Jumpy T-Stat Reading w/ Coal-Trol

I purchased a coal trol in May and am now installing it. When the t-stat displays the current room temp it varies between 69 and 73 degrees and the room is 71 according to another thermometer. Is this normal for this unit? Back in a former life I used to check and calibrate thermocouples and if the readings were erratic like this it usually meant you had a bad connection.

Hi Gambler,

No, this isn't normal. Sometimes you'll get a temperature that is right on the edge between two adjacent numbers, 70 and 71 for instance, and it might "jitter" a bit between those, but "spread" jitter isn't normal.

Did this continue after the until had been powered up for a while (30+ minutes)? Only thing I can think of is that maybe after first powering up there is a period where some components in the thermostat are heating up and an equilibrium hasn't been hit yet. Also make sure that the two air holes on the left side, top and bottom, of the thermostat are clear and that the device is oriented upright (like it would be attached to the wall). This is necessary to make sure there is airflow through the thermostat and there isn't any "heat trapping" effect throwing things off.

Please give us a call (315-299-3589) so we can do a bit more troubleshooting and arrange a replacement if necessary.

The T-stat had been mounted on the wall and powered up for a few hours when I noticed it giving these jumpy readings. It would flash the current reading and many times it would be correct but then it would flash what I would consider a bad reading. It would give jumpy readings for a few cycles then it would settle down for a few and then back to the jumpy readings. I thought how is it going to control the fire if it takes a reading of 69 one time and then 73 the next time. Anyway I purchased a new cable yesterday so I will install that and see what happens. Thanks for your responce and If the cable does not fix it I will give you a call.

It is highly unlikely the cable will have an effect. The temperature readings are all handled entirely internally to the thermostat box. The cable is used to provide power to the thermo and to send control signals to the control module for the motor plugs.

Another possibility, do you have an oscillating fan or something like that blowing onto the thermo?

No, I don't have any fans running. Let me watch it for a bit and see if it has any rhyme or reason for doing this.

The wife will think that I have really lost it when she sees me watching the wall for hours.

Well I watched the t-stat for several 10-15 minute intervals during the course of the evening and the stat was very steady so as it stands now it is working fine. I will have to keep an eye on it for a while just to make sure it stays steady.

Thanks pvolcko for the fast responce and if I have any more trouble with it I will let you know.

Well if it happens again, I would put some masking tape over the vent holes. If it stops doing it, it is probably the air moving through it. If not, it could be your low voltage transformer acting up or (this one is unlikely, but possible?) your T-stat wire crosses or runs parallel with a higher voltage power cable. Just a thought.