a/c thermostat sensivity...

Jul 11, 2004 5 Replies

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zounds 22 years ago

I live in an apartment that originally had the old "fan coil" in each apartment with a thermostat, and the water either chilled or heated on a 'seasonal' basis; the absorption chiller was too much trouble, and for many other reasons, individual heat pumps were installed (on the roof). The new air handlers with refrigerant coils "barely" fit in the small old "heater closets."

The heat pump works very well, the emergency heat never came on last winter - not even close. There's just one problem - when in a/c mode, the temperature spread between on/off cycles is WAY too large - sometimes upwards of 6-7 degrees. The thermostat (simple White-Rogers 'heat pump thermostat') was replaced about a year ago. Made no difference.

I've tried to read up on this on the internet but still have no clear idea - the engineers here tell me such thermostats are not adjustable for sensitivity. There is an anticipator dial, but I believe that only affects electric heating if/when it's ever used as backup. Is this true? Could a better thermostat result in shorter cycles (no, not REAL short, but perhaps a temperature difference of 3 degrees would be great).

Thanks for any advice - Bill

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m Ransley 22 years ago

Try the anticipator dial, reset it , if it doesnt work get a new stat , You should be able to set a 0 degree swing if you wish, it sounds like it is set completely to the extreme. But im no pro just my idea.

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Joseph Meehan 22 years ago

Most if not all thermostats have an adjustment for just that. You want to have some swing. With not enough swing you will loose efficiency. It is generally called an anticipator.

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Chip Orange 22 years ago

I've got an electronic thermostat (from home automation inc) and it has all of that as options you can adjust (even down to minimum cycle time and minimum time between cycles).

Maybe you just need a high quality electronic thermostat (I paid around $150 for mine, but it has additional capabilities including tying into various automation systems).

I have to admit it keeps the house quite comfortable; if you want to check it out you should find it at:

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zounds 22 years ago

Thanks everyone for suggestions. Last evening I adjusted the anticipator about 1/8" or less clockwise. Seemed to help, but it's too early to tell as it was cool last night. When the heat load is really high (temp upper 80's and above) the "spread" gets wider.

Placement of the thermostat, the apartment having north-south exposure (like two different worlds between living room and bedroom) probably has a lot to do with it.

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CBHVAC 22 years ago

And what NO ONE touched on, and no one on the internet can tell you, is if the unit is oversized, you will get this problem as well... You will also get this problem if the thermostat is located in the wrong place....

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