Heat Pump - to lockout or not to lockout

[steve_mtl]

Been lurking here for over a decade, fascinating board.

So for my first question here:

Live it Montreal, winters go down to -25F for a few days. I have an 11 year old contractor grade 3.5T Ruud 11 SEER heat pump (performed flawlessly all these years except for leaking reset valve that was fixed this year) with resistance heat backup, and a Honeywell Prestige touch-color thermostat with outdoor stat (love that thing!). 3000SFT house.

I have set the stat aux lockout to 24F outdoor, and heat-pump heats house fine enough with no expensive resistance AUX down to that.

However the heat-pump lockout on the thermostat can only be set to 4F outdoor at the lowest, or never lockout beyond that. At 4F my heat pump can still produce a delta T of 12F. Wish Honeywell allowed a lower setting!!!

Have read conflicting info:
1) Dont bother running heat pump below freezing (I think this mainly pertains to fuel backup, not for expensive resistance backup).
2) Dont bother running heat pump below 0F, as it will only produce negligible heat and cold drafts.
3) Never turn off heat-pump, since COP is always greater than 1 (then there are theories of defrost cycle killing efficiency, and beating your heat pump to death running it indefinitely)

Original installer just said to switch it to emergency heat on the coldest days, if I want to do the equipment a favour.

What do you all say? Set it to lockout at 4F, or let her run forever?
(I dont mind "cold blow" too much, want to save electricity if I can, and don't want to have to get a new compressor any time soon!)

[wahoo]

I'd set lock out at 4 degrees as the COP will be close to 1 to 1 at that temperature. It's probably be close to 1.5 to 1.7 at 17 degrees so once you hit zero it'll not produce enough heat to justify leaving on. Now if the mid-day temps rise enought to justify, it'll come back on.

[BaldLoonie]

One thing would be nice to know is if that beast has demand defrost or a timer. With demand, at 4° when there is little moisture in the air, the thing probably won't defrost more than once or twice a day. But a timer will go in to cool mode for 5 to 10 minutes an hour or 90 minutes, whatever the timer is set to. That usually more than wastes any savings from keeping the pump on. My house, it goes off around 10 or so.

[steve_mtl]

Thanks for the responses so far, looks like it is leaning toward lockout at 4°.

I was under the impression it was a timer defrost since it is over 10yrs old builder grade.

But checking the specs online for my RUUD UPKA-043JAZ, I found:
COP= 3 at 47°F DB / 43°F WB DOE High Temp
COP= 2.2 at 17°F DB / 15°F WB DOE Low Temp

SEER=10, HSPF Region IV= 7.35, HSPF Region V= 6.65
"Demand Defrost Controls (featured on odd numbered models.)"

So I guess I have demand defrost after all! (I do hear the reverse swooshing a few times a day)

[beenthere]

Lock out at -10 would be good. but if 4 is the lowest, set it for that.

[SSB]

This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

You can find the rules for posting and qualifications here.

Additional infractions may result in loss of posting privileges.

[jpsmith1cm]

SSB


This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

You can find the rules for posting and qualifications here.

Additional infractions may result in loss of posting privileges.

[dan sw fl]

AND here I thought < 20'F was a fairly aggressive lockout plan.
. ______ .
I guess it all depends on amount of moisture in the locale (i.e. close proximity to lake that hasn't frozen over early in season)
However, at the same time, NOT Much moisture at those temps.

[motoguy128]

AND here I thought < 20'F was a fairly aggressive lockout plan.
. ______ .
I guess it all depends on amount of moisture in the locale (i.e. close proximity to lake that hasn't frozen over early in season)
However, at the same time, NOT Much moisture at those temps.

It's called C-O-L-D. Often associated with more than 2 or 3 seasons. I know it's a foreign concept down there. No need to explain hot and humid, we get plenty of that too.


Do you heat pumps even need a defrost mode or do you just do that manually once or twice a year like a deep freeze?

[beenthere]

It's called C-O-L-D. Often associated with more than 2 or 3 seasons. I know it's a foreign concept down there. No need to explain hot and humid, we get plenty of that too.


Do you heat pumps even need a defrost mode or do you just do that manually once or twice a year like a deep freeze?

ROFL.

[dan sw fl]

It's called C-O-L-D. Often associated with more than 2 or 3 seasons. I know it's a foreign concept down there. No need to explain hot and humid, we get plenty of that too.


Do you heat pumps even need a defrost mode or do you just do that manually once or twice a year like a deep freeze?

d'frost is what happens to one's breathe
I know cold = lack of Heat ... Billings MT 10'F

Billings Heating and Cooling
________ ___ ___ ___ Jan _Feb _Mar _Apr _ May _ Jun Jul Aug _Sep _Oct _Nov Dec Annual
Heating Degree Days 1308 1008 915 582 _316 _119 _12.0 42.0 242 498 897 1225 7164
Cooling Degree Days 0.0 __0.0 __0.0 __0.0 _6.0 113 244 219 65.0 _5.0 _0.0 _0.0 652

[dan sw fl]

It's called C-O-L-D. Often associated with more than 2 or 3 seasons. I know it's a foreign concept down there. No need to explain hot and humid, we get plenty of that too.


Do you heat pumps even need a defrost mode or do you just do that manually once or twice a year like a deep freeze?

When I'm in FL, I Don't Use Heat except a few times a decade. Need A/C now.

[mixer440]

This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary, or ask questions of the OP here. Please apply to the AOPC today, thank you.

You can find the rules for posting and qualifications here.

Further infractions may result in loss of posting privileges.