temperature and it is correct 232 degrees Celsius, respectively 450 Fahrenheit. I also measured the thermistor (temperature sensor) and it indicated 28.8 when cold. Can a colleague help me with some advice? Or can someone tell me what the capacity of the thermistor is? Maybe it is defective and needs to be replaced. Thank you!

 

[Christhecaravanner84]

Sorry Ciprian, I can't help with this but just wanted to say welcome to the forum.

 

[ProfJohnL]

Hello,

Hello! I am Ciprian from Romania and I own an Abbey Vogue GTS 214 caravan, from 1998, with a Carver heating system. I am facing the following problem. When I connect the heating to 220V, and from the control panel it is set to minimum, and the speed is on auto, my resettable thermocouple is triggered. I mention that I measured the trigger temperature and it is correct 232 degrees Celsius, respectively 450 Fahrenheit. I also measured the thermistor (temperature sensor) and it indicated 28.8 when cold. Can a colleague help me with some advice? Or can someone tell me what the capacity of the thermistor is? Maybe it is defective and needs to be replaced. Thank you!

Hello RInghilescu, Welcome to the forum.

Firstly let me correct the name of the device that trips It is not a thermocouple or a thermistor it is a thermal over temperature switch. and its function is to turn the heating elements off if they get too hot. If its cutting the power, then we need to work out why.

The most common cause for this type of problem is not enough air flow through the heater. Check the hot air ducts are not crushed or damaged and that at least one outlet vent near the heater is open.

The circulation fan may be clogged with dust. This can be carefully removed and cleaned do not damage or bend any of the impellers blades as this may cause vibration.

The fan motor may worn out, Unfortunately Carver stopped making this model in 1999, and there will be very few spares, but the motor is just a 12V model and you might be able to find a similar one on Ebay or Ali Express etc. Measure the motor size to find one

I do not know what the safety laws are in Romania, but if you are removing or replacing any gas components please make sure you follow all the required safety regulations.

 

[Hutch]

Hello RInghilescu, Welcome to the forum.

Firstly let me correct the name of the device that trips It is not a thermocouple or a thermistor it is a thermal over temperature switch. and its function is to turn the heating elements off if they get too hot. If its cutting the power, then we need to work out why.

The most common cause for this type of problem is not enough air flow through the heater. Check the hot air ducts are not crushed or damaged and that at least one outlet vent near the heater is open.

The circulation fan may be clogged with dust. This can be carefully removed and cleaned do not damage or bend any of the impellers blades as this may cause vibration.

The fan motor may worn out, Unfortunately Carver stopped making this model in 1999, and there will be very few spares, but the motor is just a 12V model and you might be able to find a similar one on Ebay or Ali Express etc. Measure the motor size to find one

I do not know what the safety laws are in Romania, but if you are removing or replacing any gas components please make sure you follow all the required safety regulations.

Prof, your are more capable than myself on this, but are the temperatures that Ringhilesue quoting correct, they seem very high. ?

 

[ProfJohnL]

Prof, your are more capable than myself on this, but are the temperatures that Ringhilesue quoting correct, they seem very high. ?

Why do you suspect the temperatures are too high?

The thermal cut out is safety feature which is designed to prevent thermal runaway causing damage to the appliance , the users or its environment, and bearing in mind it was designed as a caravan heater, that means there's plenty of dry wood near by.

The ultimate surface temperature of the elements is designed to be controlled by the cooling effect of blowing air through the appliance. If there is insufficient air (eg, a blocked fan or weak fan motor or restricted hot air ducting) the cooling effect is reduced and the element surface temperatures will increase. The cut out should prevent the temperatures rising beyond a safe limit. The set point has to be above the normal expected operational temperature otherwise it would cause nuisance tripping.

 

[Ringhilescu]

Good find! I have also investigated what I need, is the value of the thermistor. Can you help me? Thank you!

 

[Gafferbill]

.......carver heaters of 1998 may of had a thermal fuse.
My 1995 model was fitted with one.
Once the fuse blows it has to be replaced. It became difficult to source the correct fuse so I modified mine by fitting a thermal over temperature cut out.
I think the cut out was rated at 120 degC.
Your photo looks like the fuse as I remember it.

 

[ProfJohnL]

The device you have shown is a Thermistor. Unfortunately I do not know the specification of the component used but the I assume the reading you told us ("28.8") was the resistance across the terminals?. "28.8" seem very low. Did you mean 28800 Ohms (28.8Kilo Ohms). This seems more likely and strongly suggests the thermistor is probably working correctly.

To test the thermistor get it to 25C, and measure its resistance , I suspect you will find it has a value of about 22kOms to 25KOhms. From experience I have found these types of thermistors to be very rugged and reliable, SO I don't think your problem is related to this thermistor.

Do other checks and maintenance I have suggested first in post #5

 

[Ringhilescu]

Dear all. Thank you for your help. I have measured the thermistor again at 20 degree Celsius and the resistence is 35 Kiloohms. I am not sure whether is it normal or not.

 

[ProfJohnL]

Dear all. Thank you for your help. I have measured the thermistor again at 20 degree Celsius and the resistence is 35 Kiloohms. I am not sure whether is it normal or not.

This is how Negative Temperature Coefficient (NTC) thermistors resistance varies with temperature


That seems like a good measurement and that likely puts the 25C value at around 33 kilo Ohms.

 

[Ringhilescu]

Good evening, all! Thank you for help. In this case, I really don't understand what's wrong with my Fanmaster when I connect it to 230V. The thermistor is within parameters, the thermocouple closes at 230 degrees Celsius, the ventilation holes are free, the motor rotates at two revolutions, the motor vanes are cleaned and yet, the thermocouple disconnects every time, shortly after starting the Fanmaster on 230V. I really don't understand anything anymore. Thank you for your help.

 

[ProfJohnL]

Hello again,
I'm sorry your Fanmaster is still not working. The Fanmaster does not have a "thermocouple" It has a thermistor which is used as a temperature sensor, and it has an Over Temperature switch which will only open if the appliance gets too hot becasue it cannot get rid of the heat the elements produce.

As you have proven the Thermistor is OK, and the fan is not blocked, and the Over Temperature Switch is still operating, then it suggests there is a problem with the control circuit. I believe replacement circuits may still be available. Try

https://arcsystems.biz/

 

[Gafferbill]

......back in post #7 I mentioned that fanmasters of that era may have a replaceable thermal fuse.
Later versions had a reset button.
These are positioned at the back of the housing and there will be either one or the other fitted.
The replaceable thermal fuse was notorious in puzzling owners as to why their fanmaster wouldn't work on the electric setting.
Have you found a reset button?
If there is not one fitted then you have the dreaded thermal fuse which may have blown cutting the electric supply to the heating elements.
There used to be a kit available to upgrade to the later reset button design....very much doubt that kit is still available.

 

[Hutch]

......back in post #7 I mentioned that fanmasters of that era may have a replaceable thermal fuse.
Later versions had a reset button.
These are positioned at the back of the housing and there will be either one or the other fitted.
The replaceable thermal fuse was notorious in puzzling owners as to why their fanmaster wouldn't work on the electric setting.
Have you found a reset button?
If there is not one fitted then you have the dreaded thermal fuse which may have blown cutting the electric supply to the heating elements.
There used to be a kit available to upgrade to the later reset button design....very much doubt that kit is still available.

The old grey cells are still working well , Bill. 🙌😂

 

[ProfJohnL]

......back in post #7 I mentioned that fanmasters of that era may have a replaceable thermal fuse.
...

Its unlikely that OP has the earlier version with a thermal fuse, becasue if the fuse was present and had blown, that would prevent the elements from producing any heat. RInghilescu stated "my resettable thermocouple is triggered. I mention that I measured the trigger temperature and it is correct 232 degrees". This implies the elements are getting hot.

But I also suspect the description he uses of it being a "thermocouple" is a translation error, becasue the Fanmaster never had a thermocouple, and even if it did, they do not "trigger" or have a defined temperature at which they trigger, so it's a very strong probability RInghilescu is actually referring to a restable over temperature switch, which as you say only appeared on the revised model.

 

[gary]

Sorry to come in late but Johns information is correct, so not much to add.
Two things spring to mind though, one is, over time the dirt building up on the fan comes free and is then thrown by the air flow onto the elements eventually blocking the air flow through them directly behind the overtemp stat. This then will cause premature tripping of stat, as will constantly tripping causing the stats contacts to become high resistance inturn causing stat to self heat and trip itself out!
Test for this measuring resistance between connections, should be less than 1ohm