Heat Pump stops cooling

[neauva]

A quick search of the threads didn't provide me with much info so forgive me if I missed the answer somewere...

I have a 20yo heat pump, 4-ton Carrier. I replaced the original manual thermostat with a new digital, programmable, heat-pump compatible one. Worked okay for a while but at random, about once per day, the system just stops cooling. It continues to blow, but it's not cool. If I shut off and reset the thermostat (using the stylus), wait a few minutes, and restart (and re-program!) it, it will start cooling again.

I don't know if it's really related to the thermostat or if there's something wrong with the compressor, etc.

Any ideas on how to determine the problem?

Thanks!
-neauva

[simpleman]

Sounds like it could be low on froen and the coil is freezing up.

Next time it start to cool and then it start blowing warm check the big line on the outdoor unit and see if its has ice on it.

If its ice up..then it time to make a call for pricing on some new equipment.

[neauva]

Ugh, I was afraid you'd say that! :)
Thank you for the quick info!

On a related note, I have 3400 sq ft. to cool, 2 stories, with another unit (equally old, 2-ton) upstairs. The downstairs area is probably about 2000-2200 sq ft. Is the 4-ton unit big enough? (btw, I live in Texas, if that's a factor).

Thanks again,
-neauva

[mjk_na]

Difficult to say without doing Manual J calculation. The load calculation has to be determined by this.

Were you comfortable before? If so, then it's OK to go for similar size. I guess your duct work is OK.

Did the problem of "cooling stopped" happen when you were using the mechanical thermostat?

That should give you some clues. Worth checking for ice as well.

[billva]

may just be the "rite-temp" stat. you get what you pay for.

[psychometric]

put the old stat back on and see if problem continues. Worked in Texas for a few years, 20 years is a long time for a HP there.