Geothermal Heat Questions
As a long time lurker I’ve learned a lot from this forum and now I need to get an answer to more specific questions. I’d post to the HVAC groups but they seem short on manners and sharing info.
I am going to build a home in Michigan’s Thumb area and am seriously considering using a geothermal heat pump, water to air exchange, for heating, A/C, and domestic hot water. This will be my retirement home and I plan to reside here all year so year-round comfort and efficiency are important. Natural gas is 450′ down the road and the cost to get it to my place is quoted at $7,000 as a high pressure line is required. Propane is out as my wife is allergic to the slightest bit of it, not to mention the high and ever-increasing price.
I’m told that the electrical service required to run the geothermal alone is 200 amps! Seem like I could just use electric heat instead if it’s drawing that much power. What happens in a power outage? A modest 5 kW generator won’t get the geothermal going will it? How do folks in my situation get by? I’m told that the power company may/will require a second heating source if I use geothermal. More $.
Is it possible to temporarily use a gas water heater to provide heat during power outages and have the 5kw generator run the hot water pump and air handler? I’d use a power vented tank in an isolated room with some valves and pump to provide hot water to the water-to-air exchanger. Even a pricey tankless heater would be cheaper than a 50 kW generator set. Has anyone done something like this?
Second question; Can a heat recovery ventilator be added to the system since the geothermal is a constantly running during the colder months?
Anything I’ve overlooked?
Your thoughful responses are greatly appreciated. TIA
Dustin
Replies
1. Your house's TOTAL sized panel should be at least 200. You'll get a sub off that for the unit.
2. Which could be impacted by you calling the local utility and asking about geothermal heat pump incentive programs. The Michigan utes are more friendly over the technology. My setup 10 years ago actually required two panels. With two meters. The heat pump, well, h2o tank all went on the second meter which was a special rate - much lower than the norm. The rest of the house went on a time of day meter so's we could control our usage.
3. Yeah, a backup is an issue. But the same event would cause a problem with a high eff gas furnace, too. The guy who tookover my place has simce installed a 50 kw automatic backup. Cost him about $10K.
But the monthly bills were incredible! About 1/3 to 1/4 of before.
4. I'm not sure about how your setup would adversely affect the manufacturer's warranty.
My geothermal unit (4 ton) runs on a 40 amp circuit (not the electric backup elements), so that alone is in the neighborhood of 10KW, a 15KW gen set might be the minimum to get your house by in the case of a power outage. Hopefully the cost for that setup would be much less than $10K.
Was not aware of any geothermal resource areas in Michigan. If there are, it only takes a 1/3 or even 1/10th HP motor to heat a house.
Or do you mean Ground source heat pump?
Junkhound,
You are correct I did want to discuss ground souce heat pumps but accidentally reverted to the 'geothermal' terminology. Thanks for settin me straight.
Dustin,
I just recently built a house outside the Ann Arbor MI area this past winter. I had a geothermal system installed (actually by a company out of Bad Axe MI). Anyhow I was required to put (2) 200 amp service panels in my house . One for the geo and one for the rest of the house. I have a seperate meter for the geo system and I get a much better electrtic rate on that meter. I also have the geo system heating my hot water. Included in the geo bid was a full house heat recovery system so I have that too.
I had a concerns about the power outages. My 5 K gene is too small to power the geo unit. I was told that I would need at least a 10-12K generator. My back up plan includes a true wood burning stove in the basement and a gas direct vent fire place on the main floor . I know the gas fireplace is not an option for you.
If you have any further questions, feel free to e-mail them to me at: [email protected]
good luck
Andy
You haven't said how big the house is. 200A alone for the heat pump is mighty big, unless you plan to have electric backup heat on the same service. Do you need to have a backup energy supply with a ground source heat pump?
I've got a 3600 sq. ft. house with a 4 ton pump served with a 30A circuit. Someone, (either you or your subs) needs to do an informed load calculation. I use propane as a backup energy source, but considering your wife's situation you will have to balance the cost of electric versus natural gas.
Good luck,
Scott.
Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
Scott,
Thanks for the reply. Seems like a separete 200 amp panel is pretty much standard here in Michigan, according to my informal survey. Local utility may want to put me on a seperate transformer so the neighbors lamps don't dim when "all the systems start at once". I agree I need more facts, I'm in the design stages now, small bungalow total of 2300 sq ft. and looking at all my options.