Emergency Heat/heat pump pipes freezing (calculating, utilities, costs)

[HB2HSV]

Gald that you resurrected this thread. Good review/ prep for the next 2 weeks.

[cornutt]

After reading through this thread, there's one thing I want to point out about heat pumps. It's true that they produce less heat as the outdoor temperature goes down. However, it's also true that as they produce less heat, they also use less power. So it's still operating with pretty good efficiency -- it's just doing it slower. This is true until you get close to the temperature where it just isn't producing any heat at all. Take this into account when you're figuring at what temperature you are going to switch to your auxiliary heat. If that's electric resistance heat, it will cost more to run at nearly any temperature at which the heat pump is still producing heat. (Unless the temperature is very low and the humidity is high, because that will cause excessive defrost cycles. However, in Huntsville, usually when the temp is below 25, it's dry.) If it's gas, though, you'll have to do some math to figure out where is the best switchover temperature.

With a lot of thermostats (some electronic ones as well as all of the old mechanical ones), it's often self-defeating to set the thermostat back at night or when the house is unoccupied. These thermostats just automatically turn on the aux heat whenever the house temp is more than 2 or 3 degrees below the setpoint, so you wind up using the strip heat to heat the house back up, using more energy than you saved by setting the thermostat back. Look for a thermostat that specifically says it properly does setback recovery for a two-stage heat pump system.

[HB2HSV]

Originally Posted by cornutt

After reading through this thread, there's one thing I want to point out about heat pumps. It's true that they produce less heat as the outdoor temperature goes down. However, it's also true that as they produce less heat, they also use less power. So it's still operating with pretty good efficiency -- it's just doing it slower. This is true until you get close to the temperature where it just isn't producing any heat at all. Take this into account when you're figuring at what temperature you are going to switch to your auxiliary heat. If that's electric resistance heat, it will cost more to run at nearly any temperature at which the heat pump is still producing heat..

So according to the AccuWeather, tonight will be at 23 deg F but will feel like only 4 deg F because of wind. Does the heat pump still work at this temperature or it is just keep running but not producing any heat. At what point is it more efficient just to switch to pure electrical (aux) heating?

[Charles]

Originally Posted by HB2HSV

At what point is it more efficient just to switch to pure electrical (aux) heating?

Doesn't your thermostat control box switch automatically to AUX Heat at some point?

[HB2HSV]

Originally Posted by Charles

Doesn't your thermostat control box switch automatically to AUX Heat at some point?

Yes but I don't want to heat the WHOLE house with AUX heating. Maybe it'll be better if I just trun it down low, like 60 deg. F, and use the space heater in our bedroom instead.

[Charles]

Originally Posted by HB2HSV

Yes but I don't want to heat the WHOLE house with AUX heating. Maybe it'll be better if I just trun it down low, like 60 deg. F, and use the space heater in our bedroom instead.

That's a different situation. If you only need to keep one room warm then, sure, you might want to consider a one room heater.

But I ask again, doesn't your central heating system automatically switch to AUX heat at some point, meaning you don't need to manually switch it to AUX heat?

[tammie2]

Originally Posted by HB2HSV

Yes but I don't want to heat the WHOLE house with AUX heating. Maybe it'll be better if I just trun it down low, like 60 deg. F, and use the space heater in our bedroom instead.

This is what we have been doing. I have the heat set at 60, and I have a space heater in 2 bedrooms...the kids have their own rooms but end up together anyway almost every night....those darn Jack and Jill bathrooms

I have also been doing my "warm the house" activities in the evening, clean the oven, run the dishwasher, wash/dry clothes, etc. Last month I found myself pre-cooking a roast at 10PM

We went to this method after hearing the neighbors heat pump run NON STOP in November when it was cold.

Our utility billl was $230 for November(just over 2500 ft2), which I didn't think was bad for as cold as it was.

As for efficiency, if anyone is interested, Honeywell makes an energy saver space heater, 38% less energy, temp setting for automatic on/off, complete with tipover and overheat protection. They are $40 at Walmart, great investment!! They are small but pump out quite a bit of heat!! I use mine all the time as I am always cold and the rest of the family is always warm, you will find me in a corner bundled in sweats with the space heater on "MAX" The rest of the family is in shorts and tshirts when it is 60

[HB2HSV]

Originally Posted by Charles

But I ask again, doesn't your central heating system automatically switch to AUX heat at some point, meaning you don't need to manually switch it to AUX heat?

Originally Posted by HB2HSV

Yes

....

[cornutt]

Originally Posted by HB2HSV

So according to the AccuWeather, tonight will be at 23 deg F but will feel like only 4 deg F because of wind. Does the heat pump still work at this temperature or it is just keep running but not producing any heat. At what point is it more efficient just to switch to pure electrical (aux) heating?

Depends on the specific model. Some of the high-end models will produce heat down to 0F. Most of them give up between 10-20F. I'm not putting any of ours on aux heat tonight. Later this week I may have to keep an eye on them.

[cornutt]

Originally Posted by Charles

Doesn't your thermostat control box switch automatically to AUX Heat at some point?

It will, but it usually also leaves the heat pump running. If the temperature has dropped below the point where the heat pump can't produce heat any more, there's no point in that; it just wastes electricity.