Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

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CULater
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Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by CULater »

Have a friend who had work done on her heat pump several months ago and in the summer her electric bills and KWh have jumped by 400% over previous year. After having two technicians look it was just discovered that the heat strips in the heat pump had been miswired and were on all the time. I understand that this will raise electricity costs, but could it fully account for a quadrupling of the cost during the summer months when the A/C is running? Haven't been able to determine if this could be the case, and seems to me that something else might be going on with the heat pump to account for such a large increase.
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neilpilot
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by neilpilot »

You don't leave enough information to do a quantitative analysis, but I wouldn't be surprised if the always-on emergency heat strips are the only culprit. Remember that in the situation you describe the heat strips will obviously increase KW draw directly, but the A/C will also need to work doubly hard to remove the energy input from the heat element as well as the normal ambient heat gain.

The issue should be repaired ASAP. If the repair cannot be done immediately, then it should be very easy to disconnect power to the heat elements temporarily.
adamthesmythe
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by adamthesmythe »

That's an amazingly stupid mistake.

Cooling the house will be like trying to fill a bucket with a hole in the bottom.
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Pajamas
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by Pajamas »

To add to what neilpilot said, the A/C would almost certainly not be sized correctly to handle that increased (double or triple or ???) load and that would affect the A/C efficiency so it probably would not be simply a matter of additional running time.

I would want whoever was responsible to reimburse me for the extra electricity, at least for the first bill and an additional week or so.
Carl53
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by Carl53 »

Pajamas wrote: Thu Jun 21, 2018 11:55 am To add to what neilpilot said, the A/C would almost certainly not be sized correctly to handle that increased (double or triple or ???) load and that would affect the A/C efficiency so it probably would not be simply a matter of additional running time.

I would want whoever was responsible to reimburse me for the extra electricity, at least for the first bill and an additional week or so.
It is likely that a just received bill being greatly increased over last year, while months prior would only be marginally higher due to cooler weather. I would suggest looking at kwhrs consumed in months since the work was done and the $ amounts of bills. Compare meter reading (and usage since last meter reading) at time the problem is corrected and request additional $ to cover bump up over last year for a comparative number of days. I would not offer to reduce the amount the repair outfit owes for hotter weather, as it was your friend that was inconvenienced.
ace1400
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by ace1400 »

It could definitely account for the increase in your bill, even without the additional load on the AC unit. Running the strip heat as my main heat supply was costing me about a $300/month increase in electricity, for a 3,000 sq ft house in a moderate climate.

This is not a hard problem though, and you don't have to guess. If you can find the specs for your unit, the strip heat capacity will be in kW. Most are on/off units, so device capacity in kW, times hours on, times electricity price per kW hour is what this mistake has cost you.
Carl53
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by Carl53 »

You might have an hourly meter on your heat pump, as I did on my old ground source unit. I still have a double 60A breaker in my box for the auxiliary heat. I believe it was intended to deliver 15Kw. If you had something similar and it ran for 50% of the time (365 hrs), and electricity cost 12 cents per kwhr, you would incur an extra charge of $657 in a single month.
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Pajamas
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by Pajamas »

Carl53 wrote: Thu Jun 21, 2018 12:57 pm
Pajamas wrote: Thu Jun 21, 2018 11:55 am To add to what neilpilot said, the A/C would almost certainly not be sized correctly to handle that increased (double or triple or ???) load and that would affect the A/C efficiency so it probably would not be simply a matter of additional running time.

I would want whoever was responsible to reimburse me for the extra electricity, at least for the first bill and an additional week or so.
It is likely that a just received bill being greatly increased over last year, while months prior would only be marginally higher due to cooler weather. I would suggest looking at kwhrs consumed in months since the work was done and the $ amounts of bills. Compare meter reading (and usage since last meter reading) at time the problem is corrected and request additional $ to cover bump up over last year for a comparative number of days. I would not offer to reduce the amount the repair outfit owes for hotter weather, as it was your friend that was inconvenienced.
Right, the first bill that would have made it clear to a reasonably prudent person that something is not right with the electricity usage.
TravelGeek
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by TravelGeek »

ace1400 wrote: Thu Jun 21, 2018 1:17 pm
This is not a hard problem though, and you don't have to guess. If you can find the specs for your unit, the strip heat capacity will be in kW. Most are on/off units, so device capacity in kW, times hours on, times electricity price per kW hour is what this mistake has cost you.
Plus whatever the AC consumed for unnecessary work.
Woodshark
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by Woodshark »

Yes, having the heat strips on all the time could definitely increase her electric bill wildly. A heat pump tranfers heat efficiently but the heat strips create heat so they use much, much more energy. They are there and should only come on when the heat pump cannot supply enough heat or has failed, but you still need heat to keep from freezing. That is why they are often referred to as emergency heat strips. We are on a heat pump system and had a simular problem when we tried to install a programable thermostat. After multiple attempts with several different programmable stats, we ended up going back to the original because of this problem.
diy60
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by diy60 »

I owned/lived in a heat pump house for many years. Without going thru calculations I would say, yes, running the emergency heat could quadruple the electrical cost. My system had 2 banks of heats strips: aux heat strips (60 amps), and emergency heat strips (60 amps), plus the AC/Heat pump condenser (30 amps). My electric bills skyrocketed 3 to 4X when both banks of heats strips activated.
Last edited by diy60 on Thu Jun 21, 2018 5:47 pm, edited 1 time in total.
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StevieG72
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by StevieG72 »

If the heat strips are running at ALL times even in the summer with the AC running, yes electric bill will go sky high as they are working against each other.

If the heat strips are just on all the time when unit calls for heat, then no it would not cause an increase in summer months. This would of course result in higher electric bills when the heat is in use.
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Dakotah
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by Dakotah »

Absolutely, it could. Assuming for a moment that she has 5kW in strips (which is on the small side): 5kW at 24hrs/day comes out to $438/month at $0.12/KwH. Although I don't care how oversized your HVAC is, the AC is not going to be able to overcome 5kW of heat strips to cool the house. And, frankly...I am kind of surprised that doing so didn't cause a fire.
criticalmass
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by criticalmass »

CULater wrote: Thu Jun 21, 2018 10:19 am Have a friend who had work done on her heat pump several months ago and in the summer her electric bills and KWh have jumped by 400% over previous year. After having two technicians look it was just discovered that the heat strips in the heat pump had been miswired and were on all the time. I understand that this will raise electricity costs, but could it fully account for a quadrupling of the cost during the summer months when the A/C is running? Haven't been able to determine if this could be the case, and seems to me that something else might be going on with the heat pump to account for such a large increase.
Electric resistance heat is very expensive to run compared to heat pump heat. Electric resistance heat running against cooling would be astronomically high.
MathWizard
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Re: Heat strips in heat pump miswired and on all the time - how much extra electricity cost?

Post by MathWizard »

I'm surprised it only quadupled the cost.
If the strips we're always on, the A/C would have needed to be on always to counter the heating.

I'd think that it could have quadrupled if the heat strips just came on when the A/C cycyled on. They are fighting each other after all.
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