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DarnEfnet 07-29-2012 01:55 PM

AC Short Cycling
So I may have created my own problem. Im in oklahoma and bought a 1824 sq ft house built in 1983 a few years ago. The first summer when it was 100+ out the house wouldnt get below 80 and the unit would run from 10am to midnight to get the house back to 86.

I had an AC company come out and they the unit was fine but undersized at 3 tons. I then had an energy audit done and they said the house was very leaky and had too little insulation and the unit was sized correctly if the house wasnt so leaky.

I also had a test done where they put a blower on the front door and identified any air leaks. I then had all the old insulation vacuumed out, all the light fixtures and penetrations sealed in the attic as well as all plumbing penetrations in the walls and even the dryer vent replaced with a weighted magnetic sealed one. Then I had r50 insulation blown into the attic, all the windows replaced with loe3 argon energy start rated windows. Other factors may be all the lighting is now led so there isnt as much load there and now the attic has 90ft of ridge vents and the attic temp is only about 10 higher than ambient now.

So here is my issue, it is 107 outside as we speak, I have it at 72 in the house and the unit is short cycling. I almost feel like the unit is oversized now.

Any advice on what to do to make the unit not short cycle when its hot enough it should be running more constant? Did I take the enrgy auditor advice too far?

turnermech 07-29-2012 02:03 PM

If your unit is a varible speed with ECM motor you can try to set the board up or have a contractor set it up for 350 cfm per ton. this won't change the fact that the unit is oversized (if that is the case) but it will remove more humidity and your confort level should increase.

DarnEfnet 07-29-2012 02:08 PM

Thanks, Ill check to see if that is an option.

The comfort level feels fine, Humidty is at 43% right now, I was more concerend with the wear and tear on the unit. Im not even sue if its really considered short cycling as it runs for about 8 minutes then stays off for about 30.

turnermech 07-29-2012 02:15 PM

if your humidity is 43% I would say your not short cycling. high humidity would result in most cases of shoet cycling as the unit would not run long enough to remove humidity before dropping the temp

ben's plumbing 07-29-2012 02:52 PM

lower the stat temp 1-2 degree ????

biggles 07-29-2012 03:40 PM

grab that thin copper line at the air handler or the condenser super hot? what freon are you running...filers and fan clean return air is solid holdsup sheet of local paper...ceiling or wall mounted...temp split on air in and out of furnace in cooling mode

scottmcd9999 07-30-2012 06:30 AM

I've always considered "short cycling" to be a system that runs for 10 minutes, stays off for 10 mintues, and so on - not one that has an on cycle of 8 mins and an off cycle of 30 mins.

As others have said, you can try moving your stat up/down a few degrees - but if the house is comfortable, and the humidity level is around 40%, then I'd say just enjoy the savings!

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