High(est) efficiency air source heat pump?

[NiHaoMike]

Originally Posted by AC_Hacker

Is this a guess?

-AC

It's definitely much cheaper to install compared to a geothermal system unless you're doing the work yourself. In hot, dry climates where the dew point is low, a well designed evaporative hybrid would be able to operate in evaporative only ("bypass") mode most of the time.

[AC_Hacker]

Originally Posted by NiHaoMike

It's definitely much cheaper to install compared to a geothermal system unless you're doing the work yourself. In hot, dry climates where the dew point is low, a well designed evaporative hybrid would be able to operate in evaporative only ("bypass") mode most of the time.

I understand the principles involved, and I agree that it looks better, my question is do you have any studies or data to support your statement?

Having data or studies is not unreasonable.

The reason I ask is that the GSHP industry began for the purpose of cooling homes in Oklahoma, where summers are both hot and dry, and GSHP was recognized for its long term economic advantage.

So, if there is data to support the comparative advantage of evaporative + vapor compression, it would be very useful.

-AC

[jeff5may]

Originally Posted by NiHaoMike

It's definitely much cheaper to install compared to a geothermal system unless you're doing the work yourself. In hot, dry climates where the dew point is low, a well designed evaporative hybrid would be able to operate in evaporative only ("bypass") mode most of the time.

This may be close to true in Arizona or New Mexico. The only problem to it in this climate is that water is scarce (expensive) and is routinely rationed during the summer months. Wells are also deep, so cost to pump is high as well.

However, the OP lives in New England. This is in no way a hot, dry climate by any stretch of the imagination. I'm guessing cooling demand is negligible compared to heating demand.

[MN Renovator]

Originally Posted by NeilBlanchard

...I called a friend who has a Hallowell Acadia 2-stage system and while he was initially very happy with it, it has now crapped out, and since that company is out of business, and the compressor subcontractor won't help him; he's got a $12K dead white elephant...

There are a few threads on HVAC-Talk that have some pretty serious horror stories of the Hallowell Acadia. They used the compressor in a way against the direction of the manufacturer and therefore they wouldn't warranty the compressor and they went out of business quickly. Your friend is an unfortunate victim here along with everyone else who touched that system.

[MN Renovator]

Looking at the AHRI ratings, I'm really loving the Panasonic XE series as a well rounded unit for heating output, cooling EER/SEER, and HSPF. The service sheet specs look beautiful to me too. Prior to this I liked the numbers of the Fujitsu the best and wanted that unit but now I'm looking at the 12k in the Panasonic XE series.

[NiHaoMike]

Originally Posted by jeff5may

This may be close to true in Arizona or New Mexico. The only problem to it in this climate is that water is scarce (expensive) and is routinely rationed during the summer months. Wells are also deep, so cost to pump is high as well.

However, the OP lives in New England. This is in no way a hot, dry climate by any stretch of the imagination. I'm guessing cooling demand is negligible compared to heating demand.

Generating electricity usually uses a surprising amount of water. Also, water is renewable, while coal and oil are not.

I was referring to heat pumps in general, not the specific use case. In a climate where heating dominates, a DIY geothermal system makes a lot of sense. Maybe even with solar thermal to boost efficiency on sunny days as well as possibly store heat (and supply hot water) during the summer.

Another option is to mine Bitcoins (or Litecoins) to "subsidize" the cost of electricity. Energy efficiency is the same as plain resistive heat, but depending on many factors, it can be economically competitive with heat pumps or even return a profit.

[AC_Hacker]

Originally Posted by NeilBlanchard

I'm wondering about solar water heaters with a large storage tank for a heat source for heat pumps?

This could work pretty well for you, if you have a very well-sealed house with better than code insulation, and goodly southern exposure with minimal obstructions.

Then there's the tank part, and insulation and all. If you figure that a pint of water can yield one BTU per every degree F, then if you look at a 60 gallon water heater...

8 pints per gallon X 60 gallons = 480 pints.

So, if your solar heated up that 60 gallon tank to maybe 160 degrees F, and you wanted to be able to draw out heat down to maybe 38 degrees F (leave a margin so you don't freeze your heat excchanger)...

delta-T = 160 - 38 = 122 degrees F

So the total heat that you'd be able to extract would be...

122 degrees F X 480 pints = 58,560 BTU

So the next question (it should be the FIRST QUESTION) is what is the heat loss of your house?

The heat loss of your house will vary according to the outdoor temperature and of course your insulation & infiltration losses.

But on a very cold New England night, a typical house could very easily lose 60,000 BTUs per hour. So on those nights your solar assisted heat pump system could keep you cozy for a bit less than an hour, assuming that your heat pump could extract the heat from the tank at that rate.

This is where radical insulation like house wrapping, and high performance windows and insulated doors, and extreme attention to infiltration losses comes into play.

So if you could reduce your heat losses by half, you'd be cozy for nearly two hours... if you also doubled the size of your solar-assisted heat pump, you'd be cozy for four hours.

It is natural, when thinking of a better heating system, to focus on the heat producing part of the problem... it is a strategy that has seen us through 80,000 years of evolution. But most of the time it's smarter to focus on prevention of loss of heat.

Originally Posted by NeilBlanchard

Also, what is the ballpark installed cost of a single zone mini split system, like the larger Fujitsu units?

This is a good job for Google.

-AC

[AC_Hacker]

Originally Posted by NeilBlanchard

I'm wondering about solar water heaters with a large storage tank for a heat source for heat pumps?

This could work pretty well for you, if you have a very well-sealed house with better than code insulation, and goodly southern exposure with minimal obstructions.

Then there's the tank part, and insulation and all. If you figure that a pint of water can yield one BTU per every degree F, then if you look at a 60 gallon water heater...

8 pints per gallon X 60 gallons = 480 pints.

So, if your solar heated up that 60 gallon tank to maybe 160 degrees F, and you wanted to be able to draw out heat down to maybe 38 degrees F (leave a margin so you don't freeze your heat excchanger)...

delta-T = 160 - 38 = 122 degrees F

So the total heat that you'd be able to extract would be...

122 degrees F X 480 pints = 58,560 BTU

So the next question (it should be the FIRST QUESTION) is what is the heat loss of your house?

The heat loss of your house will vary according to the outdoor temperature and of course your insulation & infiltration losses.

But on a very cold New England night, a typical house could very easily lose 60,000 BTUs per hour. So on those nights your solar assisted heat pump system could keep you cozy for a bit less than an hour, assuming that your heat pump could extract the heat from the tank at that rate.

This is where radical insulation like house wrapping, and high performance windows and insulated doors, and extreme attention to infiltration losses comes into play.

So if you could reduce your heat losses by half, you'd be cozy for nearly two hours... if you also doubled the size of your solar-assisted heat pump, you'd be cozy for four hours.

It is natural, when thinking of a better heating system, to focus on the heat producing part of the problem... it is a strategy that has seen us through 80,000 years of evolution. But most of the time it's smarter to focus on prevention of loss of heat.

Originally Posted by NeilBlanchard

Also, what is the ballpark installed cost of a single zone mini split system, like the larger Fujitsu units?

This is a good job for Google.

-AC