Heat Pump Efficiency in Minneapolis, MN

Drill down and use a soil interface for both heating and cooling via the heat pump.

I am talking about people who earn less than $70,000 per year per household.

Is a ground source heat pump a good investment?

Here's a link to an extensive discussion on this subject...

http://ths.gardenweb.com/forums/load/hvac/msg021501198565.html

The quality of investments is not related to income. The attraction of them, given a fixed income, can be ranked in order of priority depending on personal circumstances.

Agreed, your advice is spot on. Although there are some times where "some" money could be recouped, a heat pump that far north will take a long time to pay for itself.

Definitely go for the higher COP and check if there are loocal or federal tax incentives for the higher efficiency.

Drill down or build a soil interface is sometimes an expensive option. We have a low watertable at 30m (worse case 50 m) so to drill down and this twice for sucktion and discharge well -at 130US$ a meter is really a budget! Our simple air to water heat pump costs the same!

A mat collector for my house would not have fit under the lawn of my plot as zoning does not allow to go within 12 feet of the plot's border! You need around 2* the occupied area of the house. And you need to excave this area at least 5 feet down! you can not plant a tree in the garden - it might damage the collector with it's roots (this happened to a friend repair nearl impossible!)

The third option "collector cages" requires intensive work in the garden with deep and wide excavations. And the cages are higly expensive and performance wise overrated - and you need also the space and a channel to insulate the connection pipes. Not a real option!

Until now I know only people which had the space and the heavy machinery easily available to build their collectors on their own. Or rich guys where the money any did not matter

I invested the "drilling game money" (not all!) into a high efficient vaccuum solar heater! The system is designed for "heating system support" and delivers on a cold (-3 degC) but sunny winterday at lunch time hot water with up to 100 deg.C (close to boiling!) into the buffer tank for the heating system (around 10 to 15kWh solar heat during the day)! Which keeps the heat pump nearly off for the day!

In general the heat pump is off for 7month in the year (we could do 8 to 9 month with the support of our woodstove which we currently use extensivly) - we have it warm aund cosy in the house - hot water sufficient for us. The link to the hot water is the reason why we have to run the Heat pump 1- 2 month longer - but we still can optimize that - we live in the house now for the first year! The heatpump has an additional electical heater build in which by now will kick in at around -7deg.C - but which could be adjusted to a bit lower temperature without much loss in comfort. And the kick in happens no very often - under study by now!

We live relative close to the German Alps in Bavaria (southernGermany) with -20 deg.C for some days of the year. oK we do not need air conditioning in summer, German summers are sometimes lousy, but at max. 30 deg.C during the night we can open the doors and let the summer brise in or sweat a bit! The house is "freestanding" and exposed to winds without much protection.

And the heating bill compared to our previous oilheated house is only 20% at a floor area which nearly identical . Ok the new house is already more heat efficient (triple instead of dual glazing, wall insulation exterior 16cm styrofoam oon heat efficient bricks and 200mm Styrofoam below the foundation, lots of rockwool below the roof and 60mm insulation below the tiles and due to to the heat pump a waterbased floor heating system ( the entry temperature for the heating iis much lower than that of a furnac operatid system.)

Now 3 years later and new technologies coming up - I would have been looking into "Heating with ice" - a 30 to 40 cubic meter water reservoir below the garage with a heat exchanger - heating energy is taken from this water and over the winter this will freeze up. A small solar system on the garage roof during the summer recycles the ice into heated water. So you can store to an extend the summers heat for the winter. Such system are known for some time but the storage tanks were disqualifying expensive. Nowthe system is delivered from a "prefab" garage company by truck and the investment is much lower (Ok also the insulation of the water mass is not as good) The storage is just a prefab basement to the prefab garage and is delivered with a sppecial truch and a trailer. The heat pump and the water treatment equipment are fixed to the garage wall!

Heat pump lover!

Greetings from Germany Ulrich

Yes... with air cooled condenser, a heatpump that far north is a waste of money...

I live in Phoenix, AZ most of the time. There are some(not many for sure) nights when it gets cold enough here so that our heat pump literally runs all night and can't begin to keep the house at 72°. To add insult to injury, sometimes during the night the system gets too cold and then runs a reverse cycle to warm itself back up. During this time, the vents all blow COLD air into the house.

I would NEVER recommend a heat pump to anyone anywhere in Minnesota. Even at our place in southern Minn. it is far too cold to have a heat pump.

Gas heat is the only way to go.

Your system should have an electric booster (resistive heater) in the air handling system that takes over during the defrost cycles. This maintains hot air through your ducting. It also adds heat when the heat pump cannot maintain the set temperature during extra cold ambient temperatures.

This system doesn't have any auxillary heat. That's typical of construction in the desert. The system we have now is less than 5 years old and is 15% oversize for the square footage of the home.

It hasn't been cold enough in the last couple of years to need any aux. heat. Global warming, you know.

GLOBAL........LM*O.......HA!

There are heat pump units for low temperature environment that will preform well in that area. Whether they are affordable to your clientele is a question you or them have to answer.

I would have thought that a ground source heat pump would be a very good choice, providing you can bury the coils deep enough in your cold climate. Digging up large areas of land to bury the pipes can be very expensive. What is needed is some smart company to get together with people who drill boreholes. There are plenty of companies that do this for a living; drilling down to 300 feet is routine. The heat pump evaporator (when in heating mode) would take the form of a long coil and return pipe. Maybe this is being done - I don't know. Perhaps this qualifies as a "geothermal heat pump."

We had an air-air heat pump in Tennesse for the last 5 years. It functioned perectly, holding 74F in the house down to 9F ambient, the lowest we experienced during this period. How it would handle -20F (which they have had there) is another question!

Install the so called super insulation, AKA R2000

http://oee.nrcan.gc.ca/residential/new-homes/r-2000/7334

Better insulation and windows means the geothermal plant can be smaller to do the job.

In your area, find some people with geothermal installations. Possibly the town hall permit division will know all the people who have these installations, and their inspector might clue you in.

Using the mass of earth as the heat sink can be done with a buried field that is dug below the frost line. The modern way to do this is to use earth drilling from trenches set about 20 feet apart - back and forth about 5 feet down. Each piece of pipe then has no holes. metal pipe costs more, and has higher thermal conductivity, but corrodes. Most use plastic pipe. The trenches are where you make the connections to create the network. The trenches can also be roofed with some insulation for easy access, but most people just bury them as plastic endures if it was properly laid and tamped so it does not settle and does not break.

Many times these fields are piped directly into the house underground.

You will need a certain area, a function of the house footage, to get enough heat.

If you are in an area of deep soil or gravel, you can make a vertical drilled field. A drilled field can take less surface area. It is hard to make a drilled or trenched field into bedrock, unless you want to spend a lot of $$

If you look into the new Carrier Heat Pump with Greenspeed , you'll change your mind, it produces near the same btus at 17 degrees ,as most others produce at 45 degrees. Couple this with Hybrid/Dual Fuel and you have a winner. Bryant will have this in a few months.

Heat pumps do work, the common issue is the insulation in the structure. You need to know that ZERO degrees is really like 460 absolute and that it is not zero except on the F scale. The volumetric efficiency slips with higher compression ratios of low temps, but the cop is still above 2.+ meaning that it is twice as efficient as electric heat. Some do not have gas, and heat pumps beat propane costs hands down even with 90% furnaces that waste 10% up the stack. Woody

Heaven sakes, you're in southern MN!!! It doesn't get that cold down there!

About 40 years ago, my dad put in a heat pump on the farm in North Dakota. -40 ND cold. Over the last 40 years, there have been some condensing unit changes, but the house has had a heat pump system for that length of time.

Granted we did have REA subsidized electric rates rather than Mpls electric rates. And out on the farm fuel was limited to what comes in on the wire or what gets hauled in.

Previous to the heat pump we had #2 fuel oil for the furnace and propane for cooking. But in rural ND in the winters, fuel deliveries can become problematic. The electric supply tended to be much more reliable.

The heat pump system was set up with 4 or 5 stages of electric heat to come on as the demand for heat increased. But if you look at a BIN chart for climate data, the percentage of hours that the temps are extremely cold make up a small percentage of the year. Depending on the HP capabilities, the electric resistance heat might only operate 300-400 hours out of a 3000 hour heating season.

Most of Mpls I believe does have natural gas, which is a very economical fuel. On the other hand, newer technology pumps, as others have noted are becoming capable of better heat extraction at low ambient teemperatures. It might be worth a closer look at how the electric cost, natural gas cost, and equipment costs stack up for the Mpls area. You might be surprised at the results.