Heat Pump questions

10 years ago

We moved into a house in the summer with two heat pumps. The house is only 1600 sf so we have been assured that the units are ridiculously more capacity than we need.

Starting in the cool fall, the downstairs unit seemed to do okay but the upstairs unit seemed to have weaker air flow and the air wasn't particularly warm. But because we have two units in such a small house, we were mostly able to keep upstairs warm. We had an hvac guy come to look - he spent 4 hours cleaning the upstairs unit, confirmed the outdoor unit was brand new and said the inside unit was fully operational, but could use to be replaced (apparently the blower was weak).

It got cold this week (teens outside). Yesterday outside was chilly. Today is COLD. The downstairs unit says it shifted to aux heat. Upstairs thermostat doesn't say that (but i know it has a working aux unit, per the repair guy who checked it out). Upstairs is COLD. Has been on constantly and can't get above 67' (set to 70'). Downstairs was doing okay yesterday at 70'. But i turned off the upstairs unit because (1) i was worried about constantly running and (2) it was blowing clod-ish air onto all of us while we slept. Upstairs dropped to 62' overnight, and downstairs has dropped down to 66' too. I'm having a hard time telling if these are normal cold weather heat pump issues, and/or determining how much of the problem is contributed by one unit malfunctioning or both. For instance, it got really cold outside last night but i also turned off the upstairs unit. But downstairs can't seem to get to where it should be.

Anyone have any insight??

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Comments (5)

tigerdunes
10 years ago
last modified: 10 years ago
Age of system, brand, size, model of both indoor air handler and outside condenser? Upstairs system is mismatched? Size of heat strip-KW? Size of living area to be conditioned? Your location? What is supply air temperature?

don't like the description you offered on the upstairs thermostat. It should show when aux/supplemental heat is operating.

if you don't know the answers, these are specs a homeowner should know. Find out.

i would say you need a different HP tech/company for a second opinion.

IMO
net420
10 years ago
Mine is similar and I was told it is normal. When outdoor temp is below 30, defrost kicks in and when this happens it blows cold air like AC in the summer. Instead of turning it off, I'd lower the thermostat a couple degrees, put another layer/sweater on and if it's sunny open the blinds/curtains on the south and west sides to get passive solar. You might also compare room temp with register temp when it runs for about 10 minutes. I was told if the register temp is about 15f higher than room temp then it's normal. I notice that when outdoor temp is over 35f then my register temp is about 18f higher than room temp. Heatpump is not very efficient when outdoor temp is below 30.
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H202
Original Author
10 years ago
Problem solved. I had a new havc repair guy come by yesterday. Looks like the last guy had set up the thermostat wrong and had it set up as a heat pump WITHOUT aux. So the thermostat was never telling it to switch to aux heat. He made the switch and it immediately started pumping out warm air, and at a level higher than we've been getting all along. Upstairs warmed up pretty fast.
dadoes
10 years ago
net420,

A heat pump should not "[blow] cold air like AC in the summer" when a defrost cycle occurs, unless it doesn't have an auxiliary heat source installed. The auxiliary/backup heat strips should activate during defrost to warm the cooled air before it exits the blower unit.
net420
10 years ago
Mine has no aux option and still uses the old refrigerant type.