Heat Pumps and Electric Heating - Gibson 2 ton Split System Heat Pump

I have the above model # JT5BD-024T outside unit and GB5BM-125K inside unit. I'm new to heat pumps and wonder if this is normal operation. I don't live in house - I'm rehabbing it 10 hours a day - so system is OFF unless I'm there. House is 1400sf ranch on a crawlspace - ducting is in the attic - Poor ventilation in attic - 130F. Outside temp is 90F. Inside temp is 82F. Takes unit 3 hours from turn on to drop temp to 81F. Register air temp is 67F.

Does this sound normal?
Such a long lag time to move temp 1 deg normal for a heat pump?
Register air temp normal at 67F?

Hard to tell. On a properly sized system it can take several hours 12- 24 to get it down to setpoint heat pump or not. On a properly sized system even at setpoint on 90º days the a/c should ideally run for hours at a time between cycles.

So you have been running the unit during construction? Have you changed the air filters on a regular basis? I would start there.

I have the same heat pump Gibson 2 ton in a 1580 sq ft ranch. Difference is my ducts are below in the crawlspace. I get 20' differential in inlet/outlet temps. Love my system. Here are some thoughts for you:

a) as suggested check your filter
b) put in a thermostatic powered roof vent to suck out hot air
c) is your ductwork insulated?
d) What mode is the air handler in? ie. if the fan is running slow it is working on dropping humidity - not temp - so it could take 3 hours.
e) Check your lineset to make sure it is insulated properly and the suction and liquid lines arent touching metal to metal.
f) Check your return grill to see if it is blocked.

Good luck

Thanks guys for the helpful replies. Return filter is clean. Hosed off outside coils - they looked clean anyway. Ducts in attic are insulated. This morning at 8am - attic temp was 108F after overnight low of 65F - whew doggies, I need a ridge vent or powered pancake vents badly. I may very well need an R charge - It hasn't been used in 1.5 years. Got an HVAC man coming out Thurs.

zoneout - the outside fan does seem to rotate slowly - is there a "humidity" / "cool" switch?

Thanks, Doug

What's happening is the structure is absorbing heat during the off time hours. Then when you crank the a/c up, it has to cool down the structure as well as try to cool the interior. That hot attic in the am is telling you there's been lots of heat all night. Some units use an 825 rpm motor on the outdoor unit which might be slower than you are used to seeing on other units.

Doug,

1) I was referring to low speed fan in the air handler. The new variable speed blowers can be programmed to slow down in order to drop humidity. Not sure if the GB5BM does that. The gibson outdoor unit fan runs at only one speed. It shouldn't appear slow. When its running it should be pushing a helluva lot of air.

2) You can check the charge but keep in mind that these are sealed systems. sO IF THE charge is low its either been improperly charged before or you have a leak.

3) Either way look into doing something about that attic vent situation. You'll save on ac electric bills.

Got a charge of R-22 today - tech said it was only a bit low. Low pressure side (I think) - the big copper tubing got pretty cold afterward. Everything else looked fine. Next step - a ridge vent - gotta get hot air moving out of there. Thanks for all the replies. Doug

Ran AC for first time today after charge of R-22. Register temps are 59F (down from 67F). A little freon went a long way. Still gotta get attic venting so AC doesn't work so hard.

Doug,

Glad to hear you are getting better performance. One point worth keeping in mind is that your register outlet temp will vary depending on inside temp, outside temp, and indoor humidity. So basically it is better to check the differential in return and supply temps. In most situations there should be a 20 deg differential - again this will vary in extreme conditions.

zoneout....."there should be a 20 deg differential"
Where are these measurements taken?
1. Register?
2. Inside return box upstream of coils?