Cold-climate heat pump reliability
Please share your experience with cold-climate HP reliability.
We are doing a major energy retrofit of a 1975 ranch home in northern Colorado (CZ 5B), for year-round comfort, resiliency and low operating costs as we plan for aging in place. Shell improvements will reduce design loads to less than 15 kBtu/hr heating (at 6F), less than 10 kBtu/hr cooling (91F) with virtually no latent load in our dry climate. In our present, efficient home, nighttime ventilation has been adequate for cooling.
So which direction to go for heating/cooling systems? We would like to do our part for decarbonization and disconnect the gas line. The electric service can accommodate a heat pump. Based on research I’ve done to date, we are confident a right-sized CCHP will keep the house comfortable with minimal backup heat operation (1-2x per yr the outdoor temp dips as low as -15F). With current utility rates, a CCHP will have higher operating cost than an efficient gas furnace but – because loads are small – the absolute difference will be small (perhaps fully offset by zero monthly gas fixed fee).
The current setup is an old gas furnace and duct system in the uninsulated, vented crawlspace. Shell improvements will bring the crawl into the conditioned space. Our mechanical contractor suggests a good CCHP choice is a ducted mini-split with new air handler replacing the furnace. Existing ducts are more than adequately sized due to the load reduction.
We are willing to pay the higher up-front cost for a CCHP vs a small gas furnace. The wild card is reliability for this relatively new technology. I have been unable to find any information on the track record for today’s CCHPs. The controls for a CCHP are much more complex than for the single-stage gas furnace that is our alternative. The sophisticated, variable capacity equipment could be more vulnerable to breakdown. It would be disappointing and potentially expensive to experience more than a very occasional service call. Our mechanical contractor claims their experience so far with Carrier CCHPs – has been good but that parts are very expensive (he says, “like BMW parts”).
Please pass along your experience and/or other resources you’ve seen on this topic. Including any differences you’re aware of among brands.
Thanks in advance for your help.
Doug
PS If you’re aware of any reason to consider a more expensive, traditional “big box” CCHP vs the ducted mini-split, we’re interested to hear your thoughts on that front, too.
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Replies
I have a Mitsubishi CCHP, it’s been 3 years of AC and heating with no issues. It’s great.
How important is lifespan here? Retrofitting a house to get the heating load to 15,000 Btu in northern Colorado surely costs many heat pumps :).
I can share my personal experience switching from a 50,000 BTU gas furnace to a 2-ton Carrier CCHP in Toronto, Canada.
Short story: I recommend it!
After doing some detailed load calcs I found that my house only needed about 24,000 BTU and my old furnace was 2x the design load. I went with a 2-ton high heat Carrier 38MURAQ24AB3 (note: "AB" is the high heat model / the "AA" is the standard model). This is not premium equipment - it is in fact made by Midea in China and Carrier just puts their name on it. However it has been working well since I had it installed last May (almost 1 yr).
With your low heating loads you will do very well with a heat pump! If reliability is the question , that's a bit hard to say, since this stuff is relatively new on the market. However a heat pump is basically just an air conditioner that can work in reverse, and A/Cs can last very long time. Mind you the new heat pumps have more electronics. If you are concerned, make sure to have a surge protector installed that protects the equipment. You can even get a whole-home surge protector that will protect everything in your house. You could also look at Daikin products which I believe come with a 12 year parts / 12 year labour warranty. The Carrier has a 10 year parts warranty but you'll typically pay for labour after the first year. Also make sure your installer is reputable, experienced, and follows the installation procedure. This includes flowing nitrogen while brazing and installing the filter drier. A sloppy install will ruin any equipment.
The big cube designs are dated... I believe bosch sells this format perhaps because they think Americans find them to be more palatable. However the mini-split as you describe will be quieter, take up less space and less debris will fall into it. Make sure you get it mounted on a snow stand (Assuming you get snow where you are). Also know that it drips water in the winter, so this should be managed properly i.e. you don't want it to create ice on a driveway/walkway.
Consider the greenest thing you can do is to reduce. By replacing the furnace before the end of its usefulness you are needlessly forcing equipment to be manufactured and the copper and steel needed to make to be mined many years sooner than necessary.
You have had an air conditioner forever a heat pump is the same thing with one more valve that lets it run backward. They can be very reliable or not mostly depending on the quality of the installer.
Walta
I had similar questions while building my new house 8 yrs ago. I decided to go all electric & the savings on the monthly gas fixed charge and the gas line install helped.
I went with a American Standard split system, heat pump + air handler with heat strips. I'm in central CO (salida), perhaps similar climate to you, but not as much below zero.
I wouldn't recommend American Standard, I didn't know it at the time, but they only work with authorized dealers. I was having issues with the AS thermostat the 1st winter. The problem was solved with a firmware upgrade but they didn't want to talk to me.
I think you will find no US HVAC equipment manufacture will work with the end user!
They view their customer to be your HVAC contractor. Us end user are a nuisance and avoid contact if at all possible.
Note every transaction must go thru the reginal distributor and the local contractor.
Walta
Agreed. I couldn't get a word out of Carrier when I tried.
They were extremely resistant to working with my contractor too, because he wasn't a certified American Std dealer. Somehow he managed to order it tho.
When you say cold climate heat pump (CCHP) what do you mean Doug ?
You should be careful as what that term means can be very different depending on who is saying it.
I suspected you are talking about heat pumps with a vapor injection compressor. Every manufacture has trade marked a different name for the same technology “Hyper Heat”
Walta
Thanks to everyone who has responded, I really appreciate it. I'll be meeting with our mechanical contractor tomorrow and having a bit of feedback on this front is very helpful.
The fact that I haven't come across more information on reliability issues may be a good sign that CCHPs are indeed pretty reliable. I'm always interested to hear more users chime in.
A couple notes related to comments in the thread:
* The existing induced-draft furnace is in very poor shape, was installed in the 1990s in a dirt crawlspace with no filter rack and leaky ducts. Amazing it's still limping along. We're not losing any sleep over replacing it, it's well past its time.
* We're investing a substantial amount up front on this project, with a focus first on a quality shell that provides load reduction and year-round comfort. By doing a good project, with attention to materials and detail, our long-term operating and maintenance costs will be low. We want to carry this through to the mechanical systems.
* I'm using "cold-climate heat pump" as a general term referring to a heat pump which delivers a substantial % of it's nominal rated capacity at a reasonable COP at our outdoor design heating temp (6F); one that can meet our heating load most of the time in heat pump mode. Compared with the earlier generation of heat pumps that hit a COP of 1.0 at relatively mild temps and were most appropriate for warmer climates than Colorado. To get the enhanced performance at lower outdoor temps requires more complex machines - both in the guts and the controls; lots of modulation going on. I don't pretend to understand all the details on that front. In my experience, a more complex system typically has more failure modes than a simpler system. Hence my interest to hear folks' experience with reliability.
Cheers,
Doug
If you ask for a unit with a vapor injection port you are guaranteed to get what you want. The fast talking salesman can use your poorly defined language to sell you something less than what you are wanting.
Walta