Heat Pumps

What type of information? Do you makes and models, theoretical information, or just a general idea how they work?

Tom

 

And while you are at it, check into the viability of Geothermal Heat Pumps for your particular situation.
Geothermal Heat Pumps
EERE Consumer's Guide: Geothermal Heat Pumps

I have seen them installed in cabins in the Sierra . . . the owners' LOOOOVE them . . . so, I'm guessing New York weather will be a good fit too.

 

Not being an expert, but I'll toss some ideas in here.

Heat pumps are exactly like an air-conditioner (or your refrigerator), which works by 'moving' heat from inside the house to the outside (using pressure/expansion to release/absorb heat). If you were to run it the other direction, you would absord heat from outside, and release it on the inside of the house. EERE Consumer's Guide: Heat Pump Systems

One issue is that heat pumps lose efficiency in low temperatures, which is why most of them have a secondary electric heat capability.

I think it depends on how far south, but the above reference is really helpful, IMHO.

Hope this helps.

 

Here in south Florida heat pumps work great. It is unusual for the temps to get less than 40 at night in winter. Now and then I have seen it freeze but it is rare. I've seen maybe a dozen or so in the past 20 years.

I also lived in Michigan for many years. Trying to extract heat from 20 degree or colder air takes a lot of work and energy. Living in New York I don't think a regular air-to-air heat pump would be a wise investment.

If you have a source of warmer "stuff" to extract heat from it might work. The "stuff" might be underground water, some geothermal, as mentioned, or other heat source it might make sense.

Bob

 

I just had a couple American Standard (maker of Trane, same stuff, different warranty) replacement heat pumps installed, along with new air handlers.

Since heat pumps move heat rather than turn electricity into heat, they can achieve "efficiency" ratings over 100%. But it's not really "efficiency" since it isn't generating heat, just moving it. The performance metric is called "Coefficient of Performance", it's the ratio of how much heat is available to how much energy is consumed. Pure resistance heating would have a COP of 1. Heat pumps have COPs of around 3.5, but the number goes down as the outside temp drops.

Heat pumps work great by themselves in areas where it doesn't get too cold in the winter, and electricity rates are low. If it only gets colder than 30 degrees for a dozen days out of the year or less, it's almost a no-brainer. You can also use a heat pump in conjunction with a furnace for those areas that get cold enough. Then you have what's called multistage heating, where first the heat pump kicks in, then if it gets really cold the furnace comes on and the heat pump turns off. The thermostat will have a thermistor attached so it knows the outside temp. The temperature where the system switches from heat pump to furnace can be programmed into the thermostat, so you can decide what makes the most sense taking both cost and comfort into consideration (see lukewarm air complaint below). If you don't have a furnace, they put heat strips in the air handler and your second stage is electric resistance heat (costly to run, but gets the job done in an emergency).

One complaint of heat pumps is that the vent air is not as hot with a furnace when it's cold outside. Even when it's keeping the inside temp to the setpoint, you don't get that toasty feeling because the vent air is lukewarm. If your electricity rates are really high, it's possible (but uncommon) that using a furnace is always cheaper. You have to figure out whether there are enough hours of run-time where you can save money heating with the heat pump to offset the slightly higher cost of a heat pump vs plain A/C.

 

Heat pumps are used to good effect here for water heating. They are much more efficient as they take the heat from the atmosphere rather than the coal at the power station. They are considered as using renewable energy so subject to green rebates.
Warm you hands on the back of the fridge to feel the affect.
Even when the temperature is below freezing there is heat energy in the atmosphere you can capture and pump.

 

A few more thoughts:

This decision is easy if you have central air and were planning to replace your condensers anyway (they were on their last legs or you determined you could save money by replacing them early, as I did). A heat pump condenser is around 20% more than a plain cooling-only A/C condenser (say $2200 vs $1800 for 4 tons of cooling). In case it wasn't clear, a heat-pump compressor is a pretty much a drop-in replacement for an A/C compressor, and looks the same from the outside. It just has the ability to run in reverse and move heat into the building in addition to removing heat.

If you have new A/C equipment that doesn't need replacing, or you don't have central A/C at all, then it's questionable whether you can save any money with a heat pump. I was assuming that your A/C was close to needing replacing, and you were deciding between a heat pump condenser vs an A/C-only condenser.

Your fuel costs, furnace efficiency, electricity costs, and heat pump COP will together determine the temperature at which it is more economical to heat with the heat pump than the furnace. Typically that will be somewhere between 20F and 30F, though you may set the threshold higher for comfort reasons (you like the toasty vent air on cold days and are willing to pay for it). The more heating hours when the temps are above this threshold, the quicker the heat pump will pay for itself.

You'll need to make sure the indoor coil is matched to the condenser unit, as you can't attain the rated efficiency if the coil is not matched.

 

How much do you pay for electricity ? Here in Quebec we pay just over 7 cents per KWH after base consumption. Cheap Hydro from James Bay, but will be increasing soon. Quebec exports electric to US. Perhaps that's what you are buying in NY ?

I'm near Ottawa, Canada and google says Middletown is 6.5 hours driving distance so I imagine our climates are similar. Down to -30 in winter, -40 with windchill, up to 94 or so in summer and 100+ with humidex.

My inlaws have had one for many years and have been happy, but some models don't work so well.

I recently did quick calculations and discovered at the price of home heating oil 1 week ago, I will be paying 2 to 2.5 times as much for winter heat as I would with electric heating !

So my first thought is that we buy a small portable heater for each room in the house. Nice, easy, cheap retrofit. And we still have the oil for backup in case of power failure.

Then I started reading about geo-thermal heat pumps. They seem to cost maybe $15k and in Canada you can get $2-4k (?) in Gov't rebates. And they are SUPPOSED to reduce your electric heating and air conditioning bill by a factor of 4 !

Maybe we'd have to rely on electric backup when it's REALLY cold, say 20-30 days of winter. But rest of year we are saving over and above what we'd save from oil to electric.

There's a possibly easier, cheaper method than digging a big hole and laying pipes. It relies on digging two wells, one to suck up underground water and another to return it to aquifer. Many people here have wells and apparently the water is 80 feet down. So, I'm looking into this option first.

Central air is one nice plus to heat pump. We have a decent window unit now, but central cooling and "air quality management" would be cool...

 

I have had a geothermal heat pump installed in my house about 3 years ago.
I have a closed loop system with 1200 feet of HPDE pipe for the heat exchange and two 3 ton units for a two zone setup.
A geothermal heat pump is not affected by the cold weather at all, since the pipes are dug 6 ft below the surface and the vertical piping is 150ft into the ground. The piping is warrantied for 50 years and has a lifetime expectancy of 100 years.

The HDPE pipe and drilling for a vertical geothermal heat pump is by far the highest investment in a geothermal heat pump installation. It's cheaper when you go horizontal loops, but you need tons of space for that while the vertical loops you drill 150 feet deep holes for each ton of heating unit.

If you want to see some pictures on how an installation of a heat pump looks like, here are some when the unit and the pipes were installed:
New geothermal heating/cooling system

My setup was $22k and I'm using ClimateMaster Tranquility 27 heat pumps, which are supposed to be the units with the highest efficiency on the market.

Thomas

 

I've heard they ARE affected by really cold weather and require supplemental electric heat at cold temps, like below freezing. Or perhaps that is air-air pumps and not "ground source" ?

BTW, I was on a professional HVAC forum last night and apparently the term "geo-thermal" does not really apply, unless you have magma or hot springs near the surface. Proper term seems to be "ground source heat pump" (or water source ?).

Also read something about "outdoor boilers" to heat your house with wood from a boiler in a shed becoming popular in the North-East, regardless of their smoke problems. Apparently a surprising number of people are "pre-panicking" about coming winter heating costs due to oil price. Could be $4-5k to heat an average house for many people in NE this winter.

I'm looking to resolve my heating upgrade soon, before all the HVAC contractors are booked for fall and winter. I don't want to be run over by low heat pump inventories like with the Prius availability situation now!

 

I should have prefaced my posts by stating that I was writing about air source heat pumps, and I live in an area with very mild winters. The comments from people who live in a climate similar to yours contain much more relevant information.

 

I think you are correct. Ground source heat pump is probably the correct term as it extracts the heat from the ground which is always at a steady 48-50 degrees.

A water source heat pump is also called an open loop heat pump (an underground water source is being used for heat extraction), while a ground source heat pump is a closed loop heat pump, which could either be vertical, horizontal loops or a spiraled loops which are dropped into a lake.

My heat pumps have each 2 x 2.5kw backup electric resistance heating coils (2.5kw as auxiliary heat and 2.5kw as emergency backup heating in case the heat pump fails), which are seldom used. We had a few days this winter were the temperature dropped below 10 degrees F and the auxiliary heating coils had to be used to keep the temps inside the house at 70 degree F. But I have a ranch type, one story home which has lot's of wall and roof area and therefore lots of energy losses through the walls.
With me 2 x 3 ton units I can heat and cool 3100 sq ft of living space + 2000 sq ft of basement without any issues for about 150$/month during the coldest winter month. Price is 5.5cent/KWh for residential energy saving heating systems.

 

I understand that water source can be open or closed loop.

I think open loop water source just dumps the water anywhere, and it eventually makes it's way back to the aquifer.

Closed loop water source uses one or more return holes, and I guess it equalizes the pressure in the aquifer or something, because the result is that the pump can be smaller and it takes less power.

Water source is nice because we just drill water holes that are thinner than normal water wells I guess. With ground source we'd have to dig up a bunch of dirt to lay the pipes in.

I wonder if I could have access to some of the well water too. 1 mile away there's an old dump that caused the city to put city water in because the wells close to the dump were contaminated. But I figure it's OK for watering the lawn, which is restricted severely with city water.

I've heard a neighbors' well is about 80 feet down, so I guess that's not too expensive to drill, depending on how many holes I need. I hear a rumor though, that local drilling equipment is busy, perhaps because water source heat pumps are becoming popular.


Yes, our winter's get to -30 so I guess the supplementary heat is essential.

 

Heat pumps are best in moderate climates. Upstate NY is a bit on the cold side.They tend to be expensive in the winter with an electric backup. But propane is an expensive backup now, as well. Get as efficient a model as you can--with the new refrigerant. There are still government rebates on the efficient ones.

 

No, that is not correct. A closed loop system (which is what I have) circulates a water/antifreeze mix inside a closed loop HDPE pipe system. The water never leaves the pipes.

An open system uses the water from a well and pumps the water back into the well after it extracted the heat from the ground water.

Corrosion might be a problem with an open loop system since the well water might be aggressive, while a closed loop system doesn't have any problems with corrosion as it is closed loop and runs inside the HDPE pipes.

Open loop is cheaper of course, since you don't have to pay for the expensive HDPE piping (1200ft of piping ~8000$)

The HDPE piping which is dropped in coils into a lake is also a closed loop system since the water is entirely trapped inside the HDPE piping loop.

Thomas

 

OK, I stand corrected on the terminology; I guess all water source with a well for input are considered an open system.

Regardless, it's still my understanding that you can just dump the output water wherever you want (assuming local laws and your neighbors allow this) and this doesn't need any return wells. The downsides are that it takes a bigger pump which uses more electric power, and you might cause flooding or otherwise disturb local soil or water table, Disturbance could include lowering the water table which might require wells to be dug deeper.


.....

 

Gee, our Quebec Gov't must be ripping us off badly ! We/They sell the power to your utilities and you get it cheaper (2/3 of what we pay) than we do ! What a rip !

Regarding payback time: you really have to do an analysis for yourself. Various websites, such as a Canadian Gov't one, have analyses and formulas or calculators that depend on current prices.

Here's a US site: EERE Consumer's Guide: Geothermal Heat Pumps

Canada:
Heating and Cooling with a Heat Pump

For a rough, back of envelope calculation, If I assume I'd pay $1500 extra per year in electricity for heat and AC, I think I'd only pay about $500 in electric for an efficient heat pump in theory. Perhaps I'd have to add $300 for supplemental heating when it's really cold ? So that's a savings of $700 per year, versus full electric.

I'm ignoring an oil comparison because I think converting oil to electric is a no-brainer at this point. I think oil would have to drop back to $60-70 a barrel before break even with electric. The only question is electric versus electric with heat pump. Natural gas not available to me and I don't trust price to remain stable. Solar won't payback IMO in this northern climate at this time. Wood burning is not attractive to me.

So if you save $700 per year and the system costs $10k (????) then it will take 15+ years to pay itself back with interest.


Hmmm, I'm not sure it's worth it with these numbers, unless you're pretty sure you can get your money back from next buyer or live their a long time and have few maintenance issues or costs.

In Canada we get various tax rebates and incentives, so costs may vary depending on such incentives.

In any case, I'll be studying this further but I'm starting to think I'll just put plugin heaters in every room this winter. It's certainly less hassle than getting contractors in etc., and it will give more time to re-assess the prices of various forms of energy and energy savings.