Outdoor HP Thermostat Reading Higher

Joined
Sep 18, 2002
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Location
VA
I have a HP with back up propane heat. Propane is set to come on at 30 degrees. However, my outside thermostat is reading 5-6 degrees higher than actual temp. I have 3 outside digital thermometers (1 for each BR) which all read the same outside temp. I placed one of them beside my outside temp thermometer at the HP to validate the actual temp difference. As of right now, the outside HP temp is reading 46 and the digital thermometer right beside it is reading 40 degrees.

So, in order for my propane to come on, the actual outside temp would need to get to 24 degrees actual temp for the outside thermometer to think it is 30 degrees and send the signal to start my propane furnace.

Is there a way to calibrate the outside thermometer? I don't think it is. I have the Honeywell C7089U1006 outside thermometer. I know I can go in my inside thermostat and change the settings for the propane to come on a 35 which would probably work fine. I
 
Yeah, it is not gonna ruin my world but it would be nice for it to be within 2 degrees or so. LOL
 
Why not raise the set point from 30 to 35 degrees. Can the sensor be clean???
That was what I am thinking if there is no way to make a calibration in the system. I'll go and wipe down the sensor.
 
If that sensor is a temp/resistive thermistor type it can be calibrated using tiny trim pots. Typically on the circuit board inputs where the wires attach there will be resistors or possibly may be trimpots on the board. the resistors or trimpots can be used to set the upper, lower and span for the specific sensor used. Replace the resistors with similar value trimpots to start.

example

1637003863022.png
 
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