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View Full Version : Heat pump temp. output at registers normal?

carl333
02-05-2012, 12:31 PM
Hi, I have a Lennox XP17 2.5 Tand installed a year ago. Just wondering in my temperature output at the registers is just about normal.

With heat pump running and no heat strips engaged, I am receivng a temp of 80 degrees at the registers.

conditions:

house temp: 68F
outside air temp:14F

Is 80 that I am receiving at the registers normal or am I below what it should be??

tks

BaldLoonie
02-05-2012, 01:16 PM
At a brisk 14 out, 12° rise may not be too bad. Probably losing a little in the ductwork too. More accurate is taking a reading entering the blower and a couple feet away from it to take duct loss out of the equation. Doing it both ways alerts you to the duct loss.

Gross
02-05-2012, 01:37 PM
12 degree rise at 14 odt sounds pretty good to me BUT it may make more sense, economically, to run the strip heat at that temp. Any Trane guys have guys have performance data for this machine?

beenthere
02-05-2012, 02:06 PM
12 degree rise at 14 odt sounds pretty good to me BUT it may make more sense, economically, to run the strip heat at that temp. Any Trane guys have guys have performance data for this machine?

Whats Trane got to do with a Lennox heat pump.

It would make no sense to witch to emergency heat. The strip heat would cost more to use then the heat pump.

skippedover
02-05-2012, 02:07 PM
12 degree rise at 14 odt sounds pretty good to me BUT it may make more sense, economically, to run the strip heat at that temp. Any Trane guys have guys have performance data for this machine?

Why Trane, he said it's a Lennox system?? To me, the real question is whether the HP is keeping up with the set-point. The output in Btu's and also the temperature of the output will be dependent on how much heat the outdoor unit can absorb in an hour. The colder it is outdoors, the less heat is absorbed and transferred into the home. Since a Btu is a measure of heat, a dropping supply temperature goes hand-in-hand with the output of the HP. When balance point is reached (HP running constantly and just maintaining t-stat set-point) then the HP supply temp is at the lowest. Below balance point requires the addition of Btu's to heat your home. The use of electric resistance heat will boost the supply air temps as more Btu's are delivered into the home.

catmanacman
02-05-2012, 02:22 PM
@ 14 degree outdoor temp a 12 degree temp rise seem pretty good to me just let the thermostat add auxillary heat as needed and let that heat pump run.

Gross
02-05-2012, 04:05 PM
Whats Trane got to do with a Lennox heat pump.

It would make no sense to witch to emergency heat. The strip heat would cost more to use then the heat pump.

It has nothing to do with Trane. I saw an X and stopped paying attention.

But thanks for calling me out. I'll gladly post links to other threads I've made simple errors in if you'd like to continue to critique?

beenthere
02-05-2012, 06:34 PM
It has nothing to do with Trane. I saw an X and stopped paying attention.

But thanks for calling me out. I'll gladly post links to other threads I've made simple errors in if you'd like to continue to critique?

I probably already saw those post. But left you slide on them. LOL

Homeowner314
02-05-2012, 08:20 PM
@ 14 degree outdoor temp a 12 degree temp rise seem pretty good to me just let the thermostat add auxillary heat as needed and let that heat pump run.

Now you've got me thinking about ditching propane and going all electric with air source HP.

Many of the systems I've been looking at are claiming 1.5 COP at -10°F, when I'd always thought HPs were useless under +20°F.
I assume the electric strips are downwind of the heat pump's coil and both can run together, but by -10°F the HP is contributing a lot less heat than the auxiliary strip , so the overall COP is slightly over 1?