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Old 07-17-2010, 09:12 PM   #1
iya
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A/C and thermostat questions


We just (finally) moved into the house we just got, and are now running the central AC. Noticed a few things, and questions popped up:

1) We have the old circular Honeywell thermostat. The AC doesn't kick in even when the thermostat setting is a little higher than the room temp. It seems to be a whole 8-10 degrees off. Since this has a mercury switch, I could check the level. To do so, is it necessary to turn off breakers before loosening mounting screws? And do the mounting screws look any different than screws that hold the wires on (i suppose the wires are held on by screws).

2) The AC cycles at about 10 minutes on, 10 minutes off. Is that okay? I thought they typically run longer, and stay off longer.. Admittedly, it's not high noon when I noticed this, but it bothers me anyway. If it is NOT okay, then what can I do about it? There's no way I can change the +/- tolerance of the thermostat, that I know of.. Can anyone enlighten me? I foresee a thermostat change someday, but not just yet...

3) There's about 1,000 sq ft of living space being cooled by the set-up, and from what I could figure, a 2.5 ton unit. Is the unit oversized, considering we're in Northeast Ohio? I've always lived with window air, so I don't know just how this all works out..

I guess that's it for now. I know I had more questions, but as I was trying to phrase these, the others just kind of... fizzled away. They'll be back, though, and so will I :P

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Old 07-18-2010, 04:32 AM   #2
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A/C and thermostat questions


Unit is over sized and I would change the mercury bulb stat to a digital. It's so out of plumb its causing shortcycling every ten minutes.

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Old 07-25-2010, 06:41 PM   #3
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A/C and thermostat questions


So I followed your advice and changed the merc to a digital. Honeywell RTH2310B, I believe (off the top of my head). Set the CPH to 2. I'm getting 12-ish mins on, and about 15 off. I think it's an improvement, considering the last few days before the change, I was getting more of an 8 : 8 on:off cycle. I'm still keeping tabs on the cycling, since I think I might also need to improve the insulation, but that'll be for a different thread.

Also, I'm not going to replace my AC just yet (not in the budget) but when I do get around to it, if my 2.5 is oversized, what WOULD be the right size for our house?
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Old 07-25-2010, 09:37 PM   #4
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A/C and thermostat questions


Need to do a load calculation to be sure. My house is about the same size and has a two stage two ton heat pump. First stage puts out less then a ton and a half and it keeps the house at 73 even with the 110-115 heat indexes we have had lately.
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