New heat pumps cool well but we need heat

12 years ago

It is time to replace our heat pump, even though it is only 30-years old and still works. It is a 4-ton Westinghouse Hi/Re/Li HP048D. We bought it from a Boeing engineer who recommended it for the unique valving that gave good efficiency at low temperature. He early on replaced a leaky outdoor coil and a bad valve and for the last 25 years all I have had to do was replace the motor capacitor, and the power contactor, which probably died because of the bad capacitor. But Westinghouse unique parts are long gone, and the $1,500 tax rebate will not be around much longer.

We live in a 2,400 square foot house near Seattle with tall trees to the south so we practically never use air conditioning (nor do we have much luck with tomatoes). During the coldest 4-5 months we use about 60 kWh per day in excess of our power usage the rest of the year. At $.10 per kWh it is painful, but not out of line for an old house that is impossible to seal well.

Given our need for heat, not cooling, I am not happy with what I see in modern heat pumps. Detailed performance data are painful to acquire, but what I have seen suggest they have been engineered for cooling, not heating performance.

Here are the published heating performance of our Westinghouse Hi/Re/Li HP048D versus a Trane XL16i (2nd stage) with a 4TEE air handler, both with 1,600 CFM 70 degree indoor air:

At 17 degrees outside:

Westinghouse: 4.40 KW in; 35,000 BTU out; COP = 2.33

Trane: 2.94 KW in; 27,600 BTU out; COP = 2.94

At 47 degrees outside:

Westinghouse: 5.80 KW in; 56,000 BTU out; COP = 2.83

Trane: 3.29 KW in; 43,000 BTU out; COP = 3.29

The newer unit is more efficient, but it will give us about 20% less heat at low temp. I interpret this to mean more time with the backup heat strips sucking up electricity. I haven not tried to analyze it, but suspect the net result will be a higher heating bill.

My first thought was to move up to a 5 ton unit, but our ducts are inaccessible and really do not seem to support more than about 1,600 CFM air flow, rather than the 2,000 CFM most 5 ton units expect. Switching the Westinghouse fan between slow and fast settings yielded hardly any change in measured air velocity. My understanding is that lower than spec airflow is likely to reduce compressor life.

I am not totally locked into the XL16i, but it seemed to have one of the better heat output numbers, plus good HSPF and COP. And during those hours when we can tolerate the 25-30% lower output of the 1st Stage, our long-suffering neighbors (their patio is very close to our heat pump) will appreciate the resulting lower noise level.

Are there better solutions than the 4-ton XL16i? Do any other brands or models give us better heat output given our airflow limitations? Manufacturer websites seem to be all fluff and provide appallingly little real data. And most heat pump salesmen seem to go blank when I try to explain what I am looking for.

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Comments (11)

neohioheatpump
12 years ago
look into York/Luxaire/Coleman. I have their highest efficiency single stage. 14.5 seer at the compressor alone. It has a COP of 2.58 and 17F and 3.78 at 47. It has demand defrost.

Basically you should get the highest eff. single stage unit. Make sure it has demand defrost too.

2-stage condensors are more for hot climates that have lots of humidity. They run mostly on the lower stage.

They make new heatpumps that have full cooling and heating load numbers. Again, stick with single stage especially since your climate is heating mostly.
tigerdunes
12 years ago
rick

the numbers on the Westinghouse are from your 30 yr old Westinghouse HP? if so, I find them very suspect.

Trane's XL16i has two problems. one is dehumidication and two is poor numbers on heating BTUs.

these are my minimum specs for a new HP system. both outside and inside units should be replaced to have a properly matched system.

15 SEER, 12.5+ EER, 9 HSPF
best matching VS air handler
full BTUs in both cooling and heating for your rated size
R-410a refrigerant(same as Puron)
scroll compressor preferred
electronic demand defrost preferred
thermostat with "dehumidify on demand" feature
staged backup heat strips
new and correctly sized refrigerant lineset

you want a thorough inspection of your ductwork system. size, overall condition, supply and return lines, insulation qualities, leak test, etc.

any hot/cold spot issues in your home should be addressed.

I would only use authorized dealers for the various brands that provide quotes. see mfg websites.

I would look at Trane/AmStd,Rheem,Carrier/Bryant.

IMO
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juliekcmo
12 years ago
Rick,

You are correct in that most systems are "sized" for cooling rather than heating.

I agree that a single stage mid-tier systems will be very sufficient for your needs.

You also do have some control over what outdoor air temperature you use to switch between heatpump and backup electric heat with a low ambient kit.

Ask your dealer about what their service director suggests for the ideal temperature to changover.
rick41
Original Author
12 years ago
tigerdunes - I have learned a lot from reading your postings on this forum and I appreciate your inputs. Your minimum specs list has already been very useful (though a lot of sales people really struggle to find answers about some of the items on that list), and IÃ¢ÂÂm leaning now toward the XL15i instead of the $660 more expensive XL16i. I still havenÃ¢ÂÂt completely ruled out Carrier and Rheem, but a neighbor has had a 4-ton Trane XL14i for over three years and I like the way it does not seem to have collected very many of the evergreen needles that are everywhere around here.

I am curious though just why the XL16i has so much trouble with dehumidification, and whether that is important to our well-shaded house just outside of Seattle. We havenÃ¢ÂÂt bothered to run our heat pump in cooling mode for at least the last decade, so I remain mostly concerned with heating performance and expect to use very little cooling.

Also, is the XL16i any less reliable that the XL15i, or is it just (as I understand from other forum postings) that it is more complex to hook up and hence more prone to improper installation?

I am also puzzled when I compare ARI heating performance of the XL15i and XL16i. At 47 degrees their ARI heat capacity and COP are identical, and at 17 degrees the 15i has only 1% more heat capacity. The 16i has the better 17 degree COP, 2.86 versus 2.82, but it falls down on HSPF to 8.50 versus 9.00 for the 15i. This seems to imply that the 16i spends more time in defrost mode, but I do not understand why.

Returning of your spec list, I assume Ã¢ÂÂstaged backup heat stripsÃ¢ÂÂ refers to the capability to selectively turn on part instead of all of the backup heat? Our old heat pump has this feature, but I have yet to find a sales person who can tell be whether modern systems can do this.

One issue is not really relevant until our new heat pump is being installed, but opinions about it are so amusingly diverse I cannot resist asking. Our power utility offers an extra rebate if we install a lockout control. What should it control?

We have a lockout set at 32 degrees on our old heat pump and I understood it prevents the backup heat from coming unless the outdoor temperatures is below 32 degrees. The Ã¢ÂÂenergy expertÃ¢ÂÂ I talked to at our power company agreed, but said the lockout should also turn off the heat pump compressor at 32 degrees to Ã¢ÂÂprevent a spike in our electric bill.Ã¢ÂÂ I recognize efficiency is down at that temperature, but unless there is a lot of icing up it still seems to make sense to run the compressor. Sale personnel were about evenly split whether the lockout should turn off the compressor. Is there any clear answer on this?
dadoes
12 years ago
A "control lockout" via the power company may be their load/demand management program, which usually grants a billing credit for participation. They can remotely shut off high-wattage equipment (typically HVAC and electric water heaters) for ~15 min intervals during periods of peak demand. That's not a good idea on heat pumps during the heating season (and/or dual-speed systems during the cooling season) as the system may have to run harder (higher wattage) to catch up again.

I imagine the power company rep's recommendation to turn off the compressor at
neohioheatpump
12 years ago
You don't want to lockout your heatpump ever. It still can heat your house alone below 32F. At extreme cold temps your heatpump will run non-stop with the backup electric strip heat coming on occaisionally. Depending on well your house is insulated you may be able to heat your house with the heatpump alone to below 20f.
tigerdunes
12 years ago
in general, I agree with the above post from neohio. however in an all electric HP system and air handler with electric backup and located in very cold winter climate, the HP condenser may want to be shut off. Extreme cold temps might dictate this. Homeowner should rely on dealer/manufacturer recommendation.

IMO
junkmailhold
12 years ago
rick41,

I live in the Seattle area as well, and just last year, I got a Bryant Heat Pump installed with variable speed gas furnace. It sounds like you don't have gas and use heat strips for backup heat, but the important thing is the variable speed blower (air handler in your case).

I find that in our climate, as long as you set a FIXED indoor temp, the heat pump should have no problem maintaining the temp down to even the mid 20s... which doesn't occur here very often. Of course, this depends on how well your house is insulated... but I have a 4000+ sq ft house and I got the 5 ton model. Our house is set at a fixed 72 degrees 24/7 all winter long and my gas furnace doesn't kick on even when we hit the 20s last November during our 3 weeks or so of deep freeze. The only time the furnace turns on is when the Heat Pump goes into a defrost cycle because I selected to engage backup heat when in defrost. And I can attest to the fact that the air coming OUT of the registers even in the 30s is plenty warm and not likewarm like the older heat pumps. I think this is due to the variable blower downspeeding, but it works nicely.

Hope this helps some...
countryboymo
12 years ago
The Utility doesn't want the heat pump and all available strips running at the same time. This will also cost too much to run.

I would set things up to lock the strips out from working at any temp above 32-35.

I would go ahead and lock the heat pump out at around 20 or so if the system has timed defrost and how much the strips are running. On some with demand defrost I might let run on down closer to 0 degrees.

The strips must be staged to get the most benefit.
juliekcmo
12 years ago
you also might go back to you COP numbers and really take a look at them.

If your utility or local weather almanac has info on average temps each month, you may find that your lower degree days are not as frequent as you suspect.

In any event, I still think your overall best performance and return on investment may likely be a good mid tier HP with a single stage AH or furnace.
bsherrin156
12 years ago
Hi all, I used a Gas based Water heater and a Electric one. however as in an all electric HP system and air handler with electric backup have similar issues and when located in very cold winter climate, the HP condenser usually shuts off. We know that extreme cold temperature might be the possible culprit. So what are the best ways to keep a house warm with Heaters that are low in maintenance and are easily available. I generally use a Solar one when im out on my ranch. but thats when the sun is out.

Here is a link that might be useful: solar hot water system

New heat pumps cool well but we need heat

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