T-stat set back on aux heat???

[Nayr]

I have been following many threads on hear regarding t-stat for heat pumps. I think the general consensus is that with a heat pump the t-stat should be left alone while in operation. That made me think of the emergency heat side of the equation. Where I live we are stuck in temps that won't rise above the lockout temp on my heat pump for a couple of days. I am on propane for emergency heat and was wondering if I would be wise to manually set back t-stat for this period while we are at work and sleeping.

Whats your thoughts?

[BaldLoonie]

A modest setback while on gas backup would save you.

[gary_g]

I am on propane for emergency heat and was wondering if I would be wise to manually set back t-stat for this period while we are at work and sleeping.

Yes. A setback using your propane furnace will save you some $$.

The reason why you read that it is better not to set back using a heat pump is because the heat pump generally does not have the extra capacity to recover several degrees from the setback without using auxiliary heat. Aux heat is generally more expensive than the heat pump.

What is your lock-out temp for the heat pump currently set at?

[Nayr]

lockout is currently set at 28 degrees

[clopay]

Isn't 28 degrees a little high for lockout? I run mine 15 degrees and above.

[sktn77a]

The reason why you read that it is better not to set back using a heat pump is because the heat pump generally does not have the extra capacity to recover several degrees from the setback without using auxiliary heat.

Specifically, in most cases, resistance electric heat strip aux heat, which is generally 2-3 times more expensive than other sources.

[gary_g]

lockout is currently set at 28 degrees

Not a bad lock out temp. You should experiment a little and see if you could drop that by a degree or so, and find out if the heat pump can still keep up. The more you run the pump, and the less propane, the cheaper your operating costs.

Take care.

[amd]

Isn't 28 degrees a little high for lockout? I run mine 15 degrees and above.

For dual fuel applications I wouldn't think so.

[beenthere]

For dual fuel applications I wouldn't think so.

Many people prefer the warmer air temp of the furnace over the heat pump at temps of 30 and less. So often it is a choice between comfort, or lowest operating cost as far as what temp to lock out the heat pump at. And many people pick a happy in between temp.

[teaysvalley]

I've experimented a little with mine the last year or so and currently use 18F as the HP lockout and 35 as the gas furnace lockout. I use a 20 min runtime for the HP before the aux can kick in. I get warm air at 18F with the HP. I didn't use any gas in Nov and my Dec gas bill was only 46 despite having the third coldest Dec on record.

I use 4 temp schedules, 6AM - 9:30 AM - 73, 9:30 - 4PM - 69, 4PM - 10PM 72, 10PM - 6AM -68. I use the 90 minute ramp up feature which I think lessens the load on the HP during recovery. We always feel comfortable and no drafts. I really like the low fan speed with this Carrier Hybrid system.

[beenthere]

Many high end heat pumps have a feature to increase the discharge air temp of the heat pump. Most standard heat pumps don't have this feature. So they could have an air temp only 12 degrees warmer on an 18 degree outside temp day.

Also, standard heat pumps can't be over sized for the cooling load as much as higher end units can be, since they don't have the indoor blower control to help keep humidity in check.