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TxGreaseMonkey · Jul 11, 2007, 08:10 PM

Turn thermostat OFF, pull AC disconnect to condenser unit, and turn off furnace breaker (power to contactor coil) before performing any work. Use non-contact voltage meter to verify power is off. Finally, use a large plastic handle screwdriver between contactor and ground to confirm power is off.

Then, install a Delay on Break (DOB) Timer to your home air conditioner's condenser unit, if it didn't come with one (most don't). Anti-short cycle timers protect compressor and contactor from high Locked Rotor Amperage (LRA) damage, when lightning or other power outages cause power to slam off and then back on. Popular products include ICM 203B, which is adjustable from 2 seconds to 10 minutes. 5 minutes is usually sufficient to allow internal compressor pressures to equalize. Remove wire from contactor coil and attach to Terminal 3 (Input) on DOB Timer. Connect jumper wire from DOB Timer Terminal 1 (Load) to contactor coil. This is cheap insurance to protect a major investment.

acetc · Jul 11, 2007, 09:05 PM

You may be on the right track BUT I think you meant a time delay relay to delay on make, not break and nix the scerw driver trick, use a volt meter.

hvacservicetech_07 · Jul 11, 2007, 09:27 PM

Most newer digital thermostats have built in time delays.

hvac1000 · Jul 11, 2007, 10:26 PM

((use a large plastic handle screwdriver between contactor and ground to confirm power is off.)) When the tip of the screw driver blows up in your face you might get burns and loose an eye. Not a good idea. Timers have been around for over 30 years with Carrier using a electro mechanical one. They work great. I guess if you really want to save your A/C and make it last longer a hard start kit would be in order.

TxGreaseMonkey · Jul 12, 2007, 07:10 AM

Yes, most digital thermostats provide a 4-minute delay after shutting off the compressor before it can be restarted. This feature prevents damage to the compressor caused by rapid cycling. However, most do not provide a delay when there are power outages--this is the key point.

hvac1000 · Jul 12, 2007, 07:40 AM

Originally Posted by txgreasemonkey

Yes, most digital thermostats provide a 4-minute delay after shutting off the compressor before it can be restarted. This feature prevents damage to the compressor caused by rapid cycling. However, most do not provide a delay when there are power outages--this is the key point.

All Honeywell thermostats provide a delay when there is a power failure in the cooling position. Basically the thermostat takes the power loss as a fresh call for cooling with the standard delay as if it was a normal cycle delay. Try it. Cut the power off to the section of the unit that contains the 24 volt supply. Then reenergize the unit and the thermostat will delay the cooling call to the condenser unit. Now power surges are a different story and a time delay does not help there.

One final note. If you try to hook up a time delay and also use a thermostat with a time delay all you do is extend the delay which will make the house uncomfortable since the total delay will be so long.

TxGreaseMonkey · Jul 12, 2007, 08:09 AM

Many Hunter and other less expensive thermostats do not provide delays, when there's a power outage.

hvac1000 · Jul 12, 2007, 08:50 AM

I never sell cheat stats. They are not worth selling because of all the problems

T-Top · Jul 12, 2007, 06:20 PM

Originally Posted by acetc

You may be on the right track BUT I think you ment a time delay relay to delay on make, not break and nix the scerw driver trick, use a volt meter.

Time delay on make is like a heat sequencer, every time you have a 24 volt call, it times on (every time). Time delay on break means after the 24 volts is broke it will have to be off for that amount of time. Even if it is calling for it to close again.

hvacservicetech_07 · Jul 12, 2007, 08:42 PM

Originally Posted by txgreasemonkey

Many Hunter and other less expensive thermostats do not provide delays, when there's a power outage.

Those thermostats would better serve as paper weights.