How To Set Adjustment Lever On Ct31a Thermastat

I just bought this thermostat to replace a digital programmable unit that failed. It controls only my AC, but the principle is the same as for heating systems. I experienced "short cycle" problems right away. The unit is adjustable via the "system" setting, but the range of adjustment did not seem to help much, I managed to work around it. .. The thermostat is a simple device that is just a switch that utilizes a bi metal coil, the round spring you see in the middle, its made of two types a metal one layer on top of the other, they expand and contract at different rates causing the spring to wind and unwind as the temperature go's up and down. The center (base) of the coil is attached to the temp adjust lever on top and rotates the coil, there are two contacts located one on each side of the coil and two magnets, as the coil expands and contracts, its contact pulls away from one magnet (and contact) gradually until the force is enough to break free and then it snaps to the other side attracted by the other magnet, this can be observed. Down the right side is a slide thing with numbers, this just moves the magnet and contact on that side (the heat side) away or closer to the coils contact, increasing and decreasing the force required for that snap to happen (on that side), and adjusting the time of the cycle slightly. 1.2 is the most magnet force, and when set there the room temp will have to drop farther for the coil to rotate and have enough force to override the magnet and thus snap to cool. My AC was still short cycling on this setting.

I found that the two contacts are screws, and by backing them off slightly (lefty loosey, righty tighty) the coil contact is resting closer to the magnet on either side of its swing and thus the thermostat requires a greater swing in room temp before it cycles. Care must be taken NOT to have the coil contact touch the magnets but there is plenty of turns before that happens. Accuracy will be affected surely but comfort and equipment protection will be maintained The thing is just an on off switch, no circuitry, not even a thermometer. Its not that accurate to begin with, its how you feel, not the number anyway.

Too long I know, but I hope I helped