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View Full Version : a/c cycling on and off too much



plucka99
26-03-2007, 11:58 PM
Residential Carrier ducted with programmable thermostat. Wierd thing I've noticed lately is the a/c is cycling on and off much more frequently than it used to. When its maintaining the set temp it will come on for only a few minutes, turn off for maybe 5-10 mins then cycle on again for a few minutes, repeat. In the past I'm sure it would stay on and off much longer, eg maybe on for 20mins off for 30mins. The cooling and airflow all seem normal so cant think what would cause this. What concerns me is I know there is a huge electricity load on startup so dont really want a massive bill. Any ideas?

Electrocoolman
27-03-2007, 11:47 AM
Don't worry about the electricity....You'll soon need a new compressor!
What happens when you lower the 'stat set point? Does the unit then run continuously until it reaches the new temperature.....ie. is it a problem with the unit or the 'stat.
Are all your filters clean?

malik55
27-03-2007, 04:57 PM
Where is the thermostats location?
If it is near the supply air stream side it is possible that it may swing unusually.
Is unit capacity is as per design?
If a unit is over sized also the same could be happened.
malik55

Gary
27-03-2007, 06:16 PM
When its maintaining the set temp it will come on for only a few minutes, turn off for maybe 5-10 mins then cycle on again for a few minutes, repeat.

Words like "few" and "maybe" don't tell us much. Time the starts.

As a rule of thumb, the compressor should start no more than 6 times per hour.

Once the house and everything in it is down to temperature/humidity, which may take a few days, the unit should run shorter cycles than when everything was hot and humid.

On a warmer day, you should expect it to run more than on a cooler day.

coolments
30-03-2007, 12:05 AM
if you have tried the above good advice then first thing i would do is put a link in the stat, if it runs continous then that settles it, stat problem or stat location problem. if it still cycles then maybe its slightly short of gas and going out on LP especially if its auto reset