On my USSC 8500 it has a thermistor and I hear the term thermistor used rather often especially referring to big truck AC and how it can jack the system. Can someone tell me what the thermistor does or it’s purpose on my pellet burner and how do or can you test them.
Thermistor
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ARC
Minister of Fire
In simplest terms the thermistor is measuring the temperature of your stove. It does this by attaching one end to your board and the other usually attached near exhaust motor/housing. The end near the exhaust heats up and as it does the resistance of the flow of a small amount of electricity going through (ohm's) changes. A microprocessor on your board reads the change and that tells it what temperature it is at. I sure it can be "tested" but you would need a good ohm meter away to heat end of thermistor to exact temperatures and and would have to know what each ohm reading means temperature wise (something not generally published on line)
A very common thermistor is a 10K. If you have multimeter you can look up the resistance value on a table. I just searched for 10K thermistor and this link came up. https://www.yumpu.com/en/document/v...tput-table-10k-2-thermistor-output-table-bapi
Not to be confused with thermocouple. Instead of changing resistance it generates a small amount of voltage proportional to temperature https://www.pyromation.com/downloads/data/emfk_f.pdf
Not to be confused with thermocouple. Instead of changing resistance it generates a small amount of voltage proportional to temperature https://www.pyromation.com/downloads/data/emfk_f.pdf
Mt Bob
Minister of Fire
OK,don't have a USSC or BRECKWELL manual, but will wing it a bit. You have 2 sensors only, on that furnace, I believe. A rds and a thermister. The RDS is back in the exhaust, near outlet. Thermister somewhere probably by the air plenum.
3 jobs need fulfilled by them, proof of fire, turn convection fan on, and shut down stove if overheating.
Logic says the RDS is the proof of fire, and the thermister is the other 2 jobs.
As said, testing is mostly useless without having specs, and knowing the programming it is being used for.
But here is some info--
www.omega.com
(broken link removed to https://www.sensorsci.com/understanding-the-differences-between-thermistors-and-rtd-sensors)
3 jobs need fulfilled by them, proof of fire, turn convection fan on, and shut down stove if overheating.
Logic says the RDS is the proof of fire, and the thermister is the other 2 jobs.
As said, testing is mostly useless without having specs, and knowing the programming it is being used for.
But here is some info--
NTC Thermistors vs. Resistance Temperature Detectors (RTDs)
Thermistors and RTDs are types of resistors with resistance values that vary predictably with changes in their temperature. Read about its differences here.
Great info. Sunday morning when I was giving unit its daily quick ash scraping it was running in HR3 so door temp was up and top bonnet transition was about 125. I put it in manual to get draft fan steady on to help control smoke when I open door and forgot I did that until about a minute or so later when unit cut back. So it seems the thermistor was doing its job. Thank you for info and according to USSC 8500 manual it does have a thermistor in heat exchanger area somewhere and RTD just after draft fan. Thanks again
