Thermostat upgrade with heat pump setback experimenting

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  #1  
Old 11-29-18, 12:21 PM
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Thermostat upgrade with heat pump setback experimenting

Hi everyone,

I wrote in last winter as it was our first winter in a home with an air source heat pump and electrical aux backup. Located in Canada.

We operate under time of use electricity pricing where prices are lowest between 7pm and 7am.

When we moved in, the previous owners had a 3 degree Celsius setback overnight.
This resulted in a huge spike of hydro at approx 5am as it moved to reach the warmer set point for wake up. The cost savings (as the heat was basically off all night) were close to nil. Any savings were lost when the aux heat kicked in at 5am.

I did some research at the time and most recommendations where to NOT setback a heatpump. Made sense. So I changed it to remain constant temp all day. House is occupied all day. So far this winter, the costs do appear higher this way. Heatpump with occasional aux use over night seems to be more expensive. Costs between 15 and 70 cents an hour overnight. Say between 11pm and 5am. From what I remember, when I had the setback programmed, it was pennies an hour til the 5am mark when it would cost $1-$1.50 for the 5-7am warmup period.

I think I’m going to try a simple 1 degree setback overnight and see how it compares.
Tough to do perfect comparisons given fluctuating temps and solar heat. We can get cold days at -15 Celsius with a lot of sun and the heat doesn’t kick on all day. We’re southern facing with full windows across the length of the home.

Heatpump runs a lot during the day and night as far as I can tell. It’s been between -5 and +5 C most days. Realize we’re at the limit of exterior temperature where a heatpump can deliver adequate heat, but is having the outside compressor running all day normal? Or would having the aux kick in earlier be better from an compressor lifespan perspective? Are these units designed to run 16-18 hours a day?

I’ll let you know what I learn.
 
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Old 11-30-18, 02:10 PM
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Interesting thanks.

You don't mention comfort ; at my house we lower the temperature 5 F (~2.5C) mainly because it's more to our liking to sleep in cool air, and don't mind paying for any morning AUX hits.

The fact that the compressor is one of the few things that manufacturers are willing to give longish warranties on makes me think the compressors can run forever ...

I thought that you had relatively cheap power (hydro you say) - you don't mention the actual rates so we can't know whether to sympathize or envy
 
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Old 11-30-18, 02:22 PM
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We pay about 11 cents/kw all in, including delivery, taxes etc. Rates vary from 6.5 to 13.2 depending on what time of day. The delivery component of our bill makes up a decent portion. We use 65% of our power during the cheapest hours. 15% during the mid-range pricing and 20% during peak pricing.

I have no idea what the rest of the country or US pays for electricity. I do know my bill in Feb. was close to $600 for the month. Coming from a nome heated with natural gas where we paid about $120 a month equal billing.

Folks around here say that excluding heat, a normal hydro bill would be $150-$200 month. So paying up to$400 in heat alone during Feb is not all that bad. Although our lowest hydro bill in the last 12 months was only $133. This includes hot water heated with hydro.
 
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Old 11-30-18, 06:10 PM
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Use a thermostat or accessory control that locks out auxiliary heat based on outdoor temperature.
 
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Old 12-07-18, 09:14 AM
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Thermostat upgrade

We have a Carrier Infinity heat pump with electric aux. photo of stat is below. Unit is about 10 years old. Any value in upgrading to a more modern Carrier/other thermostat? Are newer stats about saving money or just convenience of wireless?
 
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Old 12-07-18, 08:44 PM
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Threads combined.

Rather than re-hash the whole set back issue with heat pumps....... it's already here.
 
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