Paging Tony Agile!!

[Agile]

Yes, to some extent.

But sometimes when testing heat loss of heating systems it can be useful to be able to set the boiler to a constant heat input.

 

[PullerGas]

I would be more inclined to use a 20k or 25k pot ( or switch an extra 10 K resistor in series ) .

That is so that I can test the frost protection function which many boilers have.

The best ones have two features, run pump below 3 C and start burner below 1 C. Approximate temperatures. Usually activated at about 17 k or more.

Tony

Thanks Tony. You know I Value your opinion. I guess a wee LCD displaying the setting would also be handy to incorporate in the circuit......

Who's going to be a luv & pop up a schematic for the hard of thinking & the newbies??

 

[FiremanT]

I would be more inclined to use a 20k or 25k pot ( or switch an extra 10 K resistor in series ) .

That is so that I can test the frost protection function which many boilers have.

The best ones have two features, run pump below 3 C and start burner below 1 C. Approximate temperatures. Usually activated at about 17 k or more.

Tony

Thanks Tony. You know I Value your opinion. I guess a wee LCD displaying the setting would also be handy to incorporate in the circuit......

Who's going to be a luv & pop up a schematic for the hard of thinking & the newbies??

 

[DP]

Fireman, changed your mind did you?

 

[PullerGas]

Puller, look at the MIs, what is the minimum resistance the thermistor is going to indicate i.e. at max temperature.
That will be value of the resistor you need (Ideal Icos 85 degree resistance value is 1k)
25 degree resistance is 9k7 to 10k3

I would pick 1k resistor and 10 k pot. Solder the resistor to middle connection on the pot. connect one (test) wire to other leg of the resistor and another (test) wire to right hand connection on the pot

Minimum setting would indicate 85 degrees and full travel of spindle on the pot about 25 degrees.
If you want reverse reading, move the outer wire to the tag that is 'spare'

My old one is roughly like this DP & as Tony has stated its a bit limited range wise. As someone who's well documented exclusion from the combustion chamber pot, I feel a bit ashamed to say this; should this thread be moved to the inner sanctum? While, I don't mind ruffling a few feathers - I'd hate to compromise the income of fellow RGIs!!

 

[DP]

Pullargas, sticking a fixed resistor in place of thermistor and then using the variable resistor that is the facia mounted thermostat IMHO is all that is required to test the boiler control circuitry. Let us say a fixed value resistor is the new 'thermistor', varying the thermostat now allows one to check the modulation

 

[PullerGas]

Pullargas, sticking a fixed resistor in place of thermistor and then using the variable resistor that is the facia mounted thermostat IMHO is all that is required to test the boiler control circuitry. Let us say a fixed value resistor is the new 'thermistor', varying the thermostat now allows one to check the modulation

Thanks Danny.
Yeah that would work, but I guess with the a Pot in series you can simulate the boilers temperature by varying the resistance. This may check the facia mounted thermostat's calibration & the thermistor?
Or perhaps I'm not seeing the woods for the trees?

Added problem is having compatible thermistor connections for any boiler in your tool box.