I recently installed three double pole line voltage thermostats in a customer’s home. The line voltage is 240volts.
The customer says that one of the thermostats reads a temperature of 70 deg. F even though he has it set at 60 deg. F. This thermostat is in a single gang box with two heating elements run to it. The heating elements are imbedded in the ceiling plaster. This is the only thermostat that has two elements run to it. The others have only one element.
I don’t see how controlling the two elements with this thermostat would make any difference on the calibration of the thermostat. From what I can see the thermostat should just monitor the room temperature and open and close the line voltage contacts for the heating elements. The heating elements are wired in parallel with each other. I wouldn’t think you would want them wired in series. Either way I don’t see how this would have any effect on the calibration of the thermostat.
The thermostats are supposed to be factory calibrated with a + or – 2 deg. F accuracy. There are two calibration pots on the thermostat that are sealed with a potting compound.
Does anyone have any experience with the calibration of line voltage thermostats?
Have you ever had to calibrate these in the field?
These are simple manual, non-programmable rotary dial thermostats made by King model HET-2R.
I wouldn’t think calibrating these in the field would be necessary.
I could just try replacing it with another one but was wondering if anyone else has had this problem with line voltage thermostats and what they did to correct it .
I have one sitting here at my desk right now and it’s reading a temperature of 68 deg. F. When I rotate the dial clockwise I can here it click on at about the 68 deg mark and when I rotate it counter clockwise it clicks off at about 62 deg. F. mark.
Maybe the one I installed is just not calibrated properly.
I though I’d see if I could get some input from someone before I go out to look at it.
His daughter told me she thinks he just likes to tinker with things too much and keeps turning the dial up and down and won’t leave it alone.
Any help is much appreciated.
