Heat Pump and power consumption

[goeduck]

Heat pump air handlers that have more than one breaker incorporated with them have more than one stage of resistance heat, you can turn off the stage or stages that don't include the power to run the fan and controls. However, if temp is above 40, and no one is turning the thermostat up, the resistance heat would only be running when the heat pump is defrosting, and that doesn't take long.

I did not think they defrosted above 40. My wife turns up the Tstat a number of degrees no matter what I ask, I can’t get her to turn off exhaust fans either .

 

[Old Red]

Anoterh benefit to turning off your resistive heat strips aux heat is that when your kids or wife bumps up the Tstat because they don't understand how stuff works and what they are doing to the meter outside, it will not affect much.

 

[goeduck]

Anoterh benefit to turning off your resistive heat strips aux heat is that when your kids or wife bumps up the Tstat because they don't understand how stuff works and what they are doing to the meter outside, it will not affect much.

That was my hope, but I did not want a blast of cold air coming out the registers when it goes into defrost or wifey will just turn the Tstat up even higher. So I just want to lock out above defrost cycle which is most of the time in my area if that is 40. The wood stove is always running but some times I miss feeding it and the temp drops and wifey goes straight to the Tstat.

 

[Old Red]

That was my hope, but I did not want a blast of cold air coming out the registers when it goes into defrost or wifey will just turn the Tstat up even higher. So I just want to lock out above defrost cycle which is most of the time in my area if that is 40. The wood stove is always running but some times I miss feeding it and the temp drops and wifey goes straight to the Tstat.

These girls man.....

 

[dragoneggs]

If it is a heat pump it should be your primary heat source in the winter with the outdoor unit regularly coming on.

Indeed, my heat pump was on when I got up this morning and braved the wind/rain to go check on it. My thermostat is set at 62degF at night and 68degF during the day. When I checked again with the temp showing about 2deg less than the setting, the furnace was on but no heat pump.

The other feature of this new Nest smart thermostat is that it senses when you are away and turns down/up your thermostat to your 'eco' setting based on the location of your cell phone. Seems to work. I don't know how efficient this is but I plan to monitor my usage over time and compare.

To a side note. Duke Energy sent me access to an online comparison of my energy usage versus average usage for my size of home in my area. My average consumption is over the average and they have suggestions on how to correct it. I know how to correct it. New windows and tighten up a 65 year old brick house built to 1953 standards.

Our power company, PSE (Puget Sound Electricity) website provides monthly usage and comparison to neighbors as well as daily usage charts.

 

[ultrarunner]

The upstairs has an older electric furnace... it would trip the breaker for one of the families I rented the place to.

Dad would turn the thermostat to 55 and when his teenage daughters came home from school it would go to 80... because they were cold... about 70 minutes the breaker would trip.

Never a problem prior but no one ever locked the heat on at 80 either.

My solution without saying anything was to physically disconnect one of the heat strips... not another issue... simply saying not to set at 80 would not have worked. This family has some really steep winter heat bills compared to every other occupant.

On separate note... my brother rented a condo in Hawaii... the thermostat was remote controlled and locked out... the cooling was set at 85 and they were miserable and called me...

Simple I said... take the pole lamp and shine it several inches away from the thermostat... worked like a charm. When they came home the place was 75 and stayed that way...

Sometimes the work arounds are very simple ;-)

 

[goeduck]

Heat pump air handlers that have more than one breaker incorporated with them have more than one stage of resistance heat, you can turn off the stage or stages that don't include the power to run the fan and controls. However, if temp is above 40, and no one is turning the thermostat up, the resistance heat would only be running when the heat pump is defrosting, and that doesn't take long.

Okay, I did some experimenting. My furnace has a 60A breaker and a 30A breaker. I assumed the 60A was blower, plus stage 1 heat and the 30A was stage 2 heat. I also have a 30A breaker marked for the Heat Pump, I assumed for the outdoor unit. I ran the Tstat up 5 degrees to where aux heat was called for as indicated by an LED on the Tstat and using the power company meter as my gauge, the wheel completed a spin in 4.25 seconds. I turned off the 30A breaker for the furnace assumed to be a second stage of elec heat and the wheel completed a spin in 5.38 seconds. Improvement, but not a lot. I then went inside, cycled the Tstat down and back up 1 above room temp. At this point aux heat was not called for by the Tstat. The wheel on the meter then completed a spin in 17.78 seconds! Big improvement! I turned down the Tstat and checked the meter again. Barely turning, not worth timing.

Is there a wire at the Tstat that disables aux heat?

EDIT. I guessed W2 and appear to be correct. Heat pump operates when aux heat is called for and my meter is still spinning at 17.98 seconds. So I will see how this goes. Wifey saw me at the Tstat and I asssured her she could still change the set point and that I was just trying to save money. She is ill now so I want her to be comfortable, I just need to keep my elec hill under control.

 

[TractorGuy]

The sequencer stuck on my heat strips last night. I had the thermostat set on auto and noticed the house felt too warm. Turns out the heat strips were running and the unit had switched to AC mode to try and maintain temp. It was holding at 75 where I had the AC set but it had to be eating some amps. I turned off the heat strip breaker and let it run a few minutes to cool off then shut the whole system down and opened some doors. Weather warmed up to the point I had to turn the AC back on. Unit will work fine with the heat strip breaker off for now. The sequencer clicked open when I pulled the wires to test it and it may work okay but I ordered a new piece anyways. Last time the sequencer failed it burned up my heat strips also but I caught it in time to save them this time.

I wish I could find a thermostat that would allow one setting for heat and AC but they all have a 3 to 5 degree spread. If you put it on auto and set the heat to 70 the AC won't come on till it's 73-75.

 

[TractorGuy]

Okay, I did some experimenting. My furnace has a 60A breaker and a 30A breaker. I assumed the 60A was blower, plus stage 1 heat and the 30A was stage 2 heat. I also have a 30A breaker marked for the Heat Pump, I assumed for the outdoor unit. I ran the Tstat up 5 degrees to where aux heat was called for as indicated by an LED on the Tstat and using the power company meter as my gauge, the wheel completed a spin in 4.25 seconds. I turned off the 30A breaker for the furnace assumed to be a second stage of elec heat and the wheel completed a spin in 5.38 seconds. Improvement, but not a lot. I then went inside, cycled the Tstat down and back up 1 above room temp. At this point aux heat was not called for by the Tstat. The wheel on the meter then completed a spin in 17.78 seconds! Big improvement! I turned down the Tstat and checked the meter again. Barely turning, not worth timing.

Is there a wire at the Tstat that disables aux heat?

EDIT. I guessed W2 and appear to be correct. Heat pump operates when aux heat is called for and my meter is still spinning at 17.98 seconds. So I will see how this goes. Wifey saw me at the Tstat and I asssured her she could still change the set point and that I was just trying to save money. She is ill now so I want her to be comfortable, I just need to keep my elec hill under control.

View attachment 536784

I think you will find the 60 amp breaker IS the aux heat. Should be labeled on the panel but try turning that one off and see if the heat pump/AC still works.

The E terminal at the thermostat should be the emergency heat.

 

[RalphVa]

We just got an electric bill and the usage is the highest it's been in the 9 years we've been in this house. I need to figure out if something is malfunctioning or if this is a combination of the cold weather and my wife fiddling with the thermostat. Our heat pump is about 7 years old and replaced one that was about 25 years old. The heating degree days isn't very different from the same time last year, about 10% higher. This bill has us using 103kwh/day while the corresponding bill from a year ago was 70kwh/day, an increase of almost 50%. Dec 2017 bill is roughly the same as Dec 2016 bill, with 61kwh/day and 58kwh/day, so this appears to be a sudden change. I don't doubt these numbers as they are actual measurements and not estimates. I realize that defrost cycles and big gaps (>2F) in current indoor temp versus thermostat setting will both cause aux heat strips to come on. I think we're pretty good at avoiding big gaps between current and desired temp. Defrost cycles... not sure how to track or estimate this. When the outdoor temp drops, obviously the heat pump has to use more power to keep the house at the same temp. Would this be the same amount of power for a longer time or does the amount of current go up also (ignoring the aux heat and defrost cycles)?

I took a couple readings from the meter. For a 13 hour period overnight we used 82kwh (>6kw/h ave). Looking at how long it took the meter wheel to make a revolution, it was about 1kw/h when the heat pump was off (and everyone awake, lights, tv, coffee pot, etc on) and 3kw/h when it was running - implying heat pump was using ~2kw/h. If the heat pump uses the same power but runs longer, then something else is contributing >3kw/h on average that entire 13 hour period - but wasn't when I took the measurements.

Keith

Our last month's bill here in central Va is the highest since we've lived here in 17 years. This is with a 3 kw solar panel system that saves us about $50/month. We've 3 heat pump systems. Only one (the biggest) do we allow the heat coils to kick in because it will not keep our family room warm enough with some heat coil assist. We've the upstairs heat pump's heat coils locked out via the thermostat because it is on our generator and would overload it. The basement ductless units do not have a heat coil backup and are the most efficient system we have. All are fairly new.

Ralph