Heat Pumps

[trader4]

Bob, I think one big problem, and perhaps the only problem, is that the backup is electrical resistance heat. You're electricty cost, at

14.5c KWH is substantially higher than average. Mine here in NJ is a little higher than that.

Here's a link to two calculators from a previous thread. The first one was one I found, the second one Bubba provided. Using them, you can input the cost of electricity, cost of gas, heat pump efficiency, furnace efficiency and find the temperature point below which it costs less to generate heat with gas. Whether a heat pump is cost effective overall is going to depend on how much heat you generate above that temp, versus how much you generate below it. And keep in mind that you could be generating a lot more heat below that temp, depending on how cold it gets. For example, it would probably take a couple days of outside temps in the 40s to equal one day's worth of heat required in the 20s.

I put 15c KWH and $1.50/therm gas into the above calculator and it gives a transition point of 32F. The $1.50 is my cost here in NJ, don't know yours.

On the above calculator, scroll to the bottom and go through the tabs to get to dual fuel. Using the same 15cents and $1.50 on this calculator gives 22F. Also, the heat pump efficiencies for either of these calculators is for a efficient, modern unit. IF you have an old unit, obviously it could be different.

So, with a modern unit, and assuming your gas is $1.50/therm, a heat pump should be efficient compared to gas down to somewhere between 22 and 32F. I think the thing that is killing you is that the backup is electric resistance heat. With your high electricity cost, that doesn't have to come on all that much to cost so much that you woulld in fact be better of with just a gas furnace. Also, this calculator is figuring out when it's more cost effective to go to the alternate fuel, not when you HAVE to go. Meaning, below some temp, the heat pump can no longer supply all the heat that is required. And it sounds like for your system, that point is close to 32F than 22F.

I'm curious. With such huge bills, why haven't you just put in a gas furnace? Or a dual fuel system, where you'd switch to gas below the transition temp? With $700/mth winter bills, the payback would be fast.

[Ralph Mowery]

I think there must not be much insulation in the house to run the bills up that much.

I bought a house and it seems to be well insulated. The house was built in

1985 and I bought it about 4 years ago. Don't recall the electricity cost for the old unit, but it went out in the second year. Put in a new Train unit. Not sure of the heat but the air is a 14 sear rating. It is 2.5 tons and keeps the house at 70 deg down to 20 deg. It has been down to 15 deg and the inside temp is still at the 70 deg setpoint. We only have a few days of the year it gets below 20 deg in the middle of North Carolina. The house is around 1700 sqft not counting an unfinished basement . Some of the heat is going to the basement but the door is closed going to the house. I don't try to heat that . My bills for all the electricity is less than $ 170 a month.

[Steve Barker]

would that be a burlington northern train, or a union pacific train?

s

[Ralph Mowery]

Southern train for the south. Not sure what it is called now with all the mergers and buyouts. Not Trane...

[Bubba]

BobR, You need to understand. If you have a heat pump with electric heat back up, your heat pump will continue to produce more heat for the dollar than straight electric heat. You will find the exact point by looking at a performance chart of your unit. Yes, as it gets colder out, it will seem like the damn thing runs forever and the air coming out is cold but if properly installed it WILL provide heat cheaper than your resistance electric heat until the COP's get to a 1:1 ratio. Now if your heat pump is teamed up with natural gas, propane or oil, then you will have to use one of the calculators to get an idea at what point you want to shut the heat pump off using the economic balance point and thermal balance point calculations. If you had been following along these past weeks you would have caught on to a little bit of this over the rhetoric being exchanged. Bubba

[Lp1331 1p1331]

Bob, I am in San Antonio, and granted Dallas does get somewhat colder than here, but not that drastically so. Around here, all electric houses with heat pumps started being fairly common about 25 years ago, and now probably at least half of the new houses are that way. As a rule, on those houses, if the unit cools the house satisfactorily, it will heat it fine with very minimal use of the strip heat, and at very worst, winter bills about the same as summer. Until a few years ago Trane pretty much had the HP market cornered here-- there are still some of the original Trane and even GE HP's out there cranking away. I have two old Tranes that are well over 20 y/o in my house. They were old take-outs that I installed here in the fall of 2000, and thus far have never been unable to keep it at 69 deg with NO backup heat. Here is a simple rule of thumb--I know people hate ROT's, but this was given to us at a York seminar about 12 years ago, and applied to basic

10/12 seer R22 units, so newer ones should do even better-- at 30 degress outside, you should have about 20 degree rise across the indoor coil, and for every 3 degrees the outside changes from that -either way-- it will make 1 degree change in the indoor TD. Obviously this is with the HP only, no aux, and is only a very rough approximation, but you should at least be in the ballpark. After all the above, I must say that I have a friend who has a house that is probably 70-80 y/o and AFAIK, about the same SF as yours. He always said the house was very easy to cool in summer and damn near impossible to heat-- here in San Antonio! He was able to cool it easily with several window units that probably didn't even total up to 4 tons, He had propane central heat, and said during a cold spell he could use over 100 gallons a WEEK. Do the math on that--$$$$$$$/month. Is your house older, with high ceiings etc.? If your house is like this one, your options are fairly limited. With NG not available, about your only options are propane and oil. Oil heat is very uncommon here-- we don't work on any, but I do know of a very few houses with oil heat. I would imagine Dallas would be similar. Propane is common, but probably not all that much cheaper than what you have now. I put my HP's in to get away from propane, and even my old dinosauers cost less to operate than I was spending on propane. Larry

[BobR]

nstalling a

se warm in

at a time,

A couple of nights in December and again in January the unit did not shut down throughout most of the day and not at all during the night. The air coming out of the vents was COLD and it was not able to maintain anything above 60 degrees. We finally used the oven to suplement the temperature along with space heaters. The damn thing is worthless below 30 degrees. Now above 35-40 degrees it puts out plenty of heat.

Sorry nothing but damn electric in this neighborhood. I talked with my neighbors and they have all had similar experiences even the one next door who just had a brand new unit installed this summer.

I don't know anything about the rhetoric you are talking about just the personal experience of dealing wiht a heat pump that I would gladly dump in the nearest recycling center.

[BobR]

You are right about it being the main problem.

Simple answer is that gas is not available and city won't allow use of LPG or propane. I am STUCK with only one option and that is all electric. What makes it somewhat funny in a sick sort of way is that we are sitting on one of the biggest gas fields in the country.

[BobR]

I measured the depth of the insulation in the attic and it was 15 inches deep which should be enough but it is a cellous insulation instead of fiberglass and appears to be packed down. I am not sure if it is still doing any good and am considering adding blown in fiberglass this spring. I would have done it earlier except that this stinking house has turned into a endless damn money pit and my finances do have limits.

I bought this house about 4 years ago as well and I think it was built about the same time as yours. One thing that I am certain about is that it probably wasn't built as well as yours. This is the first used home I have ever bought and it is a total piece of crap. I can't believe how poorly and cheaply everything is constructed and it is giving me constant problems. The A/C and heating is only part of the story.

Heck, I would settle for a $170 month bill even in those months when heating and cooling is at a minimum.

[trader4]

Does Hank Hill know about this? Seriously, I don't know the cost of propane, but if it would be substantially cheaper, I'd get the neighbors together and go after the municipality. Propane is widely used in most of the country without any huge safety problems.

[Chris Hill]

If the unit is as old as the house, that could explain the bills. Also, if ducts are run in the attic, they may not have been sealed very well.

[stan]

These messages about the auxiliary heat kicking in at certain temperatures (above freezing!) seem to confirm what is being discussed here. With winter temperatures up and own from just above freezing to sometimes as low 12 degrees F, or even lower overnight, the discussion is that heat pumps that get their heat from an outside air coil are not adequate. Better are systems that pump the heat out of ground based coils or in a few cases from some source of water. Although if the water source is a well a lot of water is required. We first heard of this during a rather cold winter some 12-15 years ago, in brand new house, when heat pumps were relatively new. Here we do not have natural gas and AFIK heat pumps systems using expensive propane have not even been considered; so auxiliary heating is electrcity. In summary; with an air coil heat pump, during cold weather one is heating the home primarily with electrcity. During those months the savings are much lower. Anyway just a comment.

[BobR]

No, the entire unit was replaced 5 years ago including all of the ducting. I have checked the ducts and they are in great shape with no leaks that I could find. Last night got down to about 30 degrees and once again the only thing coming out of the vents was cold air. I am going to call another A/C company to come and check it out yet again. I am starting to think the best thing to do is simply burn money in the fireplace.

[Ralph Mowery]

If it was only 30 deg outside and you are getting cold air then something is wrong. Was this by feel or actual measurment ? Heat pump air sometimes feel cold as the air may only be 80 to 90 deg comming out of the vents. They will sometimes go into the defrost mode and put out cold air for a short time. It is time to call another company and have it checked out.

[trader4]

I'd also look into geothermal. It still is a heat pump, but with ground water near 50F, it will be efficient in all outside temps. While expensive upfront, with energy tax breaks and your existing $700 a month bills, it could pay for itself in a reasonable amount of time.

An energy audit, which sometimes you can get for free from the utility company or a govt agency, would be a good idea. You might find some missing insulation or similar that could be fixed very cost effectively.

[The Daring Dufas]

You should check into a GHSP "Ground Source Heat Pump". I haven't priced them yet but when I grow up I want one.

TDD