Heat pump in New England

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B4Xt3r
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Re: Heat pump in New England

Post by B4Xt3r »

Just curious, does anyone know of an installer they could recommend in southern New Hampshire?
ondarvr
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Re: Heat pump in New England

Post by ondarvr »

Here is a video showing methods to estimate the required equipment for your area, and highlighting the Mitsubishi system.

https://youtu.be/ud5oAmTHcM4

And the finished house with more info.

https://youtu.be/mdUYFprPKFI
Last edited by ondarvr on Wed Jul 27, 2022 8:38 am, edited 3 times in total.
bluebolt
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Re: Heat pump in New England

Post by bluebolt »

For those of us in New England with a ducted A/C and natural gas hot water baseboard heating system that may be nearing the end of their lives, are there good resources that help us where to start research on the pros, cons, and costs of the various heat pump systems?
CRC301
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Re: Heat pump in New England

Post by CRC301 »

bluebolt wrote: Tue Jul 26, 2022 7:53 pm For those of us in New England with a ducted A/C and natural gas hot water baseboard heating system that may be nearing the end of their lives, are there good resources that help us where to start research on the pros, cons, and costs of the various heat pump systems?
Green Building Advisors has some great folks answering questions in their website's Question & Answer sections. Most of my cold-climate heat pump research on google led me to posts on that site and plenty of folks discussing cold-climate heat pumps on that site were in the New England area. A few of the specific "Experts" that comment regularly on the heat pump questions are Dana Dorsett and Martin Holladay.

https://www.greenbuildingadvisor.com/qa

Good luck!
servicedenied
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Re: Heat pump in New England

Post by servicedenied »

bluebolt wrote: Tue Jul 26, 2022 7:53 pm For those of us in New England with a ducted A/C and natural gas hot water baseboard heating system that may be nearing the end of their lives, are there good resources that help us where to start research on the pros, cons, and costs of the various heat pump systems?
I think this was linked earlier in the thread, but if you do decide to go heat pump the NEEP heat pump list is a great resource. It lets you compare units across manufacturers very easily, so if you do get to the point of getting estimates you can dig into the specs of each unit. Some of that data is hard to find otherwise, even on manufacturer websites.

We recently switched from a 5-ton A/C + natural gas furnace (both from 2005) to a 4 ton Daikin SkyAir heat pump. We stayed with central ducting. We are not in New England but so far we've been very happy with the unit. The real test will be this winter, but we intentionally picked a unit with good low temp performance so I don't anticipate any problems.

I recognize going with a larger, fully-ducted heat pump is somewhat less efficient than mini-splits (particularly if the ductwork is in unconditioned space, as mine are). But to me the simplicity and lower maintenance of one heat pump and one air handler won out.
meanween
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Re: Heat pump in New England

Post by meanween »

In New England and had air source heat pumps installed in our home 6 years ago.

Main goal was for AC, our house is oil heat with forced hot water baseboards. So we didn't have vents in place for a central AC system. Decided go go with two units outside and a total of 5 heads inside (2 downstairs, 1 in each bedroom upstairs). With labor the entire install was about 15k after state rebates (minimal). Expensive yes, but the mini-splits do a great job keeping the heat out and are very quiet.

As a side benefit the Daikin units we have can heat, which we do use through the spring and fall. They are rated down to 15F and could go lower if the optional wind baffle was installed. A friend of mine has a Mitsubishi unit that can deliver heat down to negative temps and he keeps his on all winter. For us, once we're into say December on I just go full oil, mostly because I don't want to fiddle with turning the units on and off and checking weather for colder than usual days. Additionally I have an office in the basement and the side-effect of running the oil furnace is that it keeps my office space warmer.

I recall doing a rough estimate that when oil was over $3 a gallon it was likely more beneficial to be on the heat pump. However I do not have exact numbers to back this up. It was more eyeballing electric cost per month vs. oil cost per month. My longer term goal is to go solar in which case utilizing the heat pumps more should help with return on investment when the time comes.

We did have some headaches with the units, I chalk these up to poor installation/maintenance
- For several years in the spring we'd turn on the system and it would error due to low refrigerant. Installer finally found the leaks and fixed them
- During one checks for the leak the tech managed to "blow a control board" when investigating the issue. Was covered under warrantee.
- For two years we also had water dripping from one unit. This ended up being condensation building up and dripping down on of the lines. Once the installer came back and found where the pipe was exposed going to one of the heads this went away.

If I could do it again I would have both units wall mounted to the side of my house to keep them out of the snow. One is on a small concrete pad on risers but not high enough to keep it completely free from snow during major storms.

Overall, I am happy with the mini splits, but quiet comfort comes at a price I suppose.
bluebolt
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Re: Heat pump in New England

Post by bluebolt »

servicedenied wrote: Wed Jul 27, 2022 8:07 am
bluebolt wrote: Tue Jul 26, 2022 7:53 pm For those of us in New England with a ducted A/C and natural gas hot water baseboard heating system that may be nearing the end of their lives, are there good resources that help us where to start research on the pros, cons, and costs of the various heat pump systems?
I think this was linked earlier in the thread, but if you do decide to go heat pump the NEEP heat pump list is a great resource. It lets you compare units across manufacturers very easily, so if you do get to the point of getting estimates you can dig into the specs of each unit. Some of that data is hard to find otherwise, even on manufacturer websites.

We recently switched from a 5-ton A/C + natural gas furnace (both from 2005) to a 4 ton Daikin SkyAir heat pump. We stayed with central ducting. We are not in New England but so far we've been very happy with the unit. The real test will be this winter, but we intentionally picked a unit with good low temp performance so I don't anticipate any problems.

I recognize going with a larger, fully-ducted heat pump is somewhat less efficient than mini-splits (particularly if the ductwork is in unconditioned space, as mine are). But to me the simplicity and lower maintenance of one heat pump and one air handler won out.
That seems really helpful. However, I'm at the step before that where understanding the general pros/cons/tradeoffs of the various types of systems based on my climate and existing systems is what I need as a first step.
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just frank
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Re: Heat pump in New England

Post by just frank »

bluebolt wrote: Wed Jul 27, 2022 12:56 pm That seems really helpful. However, I'm at the step before that where understanding the general pros/cons/tradeoffs of the various types of systems based on my climate and existing systems is what I need as a first step.
Perhaps I can suggest going back a step. Every HP system a nominal HSPF. Code minimum is 8.2, inverter systems get to 10 and super fancy tech gets to 12 (more is better).

HSPF is the ratio of (heat power)/(electrical power) in units of (kBTU/h)/(kW_elec) or equivalently with energy kBTU/kWh.

Of course, this factor depends on the outside temp, the 'S' in HSPF tries to make a seasonal average. It ofc then assumes some climate, which is likely a bit warmer than your area (years ago, it was comparable to Atlanta, GA).

So, if you have a HSPF = 10 unit, and want to make 1 million BTUs (enough to heat a home for a few days), you need 1000 kBTU / 10 (HSPF) = 100 kWh.

If you have nat gas, and 90% eff equipment, you need 11 therms (a therm is about 100 kBTU) to make 1 MMBTU, or (best case) 100 kWh.

So, compare the price of a therm in your area, to the price of 100 kWh. If you are using heating oil, it takes 8-10 gallons of oil to make a MMBTU, so you can compare THAT price to 100 kWh.

That figure (HSPF = 10) assumes NO use of backup electric strips, and your climate is not much colder than the reference climate. One way to estimate what HSPF you would get is to consult the degradation factors in this peer-reviewed paper, Figure 3:

http://publications.energyresearch.ucf. ... 413-04.pdf

Looks like colder climates see a 20-30% decrease.

So, if you installed an HSPF = 10 system, and use it as your sole heat source, then you should expect something more like 7-8 in a cold climate. Then use the 'degraded' HSPF in your financial calculation.

If you know your seasonal energy bill in therms or gallons of oil, you can then predict (±10%) your cost for running your HP for a season.

HPs are generally low maintenance, and should be good for 10-15 years in practice. This is shorter than most fossil equipment, so if you care you might try to factor that higher equipment (and equipment replacement) cost into your TCO.
CloseEnough
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Re: Heat pump in New England

Post by CloseEnough »

Are there limitations on heat pump viability for installation in a very old (1800s) farm house? Wondering if this is an option I should look at when the time comes to replace current boiler for baseboard heat. Prior to that, heat was from a coal burner converted to run on propane, very inefficient. There is some ductwork related to the coal burner. No AC in this house, although with changing climate would be good to have. House does have solar panels on the roof. Thanks.
Valuethinker
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Re: Heat pump in New England

Post by Valuethinker »

CloseEnough wrote: Thu Jul 28, 2022 10:55 am Are there limitations on heat pump viability for installation in a very old (1800s) farm house? Wondering if this is an option I should look at when the time comes to replace current boiler for baseboard heat. Prior to that, heat was from a coal burner converted to run on propane, very inefficient. There is some ductwork related to the coal burner. No AC in this house, although with changing climate would be good to have. House does have solar panels on the roof. Thanks.
The efficiency of a heat pump is in inverse to the gap between input and output temperatures. Bigger gap, less efficient.

That does mean that the temp output of a HP is usually lower than it is for a boiler/ furnace. That can make an old house quite cold - it struggles to get up to temperature.

HPs are run "Low and slow" whereas boilers are "hot and fast". Best strategy with a HP is to set it to the temperature you want the house to be at, and let it stay there. Whereas with a boiler you set it down whenever you are out and "boost" it about an hour before you get home/ get up in the AM.

If you are going to size for new ducts then I would imagine you can get the new ducts sized for HP. My parents use hot water rads & had a miniduct system for AC installed about 30 years ago (1920s house)-- I don't think that would work for a HP for heating.

What I don't know is, with these latest technologies of HP, how serious an issue this is. ie if you run it more like a boiler with a higher output temperature, does it just default to electric bar heating (which tends to be very expensive)?

The Green Building link in a post above is probably a good place to ask these sorts of questions.
CloseEnough
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Re: Heat pump in New England

Post by CloseEnough »

Valuethinker wrote: Thu Jul 28, 2022 11:24 am
CloseEnough wrote: Thu Jul 28, 2022 10:55 am Are there limitations on heat pump viability for installation in a very old (1800s) farm house? Wondering if this is an option I should look at when the time comes to replace current boiler for baseboard heat. Prior to that, heat was from a coal burner converted to run on propane, very inefficient. There is some ductwork related to the coal burner. No AC in this house, although with changing climate would be good to have. House does have solar panels on the roof. Thanks.
The efficiency of a heat pump is in inverse to the gap between input and output temperatures. Bigger gap, less efficient.

That does mean that the temp output of a HP is usually lower than it is for a boiler/ furnace. That can make an old house quite cold - it struggles to get up to temperature.

HPs are run "Low and slow" whereas boilers are "hot and fast". Best strategy with a HP is to set it to the temperature you want the house to be at, and let it stay there. Whereas with a boiler you set it down whenever you are out and "boost" it about an hour before you get home/ get up in the AM.

If you are going to size for new ducts then I would imagine you can get the new ducts sized for HP. My parents use hot water rads & had a miniduct system for AC installed about 30 years ago (1920s house)-- I don't think that would work for a HP for heating.

What I don't know is, with these latest technologies of HP, how serious an issue this is. ie if you run it more like a boiler with a higher output temperature, does it just default to electric bar heating (which tends to be very expensive)?

The Green Building link in a post above is probably a good place to ask these sorts of questions.
Interesting. Great answer, thanks!
ondarvr
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Re: Heat pump in New England

Post by ondarvr »

CloseEnough wrote: Thu Jul 28, 2022 10:55 am Are there limitations on heat pump viability for installation in a very old (1800s) farm house? Wondering if this is an option I should look at when the time comes to replace current boiler for baseboard heat. Prior to that, heat was from a coal burner converted to run on propane, very inefficient. There is some ductwork related to the coal burner. No AC in this house, although with changing climate would be good to have. House does have solar panels on the roof. Thanks.
Insulation and tightening up the house will have the biggest long term benefits, then size a new system accordingly.

We keep drifting back to the old school conversation of low and slow, or heat strips as backup. Use up-to-date technology and size the HP correctly and those things aren't really a concern.
ondarvr
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Re: Heat pump in New England

Post by ondarvr »

This study discusses most of the same topics in this thread, only with actual data to show their results. This was from 2018, so prices may be changing, plus available heatpump technology in the US has improved since then. I will also add, this was a study in the Southwest, but it includes zone 5 climates, so similar to what's being discussed here. But the local costs should be taken into account for NG, propane, oil and electricity.

The short version is. If you have a combination of heatpump and natural gas
backup system, it may be the lowest cost system, and staying with this as a replacement will probably be the lowest cost option.

If you have a heatpump with propane, oil or electric backup, converting to a cold climate heatpump and eliminating the backup heat source will probably be a good option.

This assumes your current ducting is in good condition and is in a controlled space. If new or significant upgrades are needed, then going to ductless is normally a better option.

In new construction, ductless comes out ahead because eliminating ducting reduces the upfront cost by many thousands, and is more efficient in use.

They also looked at greenhouse gas emissions, which made heatpumps even more attractive.


https://acrobat.adobe.com/link/review?u ... 64090b57bb
1moreyr
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Re: Heat pump in New England

Post by 1moreyr »

OP,
I have oil heat with radiators and live in New Hampshire.

I (finally, after many complaints from DW) installed an Fujitsu AC unit last year. It's actually 2 units. because of the radiators., it's a split on the first floor and central via the attic upstairs. Upstairs is completely balanced and downstairs is adequate.1-2 degrees between one end of house and other).

I use 700-750 gallons of oil every winter for the last 20. This past year, I used the first floor ductless in September, October, November as needed and set the upstairs zone for oil to about 65 (we like to sleep cold anyway). the furnace provides the hot water so it needs to run some anyway and I had locked in the oil price last year at $2.5/gallon. So I used the oil I had pre-purchased.

We used only 600 gallons this past year which was a first. At Todays prices that's about $750 savings. I forgot to use it in the spring as I probably would have saved closer to 250-300 gallons (potentially $1500 total?) . I also saw limited impact in the electric bill using it on first floor only

It worked very adequately as a supplement in reducing oil costs and probably could have run longer into the winter had I tried. With this years prices I will be using it longer and earlier in the spring.

full disclosure, I have also installed a pellet stove insert in my fireplace and pre-bought pellets for heat as well. last year the winter bill was $1850, this year if I changed nothing, I was looking at $4,000+ :shock:
Valuethinker
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Re: Heat pump in New England

Post by Valuethinker »

ondarvr wrote: Thu Jul 28, 2022 1:39 pm
CloseEnough wrote: Thu Jul 28, 2022 10:55 am Are there limitations on heat pump viability for installation in a very old (1800s) farm house? Wondering if this is an option I should look at when the time comes to replace current boiler for baseboard heat. Prior to that, heat was from a coal burner converted to run on propane, very inefficient. There is some ductwork related to the coal burner. No AC in this house, although with changing climate would be good to have. House does have solar panels on the roof. Thanks.
Insulation and tightening up the house will have the biggest long term benefits, then size a new system accordingly.

We keep drifting back to the old school conversation of low and slow, or heat strips as backup. Use up-to-date technology and size the HP correctly and those things aren't really a concern.
I don't think the physics of a heat pump have changed? The bigger the gap input to output temperature, the lower the COP?

It may be simply how HPs are installed here (England) but they are usually coupled with an underfloor heating system, and they run all the time. The standard advice from the industry is to not turn them off when you go out (as you would with an ordinary gas fired boiler) but to keep them more or less at desired temperature all the time. That advice is from heat pump gurus, not just official bodies.

Agree that the technology has really come on with low temperature performance (sub 0 degrees C).
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just frank
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Re: Heat pump in New England

Post by just frank »

Valuethinker wrote: Fri Jul 29, 2022 5:46 am
ondarvr wrote: Thu Jul 28, 2022 1:39 pm
CloseEnough wrote: Thu Jul 28, 2022 10:55 am Are there limitations on heat pump viability for installation in a very old (1800s) farm house? Wondering if this is an option I should look at when the time comes to replace current boiler for baseboard heat. Prior to that, heat was from a coal burner converted to run on propane, very inefficient. There is some ductwork related to the coal burner. No AC in this house, although with changing climate would be good to have. House does have solar panels on the roof. Thanks.
Insulation and tightening up the house will have the biggest long term benefits, then size a new system accordingly.

We keep drifting back to the old school conversation of low and slow, or heat strips as backup. Use up-to-date technology and size the HP correctly and those things aren't really a concern.
I don't think the physics of a heat pump have changed? The bigger the gap input to output temperature, the lower the COP?

It may be simply how HPs are installed here (England) but they are usually coupled with an underfloor heating system, and they run all the time. The standard advice from the industry is to not turn them off when you go out (as you would with an ordinary gas fired boiler) but to keep them more or less at desired temperature all the time. That advice is from heat pump gurus, not just official bodies.

Agree that the technology has really come on with low temperature performance (sub 0 degrees C).
After reading a bit about the new tech (hat tip @ondarvr), it looks like inverters give a 15-20% improvement in COP over single speed compressor motors... and vapor injection gives another 15-20% more. Inverters obv level the BTU output (allowing some upsizing the BTU output at low temps without overloading the system at higher ambient temps, units are rated in tons at 47°F). Vapor injection also allows about 10-15% higher BTU/h output at lower ambient by itself.

Bottom line is is that COP has gone up 30-50% at low temps while the BTU vs ambient temp is MUCH less steep than it used to be. While it was previously impractical to design a system for a balance point much below 20°F, now it is straightforward to design a balance point below 10°F or even lower.

Such tech describes the 'cold climate' mini tech. And is still rippling through the split systems.

Also, modern smart thermostats (even my old Ecobee3) can do smart recovery on HPs without firing the strips. And I can lock out the strips completely 10°F above my balance point (about 21-2°F ambient) without any problems. So I do a setback for comfort with no problems.
Valuethinker
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Re: Heat pump in New England

Post by Valuethinker »

just frank wrote: Fri Jul 29, 2022 11:58 am
Valuethinker wrote: Fri Jul 29, 2022 5:46 am
ondarvr wrote: Thu Jul 28, 2022 1:39 pm
CloseEnough wrote: Thu Jul 28, 2022 10:55 am Are there limitations on heat pump viability for installation in a very old (1800s) farm house? Wondering if this is an option I should look at when the time comes to replace current boiler for baseboard heat. Prior to that, heat was from a coal burner converted to run on propane, very inefficient. There is some ductwork related to the coal burner. No AC in this house, although with changing climate would be good to have. House does have solar panels on the roof. Thanks.
Insulation and tightening up the house will have the biggest long term benefits, then size a new system accordingly.

We keep drifting back to the old school conversation of low and slow, or heat strips as backup. Use up-to-date technology and size the HP correctly and those things aren't really a concern.
I don't think the physics of a heat pump have changed? The bigger the gap input to output temperature, the lower the COP?

It may be simply how HPs are installed here (England) but they are usually coupled with an underfloor heating system, and they run all the time. The standard advice from the industry is to not turn them off when you go out (as you would with an ordinary gas fired boiler) but to keep them more or less at desired temperature all the time. That advice is from heat pump gurus, not just official bodies.

Agree that the technology has really come on with low temperature performance (sub 0 degrees C).
After reading a bit about the new tech (hat tip @ondarvr), it looks like inverters give a 15-20% improvement in COP over single speed compressor motors... and vapor injection gives another 15-20% more. Inverters obv level the BTU output (allowing some upsizing the BTU output at low temps without overloading the system at higher ambient temps, units are rated in tons at 47°F). Vapor injection also allows about 10-15% higher BTU/h output at lower ambient by itself.

Bottom line is is that COP has gone up 30-50% at low temps while the BTU vs ambient temp is MUCH less steep than it used to be. While it was previously impractical to design a system for a balance point much below 20°F, now it is straightforward to design a balance point below 10°F or even lower.

Such tech describes the 'cold climate' mini tech. And is still rippling through the split systems.

Also, modern smart thermostats (even my old Ecobee3) can do smart recovery on HPs without firing the strips. And I can lock out the strips completely 10°F above my balance point (about 21-2°F ambient) without any problems. So I do a setback for comfort with no problems.
Thank you.

As you know, our winter temps very seldom get down to say -5 C. 0-5C is more likely.

I have no reason to think we lack HPs as efficient as yours. Daikin is certainly a name here. Mitsubishi for commercial equipment (and possibly residential).

However, in a Victorian house without wall insulation, the advice is still that HPs won't do it. Part of the problem is the H/W rads & pipes -- steel panel radiators & small diameter pipes (equivalent houses in N America would have much thicker diameter piping & rads).

But my Vaillant gas boiler puts out 30 kw (but can modulate down to something like 15 kw). The biggest HP I could buy would be something like 12.5 kw. So in principle I might need at least 2 if not 3. I am trying the rads at 55- 60C rather than the 70C they were set up for, just to see how uncomfortable that is in winter.

So it's not at all clear to me how I would retrofit a HP. Not without installing solid wall insulation. At some point this will probably happen, but it would cost me a lot more than it would save me, even at this winter's prices. (I might finally break down & order double paned windows - we still have quite a bit of the original glass, unfortunately, and it will be sad to lose that; in addition with the cost of natural gas, the price of glass is going to be scary this winter).
cmr79
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Re: Heat pump in New England

Post by cmr79 »

Valuethinker wrote: Fri Jul 29, 2022 12:24 pm
just frank wrote: Fri Jul 29, 2022 11:58 am
Valuethinker wrote: Fri Jul 29, 2022 5:46 am
ondarvr wrote: Thu Jul 28, 2022 1:39 pm
CloseEnough wrote: Thu Jul 28, 2022 10:55 am Are there limitations on heat pump viability for installation in a very old (1800s) farm house? Wondering if this is an option I should look at when the time comes to replace current boiler for baseboard heat. Prior to that, heat was from a coal burner converted to run on propane, very inefficient. There is some ductwork related to the coal burner. No AC in this house, although with changing climate would be good to have. House does have solar panels on the roof. Thanks.
Insulation and tightening up the house will have the biggest long term benefits, then size a new system accordingly.

We keep drifting back to the old school conversation of low and slow, or heat strips as backup. Use up-to-date technology and size the HP correctly and those things aren't really a concern.
I don't think the physics of a heat pump have changed? The bigger the gap input to output temperature, the lower the COP?

It may be simply how HPs are installed here (England) but they are usually coupled with an underfloor heating system, and they run all the time. The standard advice from the industry is to not turn them off when you go out (as you would with an ordinary gas fired boiler) but to keep them more or less at desired temperature all the time. That advice is from heat pump gurus, not just official bodies.

Agree that the technology has really come on with low temperature performance (sub 0 degrees C).
After reading a bit about the new tech (hat tip @ondarvr), it looks like inverters give a 15-20% improvement in COP over single speed compressor motors... and vapor injection gives another 15-20% more. Inverters obv level the BTU output (allowing some upsizing the BTU output at low temps without overloading the system at higher ambient temps, units are rated in tons at 47°F). Vapor injection also allows about 10-15% higher BTU/h output at lower ambient by itself.

Bottom line is is that COP has gone up 30-50% at low temps while the BTU vs ambient temp is MUCH less steep than it used to be. While it was previously impractical to design a system for a balance point much below 20°F, now it is straightforward to design a balance point below 10°F or even lower.

Such tech describes the 'cold climate' mini tech. And is still rippling through the split systems.

Also, modern smart thermostats (even my old Ecobee3) can do smart recovery on HPs without firing the strips. And I can lock out the strips completely 10°F above my balance point (about 21-2°F ambient) without any problems. So I do a setback for comfort with no problems.
Thank you.

As you know, our winter temps very seldom get down to say -5 C. 0-5C is more likely.

I have no reason to think we lack HPs as efficient as yours. Daikin is certainly a name here. Mitsubishi for commercial equipment (and possibly residential).

However, in a Victorian house without wall insulation, the advice is still that HPs won't do it. Part of the problem is the H/W rads & pipes -- steel panel radiators & small diameter pipes (equivalent houses in N America would have much thicker diameter piping & rads).

But my Vaillant gas boiler puts out 30 kw (but can modulate down to something like 15 kw). The biggest HP I could buy would be something like 12.5 kw. So in principle I might need at least 2 if not 3. I am trying the rads at 55- 60C rather than the 70C they were set up for, just to see how uncomfortable that is in winter.

So it's not at all clear to me how I would retrofit a HP. Not without installing solid wall insulation. At some point this will probably happen, but it would cost me a lot more than it would save me, even at this winter's prices. (I might finally break down & order double paned windows - we still have quite a bit of the original glass, unfortunately, and it will be sad to lose that; in addition with the cost of natural gas, the price of glass is going to be scary this winter).
Is this because of your limited need for heating/cooling over the course of the year? With how much higher the electricity and natural gas prices are in the UK vs US, I would imagine that improving your home's thermal efficiency would have the best ROI vs anything else you could do.

With natural gas prices being disproportionately higher there, though, I could see an argument for installing a heat pump to use when temperatures are more mild while keeping the gas furnace for occasional use during the coldest periods. That is our setup and a slam dunk (in my mind) for OP...I don't see any reason why it couldn't work for you, even if your house is too leaky to rely on ASHP technology as a sole heating solution.
ondarvr
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Re: Heat pump in New England

Post by ondarvr »

From a site listed earlier in this thread, GreenHome Institute.

This goes over ducted mini splits and other information relevant to this subject, like cold climate applications and optimizing performance.

https://youtu.be/DbOVrk-J1_s
Valuethinker
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Re: Heat pump in New England

Post by Valuethinker »

cmr79 wrote: Fri Jul 29, 2022 4:15 pm
Valuethinker wrote: Fri Jul 29, 2022 12:24 pm
just frank wrote: Fri Jul 29, 2022 11:58 am
Valuethinker wrote: Fri Jul 29, 2022 5:46 am
ondarvr wrote: Thu Jul 28, 2022 1:39 pm

Insulation and tightening up the house will have the biggest long term benefits, then size a new system accordingly.

We keep drifting back to the old school conversation of low and slow, or heat strips as backup. Use up-to-date technology and size the HP correctly and those things aren't really a concern.
I don't think the physics of a heat pump have changed? The bigger the gap input to output temperature, the lower the COP?

It may be simply how HPs are installed here (England) but they are usually coupled with an underfloor heating system, and they run all the time. The standard advice from the industry is to not turn them off when you go out (as you would with an ordinary gas fired boiler) but to keep them more or less at desired temperature all the time. That advice is from heat pump gurus, not just official bodies.

Agree that the technology has really come on with low temperature performance (sub 0 degrees C).
After reading a bit about the new tech (hat tip @ondarvr), it looks like inverters give a 15-20% improvement in COP over single speed compressor motors... and vapor injection gives another 15-20% more. Inverters obv level the BTU output (allowing some upsizing the BTU output at low temps without overloading the system at higher ambient temps, units are rated in tons at 47°F). Vapor injection also allows about 10-15% higher BTU/h output at lower ambient by itself.

Bottom line is is that COP has gone up 30-50% at low temps while the BTU vs ambient temp is MUCH less steep than it used to be. While it was previously impractical to design a system for a balance point much below 20°F, now it is straightforward to design a balance point below 10°F or even lower.

Such tech describes the 'cold climate' mini tech. And is still rippling through the split systems.

Also, modern smart thermostats (even my old Ecobee3) can do smart recovery on HPs without firing the strips. And I can lock out the strips completely 10°F above my balance point (about 21-2°F ambient) without any problems. So I do a setback for comfort with no problems.
Thank you.

As you know, our winter temps very seldom get down to say -5 C. 0-5C is more likely.

I have no reason to think we lack HPs as efficient as yours. Daikin is certainly a name here. Mitsubishi for commercial equipment (and possibly residential).

However, in a Victorian house without wall insulation, the advice is still that HPs won't do it. Part of the problem is the H/W rads & pipes -- steel panel radiators & small diameter pipes (equivalent houses in N America would have much thicker diameter piping & rads).

But my Vaillant gas boiler puts out 30 kw (but can modulate down to something like 15 kw). The biggest HP I could buy would be something like 12.5 kw. So in principle I might need at least 2 if not 3. I am trying the rads at 55- 60C rather than the 70C they were set up for, just to see how uncomfortable that is in winter.

So it's not at all clear to me how I would retrofit a HP. Not without installing solid wall insulation. At some point this will probably happen, but it would cost me a lot more than it would save me, even at this winter's prices. (I might finally break down & order double paned windows - we still have quite a bit of the original glass, unfortunately, and it will be sad to lose that; in addition with the cost of natural gas, the price of glass is going to be scary this winter).
Is this because of your limited need for heating/cooling over the course of the year? With how much higher the electricity and natural gas prices are in the UK vs US, I would imagine that improving your home's thermal efficiency would have the best ROI vs anything else you could do.

With natural gas prices being disproportionately higher there, though, I could see an argument for installing a heat pump to use when temperatures are more mild while keeping the gas furnace for occasional use during the coldest periods. That is our setup and a slam dunk (in my mind) for OP...I don't see any reason why it couldn't work for you, even if your house is too leaky to rely on ASHP technology as a sole heating solution.
The basic problem with a HP and an uninsulated, single solid brick wall, house is that it can't keep the house at the desired temperature. That seems to be the consensus here. 30kw boiler output v 12.5kw for a heat pump.

I have not heard of hybrid arrangements, here. It must be possible but more probably in large detached homes. Ours is a terrace ie row house, end of terrace. The loss of internal space of having 2 systems is a concern & that would be true of most London houses (but it's not impossible).

Gas boilers are also far, far cheaper than HPs at this point (like £2000 v £6000 sort of numbers ie 3x). Throw in a complete replacement of pipes & rads (bigger diameters) then it's a £10-15k conversion. Solid wall insulation would be extremely disruptive (internal) and could produce serious condensation problems in the walls (without an air cavity, the dew point could wind up being inside the wall). Probably another £15-20k. There's also a problem with flammability of external cladding (I might get away with external wall insulation down the side and back ie not changing the fundamental street appearance of the house). I am probably most worried by the absence of skillsets in the building trades to do this-- I don't think enough is known about condensation/ dampness in retrofits. Plus the hassle factor.

Electricity has now jumped to about 35p/ kwhr (so something like 42 US cents). Gas to 10p/ kwhr. So the greater efficiency of a HP is marginal - just about breakeven.
cmr79
Posts: 169
Joined: Mon Dec 02, 2013 4:25 pm

Re: Heat pump in New England

Post by cmr79 »

Valuethinker wrote: Fri Aug 05, 2022 4:16 am
cmr79 wrote: Fri Jul 29, 2022 4:15 pm
Valuethinker wrote: Fri Jul 29, 2022 12:24 pm
just frank wrote: Fri Jul 29, 2022 11:58 am
Valuethinker wrote: Fri Jul 29, 2022 5:46 am

I don't think the physics of a heat pump have changed? The bigger the gap input to output temperature, the lower the COP?

It may be simply how HPs are installed here (England) but they are usually coupled with an underfloor heating system, and they run all the time. The standard advice from the industry is to not turn them off when you go out (as you would with an ordinary gas fired boiler) but to keep them more or less at desired temperature all the time. That advice is from heat pump gurus, not just official bodies.

Agree that the technology has really come on with low temperature performance (sub 0 degrees C).
After reading a bit about the new tech (hat tip @ondarvr), it looks like inverters give a 15-20% improvement in COP over single speed compressor motors... and vapor injection gives another 15-20% more. Inverters obv level the BTU output (allowing some upsizing the BTU output at low temps without overloading the system at higher ambient temps, units are rated in tons at 47°F). Vapor injection also allows about 10-15% higher BTU/h output at lower ambient by itself.

Bottom line is is that COP has gone up 30-50% at low temps while the BTU vs ambient temp is MUCH less steep than it used to be. While it was previously impractical to design a system for a balance point much below 20°F, now it is straightforward to design a balance point below 10°F or even lower.

Such tech describes the 'cold climate' mini tech. And is still rippling through the split systems.

Also, modern smart thermostats (even my old Ecobee3) can do smart recovery on HPs without firing the strips. And I can lock out the strips completely 10°F above my balance point (about 21-2°F ambient) without any problems. So I do a setback for comfort with no problems.
Thank you.

As you know, our winter temps very seldom get down to say -5 C. 0-5C is more likely.

I have no reason to think we lack HPs as efficient as yours. Daikin is certainly a name here. Mitsubishi for commercial equipment (and possibly residential).

However, in a Victorian house without wall insulation, the advice is still that HPs won't do it. Part of the problem is the H/W rads & pipes -- steel panel radiators & small diameter pipes (equivalent houses in N America would have much thicker diameter piping & rads).

But my Vaillant gas boiler puts out 30 kw (but can modulate down to something like 15 kw). The biggest HP I could buy would be something like 12.5 kw. So in principle I might need at least 2 if not 3. I am trying the rads at 55- 60C rather than the 70C they were set up for, just to see how uncomfortable that is in winter.

So it's not at all clear to me how I would retrofit a HP. Not without installing solid wall insulation. At some point this will probably happen, but it would cost me a lot more than it would save me, even at this winter's prices. (I might finally break down & order double paned windows - we still have quite a bit of the original glass, unfortunately, and it will be sad to lose that; in addition with the cost of natural gas, the price of glass is going to be scary this winter).
Is this because of your limited need for heating/cooling over the course of the year? With how much higher the electricity and natural gas prices are in the UK vs US, I would imagine that improving your home's thermal efficiency would have the best ROI vs anything else you could do.

With natural gas prices being disproportionately higher there, though, I could see an argument for installing a heat pump to use when temperatures are more mild while keeping the gas furnace for occasional use during the coldest periods. That is our setup and a slam dunk (in my mind) for OP...I don't see any reason why it couldn't work for you, even if your house is too leaky to rely on ASHP technology as a sole heating solution.
The basic problem with a HP and an uninsulated, single solid brick wall, house is that it can't keep the house at the desired temperature. That seems to be the consensus here. 30kw boiler output v 12.5kw for a heat pump.

I have not heard of hybrid arrangements, here. It must be possible but more probably in large detached homes. Ours is a terrace ie row house, end of terrace. The loss of internal space of having 2 systems is a concern & that would be true of most London houses (but it's not impossible).

Gas boilers are also far, far cheaper than HPs at this point (like £2000 v £6000 sort of numbers ie 3x). Throw in a complete replacement of pipes & rads (bigger diameters) then it's a £10-15k conversion. Solid wall insulation would be extremely disruptive (internal) and could produce serious condensation problems in the walls (without an air cavity, the dew point could wind up being inside the wall). Probably another £15-20k. There's also a problem with flammability of external cladding (I might get away with external wall insulation down the side and back ie not changing the fundamental street appearance of the house). I am probably most worried by the absence of skillsets in the building trades to do this-- I don't think enough is known about condensation/ dampness in retrofits. Plus the hassle factor.

Electricity has now jumped to about 35p/ kwhr (so something like 42 US cents). Gas to 10p/ kwhr. So the greater efficiency of a HP is marginal - just about breakeven.
We have a hybrid system...we have a propane furnace and an ASHP, though we are in a detached SFH in the mid-Atlantic US. Our furnace and heat pump function seamlessly and use the same ducting, which is also necessary as the heat pump is also our air conditioning in the summer. I think the only thing necessary to have upgraded our AC unit to an ASHP was a new smart thermostat that could handle managing the primary/backup heating options based on outside air temperatures, though admittedly I didn't own the house when this was done 10+ years ago.

It sounds like systems might have significantly different design strategies in England, which is why I wondered whether it was due to more months/year where the milder weather makes any climate control unnecessary. The crazy high (from my perspective) energy prices over there would seem to make even expensive insulation costs cost-effective regardless of what your heating source is, unless you don't need to use heat nearly as often as we do.
Valuethinker
Posts: 45273
Joined: Fri May 11, 2007 11:07 am

Re: Heat pump in New England

Post by Valuethinker »

cmr79 wrote: Fri Aug 05, 2022 10:12 am

We have a hybrid system...we have a propane furnace and an ASHP, though we are in a detached SFH in the mid-Atlantic US. Our furnace and heat pump function seamlessly and use the same ducting, which is also necessary as the heat pump is also our air conditioning in the summer. I think the only thing necessary to have upgraded our AC unit to an ASHP was a new smart thermostat that could handle managing the primary/backup heating options based on outside air temperatures, though admittedly I didn't own the house when this was done 10+ years ago.

It sounds like systems might have significantly different design strategies in England, which is why I wondered whether it was due to more months/year where the milder weather makes any climate control unnecessary. The crazy high (from my perspective) energy prices over there would seem to make even expensive insulation costs cost-effective regardless of what your heating source is, unless you don't need to use heat nearly as often as we do.
How much insulation does your home have?

We have proper insulation, the full 9 yards (18"?) in the roof because we extended into the loft.

The rest of the house... none. Brick walls (single shell). No basement (they are not common here).

The thermal characteristics of my house, it doesn't "heat up" and then stay that way in cold weather (sub about 50 F). It heats up & then needs constant refreshes from the system to stay hot. To conserve gas, I am experimenting with a lower water temperature in the rads (60C rather than over 70C)-- we will see if that works. If it does then that might prove to be a way forward to a HP.

I assume that eventually houses like mine will either be compulsorily upgraded in insulation OR will have hybrid hydrogen burner + HP system.

People do not have AC. But they are starting too - we had 2 days over 100F a couple of weeks ago, and it's not a dry heat.

Heating systems are "indirect" -- same boiler heats hot water to the tank & heats the rads.
cmr79
Posts: 169
Joined: Mon Dec 02, 2013 4:25 pm

Re: Heat pump in New England

Post by cmr79 »

Valuethinker wrote: Fri Aug 05, 2022 12:12 pm
cmr79 wrote: Fri Aug 05, 2022 10:12 am

We have a hybrid system...we have a propane furnace and an ASHP, though we are in a detached SFH in the mid-Atlantic US. Our furnace and heat pump function seamlessly and use the same ducting, which is also necessary as the heat pump is also our air conditioning in the summer. I think the only thing necessary to have upgraded our AC unit to an ASHP was a new smart thermostat that could handle managing the primary/backup heating options based on outside air temperatures, though admittedly I didn't own the house when this was done 10+ years ago.

It sounds like systems might have significantly different design strategies in England, which is why I wondered whether it was due to more months/year where the milder weather makes any climate control unnecessary. The crazy high (from my perspective) energy prices over there would seem to make even expensive insulation costs cost-effective regardless of what your heating source is, unless you don't need to use heat nearly as often as we do.
How much insulation does your home have?

We have proper insulation, the full 9 yards (18"?) in the roof because we extended into the loft.

The rest of the house... none. Brick walls (single shell). No basement (they are not common here).

The thermal characteristics of my house, it doesn't "heat up" and then stay that way in cold weather (sub about 50 F). It heats up & then needs constant refreshes from the system to stay hot. To conserve gas, I am experimenting with a lower water temperature in the rads (60C rather than over 70C)-- we will see if that works. If it does then that might prove to be a way forward to a HP.

I assume that eventually houses like mine will either be compulsorily upgraded in insulation OR will have hybrid hydrogen burner + HP system.

People do not have AC. But they are starting too - we had 2 days over 100F a couple of weeks ago, and it's not a dry heat.

Heating systems are "indirect" -- same boiler heats hot water to the tank & heats the rads.
We have a relatively new (<25yo) house, and the thermal efficiency overall is better than the 90yo solid brick walled house we were in previously despite being 3x the size. Couldn't tell you what is actually inside of the walls, but I can say that our windows are--by a significant margin--the thermal weak point currently.

Seems like it would be overly complex to add an ASHP to your current boiler/radiator system, or at least less likely to be cost effective. If this summer heat persists in England/Western Europe, though, perhaps a ductless mini split heat pump system in a few specific rooms might be a reasonable investment as much for cooling as heating! We are just finishing vacationing in an 1800s Victorian beach house with Mitsubishi mini splits--can't comment on the heating, of course, but the cooling has been great despite the house being overtly terrible in terms of thermal efficiency.
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