Central Air problem - thermostat or what ?

Old 05-12-07, 09:06 PM
mobile_man's Avatar
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Central Air problem - thermostat or what ?

I had some questions about my air conditioning. I don't know what's going on so any help would be appreciated. This post is lengthy, so bear with me here.

Outside unit:
Heil air conditioner manufactured in 2001. (2 ˝ -ton unit)
Model: HACD30AKA1
Rated voltage 208

Inside unit:
York Natural gas heat pump Evaporative coils (3-ton unit) and Gas furnace (60,000 btu’s) manufactured in 1994.
model: XAC0136BAC

Both are controlled by Model 9600 Maple/Chase digital thermostat that uses batteries.

This afternoon my wife and I came back from errands. Normally, we leave the thermostat in the "off" position when we're not home. The display on the thermostat said it was 86 F in the house when we came in. I did what we usually do which was to move it to "cool" with the fan set to auto. Normally, I would hear the inside and outside part come on.

The inside part came on, but the outside part did not. I waited a little bit, but outside part did not come on.

I was able to determine we had a power outage here. The breaker box is marked two 20 amp breakers for the AC. After reseting both the 20 amp breakers, move it to "cool" with the fan set to auto, the outside unit didn't come on. Only after reseting both the 20 amp breakers and a 15 amp breaker, then the unit came on. The thing is, the breakers weren't tripped at all.

Later on, the Lo Battery indicator came on the thermostat. I've replaced those batteries.

My questions are as follows:

1)What's going on?
2)Do I need to keep foliage (grass and the like) away from the outside unit? Wife has a flower bed on the one side but no plants near the unit really.
3)Is there a page some one can direct me to about maintenance a homeowner can do on the outside unit? I see leaves inside of
the casing and would think those need to come out of there.
4)On the thermostat, even with new batteries, it'll say the room temp is 78 F. I have a thermometer in the same room that says the room temp is 75.6 F. The thermometer was part of a weather station so I would trust it's reading. How do you calibrate one of these?

Thanks in advance.

Last edited by mobile_man; 05-12-07 at 09:07 PM. Reason: spelling
Old 05-13-07, 11:47 AM
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Very Interesting post.

Lengthy is good, the more info provided allows for the wheels to turn and try and figure out the problem.

A power outage and restoration with the A/C on would point to a capacitor in the outdoor unit. But since the unit was off we can rule that out at this point. But a visual look see wouldn't hurt. If you turn off the power to the outside unit, take the electric panel cover off look for a round silver capacitor with wires on top. Top should be flat and not convex.

Your thermostat is 5 - 2 day programmable 24volt with battery back up to hold the program. The manual can be found here: http://www.icca.invensys.com/manuals/robertshaw/110-653B.pdf

Resetting breakers that are not tripped probably had no effect.

All I can think of is the stat itself. Do you mave a multi meter or 20 bucks to get a cheap one at Lowes or a Radio Shack?

If this happens again read a/c volts from "C" to "Y" at the stat. Less that 18 volts while calling for cooling it's the stat. But at the same time check "C" to "R" ("RH" and "RC" should be jumperd in the stat) refer to manual linked above.

Yes keep obstructions way from the outdoor unit, you need good airflow through the coil. If you are mechanically inclined enough to turn off power to the outdoor unit and do some disassembly so you can clean the coil (from the inside out). If your not comfortable have a pro come each spring and do it for you. And make sure the tech uses a nucalgon coil gun and not the inefficient pump up sprayer and a water hose.

No there is no provision in your stat to calibrate the temp. But come to think of it there is a reset button which you may have done by resetting the breakers with a low battery condition.

I don't know of any place to point you as far as DIY maintenance. When I did sidework I would teach my customers how to DIY. Kind of hard to do over the net.

Hope this helps.


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