heat pump temp rise

[lyork]

Okay, just a quick question on a heat pump. How much temp rise can I expect to get? I was getting 18 to 22 degree drop in a.c. mode depending on outside conditions. Should it be about the same in heat mode. This is measuring air temp in the return right before the air filter and right after the A coil. Thanks in advance for your time.

[Black Adder]

Depends on outdoor temp, 20 to 25 is very acceptable. Colder it gets the less temp rise you will have.

[dan sw fl]

Originally posted by lyork
Okay, just a quick question on a heat pump. How much temp rise can I expect to get?

Review specs ( BTU Capacity) to determine temperature rise at lower outside temperature.

BTUh = CFM x 1.08 * Temp Diff

Temp Diff = BTUh / ( CFM * 1.08)

3-ton at > 50'F outside might be
delta T = 30,000 BTU h / ( 1,200 CFM * 1.08) = 23'F

Inside Room Temp 72'F
_Air Supply Temp 95'F

___ Signficantly less when outside temp < 40'F.

[lyork]

Thanks guys--I have a 4 ton Lennox Heat pump with TXV. Outside temp is 41 degrees, return is 70 degrees, supply is 95 degrees. Sounds like everything is running good then!

[dan sw fl]

Originally posted by lyork
Thanks guys--I have a 4 ton Lennox Heat pump with TXV. Outside temp is 41 degrees, return is 70 degrees, supply is 95 degrees. Sounds like everything is running good then!

That sounds great at 41'F outside temp,
IF you currently have your
"Aux Heat" turned off.

[lyork]

No aux heat here, fossil fuel back up with 4 degree differential before it calls for back up heat.I guess it just goes to show my install company knew what they were doing!

[BaldLoonie]

Depends upon the unit. I've found high SEER scroll units will be warmer than standard SEER recip units. Trane recips tend to have the lowest rise in our experience.

[ksspartan]

Lyork,

I'm in Olathe. I am also looking at Lennox as my manufacturer. Would you recommend your installer. Is it Shawnee Heating and Cooling?

[lyork]

ksspartan, my friend works for Fagan, commercial applications, and did this as a favor for me. We use Shawnee heating and cooling at my shop, I couldn't really give them a whole hearted recomendation, but they seem to get the job done. I WOULD recomend Cates heating and cooling, or McCarty mechanical down in merriam. Cates did my mom's installation a few years back and did a superb job, however it wasn't a heat pump. I have several friends in the business and nobody has anything bad to say about those two companies. I will say that if you use the information you find on this web site, you will be one very informed customer. What I've learned here has only been verified by my more informed friends. Over-size the heat pump going with a two stage unit,--two stage requires a variable speed furnance, even though my friend says that with todays gas prices and the rate we get from KCP&L we should of went all electric---he would still go fossil fuel back-up, it's a comfort thing for the -10 degrees we see from time to time. Lennox, Trane, or Carrier are all excellent brands. I could go on and on, but don't want to tie up this forum with my OPINIONS. Not sure if you can e-mail me direct though here, if I could get your e-mail address of phone number, we could talk outside of here. Or click on my profile, my e-mail address is in there.

[Edited by lyork on 10-23-2005 at 12:38 AM]

[wyounger]

<gasp>

Four degrees differential before it calls for aux heat?

I'd freeze to death... or keep the thermostat on about 74 :D

[dan sw fl]

Originally posted by wyounger
4'F differential before it calls for aux heat?

I'd freeze to death... or keep the thermostat on about 74 :D

'F not 'C.

62'F ought to be THE NORM
given today's Natural Ga$

[Black Adder]

I don't care if it is F or C, 4 degrees drop before the aux cuts in is an awful big differential. Why not an outdoor sensor to shut down the hpump and change over to fossil fuel?

[lyork]

4 degrees right now until outside stat gets installed and balance point set so that the furnace does not come on at all. Dual fuel set-up that we are basically locking out until the temp drops.

[Black Adder]

Does the heatpump cut out completly when the furnace comes on? It is definetly not recommended to run furnace and heatpump at the same time. That is the purpose of a fossil fuel kit or outdoor temp stat on Vision Pro tstat. The Hpump MUST be turned off before the furnace comes on. You can set any differential you want but I would turn the gas off to the furnace until this situation is rectified. Other wise you may find yourself shopping for a new heat pump.

[lyork]

Yes--thermostat is set for add-on heat, locks out compressor when calling for aux heat/second stage.