Geothermal Heatpumps: An Introduction

[que3jxp]

Originally Posted by Phatboyc

Thats not so much bigger than a regular furnace.

Nope. Matter of fact, if you discount the foam board that it is sitting on and the huge T plenum on top and the unit itself is quite small. Maybe even smaller than an electric forced air unit.

Originally Posted by Phatboyc

Except you have insulation on the main vents going to the house.

That is actually code here.

Originally Posted by Phatboyc

Only six pipes? So that is two pipes per trench? I though it would be lots more than that.

It is actually 3 long pipes and in the house, you see the 2 ends of each loop as "two pipes". That is why there are "6 pipes". The black "pipes" you see are actually 1/2 inch copper that are only wrapped in the black foam in the house.

For a GHP installation, it is generally one well/"well" per ton of cooling/heating that you need (Horizontal systems require a notable percentage more piping). Roughly, it works out to one well/"well" for every 1000 to 1200 square feet of heated area. Any variance is caused either by the choice in system (water vs. DX) or is caused by a lower than average ground temperature (You will find in nearly all of the GHP unit's manuals that there are a series of ratings based on several ambient ground temperatures.

A Depth Note

In a DX system, the vertical loops are only required to go down to between 100 and 125 feet. Closed loop water is about the same but open loop water is based totally on how far down you have to go to get to the water table.

[Monobloc]

que3jxp, what are these "humidity control capabilities" you speak of?

With my electric baseboard and electric hot water tank setup, I have a timer set on my hot water tank to be off from 10PM-6AM. Setback thermostats also shut off the heat at 10PM (during the heating season)....You mentioned way back on page 1 that it's better to set the thermostat on the DX system and leave it. But could you do a hot water tank timer setup like me and then shut the whole system down at night?

[que3jxp]

Originally Posted by Monobloc

que3jxp, what are these "humidity control capabilities" you speak of?

A dehumidifier is a water condenser that is based 100% around air conditioning technology. The GHP uses a heating/cooling grille that is the size of a VERY large vehicle radiator. When you are cooling your house, the unit will naturally act as a giant dehumidifier. So much so that you need to have a hose/pipe that comes from the catch pan in the bottom of the unit so you can drain it into your sewer.

I have a lift pump in my basement due to how high the floor is to the septic tank and in the summer, the GHP draws so much moisture out of the air that the pump will run at least once everyday due exclusively to the GHP.

To further define how cold these GHPs can run at in the summer, a few years ago, we went away on vacation and turned the system off (Not knowing better). When we returned a week later, the house was about 84 F so we turned on the system. about an hour later, there was no sign of things getting cool. I went down to open the unit and see what was going on. Well, when I opened it, there was 2 inches of ice that went about 3/4 the way up the coolant grille!!! So I carefully knocked off the ice and off it went again. It still made some more ice on the bottom portion later, but it eventually caught up and stopped making ice.

One of the curious ratings of my GHP is that if you wnated to make ice, that it has the heat transfer capacity to generate over 3 tons of ice per day. Wild eh?

[Hurricane]

Originally Posted by Monobloc

You mentioned way back on page 1 that it's better to set the thermostat on the DX system and leave it.

My understanding is that this only applies to the heating cycle. Heat pumps don't typically generate as high of an air temperature as a regular forced air system. So it takes longer to increase the temperature in the house. To compensate, heat pumps have electric heaters built in to supplement the heat pump itself for emergency purposes or is the heating demnd becomes too high for the heat pump itself to handle. As a result, if the set temperature is more than just a few degrees higher than the current temperature, many heat pumps will start using the electric heaters. Once you start using these electric heaters, you're defeating any added energy savings that you would have gained from using a heat pump.

Note that there are some units can be programmed to increase the heat in small increments in order to avoid using the electric supplement.

So in a nutshell, with a heat is costs less to maintain a constant temperature than it does to try and quickly reheat a house.

[que3jxp]

Originally Posted by Monobloc

You mentioned way back on page 1 that it's better to set the thermostat on the DX system and leave it.

I'm sorry, I missed that part of the question...

Hurricane is correct to a great extent. For a GHP, the electric backup is there as a backup. But due to the fact that even as slow (Compared to electric or oil/gas) as a GHP is to heat up a house, the controls and the control panel will very often never call for the backup heat unless there is simply no heat coming from the system at all. This is where air based HPs are so bad as in the winter, there are FAR more times when there is likely no heat to be had from the air.

I have never had my electric backup come on except when I tested it right after it was installed.

Originally Posted by Monobloc

But could you do a hot water tank timer setup like me and then shut the whole system down at night?

There is not much point in this. Electric heated water is wickedly expensive. If you look back at the very first posts when I started this thread, you will find a recountment of what happened when my wife and I turned our GHP off for 5 days and let the hot water tank heat itself. The consumption for the month was and still is the highest Aug/Sept billing period in the 7 years in the house with the GHP. It was 263 KWh higher than the average for that billing period. At the current KWh cost here in NB (Relative to my total average usage), the cost on that 263 KWh is about $36 with tax.

AND THAT WAS FIVE, 5, DAYS!!!!!

As for using a timer on your tank, there is not a whole lot of point at all. The only time I might see it as useful would be in the spring or fall when the system runs the least. That would be the times you would experience the most reliance on electric hot water and therefore could expect the greatest benefit from having your tank on a timer.

[acadien]

que3jxp,

Does the DX system only heat your water when it is running to heat or cool your home? If so, then at other times, the water is heated like an electric hot water tank would?

So what happens in the spring/early summer or fall when the temperature outside is low 20s (Celsius). There is no need for heating/cooling at that time.

So how is the hot water heated? Does the DX system still run from time to time to heat up the water? Or do you need to keep the DX system running all the time in cool mode to keep the water hot?

Another DX question - anyone has it hooked up to a backup generator in case power goes out? Of the 3 bids we got for a backup generator (running on NG), they all mentioned how it could run our NG furnace. When we told them we were thinking of a geothermal system, they all said that a generator would not be able to handle that. Now I'm not sure if they were thinking of a heat pump, or if they are just ignorant about how much energy a DX system needs. My wife was the one making the calls, so I did not get a chance to question them more on it.

Thanks for the help!

[que3jxp]

Originally Posted by acadien

Does the DX system only heat your water when it is running to heat or cool your home? If so, then at other times, the water is heated like an electric hot water tank would?

That is correct. There is a heat siphon of sorts that captures waste heat from the heating and cooling of the house and heats the hotwater to about 145 F.

I believe that newer units are capable of sensing that the water passing through the circulator pump is below 130 and to set your tank at 120 so the GHP will actually actively try to keep the water in the tank at or above 130.

To all of my knowledge, my setup only heats when the system is running. I only set my tank to run when below 120 so it is extremely rare to see it on except when putting really high demand on your tank. In effect, the GHP is keeping a tank of water ready at all times and when you exceed its abilities, the tank acts more like an "On demand" heater.

Originally Posted by acadien

So what happens in the spring/early summer or fall when the temperature outside is low 20s (Celsius). There is no need for heating/cooling at that time.

The funny thing there is that when you are running your house at the same temperature all year round, you find out that the system runs more than you expect.

Originally Posted by acadien

anyone has it hooked up to a backup generator in case power goes out?

This is a legitamately big issue. Any Heat Pump (GHP, DX-GHP, air to air, air conditioner, fridge, freezer, etc..._ has a very current hungry compressor on it. The compressor that is in my vintage of DX-45 has a peak starting draw of 105 amps for about 0.5 seconds and a constant draw of about 30 amps. The only safe and proper way to handle this kind of draw is to have a fairly large bank of deep cycle batteries and one hell of an inverter.

This issue has bothered me when in reference to going to solar or wind as it is inherenetly the same issue as soon as you go "off grid". The one option you do have is to install the backup heater element in the system and have the ability to heat the house with what works out to the equivalent of a forced air electric furnace. I am unsure if you can wire the system to behave like this though...

[Ricketty Rabbit]

We didn't consider installing a b/u generator, but do have a sealed natural gas fireplace which we use as b/u for heating. While the house was under construction (before the GHP system was connected) the fireplace kept the house at ~ 62F during a December cold snap. Not "room temperature", but with a few sweaters, you wouldn't have to move to a hotel during an extended power outage.

Ricketty

[realityintrudes]

hello all- my first post. We have a 40kW propane-fueled generator as back up for our home. I wanted to be sure we could make toast in the event of a power failure . When we were trying to decide what to hook up to it, the engineer had some type of capacitor(?) added to the pump which allowed for a 'soft start' which meant the load on the system at generator start up was a fraction of what it would have been.
The biggest costs we have experienced down here in the states for both the generator and the geothermal is the paucity of service people for the units in our geographic area, which means we are paying MANY $100s just for their travel expenses each service call- even when they forgot to rehook something up on their previous visit . What a racquet.
kurt

[madwayne]

Thanks for info guys, I'm new to the forum. I will add info to this thread from som eof my research I have done.

In Ontario for an approved GHP, you get a $3500 rebate and the federal govt matches that $3,500.

The catch: only on existing homes and you need a energy assessment done which costs up to $300 (which Ontario will rebate up to $150) and a follow up assessment which costs up to $150.

I'm on BB heating with 3 acres of land, so no duct work. The $7,000 in rebates is enticing. I havent gone out yet to get some quotes. I live about 30 minutes east of Ottawa.

Any suggestions or am I wasting my time AND money?

[que3jxp]

Originally Posted by madwayne

I'm on BB heating

See, this part is key. Where you would go from using electricity to using electricity, there are very easy numbers to crunch. Even conservatively, I can say that you would see, over the whole year, a reduction of about 40% off your power bill. So you should be able to confidently take your annual bill, knock 40% off and see how many years it would take to amortize the remaining cost that you have to eat.

As an example, if you save $1500 per year, and you have to cover $15k of the cost even after the grants/rebates, it would take 10 years. Are you going to live there that long? Even if you may not, are you interested in the highly efficient air conditioning that you get with a GHP?

If every house/structure was built with a GHP, I would be happy and there would be nothing to figure out. However, where the pricing is still a little high, you need to see if it fits your budget, life style and long term property ownership plans.

I guess a couple of questions that I should ask are:

• How big is your house?
• Is the ceiling in the basement closed in with sheet rock?
• Do you have a room in the basement that can be assigned to having the heat pump in it?

[madwayne]

Originally Posted by que3jxp

I guess a couple of questions that I should ask are:

• How big is your house?
• Is the ceiling in the basement closed in with sheet rock?
• Do you have a room in the basement that can be assigned to having the heat pump in it?

1. 1300 sq ft, its a bungalow
2. partially sheet rock , partially false ceiling, (I'm planning to knock down the shet rock ceiling)
3. yes

This is our retirement home, so we plan to stay here for quite some time.

[que3jxp]

1. 1300 sq ft, its a bungalow

Is this per floor? (1300 on the main and 1300 in the basement?)

2. partially sheet rock , partially false ceiling, (I'm planning to knock down the shet rock ceiling)

This is a good situation given the need to install of the ductwork. It at least indicates that you are planning an expense regardless of if you are doing a GHP.

3. yes

Perfect. Like any forced air system, it takes up some space and you do not want to just cram it in there as you will need to get in and change the filters on a regular basis and you will need to inspect the fan belt no less than every 2 years.

This is our retirement home, so we plan to stay here for quite some time.

This is also good as it means that you can amortize the cost that you are left with over a longer period without feeling too jipped. Say at max, 15 years. After that, no matter who you are, it starts to feel unpleasant and unrewarding. (The big reasons that I am not doing wind or solar)

[madwayne]

Originally Posted by que3jxp

Is this per floor? (1300 on the main and 1300 in the basement?)

1300 sq ft per floor. (2 floors (basement and main floor))

[oldVWdude]

Madwayne this is what I did, my house is about 1100sq/ft plus 1000sq/ft finished basement. For the most part open concept and that would be needed for the below system. As long as you leave you BR doors open the heat will get in there.
I was, like you, on BB heat, no ducts.

We installed a ductless-split heat pump (air to air) made by KeepRite (the new Panasonics are even better), but LG and others also make them.
These have a 2 units inside (upstairs and down) high up on the wall, with the heat pump outside.

Then we installed a gas (propane) fireplace upstairs and a gas stove type downstairs.

Pro, our hydro went down $1300per/yr, factor in our propane at $600/yr, for a savings of about $700/yr. Plus that includes the fact we now have air conditioning in the summer!
Gas fireplace/stove needs no hydro to work (9v battery), so no heat worries with blackouts.
I still have my BB heat as back-up.
Very quiet, except for the fans on the gas units.
Very good heat and AC.

Con, the heat pump shuts off if there is a power interruption.
Heat pump only works to -3C and it does not automatically shut off.
One BR does get a little cold so the BB heat does run a bit in that room.
You (DYI) have to clean/vacuum out the fireplace/stove 2-3 times per year.

Cost was a bit high, but way cheaper than a GSHP, around $10,000 for all.

Over all we’re very happy with our investment.