Actual Performance of Cold Climate Heat Pump in Upstate NY

SteamingatMohawk

My home has a 1980s vintage heat pump with gas backup that continues to work well. We don't use the heat pump for heat because I believe at the time of manufacture they were not very efficient below 40F.

I also own a nearly 100 year old converted 2 family that has a very well working steam system. Thanks to the help on HH and Charlie Garrity in the Springfield, MA area.

I have been interested in cold climate units and several years ago, I read about some studies in them.

Occasionally, when I go to the Orange store, I get asked if I am interested in the more modern units.

My first question is always, "What do you do when the temperature gets well below zero?"

I have gotten answers like,

"Wait until it warms up.", which doesn't work for my house or for my rental property.

"These are not for whole houses, just things like add-ons."

"Keep your rental house steam system as a backup.", which is not very satisfying, since the purpose of the change would be to get rid of the steam system.

Are there in existence any systems that can serve a whole house, and how do they deal with colder than -15F conditions?

In_New_England

I looked into heat pumps to move off oil heat hot water baseboard near Boston. My takeaways were

Tight house needed
Fossil fuel or electric strip backup needed

Annoying if you don't have central air

I have colleagues who swear by the Mitsubishi hyper heat, but they all have backup systems and newer construction.

Jamie Hall

There are a number of threads on this sort of thing, @SteamingatMohawk , but I'll give a shot a summarizing. First, heat pump systems certainly can heat a whole house, if the situation is right. Just a matter of sizing and source temperatures.

Which is the second question: at the present time, so far as I know, there are no air to air heat pumps which can manage with a source temperature of -15, although I believe that some progress is being made. Somewhere around 5 to 10 above seems to be the reasonable lower limit for air to air heat pumps without resistance backup at the moment Now: if you go to ground source heat pumps, that's a different story, since there the source temperatures are high -- 40 to 50 -- as the source is either a buried grid (below frost level) or deep wells.

Then the next question is how does the heat get into the house? Heat pumps -- of any source -- top out at around 130 for hot water units, and a bit less than that for forced air. This would mean that while you could get rid of your steam system and use a ground source heat pump, either forced air or hot water, it would be a complete rework of the heating in the house. There would literally nothing, except possibly the thermostat, that you could reuse (not even the power circuit: your steam system takes 15 amps at 120 tops, the heat pump would be looking for 50 to 100 amps at 240)

leonz

The Northeast Energy News highlighted Ithaca, New York today and its craziness in converting the businesses and homes in the city limits to heat pumps with its desire to become carbon neutral.

They are finding its going to be extremely difficult to do especially with how much it is going to cost the home and business owner.

The other thing is heating a home in periods of near zero weather is extremely difficult with even new air to air heat pumps and we have long periods of low temperatures to live with in some winters.

GW

Most Contractors are simply managers of physical work, mental energy, risk and reward. Then sprinkle in a couple dozen more factors and Poof- you have an hvac guy 

The older the house, the less jubilant contractors are to stick their neck out on the line (all Heat Pump with no backup): more risk for the same reward. If they have no work, they’ll probably stick their neck out a little bit further. If they are slammed- well you get the point 

The time needed properly calculate this situation is a bit. If you throw the question out there like you’re trying to corner the fella at Big Orange, you may get a similar response. 

If the house has been modernized, that’s a totally different conversation

Virtually none of these people selling HVAC have a blower door. If the house is old and leaky, it’s a bit of a waste of everybody’s time

One of my simple go-to sayings is, “we can add more heat or you can reduce heat loss” (Either option is perfectly wonderful) 

Your 1980s house seems more doable 

Good luck with the heat pump install; they are all the rage here in Massachusetts. Wicked rebates this year 

SteamingatMohawk

Your comments all pretty much match my impression of the state of the art.

The apartment lot is only 40 x 140 with a 6 car side load parking lot and 25 x 50 building on it. I'm very skeptical of using ground source there and there isn't enough land available for horizontal, except going under the parking lot, then repaving $$$$(heat gain from the asphalt could be a help). Keeping the steam system and letting the tenants use window units has been the way of operating and no one complains about AC. As I said earlier, HH and Charlie have been great resources to get my steam system working properly.

My house is 500+ feet from the road (long neck funnel shape) so I could run lines but that part of the lot is only 41 feet wide with a 10 foot wide driveway. There is probably room for vertical somewhere else on the 2.28 acre lot. I have a backhoe, so that could be a fun project as long as I don't hit water, gas, cable or power lines.

All that being said, I am not interested in a backup separate system and I think electric backup would be cost prohibitive. The only minor issue with my existing home system is it is not zoned (wasn't considered when the house was built in 1987).

Hot_water_fan

@SteamingatMohawk for your house, geothermal is a tough sell. The increased loop expense is hard to recoup as air source heat pumps have closed the efficiency gap (sometimes even exceeding ground source applications in practice). Since it’s ducted, the most obvious solution is air source heat pump + electric or fossil backup. Will electric backup be expensive to operate at -15? Of course. Will it matter? Probably not. Pretty vanilla setup all things considered. 

fentonc

@SteamingatMohawk - Do you have hourly temperature bin data for your location? That would let you quantify the operating cost of electric backup to see how prohibitive it would actually be. I was genuinely surprised how few very cold hours my location experienced when I measured it, compared to how I perceived it. It got down to about 4F this year (for about 2 hours), and there were 3 total days with an average temperature of less than 15F. You can probably make a very good estimate of the actual operating cost using available data.

leonz

If you do not already have a double drop header on your boiler it would save you a lot of money and gas to have one installed to make more dry steam faster and reduce your gas consumption

MY brothers have a brood herd of Mitsubishi and Carrier heat pumps in their rental and condo units and they do not do well in near zero / below zero conditions and require the tenants/owners to use supplemental heat.

Vertical geothermal using the semi open loop method will work as long as a large diameter bore hole-14 inches in diameter is mud drilled and 12 inch steel casing in high strength sand mix cement is set to the final depth and the water in the well pipe and the captive well water is pumped with a jet pump.

Using a jet pump eliminates the need for a submersible pump in the well and reduces the chance of lightning destroying a jet pump to almost zero.

Every 100 feet of depth will provide you with one ton of heating and cooling power until you get near 1,000 feet in depth where the rock begins to warm up.

If a geothermal driller suggests using a well with thermally enhanced grout for a heat pump walk away!!!!!!!!!!!!!!!!!!

I say this because these grouts contain clay in them and clay is an insulator.

GW

Leonz, clay is the best- it’s a conductor. You want conductivity in a loop. Sand is the worst. 

That’s why geothermal has up and down reviews- the loop performance will make or break the system 

SteamingatMohawk

@leonz Great suggestion, but the double drop header is not available, because the boiler has only one 3" steam tapping. The pipe comes straight up about a foot, turns right for about 2 feet, then turns back another 1-1/2 feet to connect to 2 vertical mains to the front, then rear of the house.



@fentonc I don't have any digital recording capability. I use a Honeywell wireless thermostat with WiFi capability and the WiFi adapter so I can monitor the system status with my cell phone. It wasn't cheap, but I have only one thermostat for the entire house (90+ year old 2 family converted to 4 units) and the thermostat is the furthest away from the boiler. I also like it because I can relocate the thermostat anywhere without doing any wiring.

Having the WiFi capability makes it so I can turn the heat on and off without leaving the basement and going through 4 door, 3 of them locked. Sorry for the side comment, but anyone thinking about changing their single hard wired thermostat, might be interested in what I did.

Thanks to both of you.

fentonc

Oh, I just meant look it up for your location (or somewhere close enough). I did actually measure mine, but I really was surprised how much warmer it was than what I would have guessed if asked previously. 

leonz

GW said:

Leonz, clay is the best- it’s a conductor. You want conductivity in a loop. Sand is the worst. 

That’s why geothermal has up and down reviews- the loop performance will make or break the system 

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A poorly designed and implemented geothermal system will not heat or cool very well at all.

I use firebrick as the best negative example as the clay used make it a firebrick holds heat and sheds it very slowly which is something you do not want in a geothermal system using the closed loop method of heating and cooling as you want the heat to migrate to the cold ground and mason sand will take the heat and shed it into the surrounding rock strata.

Using fine mason sand in an uncased well would work well as its exposed to the sediment and rock in the bore hole but a semi open loop or open loop method of geothermal heat exchange is better UNLESS you have a source of water like a river or lake that is unaffected byu deep freezing and has perpetual flow that can be used.

This is why I suggested using a large diameter well casing (12") sealed at the bottom with a pipe cap or pipe plug if collared casing pipe is used and concrete ballast for a sealed semi open loop method of heat exchange as the warm water sinks to the bottom over time and becomes chilled.

Using a 2 pipe jet pump would use the cold water in the well to drive the dense cold water in the base of the well to the surface to pass through the heat pump plumbing and either chill or heat the living space/workspace.

If the sealed well was in an insulated pump shed or well pit you could avoid the use of a below ground sanitary well seal and use a 2 pipe sealed/gasketed well cap.

If a three hundred foot well is drilled and 12 inch casing is used you could have the benefit of 5.875 gallons per foot of depth. If you have 280 feet of water column in a 12 inch casing you could make use of 1,645 gallons of water in a sealed water column to use in geothermal heat exchange.

A standard 6 inch cased well will only give you 420 gallons of captive water to use in a sealed water column that is 280 feet in depth.

The drilling of multiple wells in sealed loops with "geothermal grout" ugh, is a waste of money when single captive water well could do the same work in my opinion.