What's the latest on air to water heat pumps in the US market?

JakeCK

Jamie Hall said:

I don't think folks are making it more complicated. The plain problem is this: so far as I know, no one makes an air to water or steam heat pump which will provide 180 degree water never mind steam, when it's 10 below out. When that happens, maybe a lot of folks will be able to use the technology.

I guess I'm lucky I've never needed 180f water. My aquastat is set to 165f I believe. I've only bounced off that during recovery from large setbacks on cold nights, and twice during normal operation. Both of those times were during a polar vortex. The most recent a few years back it got down to -15 with a -30 wind chill. Decidedly colder than design... by over 20f. And that last time I just pointed a couple fans at the largest radiators. It recovered quickly and then proceeded to over heat the house. 

I wouldn't expect most to have the presence of mind to do that with fans though so I guess we can ignore that.
Its interesting to think though, had my boiler been sized correctly. I wouldn't have bounced off the stat, it just wouldn't have had enough @ $$ to meet the demand.

The Steam Whisperer

The fact that typical air to water heat pumps probably can't generate 180F water really is only a minor issue with a retrofit. I believe someone has already said this that for the typical heat pump can probably handle 90% of the heating season at only 60% of the system capacity. On a system that requires 180F on design day, that puts the supply water temp at around 135F or less for 90% of the heating season I have found very very few hot water systems that need 180F water at design.... even newer baseboard systems usually need only 160F, especially in multi-family buildings. Old Gravity radiator systems usually only need 140F to 150F. And you would be installing a much smaller unit at 60% capacity that would not have as much impact on the peak load on the home's electric service and the grid.
This is simply good baseloading system design.

On most of the two pipe steam systems we work on, an air to water heat pump could be used to preheat the very cool condensate water......usually around room temperature most of the year and topping out at around 85F at design.
Of course the fundamental problems still remain.....
1) Widespread adoption of this technology would likely cause the electrical grid to be overloaded.
2) Little or no reduction in pollution produced from energy sources unless the electricity is generated from low or non polluting sources.
3) Short lived equipment compared to the 30 to 40 year life of conventional boilers. Fortunately this is not a huge issue with and add on retrofit to an existing system system. The current craze with installation ductless split systems for both heating and cooling is incredibly expensive since the owners have now bought into having to replace complete systems every 15 years or so. Not very green either considering the embodied pollution in producing products multiple times instead of only once with most conventional systems.

hot_rod

The current craze with installation ductless split systems for both heating and cooling is incredibly expensive since the owners have now bought into having to replace complete systems every 15 years or so. Not very green either considering the embodied pollution in producing products multiple times instead of only once with most conventional systems.

Looks like cleaning and servicing mini splits is not that much fun. You drape a lobster bib under them to clean the coils?
What is the cost to have them cleaned every few years.
I think you are correct in that they are intended to be throw away units.
I think of mod cons and A2WHP as a 15- 20 year product.
Plenty of Munchkins made the 20 year mark and they were the pioneer product

Solid_Fuel_Man

Here in Maine we are having an 80%.....yes 80% increase in electricity cost. We were at $0.157 per Kw hour all said and done....and now we will be over $0.22!

Makes anything using electricity not look so good. But with $3.50 a gallon oil it is all relitive I guess. 

I've been waiting for a good Air to Water HP for slab applications. Buy electric based heating (even if it is 300% efficient) is making less sense. And I'm a sparky! 

I'll keep burning wood....it grows on trees ya know.

JakeCK

Solid_Fuel_Man said:

Here in Maine we are having an 80%.....yes 80% increase in electricity cost. We were at $0.157 per Kw hour all said and done....and now we will be over $0.22!

I say bring it, I dare CEI to double my rate. lol

This is literally at the winter solstice, and with a hpwh.  1.4mhw since mid Oct, I can't wait to see June.

Jamie Hall

@The Steam Whisperer is right -- one could use a heat pump as a feedwater preheater for steam systems with current technology. Unfortunately, only about 10% of the energy involved in a steam system is accounted for in feedwater preheating.

There is no thermodynamic reason why a heat pump -- probably two stage -- can't be made which creates steam. Given the correct choice of refrigerant or refrigerants for two stage, it could probably have reasonably high COP even.

I'm not sure if the market is there. But I'm also not sure if anyone has even looked at the market. Spacepak ( @megharrington ) are you listening?

pecmsg

Jamie Hall said:

@The Steam Whisperer is right -- one could use a heat pump as a feedwater preheater for steam systems with current technology. Unfortunately, only about 10% of the energy involved in a steam system is accounted for in feedwater preheating. There is no thermodynamic reason why a heat pump -- probably two stage -- can't be made which creates steam. Given the correct choice of refrigerant or refrigerants for two stage, it could probably have reasonably high COP even. I'm not sure if the market is there. But I'm also not sure if anyone has even looked at the market. Spacepak ( @megharrington ) are you listening?

Reverse Cascade System. 

In theory it’s possible. The problem is the temperatures required. 

Jamie Hall

True, @pecmsg . It's in the choice of refrigerant...

The Steam Whisperer

Jamie

" @The Steam Whisperer is right -- one could use a heat pump as a feedwater preheater for steam systems with current technology. Unfortunately, only about 10% of the energy involved in a steam system is accounted for in feedwater preheating."

I am just double checking.....is "feedwater" fresh water added to the system or water returning from the system. I was referring to water returning from the system, which is typically around room temperature on the two pipe systems we have upgraded. This water could also be used for a condensing heat exchanger on a steamer. The Art Institute in Chicago has a condensing economizer that brings the steam boilers efficiency up to 90 to 91 %.

Jamie Hall

I was referring to the returning condensate, @The Steam Whisperer . If there's enough of it, using a feedwater heater from low temperature stack gas as the Art Institute does is a very good idea indeed. I can easily see picking up a good 8 to 10 percent on efficiency that way. The same principle, of course, could be used on residential/small building sized systems as well, but first off I don't know anyone who makes a suitable heat exchanger (the stack side would have to be really corrosion resistant!), and one would almost have to use induced draught -- and on the whole I question the economic benefit and rate of return.

The Steam Whisperer

Yes, I've looked at smaller scale heat exchanger but the main problem is that there is not enough return water flow volume to get a decent increase in efficiency. Of course you get most of that efficiency back in electrical savings if you have to pump the condensate. You're moving about 1/80 the water volume as a hot water system, so 1/80 the pumping power is needed.
Also, I think the increase in efficiency is probably more like 4%..... good old steam boilers tend to run in the mid to upper 80's in efficiency in many cases. We've had sub 300Fnataural gas stack temps with tight mixtures on some old Pacifics running vacuum pressure steam.

I suspect the best use for condensing economizers on steamers is for heating DHW... probably much higher water flow volume to make the heat exchange more effective.
I hadn't thought of the heat pump option until now.

Solid_Fuel_Man

JakeCK said:

Solid_Fuel_Man said:

Here in Maine we are having an 80%.....yes 80% increase in electricity cost. We were at $0.157 per Kw hour all said and done....and now we will be over $0.22!

I say bring it, I dare CEI to double my rate. lol

This is literally at the winter solstice, and with a hpwh.  1.4mhw since mid Oct, I can't wait to see June.

Pretty much the same attitude I've had with any of the fossil fuel price issues of the last 15 years. I keep burning wood and am completly isolated from the electricity and fossil fuel market. If only I could make my van run on wood practically 😫 

JakeCK

Solid_Fuel_Man said:

Pretty much the same attitude I've had with any of the fossil fuel price issues of the last 15 years. I keep burning wood and am completly isolated from the electricity and fossil fuel market. If only I could make my van run on wood practically 😫

Wood gas generator on the back of your van? lol