Heat Pump for 1838 Farm House?

Questions on how we spend our money and our time - consumer goods and services, home and vehicle, leisure and recreational activities
Post Reply
Topic Author
CloseEnough
Posts: 1587
Joined: Sun Feb 14, 2021 7:34 am

Heat Pump for 1838 Farm House?

Post by CloseEnough »

I have not started to research this in earnest, but will need to do something with current system, and wondering if I should look at heat pumps. Current system is forced hot water baseboards, propane fuel source (Buderus heater, wall unit). House is not that tight, as it is an old farm house, not sure how big an issue that is, also has a newer addition, 1990, that is tight. Probably about 2,500 sq. feet total. Also have solar on the roof, although it only covers perhaps 80% roughly, of current electrical usage. We could add more panels if that was relevant to heat pump. It is in zone 3. Any reactions and thoughts appreciated. One option, probably the easiest, would be to just replace the Buderus with it's new better like thing, whatever that is (current one is about 15 years old, near end of life).
dbr
Posts: 48434
Joined: Sun Mar 04, 2007 8:50 am

Re: Heat Pump for 1838 Farm House?

Post by dbr »

CloseEnough wrote: Fri Jan 31, 2025 7:50 am I have not started to research this in earnest,
Then start the research. The worst that can happen is that you find for some reason or another that heat pumps are not your choice.

Heat pump technology is such that now heat pumps are practical to fairly low temperatures. So issues are what climate you are in and, if economics are a main issue, what are the competitive costs of propane and resistance heating. Even at the lowest efficiency a heat pump is still more efficient than resistance heating.

An energy inefficient house is an energy inefficient house no matter what you do. Heat pumps of the mini-split variety can allow separate control of zones, which may allow more efficient distribution of heat where you want it, though baseboard heaters are presumably also individually controllable.
exodusNH
Posts: 11732
Joined: Wed Jan 06, 2021 7:21 pm

Re: Heat Pump for 1838 Farm House?

Post by exodusNH »

CloseEnough wrote: Fri Jan 31, 2025 7:50 am I have not started to research this in earnest, but will need to do something with current system, and wondering if I should look at heat pumps. Current system is forced hot water baseboards, propane fuel source (Buderus heater, wall unit). House is not that tight, as it is an old farm house, not sure how big an issue that is, also has a newer addition, 1990, that is tight. Probably about 2,500 sq. feet total. Also have solar on the roof, although it only covers perhaps 80% roughly, of current electrical usage. We could add more panels if that was relevant to heat pump. It is in zone 3. Any reactions and thoughts appreciated. One option, probably the easiest, would be to just replace the Buderus with it's new better like thing, whatever that is (current one is about 15 years old, near end of life).
A poorly insulated home in a very cold climate probably isn't ideal for a heat pump. Newer ones do work down pretty cold, but they don't get as hot as burning hydrocarbons. In a well-insulated building, it isn't a problem because the constant 130F temp is able to keep up with the heat loss.

It will probably work in the addition and maybe in the "shoulder season", but you're going to need to maintain another heating source. Unless you want to fall back to resistive electric heating. I the northeast, the latter is very expensive due to high electricity prices.
Chogy
Posts: 10
Joined: Sat Jan 18, 2025 3:36 pm

Re: Heat Pump for 1838 Farm House?

Post by Chogy »

We live in Zone 3 as well. Dallas area. We have a pair of heat pumps for a fairly large home, and while they do fine and are quite economical for 95% of Zone 3 weather, the outlier weather events can tax the system. The worst are the 2x or 3x a year in the winter with a severe cold snap. Heat pumps can really struggle in this environment to keep things reasonably warm, which is why most have an "emergency" heat in the form of electrical resistance strips, which send the electric bill through the roof.

Depending on how your home is plumbed for propane, probably the better solution would be to have a LP gas "emergency" furnace as part of the system. In the summer, heat pumps seem to work fairly well to keep things cool, but cool is relative. When it's 105 degrees outside, we set the thermostat to about 78 degrees, or higher. With a leakier, older home (ours is as well) if the thermostat is set to say 72, the heat pump will simply run 100% of the time. If it's not cycling on and off, it's not efficient.

Regardless, talk to a good HVAC man. Our thought was to buy an oversized unit to simply crush any heating/cooling concerns, but he nixed that, saying it was very important to size a heat pump properly. Not too big, not too small.

As far as how solar would fit in, I know little about that. Good luck!
User avatar
id0ntkn0wjack
Posts: 484
Joined: Wed Nov 30, 2022 3:12 pm

Re: Heat Pump for 1838 Farm House?

Post by id0ntkn0wjack »

During your research, consider looking into an air-to-water heat pump in addition to the more common air-to-air. Given your existing baseboard situation, it could be a good solution for you:

https://www.greenbuildingadvisor.com/ar ... heat-pumps
dbr
Posts: 48434
Joined: Sun Mar 04, 2007 8:50 am

Re: Heat Pump for 1838 Farm House?

Post by dbr »

Zone 3 should be a gimme. I use mini-splits for air conditioning in Zone 6 and for shoulder season heat. With a system like a Mitsubishi hyper heat (that we don't have) we could almost heat all year including down near 0F. Hyper heat is not a resistance heat back-up but a heat pump with a -15F cut out. Our heat pumps are not used below maybe 25F. But we have effective gas heated hot water radiators for basic winter heating. By -20F/-30F which does happen from time to time you need a reliable winter heat system for sure. In Zone 3 you should not be pushing any of these limits.

But I do agree real life experience from people in your zone is the most valuable advice.

Also, agree with air-water possibility.
ETK517
Posts: 588
Joined: Sun Aug 13, 2023 7:19 am

Re: Heat Pump for 1838 Farm House?

Post by ETK517 »

I investigated and ultimately did not get a heat pump to replace an oil-powered steam radiator heat system in an antique house. A heat pump alone would not be sufficient to maintain comfortable (68ish) indoor temperatures in ordinary winter weather without a supplemental heat source where I live (climate zone 4, NYC metro area). Certainly not in multiple days of single-digits like we had last week, which happens once a year or so. The recommended solution for supplemental heat was a simple electric coil system hooked into my air handler, but due to space constrictions it wasn't feasible to do that without moving the air handler and rerouting all the ductwork at a total cost of $60k. The other option was to leave the radiator system in place as a backup, but then you still are buying fuel and maintaining and servicing that system. Ultimately, I am happy to continue to have radiators as they produce a nicer feeling of warmth than forced air and don't blow dust around. Oh, and they actually keep my house warm. When and if heat pumps can do that reliably on their own, I will reconsider.

Takeaways for you are that the feasibility is highly dependent on the layout of your house and existing ductwork, if any, so I'd talk to a good HVAC contractor. The other takeaway is that in relatively cold climates, at least right now, an air-source heat pump requires you maintain two separate heating systems. I doubt the cost savings, if any, are worth it, and the environmental benefits are very difficult to gauge.
dbr
Posts: 48434
Joined: Sun Mar 04, 2007 8:50 am

Re: Heat Pump for 1838 Farm House?

Post by dbr »

For a house with hot water heat the usual motivation for heat pumps of the mini-split variety is air conditioning with a side benefit of shoulder season heating. One would want to look at the whole system for what it is one wants to achieve. The option of an air to water system for whole house heating could also be feasible, but it does depend on what the plan is for very low temps. But with a hot water system already in place having both might be ok.
User avatar
oldcomputerguy
Moderator
Posts: 19650
Joined: Sun Nov 22, 2015 5:50 am
Location: Tennessee

Re: Heat Pump for 1838 Farm House?

Post by oldcomputerguy »

This topic is now in the Personal Consumer Issues forum (home maintenance, consumer goods).
There is only one success - to be able to spend your life in your own way. (Christopher Morley)
JoeNJ28
Posts: 811
Joined: Sat Aug 25, 2018 9:13 am

Re: Heat Pump for 1838 Farm House?

Post by JoeNJ28 »

I don't understand how all these people can't heat there homes in cold weather, come on Zone 3 in Dallas, is everyone using the home depot special or something? Fujitsu and Mitsubishi as well as Dakin can do cold weather heating zero issue. We use a 1.5 ton unit for 1,400 sq ft 1960s house and it has zero problems keeping the house at 72 even when it is -2 outside.
dbr
Posts: 48434
Joined: Sun Mar 04, 2007 8:50 am

Re: Heat Pump for 1838 Farm House?

Post by dbr »

JoeNJ28 wrote: Fri Jan 31, 2025 8:44 am I don't understand how all these people can't heat there homes in cold weather, come on Zone 3 in Dallas, is everyone using the home depot special or something? Fujitsu and Mitsubishi as well as Dakin can do cold weather heating zero issue. We use a 1.5 ton unit for 1,400 sq ft 1960s house and it has zero problems keeping the house at 72 even when it is -2 outside.
That was my reaction as well. Specifically a Mitsubishi hyper heat mini split runs to -15F, and the plain vanilla Mitsubishi to 5F. Efficiencies may drop from COP above 3 or better to much lower values, but you are still above a baseline of 1 as you would get from resistance heating.
User avatar
Epsilon Delta
Posts: 8175
Joined: Thu Apr 28, 2011 7:00 pm

Re: Heat Pump for 1838 Farm House?

Post by Epsilon Delta »

Chogy wrote: Fri Jan 31, 2025 8:12 am Regardless, talk to a good HVAC man. Our thought was to buy an oversized unit to simply crush any heating/cooling concerns, but he nixed that, saying it was very important to size a heat pump properly. Not too big, not too small.
A modern heat pump should have a variable speed motor and a proportional expansion valve. With these it can run efficiently in a much wider range of loads. Which is good because it is rarely the coldest day of the year, so any heat pump is running at a fraction of its capacity almost all the time. It also reduces the need to exactly size the system.
User avatar
CAsage
Posts: 4265
Joined: Sun Mar 27, 2016 6:25 pm

Re: Heat Pump for 1838 Farm House?

Post by CAsage »

A lot of this depends on your floor plan/layout. You might put a heat pump on the newer sections, allowing for a smaller dead-fuel heat supply on the old section. New heat pumps are incredibly efficient, and will work to much lower temps than those even a few years older. I will note - insulation and weatherstripping has the best return on your money, and has current Inflation Reduction Act rebates which are quite helpful. We are trying to do that to our circa 1965 house - built with no insulation! Incredible, trying to fix that....
Salvia Clevelandii "Winifred Gilman" my favorite. YMMV; not a professional advisor.
SmallSaver
Posts: 706
Joined: Mon Mar 26, 2012 11:34 am

Re: Heat Pump for 1838 Farm House?

Post by SmallSaver »

I spend a fair bit of time researching this for my day job, and I have been told by several engineers and architects that heat pumps are poor performers in t leaky houses. The reason, as others have said, is that the instantaneous heat output is low. It's not like a gas furnace that kicks out 140 degree air, instead the output air is a few degrees above ambient and if you're losing heat through the envelope it won't keep up and you'll be unhappy. Also, it sounds like you don't have ducting, so you'd be talking about multiple mini-splits, or maybe a heat pump hot water heater? I'm pro-heat pump, but this is going to be a challenging application.

If you want to increase comfort and efficiency, your first step is almost always going to be air sealing and maybe some insulation retrofit. Depending on where you are, there may be some very good utility / government programs to help figure this out.
Topic Author
CloseEnough
Posts: 1587
Joined: Sun Feb 14, 2021 7:34 am

Re: Heat Pump for 1838 Farm House?

Post by CloseEnough »

Thanks everyone. Turns out we are in zone 4b, used to be 3, but with warming that has changed. I doubt that changes much in these responses, and will continue to investigate. But, am leaning toward just replacing the Buderus. I don't like the look of mini-splits and we already have baseboard, which I also don't like the look of. Need heat though :happy
TheGreyingDuke
Posts: 2369
Joined: Fri Sep 02, 2011 10:34 am

Re: Heat Pump for 1838 Farm House?

Post by TheGreyingDuke »

Regarding air to water heat pumps...

It does seem like a good approach to retrofit houses with gas boilers, just switch the heat source. Unfortunately, except for a few exceptions, the available models are not an easy retrofit. The gas boiler is outputting 180 degreeF water and the best the air to water systems can do is around 130 degreesF. Assuming that the radiant devices are sized properly for the 180 degree water they will be seriously undersized for 130.

This leads to increasing the radiating surfaces, can be a big, expensive project. Faced with a similar situation, but in a very tight 21st Century house, when our boiler reached the end of its life I replaced it with another high efficiency unit. Use about 400 therms a year for heat and domestic
"Every time I see an adult on a bicycle, I no longer despair for the future of the human race." H.G. Wells
Valuethinker
Posts: 51511
Joined: Fri May 11, 2007 11:07 am

Re: Heat Pump for 1838 Farm House?

Post by Valuethinker »

CloseEnough wrote: Fri Jan 31, 2025 7:50 am I have not started to research this in earnest, but will need to do something with current system, and wondering if I should look at heat pumps. Current system is forced hot water baseboards, propane fuel source (Buderus heater, wall unit). House is not that tight, as it is an old farm house, not sure how big an issue that is, also has a newer addition, 1990, that is tight. Probably about 2,500 sq. feet total. Also have solar on the roof, although it only covers perhaps 80% roughly, of current electrical usage. We could add more panels if that was relevant to heat pump. It is in zone 3. Any reactions and thoughts appreciated. One option, probably the easiest, would be to just replace the Buderus with it's new better like thing, whatever that is (current one is about 15 years old, near end of life).
So there are now high performance heat pumps which work well in cold weather. From what poster talzara said here, Mitsubishi is the main vendor of same in the USA. The domestic manufacturers have limited/ no offer.

Air-to-Water is probably the technology you want, because it would work well with your existing baseboards. Probably can do hot water at 60C or so (I am afraid I think in Centigrade, and we keep our hot water rads at about 60C, in a London UK climate (which is milder in winter).

And this would probably do what you needed it to do. Down to 10-ish degrees F, anyways.

However:

- it may struggle if you have a cold wind
- it feels different - you run the HP pretty much all the time
- you will need electric strip backup and/or propane, for very cold days. At NYS electricity prices, that could be quite expensive to run**

What are the walls of your home? Because a brick house the walls will warm up and retain some heat. However if lumber (more likely in your part of the world) that won't be the case.

** electricity in lower NYS is not particularly green. (Rant on) if you close a nuclear power plant, but block new transmission lines from Hydro Quebec, then you are going to burn more gas for electricity, at a relatively high cost (Rant off)
lex4
Posts: 3
Joined: Mon Sep 08, 2014 2:02 am

Re: Heat Pump for 1838 Farm House?

Post by lex4 »

Unless your hot water system needs a total rebuild I wouldn't get rid of it. Most people who switch from radiant heat to forced air systems find that their homes feel colder even if the air temperature is the same. Forced air systems don't heat the flooring, furniture, walls, etc as effectively as radiant heat. Not to mention since you don't have existing ducting you'd either be looking at a mini-split with ugly units in every room (even if you don't mind them, future home buyers might) or major renovations to add ducting. Also the life expectancy of new heat pumps is only 7-10 years. Unless you really don't want to be burning propane I doubt switching to HP would make financial sense.
Irene
Posts: 128
Joined: Sun Jun 09, 2024 9:39 pm

Re: Heat Pump for 1838 Farm House?

Post by Irene »

lex4 wrote: Fri Jan 31, 2025 6:53 pm Also the life expectancy of new heat pumps is only 7-10 years. Unless you really don't want to be burning propane I doubt switching to HP would make financial sense.
I wonder why Mitsubishi has a 12-year warranty on parts and compressor, then? My heat pump turns seven this year, and it's had no problems at all. I would be very surprised (and not happy) if it didn't last quite a while yet. And it's a ducted version, which is supposed to have to work harder and therefore wear out sooner than a minisplit.

Air-to-water heat pumps are less common in the US (apart from heat pump water heaters for domestic hot water), but they do exist.
finite_difference
Posts: 3891
Joined: Thu Jul 09, 2015 7:00 pm

Re: Heat Pump for 1838 Farm House?

Post by finite_difference »

id0ntkn0wjack wrote: Fri Jan 31, 2025 8:19 am During your research, consider looking into an air-to-water heat pump in addition to the more common air-to-air. Given your existing baseboard situation, it could be a good solution for you:

https://www.greenbuildingadvisor.com/ar ... heat-pumps
+1.

I love radiant heat so personally would try to keep that, even if it meant having to go with a high-efficiency NG furnace.
The most precious gift we can offer anyone is our attention. - Thich Nhat Hanh
talzara
Posts: 5401
Joined: Thu Feb 12, 2009 6:40 pm

Re: Heat Pump for 1838 Farm House?

Post by talzara »

JoeNJ28 wrote: Fri Jan 31, 2025 8:44 am I don't understand how all these people can't heat there homes in cold weather, come on Zone 3 in Dallas, is everyone using the home depot special or something? Fujitsu and Mitsubishi as well as Dakin can do cold weather heating zero issue. We use a 1.5 ton unit for 1,400 sq ft 1960s house and it has zero problems keeping the house at 72 even when it is -2 outside.
Most homeowners in Texas do not have low-temperature mini-splits.

According to the 2020 Residential Energy Consumption Survey (RECS), only 0.8% of homes in the United States have ductless mini-splits. Even fewer will have low-temperature mini-splits. https://www.eia.gov/consumption/residen ... %206.8.pdf

In the East South Central region, ductless mini-splits were so rare that the 2020 RECS could not calculate a statistically valid number. It is reported as Q, "Data withheld because either the relative standard error (RSE) was greater than 50% or fewer than 10 households were in the reporting sample."
Legoman666
Posts: 49
Joined: Mon Jun 10, 2024 6:44 pm

Re: Heat Pump for 1838 Farm House?

Post by Legoman666 »

CloseEnough wrote: Fri Jan 31, 2025 2:52 pm Thanks everyone. Turns out we are in zone 4b, used to be 3, but with warming that has changed. I doubt that changes much in these responses, and will continue to investigate. But, am leaning toward just replacing the Buderus. I don't like the look of mini-splits and we already have baseboard, which I also don't like the look of. Need heat though :happy
Look at Mitsubishi’s ceiling mount units. Much less obtrusive. We have 6 of them throughout the house and 1 wall mount unit in the garage. A little over 3000sq ft of conditioned space in Cincinnati. We love them. Room by room temperature control is awesome. One 5 ton unit powers all 7 heads on a 1970’s house that I would not call tight. It was -8f a year or two ago with 40mph winds. Inside 68f no problem. Anyone who says they don’t blow warm air is blowing smoke, they get plenty hot, haha. We don’t even have the hyper heat unit, just the regular one.
talzara
Posts: 5401
Joined: Thu Feb 12, 2009 6:40 pm

Re: Heat Pump for 1838 Farm House?

Post by talzara »

CloseEnough wrote: Fri Jan 31, 2025 2:52 pm Thanks everyone. Turns out we are in zone 4b, used to be 3, but with warming that has changed.
That would not be global warming.

Higher zone numbers are colder than lower zone numbers.
Valuethinker
Posts: 51511
Joined: Fri May 11, 2007 11:07 am

Re: Heat Pump for 1838 Farm House?

Post by Valuethinker »

talzara wrote: Fri Jan 31, 2025 9:43 pm
CloseEnough wrote: Fri Jan 31, 2025 2:52 pm Thanks everyone. Turns out we are in zone 4b, used to be 3, but with warming that has changed.
That would not be global warming.

Higher zone numbers are colder than lower zone numbers.
Because of instability in the jetstream, leading to "polar vortex" conditions where very cold air masses move south from the Arctic and sit over North America or Europe for much longer periods than historically, it might be. We seem to be experiencing greater extremes of both heat and cold.
dbr
Posts: 48434
Joined: Sun Mar 04, 2007 8:50 am

Re: Heat Pump for 1838 Farm House?

Post by dbr »

Legoman666 wrote: Fri Jan 31, 2025 9:42 pm
CloseEnough wrote: Fri Jan 31, 2025 2:52 pm Thanks everyone. Turns out we are in zone 4b, used to be 3, but with warming that has changed. I doubt that changes much in these responses, and will continue to investigate. But, am leaning toward just replacing the Buderus. I don't like the look of mini-splits and we already have baseboard, which I also don't like the look of. Need heat though :happy
Look at Mitsubishi’s ceiling mount units. Much less obtrusive. We have 6 of them throughout the house and 1 wall mount unit in the garage. A little over 3000sq ft of conditioned space in Cincinnati. We love them. Room by room temperature control is awesome. One 5 ton unit powers all 7 heads on a 1970’s house that I would not call tight. It was -8f a year or two ago with 40mph winds. Inside 68f no problem. Anyone who says they don’t blow warm air is blowing smoke, they get plenty hot, haha. We don’t even have the hyper heat unit, just the regular one.
Are you saying that Mitsubishi heat pump continued to run at -8F. I am not sure what unit you have but the published low temp cut out for the standard unit is +5F. Hyper heat I think still runs at -15F. I would be curious what model you are running.
Legoman666
Posts: 49
Joined: Mon Jun 10, 2024 6:44 pm

Re: Heat Pump for 1838 Farm House?

Post by Legoman666 »

Yes it still ran.

The published lockout temp for non hyper heat is -24F, and it won't restart until -14F. Hyper heat is the same. The difference is the capacity at low temps.

Hyperheat:
Image

Regular:
Image
ETK517
Posts: 588
Joined: Sun Aug 13, 2023 7:19 am

Re: Heat Pump for 1838 Farm House?

Post by ETK517 »

There's another active thread on heat pumps right now with some interesting information, including the observation that getting a temperature above 65 degrees may be a challenge in winter and that heat pumps do not work well if you prefer lower temps at night. I'd stick to hot water.
ncbill
Posts: 2151
Joined: Sun Jul 06, 2008 4:03 pm
Location: Western NC

Re: Heat Pump for 1838 Farm House?

Post by ncbill »

CloseEnough wrote: Fri Jan 31, 2025 2:52 pm Thanks everyone. Turns out we are in zone 4b, used to be 3, but with warming that has changed. I doubt that changes much in these responses, and will continue to investigate. But, am leaning toward just replacing the Buderus. I don't like the look of mini-splits and we already have baseboard, which I also don't like the look of. Need heat though :happy
Buderus seems to be a quality brand, and IIRC hot water radiator heat should be fairly efficient.

I'd check to see if your local utility offers a free or inexpensive energy audit.

And maybe pre-screened contractors for air sealing/adding extra insulation.
dbr
Posts: 48434
Joined: Sun Mar 04, 2007 8:50 am

Re: Heat Pump for 1838 Farm House?

Post by dbr »

Legoman666 wrote: Sat Feb 01, 2025 8:49 am Yes it still ran.

The published lockout temp for non hyper heat is -24F, and it won't restart until -14F. Hyper heat is the same. The difference is the capacity at low temps.
We seem to be talking completely different models here. My information is for MXZ-4C36NA3-U1 (the unit I have) or the hyper-heat MXZ-SM36NAMHZ. The lockout/restart on the 4C36 is 1.4/5.0F or -17/-15C. The hyper heat is very different and does indeed spec much lower around -15F.

Note I live in a cold enough climate that low lows can reach -20F to -30F so there is no question of doing without gas heat for the house when all is said and done.
Legoman666
Posts: 49
Joined: Mon Jun 10, 2024 6:44 pm

Re: Heat Pump for 1838 Farm House?

Post by Legoman666 »

dbr wrote: Sat Feb 01, 2025 9:24 am
Legoman666 wrote: Sat Feb 01, 2025 8:49 am Yes it still ran.

The published lockout temp for non hyper heat is -24F, and it won't restart until -14F. Hyper heat is the same. The difference is the capacity at low temps.
We seem to be talking completely different models here. My information is for MXZ-4C36NA3-U1 (the unit I have) or the hyper-heat MXZ-SM36NAMHZ. The lockout/restart on the 4C36 is 1.4/5.0F or -17/-15C. The hyper heat is very different and does indeed spec much lower around -15F.

Note I live in a cold enough climate that low lows can reach -20F to -30F so there is no question of doing without gas heat for the house when all is said and done.
I think mine has lower cutout temp because the branch box is inside whereas on yours all 3 units are plumbed directly to the outdoor unit. I have a 2022 MXZ-SM60NAM-U1.
dbr
Posts: 48434
Joined: Sun Mar 04, 2007 8:50 am

Re: Heat Pump for 1838 Farm House?

Post by dbr »

Legoman666 wrote: Sat Feb 01, 2025 9:27 am
dbr wrote: Sat Feb 01, 2025 9:24 am

We seem to be talking completely different models here. My information is for MXZ-4C36NA3-U1 (the unit I have) or the hyper-heat MXZ-SM36NAMHZ. The lockout/restart on the 4C36 is 1.4/5.0F or -17/-15C. The hyper heat is very different and does indeed spec much lower around -15F.

Note I live in a cold enough climate that low lows can reach -20F to -30F so there is no question of doing without gas heat for the house when all is said and done.
I think mine has lower cutout temp because it is newer; I have a 2022 MXZ-SM60NAM-U1.
Thanks, I appreciate the info.
dbr
Posts: 48434
Joined: Sun Mar 04, 2007 8:50 am

Re: Heat Pump for 1838 Farm House?

Post by dbr »

Legoman666 wrote: Sat Feb 01, 2025 9:27 am
dbr wrote: Sat Feb 01, 2025 9:24 am

We seem to be talking completely different models here. My information is for MXZ-4C36NA3-U1 (the unit I have) or the hyper-heat MXZ-SM36NAMHZ. The lockout/restart on the 4C36 is 1.4/5.0F or -17/-15C. The hyper heat is very different and does indeed spec much lower around -15F.

Note I live in a cold enough climate that low lows can reach -20F to -30F so there is no question of doing without gas heat for the house when all is said and done.
I think mine has lower cutout temp because the branch box is inside whereas on yours all 3 units are plumbed directly to the outdoor unit. I have a 2022 MXZ-SM60NAM-U1.
Yes, the issue of a branch box is a technical difference.

Of course we have the unit in the first place for air conditioning as with hot water radiators we don't have whole house AC. The AC function works very well. Our gas hot water heat also works very well.
talzara
Posts: 5401
Joined: Thu Feb 12, 2009 6:40 pm

Re: Heat Pump for 1838 Farm House?

Post by talzara »

Valuethinker wrote: Sat Feb 01, 2025 4:48 am Because of instability in the jetstream, leading to "polar vortex" conditions where very cold air masses move south from the Arctic and sit over North America or Europe for much longer periods than historically, it might be. We seem to be experiencing greater extremes of both heat and cold.
IECC climate zones are based on the average annual number of heating and cooling degree-days. If polar vortexes are sitting over the area for longer, it will not change the climate zone as long as they are offset by equally large positive temperature deviations.

To move to a higher-numbered climate zone, you have to experience more heating degree-days in total, not just for a few days.

This is why climate zones are not enough for sizing equipment. The climate zone tells you the totals, not the extremes. You have to look up the design temperature in Manual J. Boston and Omaha are both in zone 5A, but Boston's design temperature is 13°F higher than Omaha's design temperature.
User avatar
Epsilon Delta
Posts: 8175
Joined: Thu Apr 28, 2011 7:00 pm

Re: Heat Pump for 1838 Farm House?

Post by Epsilon Delta »

talzara wrote: Sun Feb 02, 2025 9:56 pm IECC climate zones are based on the average annual number of heating and cooling degree-days. If polar vortexes are sitting over the area for longer, it will not change the climate zone as long as they are offsn et by equally large positive temperature deviations.
The hot and cold tails are not averaged in figuring the zone.
The criteria in table C301.3
zone 2 is 6300 < CDD50 <= 9000
zone 3 is CDD50 <= 6300 and HDD65 <= 3600
zone 4 is CDD50 <= 6300 and 3600 < HDD65 <= 5400
So an increase in HDD can change the zone whether or not there is a change in CDD. Though if CDD increase enough you move to zone 2, even if HDD also increase.

Perhaps more importantly the definitions in 2012 were different.
Zone 3A and 3B are 4500 < CDD50 <= 6300 and HDD65 <= 5400
Zone 4A and 4B are CDD50 <= 4500 and HDD <= 5400

So if HDD = 5000 and CCD = 5000 a county moves from zone 3A to zone 4 without any climate change at all! I'm a bit surprised there weren't more changes, but I suspect data mining and careful selection of criteria so that most of the envelope that moved is unoccupied.
Valuethinker
Posts: 51511
Joined: Fri May 11, 2007 11:07 am

Re: Heat Pump for 1838 Farm House?

Post by Valuethinker »

ETK517 wrote: Sat Feb 01, 2025 9:10 am There's another active thread on heat pumps right now with some interesting information, including the observation that getting a temperature above 65 degrees may be a challenge in winter and that heat pumps do not work well if you prefer lower temps at night. I'd stick to hot water.
Air to Water heat pumps are coming into the North American market, but I don't think widely available as yet (they are the norm in Europe).

60C (140F) rad water temperature is entirely possible. Gas system (indirect) would be about 65C. You do need a High Performance HP or the performance could be quite poor on colder days - and probably you would run it at 50C w bigger rads (Europe you get a lot of steel flat panel rads, whereas in North America they tend to be the much bigger cast iron things). 80% of new Heat Pumps in Scandinavia are Air to Water (not geothermal) I believe. They have similar winters to Wisconsin except right along the Norwegian coast.

Gas is cheap in America compared to Europe. Electricity is mostly cheaper but with some big exceptions (California, and NY-New England primarily).
talzara
Posts: 5401
Joined: Thu Feb 12, 2009 6:40 pm

Re: Heat Pump for 1838 Farm House?

Post by talzara »

Epsilon Delta wrote: Sun Feb 02, 2025 10:50 pm
talzara wrote: Sun Feb 02, 2025 9:56 pm IECC climate zones are based on the average annual number of heating and cooling degree-days. If polar vortexes are sitting over the area for longer, it will not change the climate zone as long as they are offsn et by equally large positive temperature deviations.
The hot and cold tails are not averaged in figuring the zone.
I never said the hot and cold tail for an entire year are averaged in figuring the zone.

I said that climate zones are based on the heating and cooling degree-days. Those are two separate numbers. The hot tail is in the cooling degree-days, and the cold tail is in the heating degree-days. Therefore, they are not averaged with each other.

Greater variability may make the lows more extreme, but they will also make the lows less extreme. A polar vortex may reduce a day's temperature from 30°F to 10°F, but the jet stream may also rise to higher latitudes and increase the next day's temperature from 30°F to 50°F. Both are temperature departures: a -20°F departure and a +20°F departure.
User avatar
Epsilon Delta
Posts: 8175
Joined: Thu Apr 28, 2011 7:00 pm

Re: Heat Pump for 1838 Farm House?

Post by Epsilon Delta »

talzara wrote: Mon Feb 03, 2025 10:26 pm
Epsilon Delta wrote: Sun Feb 02, 2025 10:50 pm
The hot and cold tails are not averaged in figuring the zone.
I never said the hot and cold tail for an entire year are averaged in figuring the zone.

I said that climate zones are based on the heating and cooling degree-days. Those are two separate numbers. The hot tail is in the cooling degree-days, and the cold tail is in the heating degree-days. Therefore, they are not averaged with each other.

Greater variability may make the lows more extreme, but they will also make the lows less extreme. A polar vortex may reduce a day's temperature from 30°F to 10°F, but the jet stream may also rise to higher latitudes and increase the next day's temperature from 30°F to 50°F. Both are temperature departures: a -20°F departure and a +20°F departure.
You didn't say "average", but you did say "offset". There is no offset. If you increase CDD > 6300 it moves from zone 3 to zone 2. If you increase HDD > 3600 it moves to zone 4. If you increase both over the limits it moves to zone 2. If HDD remains <= 3600 there is no value of CDD that will move it to zone 4. If HDD > 3600 there is no possible value of CDD that remains in zone 3. The boundaries of the zones are square, not sloped.
talzara
Posts: 5401
Joined: Thu Feb 12, 2009 6:40 pm

Re: Heat Pump for 1838 Farm House?

Post by talzara »

Epsilon Delta wrote: Tue Feb 04, 2025 1:27 am You didn't say "average", but you did say "offset". There is no offset. If you increase CDD > 6300 it moves from zone 3 to zone 2. If you increase HDD > 3600 it moves to zone 4. If you increase both over the limits it moves to zone 2. If HDD remains <= 3600 there is no value of CDD that will move it to zone 4. If HDD > 3600 there is no possible value of CDD that remains in zone 3. The boundaries of the zones are square, not sloped.
I also never said that CDD is increasing, or that HDD is increasing, or that changing CDD with HDD ≤ 3600 would move climate zones, or that changing CDD with HDD > 3600 would stay in the same climate zone, or that the boundaries of the zone are sloped.

Please read my example again:
talzara wrote: Mon Feb 03, 2025 10:26 pm Greater variability may make the lows more extreme, but they will also make the lows less extreme. A polar vortex may reduce a day's temperature from 30°F to 10°F, but the jet stream may also rise to higher latitudes and increase the next day's temperature from 30°F to 50°F. Both are temperature departures: a -20°F departure and a +20°F departure.
These temperature departures are one day apart. The -20°F departure is offset by a +20°F departure the next day. It is offset within the same season (heating), not across different seasons (heating and cooling).

I was replying to a post that said that climate zone could change because of greater variability, and it gave the example of polar vortexes. However, this is based on a misunderstanding of climate zones. HDD is a sum. As long as the increased frequency of polar vortexes is offset by equally large temperature departures in the other direction during the same season (heating) over the 15 or 30-year climate averaging cycle, it will not change the HDD, and it will not change the climate zone.
bombcar
Posts: 2444
Joined: Sun Aug 12, 2007 6:41 pm

Re: Heat Pump for 1838 Farm House?

Post by bombcar »

How is the temperature and usage of the house overall?

It may be that getting a heat pump is fine, and then compensating for coldest days by having supplemental heat available in your most active rooms.

This can also be setup to get different temperatures as needed.

When in doubt, replace what's there with the same thing.
Post Reply