condensor going on/off

I inspected a brand new heat pump system where the condensor cut on /off in 5-8 second intervals. I checked the temp going in//out of the sytem-the difference is 8 degrees. Does someone know whats going on with this unit? It was manufactured in 2006.

Yep, the technical term for that condition is “it’s broke, call the repair man”! Seriously, probably a defective starting capacitor but one of the HVAC gurus will chime in shortly I’m sure.

For some reason it’s short-cycling, but that’s the most severe short-cycling I’ve ever heard of. As my wise ol’ grandmother said, “Call the repairman.”

I work for an HVAC company in PA. It’s $69.50 / hr with $20.00 travel charge plus parts. It could be a couple of different things, the start capacitor for one, loose wire even a bad thermostat will cause that.


I would have it checked out by a qualified HVAC mechanic, but here are some of my thoughts why it might be short cycling. The start or run capacitor might be defective. The thermostat might be wired incorrectly. It seems strange that if it’s a new system that there is only an 8 degree temperature differential. It could be possible that the heater and air conditioner are running at the same time or the system is under/over charged. Check the thermostat to make sure it is level and mounted securely if it’s the old mercury style kind. That kind of problem is pretty hard to diagnose without being there to hook up testing equipment to the unit and shouldn’t be done by anyone without an EPA certification. You can still check the little stuff like the thermostat and listen if both units are running at the same time though.

The start capacitor is the most common choice. In that case, the motor tries to start but does not, so it quickly overheats and the thermal overload kicks it out. The motor cools briefly, resets itself, then tries to restart. Chances are, if a loose or intermittent thermostat connection is the culprit, the time between starts would be longer as there is usually a timer (set for several minutes) that prevents short cycles.

Low voltage can cause the motor to not start with the capacitor furnished, or the capacitor itself could be weak/defective. Also, voltage could be dipping during starts due to undersized wiring. If the voltage is as called for on the nameplate, the problem can often be cured by installing what some call a ‘hot shot kit’ which is essentially a booster for the capacitor.

In any case, the problem is beyond the scope of a home inspection :mrgreen:

If it’s a newly installed split, then maybe the installer didn’t check for leaks properly. It could be cycling on the low pressure switch, an auto reset type.
Where is this located and how much is it worth to you to fix it? I can be there poste haste.:mrgreen: