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insane bill with new heat pump system.. help please! setbacks, et

Posted by shabruo (My Page) on
Thu, Dec 29, 11 at 15:16

Hello,

We had a heat pump system installed in our home last Jan. The weather was likely similar that month to this last December, but we did have a pretty good cold spell in the Pac. NW for a couple of weeks, with highs in the low 40's, and lows in the 20's for about 2 weeks.

Our bill that we just received was an increase of $200 from last month! YIKES. We do have a large home - aprx. 3400 sq ft, but the bill never looked anything like this last year during the cold months when we first had the system installed (before this we used pellet stoves and electric heat - new system is all new ducting, heat pump, etc). Our bill for electric was just outrageous, and considering our history with it, and the conservative settings we use, we're confused!

Currently, we have it set for 67F during home hrs (7am-8:30am), then it goes to 63F until 3:30pm, as we arrive home from work around 4. Back to 67 during that time until 10pm bedtime when it drops back to 63F. We have it set to lock out emergency heat unless outdoor drops to 32F or below (we have an outdoor sensor). We have a 5ton HP Goodman unit.

I'm reading conflicting things about setbacks and heat pumps, and am really confused. Last year, we did a similar setting, and the weather was pretty much the same, so what might be our problem?? The largest bill we encountered last year was at least $150 LESS than this most recent bill we've received We can't handle $400 electric bills all winter long! =(

Thanks in advance for any tips or insight you can offer!


Follow-Up Postings:

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RE: insane bill with new heat pump system.. help please! setbacks

Not enough information to pinpoint problem.

Just guessing, I would say this is an install problem relating to heat strips and setback. Generally I do not like setbacks more than 3 degrees. Perhaps your lockout is not functioning as you think it is.

Perhaps bad refrigerant charge. Any idea of supply temps you are getting without auxiliary and at various outdoor temp? You might take some readings and note time of day, location in home, and outdoor temperature.

Above are possibilities that should be looked at and eliminated.

I love Goodman stories.

Sorry for your trouble.

IMO


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Any other possibility

I will assume you have eliminated the possibility of another electrical appliance in home that could be the culprit?

Just a thought.

IMO


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RE: insane bill with new heat pump system.. help please! setbacks

You're probably hitting the electric strips more often for some reason. Try leaving the temp constant and see if that helps.


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RE: insane bill with new heat pump system.. help please! setbacks

Thanks for the responses.

I've actually not noted the emergency heat coming on at all. Our lock out was set so low, that we were even having some issues with the temp hitting the target b/c the aux heat was not coming on - and I had to manually switch it to emergency heat, but I switched it back to automatic after the house hit target temp, not more than 30 min. later. Only did that once.

What could a bad refrigerant charge do? Could you explain a little more about this to me?

Other electrical appliances are ruled out. This is our only change in major electrical consumption and all our other appliances that draw any sort of traceable electricity are quite new/energy star. Our hot tub has been turned off since summer - know it's not that!

I will change our tstat to stay constant at 66 and see how that goes - but that's almost too warm for us at night now.

Also Tigerdunes - what am I looking at for "supply temps" Sorry - not too familiar with the lingo! I can take various readings in the house at different times of day and compare that to outdoors temp - what would this information result in telling me? How do we find out about a bad refrigerant charge?

In all, we've actually been quite happy with the system, but NEVER had a bill like this last winter - all winter long, with very similar settings. Just too strange.

Thanks for all the input - greatly appreciated. By both myself, and my checking account. =)


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RE: insane bill with new heat pump system.. help please! setbacks

Our bill was higher this year too, but it had to do with only a little bit more usage, and much more, the expiration of a credit. Are you checking to make sure you are actually using more kW than expected or what seems reasonable? We have PSE, and they graph our usage with information such as:

#days in billing cycle v last
#kW used/day v last
ave temperature per day v last

So, it is easier tell, more than just the absolute cost of your electric bill, whether you are really using more electricity or not.


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RE: insane bill with new heat pump system.. help please! setbacks

Hi Kirkhall,

Yes, we also get a breakdown on our bill. Last month, we had 52/kwh per day usage, and this month, 109/kwh per day. More than double! Our settings haven't changed on the t-stat, and although our month was colder this month, it wasn't THAT much colder. More than double usage in one month just doesn't seem right to us. And, it's more than double the usage in comparison to last year.

Sigh... just feeling like something is not quite right, here.

Thanks for the input.


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RE: insane bill with new heat pump system.. help please! setbacks

If the heat pump was installed in January then I assume it is still under warranty. Have it checked out by the HVAC contractor.


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RE: insane bill with new heat pump system.. help please! setbacks

Shabruo

Without being too technical, a HP system is refrigerant based and performs by transferring heat. In AC cooling, heat is transferred through the evap coil to the outside condenser. The same process is reversed for heating moving warm air inside through the evap coil.

A HP system must be charged correctly by a qualified tech within certain
parameters. If the charge is not correct, efficiency and performance will be diminished costing you both in comfort and operating cost.

Supply temps for heating drop depending on outside temperature. This is normal. For outside temps above 40 degrees, you would expect supply temps from your register to be 90 degree plus. Something less could indicate a problem with your system.

I agree that installing company should come back out and recheck your system. Refer back to my previous post.

Let us know what they find. For an electric bill nearly double certainly raises a concern.

IMO


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RE: insane bill with new heat pump system.. help please! setbacks

"...lows in the 20's for about 2 weeks. "

You likely hit the backup heat strips for hours per day for two weeks.

How do the degree days compare to the previous year?

hat is how you compare heating loads.


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RE: insane bill with new heat pump system.. help please! setbacks

If your heat pump is set like my geothermal any temperature change greater than a degree activates the heat strips. Our HVAC installer recommended not doing changes at all.


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RE: insane bill with new heat pump system.. help please! setbacks

Yes sounds like electric heat strips are powered most of the time. How do you know they weren't on during high demand?


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RE: insane bill with new heat pump system.. help please! setbacks

Our t-stat shows when back-up or emergency heat is activated, and except for the time that I manually called for the emergency heat, to get to the target temp (which only took about 20 min, it was off by 2 degrees), it was never showing as on.

It is set to lock out the heat strips unless the outdoor temp is below 30. Our lows in the 20's were only for late, late night temps and early mornings. So, even if during those early am hrs the heat strips were coming on (and heat at that time is set to 63 in our house, so it's not working hard to get there), I can't imagine that for less than 8 hrs. of time, for maybe 10 days - and that's probably stretching, that we would see that big of an increase. I haven't sat and calculated it out, but that seems unlikely to me. Maybe if we were running solely off of the heat strips for the whole month, all day long, I could imagine this happening, but that's definitely not the case. 2500 KwHrs is a lot of energy use!

I'm calling our utility energy management division today and am going to chat with them about it, as well as the installing HVAC co. Hopefully someone can get me an answer. Can't handle these bills!


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RE: insane bill with new heat pump system.. help please! setbacks

It sounds like your setbacks are too far apart and it's using aux heat to recover. I had ours at 62 and 65 and programmed for a less aggressive recovery and still the aux heat came on during recovery. I was told by a lot on here to avoid setbacks greater than 2 degrees with heat pumps.


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RE: insane bill with new heat pump system.. help please! setbacks

shabruro,

You say it is impossible for the increase in electrical usage to be other loads, such as lights and appliances.

That leaves the heat pump and strip heaters. Numerous people here have told you it has to be the Aux strip heaters, however you say that is impossible.

You also suggested say, I believe, that the heat pump is functioning to heat your home.

You said that your increase in usage over the previous month was about 57 Kwh per day.

That would equate to about 3-4 hours daily of 15 Kw heat strip operation. (Is 15 Kw typical for strip heaters?)


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RE: insane bill with new heat pump system.. help please! setbacks

FWIW, our Vision Pro (dual fuel system) doesn't show emergency heat unless you tell it you want it. So, it's likely that your stat is running the strips and not indicating. If you aren't totally dependent on your installer, check your stat settings against the manufacturer's guide to see if there's a way to make the use of the strips less aggressive. The point about checking your air temperature at registers is good too. That'll give you an idea whether your charge is too low.

The only other thing that hasn't been mentioned is the sizing of the HP. If the sizing wasn't done well relative to what you had previously, I guess there's a chance that the HP output is too small and the system has to rely on the strips to keep up. That's more complicated to address.


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RE: insane bill with new heat pump system.. help please! setbacks

Thanks for input -

The installing company is coming to check things out on Friday morning. I looked under the menu of options on our t-stat last night, (we have a Honeywell Prestige 2.0® Comfort System) and there is a menu for looking at what stage of heating is running. It shows 2 stages, and then aux. heat after that. This is a different screen than the home screen, but I I'm still pretty sure that emergency heat when called would show there, but I have to confirm with the installing co. when they come out.

We do have 15kw heat strips in the system. It is a 5 ton unit. We did have a load calc done prior to having it installed (per the utility boards requirements for rebates).

Our heat coming out of the registers does seem cool in many spots of the house - so I'm definitely going to ask to have that checked. I need to get an independent thermostat to try and read it myself as well, but it feels cool when I hold my hand over it much of the time, hardly warm. I thought this was due to the fact the heat pumps don't put out heat the way that gas does, but what I'm reading on the forums here has me thinking that it should at least feel warm. Also, I'm thinking I'll ask to have the charge of the refrigerant line checked, and the compressor as well, as these seem to be things that I'm reading about that could cause problems. Any other suggestions for questions to ask?

Any suggestions if this does come to an aux. heat strip issue of what we can do? With the t-stat set at only a range of 63-67 for the day, I just still can't understand why we would be hitting aux. heat that much and doubling our bill. Our "cold spell" where we dipped in the high 20's was such a short amount of time, I'd hate to imagine what would happen with a really prolonged one!

And apologies - my last post mistakenly said 2500kwh of usage, when in fact is was 3500 for last month. My stomach hurts just typing that.


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RE: insane bill with new heat pump system.. help please! setbacks

I hadn't looked at the info for that thermostat until just now. Wow. That really is the next generation (web connectable, controls every equipment permutation, wireless sensors). Fair warning that I know enough to be dangerous, so take that into account when reading the rest of this.

The link below shows the install manual. Pages 19-20 explain some of the backup heat options/settings (although not in as much detail regarding settings as the manuals for the Vision Pro series). I'd let the installer make any changes, but this may help you get a little better informed about the options- or it may just confuse things worse.

The adaptive intelligent recovery (set 'on'), not having too big a setback due to the HP system, the backup heat differential setting, and the backup heat upstage timer setting look to be the key settings to minimize how much your backup heat gets used.

As for the register air temperature, the important thing is the temperature differential between the room and the air coming out. For example, it was 32F outside at my house last night, my house was holding at 68F, and the air coming out of a register at the end of a branch of my HVAC was 81F. For my system, a 13F differential is OK (not great), but it's also right above the outdoor temperature where my heat pump is locked out and the gas furnace comes on. As the outdoor temperature rises into the upper 30's, the register air temperature rises to 88F or higher.

You want to know what this temperature differential is, with just the HP running (no strips) to tell whether the HP is doing its job. Low temperature differential means the charge is off or something else is going on.

I have a BBQ/oven temperature probe that's stuck in the register in my laundry room (when I'm not using it for BBQ). After my system lost most of its refrigerant 18 mo.s ago, I started watching to get an idea if it was happening again. It looks like you could add sensor(s) to your super-snazzy Honeywell and it could measure this and warn you all by itself.

Here is a link that might be useful: Honeywell Prestige stat install manual


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RE: insane bill with new heat pump system.. help please! setbacks

I live in Olympia and saw a total increase of 30 KWH over last year's billing. That's a $3.20 increase and it was 1.5 degrees colder on average.

I have my setbacks at WAKE: 69, LEAVE: 68, RETURN: 70, SLEEP: 67. I used 2442 KWH of electricity and 10.85 therms of gas. I have 2,981 square feet, nine foot ceilings downstairs and a 1.5 story home.

Those two weeks of the 20s were basically at night and early morning before 8:30 a.m. I think the pros are right about your charge being incorrect and/or the heat strips e coming on. Setbacks need to be no more than three degrees. I found two degrees when it gets in the 20s to be better. I change mine when we get that type of weather.

My usage also included Christmas lights, mostly LEDs and the wife being home two weeks for holiday baking(electric dbl. ovens) and vacation.


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RE: insane bill with new heat pump system.. help please! setbacks

Brickeye, the heating degree days would have been higher. In Olympia it was 865 and the previous year was 758. I don't know for certainty where the OP is, but if in Seattle or the Puget Sound region those numbers will be pretty close.


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RE: insane bill with new heat pump system.. help please! setbacks

Just 2 cents here. I live in the southeast and have used larger setbacks with good success with a heatpump with electric strips. The trick is to manually work the stat upon bumping the temp up so as to call just enough heat that the strips do not come on. My current house that means bumping 1 degree, then catching another bump during the cycle, but late enough that the stat does not see a full 1 degree bump. This will work with 40 degree temps outside and a swing from 66 to 68 inside. Its not as easy as it sounds though. Sometimes I mis the mark and activate the strip, then I have to bump back down 1 degree to maintain heating and the strip will turn back off. Doing it this way saves me around 50 to 80 bucks per month. This is in part due to me setting back at night 7 hrs and during the day 8 hrs. The trouble hits when it gets colder than 66 in our current (large) house and its 40 to 50 outside. The furniture, slab floor and counter tops are all cold so they help sink the heat. There is a sweat spot for setbacks and lifestyle, outside temp, humidity, size and furnishings make a difference. Also, the time you are willing to spend tweaking the heat. For my current situation, I need a better system, I just have not looked into it yet.

From what I found, if I do not work the setback properly, I spend equal or perhaps more in cost due to the strips than I would have used if I set the system at one temp and left it. The temp would have to be cool though like 67 or 68. If I were to set at 73 to 74 Id be broke.

Now here is another thing. I also include wood heat. I have an epa rated zero clearance built in fireplace/stove. 50000 btu at leas on a full load. By using that as a suppliment, I cut heating costs in half. Wood to me is free, takes time though but I enjoy that work. This was a new construction house and I was going to have a fireplace anyway, so I spent more on a stove. It will take me 4 years of savings that it provides to pay for it.

Anyway, just my 2 cents.


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RE: insane bill with new heat pump system.. help please! setbacks

have you considered an increase in taxes or $/Kwh?


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