Do Cold Climate Heat Pumps perform as advertised?
Tucker2
| Posted in Mechanicals on
I design/build homes in a Cold Climate area in WV with an average yearly temp. of about 45 degrees F.
I have read about a few new Cold Climate Heat Pumps that have come on the market in the last few years. Unlike conventional Heat Pumps these new models claim to perform effeciently below freezing temps. I believe a company called Nypl as well as a company called Hallowell have models available. I have read that the Hallowell Acadia model offers a Coeffecient of Performance of 2.55 at 17 degrees F.
Do these Cold Climate Heat Pumps truly perform as advertised?
Do you have any information on actuall field collected data?
Thank You, Tucker
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I'm in south central Pa, not far from you, and I think a heat pump can do that COP. Geothermal ground source heat pumps can be upwards of 4-5 COP. You may use more electricity at times at lower temps, but as long as you get a decent COP (and research it thoroughly!! not just a laboratory test under optimal conditions....!!!!) you should be on the positive end of energy curve.
Good luck.
Dave
Here's an alternative option that's maybe kind of out there, but might be worth considering if you live in a place that is sunny but cold:
Get a water-source heatpump, some solar thermal collectors, and an appropriately-sized tank. Put the heatpump's HX in the tank, and plumb up the solar collectors. Direct solar thermal hydronic heating almost never works out, because you need too much collector to get useful water temperatures directly. But if you are using the water as the source of heat to be concentrated by the heatpump, you don't need particularly high temperatures -- just keep the water well above freezing, and you're good.
Note: I HAVE NOT TRIED THIS so I cannot claim that it does work, merely that it seems like it should (given the right climate, as noted).
Brent,
Your suggestion has been tried; it's not cost-effective. For the suggested system to work, you would need a very large water tank. While water-source heat pumps have been successfully used with ponds, most people don't have room for a pond in their basement.
There are several problems:
1. As the (cloudy) winter progresses, the heat pump lowers the temperature of the water until the water in the tank begins to freeze.
2. The cost of the very expensive equipment -- especially the huge cost of a very large water tank, but also the cost of the active solar thermal equipment -- can't be justified by any possible energy savings.
The moral: build a small, very well insulated house with a low heating load. Then use simple, inexpensive equipment to satisfy the very small heating load.
another possibility, that has been tested and DOES work is a ground source heat pump with a solar panel that reheats the ground (even in the winter on a sunny day) the solar panels and the ground loop are hooked up to a differential thermostat that kicks in the solar panel whenever there is enough of a temp difference to make it worthwhile. This of course changes as the ground gets cooler. In earlier ground source heat pump installations problems with ground freezing and frost heaving occurred after a couple of years, with appropriate sizing of the solar panels and the ground loop this problems is avoided, and the additional heat keeps the heat pump in a more efficent state of operation.
I saw the precursor of the Hallowell heat pump working in an overheated warehouse on a July day. That heat pump was drawing 4 degree F air from a freezer room and producing very hot air. It was very impressive, and now, more than a decade later, I am sure that the systems work well.
The issue is not whether or not heat pump systems (whether air to air, or water to air in all varieties) work, but whether or not the building structure is has been properly insulated so that the heat pump system is not being required to perform as well as an obsolete conventional heating system. Just plugging a heat pump into an old house that is improperly insulated, has outdated and leaking windows and doors will only chew up an awful lot of electricity.
The primary drawback to heat pumps is that they require electricity to operate, and thus can be extremely expensive if the dwelling or building is incompletely designed for their use.
To answer no.2 I have a system just as you discribed. I have 2 sets of 25 evacuated solar tubes with a 500 gal. tank. I have a 1480 sq. ft. and have a Climate Master 1 and 1/2 ton geothermal split system. It does work cause I've been using it for 2 yrs. and it works. I live in Prescott Az 5300 ft elevation. The coldest the water temp. ever got was 40 F after a week of clouds. The most incoming temp. can be 90 F
**For more information on heat pumps, read these articles:**
Heating a Tight, Well-Insulated House
Heat Pumps: The Basics
PRO/CON: Are Heat Pumps Green?
**From the GreenSpec Product Guide:**
Heat Pumps
I am looking for craig heerlein in arizona that his answer is #6 on here
heat pumps are terrible, if it is below 38 degrees, your heat strips come on, and your electric meter spins so fast, you can see your money going down the drain!
Anonymous,
Your information is out of date. For example, Mitsubishi makes a heat pump (a ductless minisplit) that performs well without any electric resistance heat down to -13 degrees F.
Regarding heat strips coming on at 38 degrees...How fast does the money wheel spin if you are using propane? Pretty darn fast! I use a 5 ton heat pump to heat my 2300 sf house in Indiana. I used to switch to a high efficiency propane heater when the temp got below 38. However, one winter my propane bill for December was $600. I had a special board installed that allows my heat pump to use the gas furnace to defrost. Now my december electric bills are about up about $80 and my propane bill for the entire year is about $400 (it would have been $1800 with my old system.) So I save a ton of money. Not sure what it would be if I used electric resistance heat instead of propane as defrost/backup but I can't imagine it being more than propane.
We installed one of the first Nyle heat pumps in southeastern Idaho in 2004. Here is what we have learned. Yes, it does heat the house all by itself, with no problem, even when it is 35 degrees below zero. That is without any electric grid heat at all--as we cut the wire to the grid heater so it would never turn on and run up our power bill. However, it takes it little more than an ordinary HVAC person to install and service these things. It took us a while (and several people) to get it working right once it was installed. It worked flawlessly until the other day (january 2011) when a compressor went out. Nyle is out of business and Hollowell is now manufacturing a similar heat pump (same guy behind this operation). Now there are no parts available for our heat pump so we must replace it. To answer your question: it is real and it does work!
Anonymous,
Thanks for your story; very interesting.
Short version: The Nyle heat pump worked, although it was difficult to get it operating correctly; knowledgeable repair people are hard to find; it lasted only 7 years before conking out; and parts are now unavailable.
I have the cold climate Mitsubishi mini split that Martin mentioned and I have been extremely happy with it. The coldest outdoor temperature Ive experienced with it thus far was -4f and it was producing plenty of heat. The forecast calls for more negative temps this weekend so I'm looking forward to putting it through its paces!
NLEHTO - I'm very interested in the Mitsubishi. What size did you get? I see they have a 23K BTU now.
Do you have fears about reliability? It seems Mitsu has been in this business awhile. Keep us informed as it gets colder. What area are you located? Is anyone other than Mitsu and Hallowel making these? THanks.
MSZFE12NA
-10F is in the forecast for this weekend. I'll keep everyone updated on how it performs.
Ed: Their are numerous mini-split manufacturers......I believe the 2 most spoken about and I'm interested in for near future are fujitsu and mitsubishi. I've yet to hear bad about them when used in. say,a tighter built home, but surely can be used in most any app. Be careful when discussing around old school HVAC folks......they'll try to talk you into old tech!!! The 2 to 3 COP is what makes it comparable to other fuels, and in many cases is an easier/cheaper install than the others!
Steve
I live in Fargo, ND and have used the Mitsubishi mr slim for 2 years now with a 2300 sq foot house ... no problems in the winter when temperatures reach -30 below with a -65 below windchill... my electric bills run me about $80 in the summer and $250 in the winter.
Anonymous what model Mitsubishi are you using, and what are the specs on your house?
Heat pump effectiveness depends on the local utility costs, local climate, system controls and installation. I have owned several homes with heat pumps. The unit with my last home had poor defrost logic and was located in a very humid climate. That unit became a block of ice when it was cold outside. Because my backup heat was natural gas I did not use the heat pump in the winter with that unit.
You should be aware a heat pump will not put out air as warm as other heating systems. Mine runs about 95 F at the register outlet.
My current unit is a Ruud heat pump with demand defrost logic. This works much better than the older Trane unit that I had in the past. I was also able to adjust the demand logic to use even less electricity, but still defrost the unit well.
My current home is all electric and natural gas is not available in this market. I live in central Missouri. My home is 3300 sq. ft. and currently uses a maximum of 2200 KWh total a month in the winter.
I was able to improve the system performance as originally installed by 35% by managing the strip heating better by doing the following. I added an outside temperature sensor and replaced the White and Rodgers thermostat with a Honeywell IAQ thermostat. The Honeywell unit is much better at managing the strip heat and maintaining a more even temperature in the home. I have set my system to run no more than twice an hour to prevent the heat pump from cycling on and off and not operating as efficiently. I also determined my system will operate well to 5 F outside temperature. The compressor will not operate below -5 F because of a low pressure limit on the compressor. I have set the thermostat to allow the heat pump to run from 5 F and higher. The strip heat is locked out at 35 F and higher.
I am very happy with the performance of this unit in a climate that has about 5000 heating degree days a year and minimum outside temperatures around -10 F.
I would be very careful about purchasing units like the Hallowell Acadia which is now bankrupt. The benefits of these units was overstated in their marketing materials. I would not purchase anything that did not have extensive local support.
Jeff, fantastic post. But I bet you are one of a kind. You need to write a book with your custom set up knowledge. The problem to me with heat pumps is the missing advanced technical knowledge that you seem to have. I bet no residential heat pump techs near me could ever tweak a system as you describe. Never.
You should be helping OEMs regionally customize heat pump packages so they set up right out of the box, as well as you say your system is set up.
Email me if you would. Ajbuildernyatgmaildotcom
Thanks for bumping this up AJ. It would be nice if other HP users share their experience in here too.
Is anyone familiar firsthand with the cold/heat pumps made by Sanyo? I'm interested in putting one into a small, well-insulated home to be built later this year, and specifically as a source of A/C and back-up heat. Sanyo makes a 11,900 Btu cool/heat pump ductless split that's Energy Star certified. The specs claim it will work at a minimum outdoor air intake temp of 0°F. I'm curious to hear just how accurate this is and how effectively it works when it gets this cold outside. Any ideas?
Litawyn
LIT-
why not stick with the hyperheats from Mitsubishi? Is it because you are after the recessed option vs the wall mount? They do have the 36k BTU unit (most likely too large for your house by a long shot) that can be had in recessed, ducted and wall mount heads. It can also be "twinned" so you can use 2 heads with it.
Jesse:
I took a closer look at the Mitsubishi ceiling cassette units and have decided to make the switch. I'll be going with the 15,000 Btu/h Mr. Slim cool/heat pump, so I've got the A/C capabilities in the summer, as well as a back-up heat source in the colder months. My place has a heatload requirement of just under 11,000 Btu/h, so I should be good to go. Even at 17°F, this unit will still produce 12,000 Btu/h of heat. It'll also continue to function down to -4°F. I'll be using a small efficient pellet stove as my primary heat source. The Mitsubishi will simply kick in as needed.
By the way, the ceiling cassette works better for my place (even though it's just 16 SEER) because of the directions in which I need it to blow air. Also, I won't have a lot of wall space and like the idea of mounting the inside unit to the ceiling.
Thanks for the suggestion.
Litawyn
Jesse:
I just ran the numbers for the 12,000 Btu/h (23 SEER) wall-mount Mitsubishi unit and will likely switch over to this system instead. It appears it would only cost me around $70/year for the 1,000 hours of A/C I'd likely require. With the 15,000 Btu/h (16 SEER) ceiling cassette unit, the same amount of A/C would cost around $121/year. I guess I can put up with having to stare at a wall-mount unit, as long as I've got an efficient ERV running at 78 cfm continuously circulating the air. Also, the ceiling cassette model shuts off when the outdoor temp drops below -4°F, whereas the wall unit will function down to -13°F. This may not seem like much of a difference, but here in Maine, this is a definite bonus. An even bigger one is the fact that the wall-mount unit is only 60% the cost of the ceiling model.
One odd thing I noticed: The specs for the 15,000 Btu/h ceiling unit say it's got a Maximum Heating Capacity of 12,000 Btu/h at 17°F, whereas the specs for the 12,000 Btu/h wall unit list its Maximum Heating Capacity as 13,600 Btu/h at 17F. That's pretty cool how those numbers flip flop. Or pretty hot, depending on how you look at it. I'm impressed.
Thanks again.
Litawyn
My planned project is 1380 sqft on the main level and the same below grade/basement walkout area. My total load is around 18,000 between the 2 levels. I plan on putting the 12k Hi2 unit on each floor with a 2' electric base board below the windows in the bedrooms for backup heat. The bathroom will have electric mat under the tile floor. Similar to you, the plan is to use an HRV or ERV as a form of circulation as well a ceiling fans in each bedroom and living room. I am in zone 6.
Litawyn,
Aren't you in Maine? You say you're predicting 1,000 hours of cooling per year. That seems really high. Are you sure?
Jesse:
I like the specs of the project you're undertaking. That's terrific. As for HRV/ERV, I strongly recommend you consider the Zehnder ComfoAir 200 ERV that I referenced in a previous post in this thread. It's Passive House certified and very impressive. And I say that after having seriously considered a number of UltimateAir and Venmar systems.
Litawyn
John:
Yup, I'm on the Maine Coast. I had no idea how to estimate how many hours a year I'd have the unit cooling the inside air, so I erred on the side of conservatism. I'm guessing I'd use the A/C for all of July and August (62 days) and probably have it on the lowest speed from sun up to sundown. That would be 62 days x 16 hours/day = 992 hours. If it's less--and it likely will be--even better.
Litawyn