Heat Pumps and Electric Heating - Locate heat pump compressor in basement?

For improved efficiency, I'm wondering why I wouldn't locate a heat pump compressor in my storage basement rather than outside. Basement is 50% underground and half the square footage of my well insulated living space.

In the winter heating season it might work but in the summer cooling season it will end up overheating.

If it happened to work in the summer your basement would be hot and in the winter it would be cold.

If you really want increased savings go with a geo system. The refrigerant lines are burried in the ground and then the compressor is or can be in the basement.

Thanks for your reply mattison.

I'm located in the foothills of North Carolina and temperature in summer is rarely above 90. I presently don't even have AC and only wish I did for about 2 weeks in August. Why would this system overheat anymore than a standard air source geothermal system? I could circulate outside air in basement if temperature differential is favorable. Doing that I would always have cooler air in summer and warmer air in winter to pull from.

Of course a buried line geothermal system would be the norm but why wouldn't basement serve the same purpose? Basically what I'm looking for is a geothermal system without the extra cost of labor and materials to install an underground system. Basement being hot in summer and cold in winter is not a problem as I use it only for storage.

How does one crunch the numbers for this?

even though the basement is cooler in the summer it would quickly warm up from the output of the compressor. block walls are not very good heat sinks. it's the same thing as parking a window air conditioner in the middle of a room. cold air out the front and hot air out the back.
no change in the room temp.

Hi Norville,
I'm new to this forum and am very interested in the topic you posted. I have an oil fired boiler in Connecticut and the price of oil this year is killing me. This feeds an air handler in the winter, which is also fed in the summer by a 3.5 ton outdoor AC unit, which is used very little. Electricity is ridiculous here too, .18 per kwh, so for a heat pump to make sense it has to run at at least 200% efficiency. I'm hoping with the basement heat sink that the temp might never go below 40F, leading to an efficiency of 300-400%. If the basement did get too cool then the existing oil could still kick on.

So anyway I'm looking for data and experiences too, I think there's very good chance it could work. I have trouble agreeing with flopshot. Its definitely not the same thing as putting a window AC in the middle of a room.
Thanks
For improved efficiency, I'm wondering why I wouldn't locate a heat pump compressor in my storage basement rather than outside. Basement is 50% underground and half the square footage of my well insulated living space.

norville2,

Your terminology is not clear.

The compressor is a component of the outdoor condensing unit.
It raises the pressure of the refrigerant and adds heat to allow the refrigerant to condense in the condenser.
If you mean install the compressor in the basement as long as the condenser is located outside it would still work normally.

If you mean install the condensing unit in the basement the space would not be able to dissipate the heat fast enough which would cause the temp to rise and the unit to overheat.

To know how much heat that an a/c condensing unit rejects and roughly 1/3 to the btu capacity of the unit.
That would be about 24,000 btu of heat for an 18,000 btu a/c or about 5200 watts of heat.

Id say you got to think about it. In the winter you would be trying to heat the up stairs and make the floor cold from the basement. in summer make the house cool and heat the basement One would fight the other?????:wall: :wall:

Hi, I'm not Norville, but the thought is put the whole unit in the basement. I have an existing AC which works well outside (about $300 per year) so in the summer I'd use that, then for the winter switch to the heatpump in the basement. I have 2200 ft2 in the one story house and the same in the basement, with 8 ft ceilings so its plenty deep to get ground heat. I have good insulation between floors and basement. Now the temp never goes below about 55 in the basement, my guess is the heat pump would drive it down as low as 40F, but there the heat pump still has good efficiency. Outside at 10F would be lousy efficiency though, and here electricity is .18 per kwh so it has to be a good system to make sense. If the basement got too cold I could go back to my existing oil system. I spent about $4000 on 1100 gallons oil this year and don't like that at all.
One thing that made me think of this is my separate insulated garage never goes below freezing even without any heat at all in it, even a slab at the ground surface brings up enough heat to keep the snow melting off the cars.
Dave in Connecticut

Dave
i'd say it is a worthy experiment.
The unknown is how fast the basement will warm back up.
My idea would be to heat your favorite room or 2. Then it could cycle on and off giving the basement time to warm up.
BUT
the floor will need insulation like your freezer.
and fans might be needed to help draw heat off the basement floors and walls.
.
imo it will get colder than outside if it runs steady, all day. There are btu's to be found down there; i doubt anybody really knows the true supply. good luck and don't let the naysayers stop you.

I just completed an experiment to give me some idea if this will work. Initial average basement air temp 62, walls/floors 55, outside 60, house 66 so not much of a difference anywhere. Basement ceiling insulated with 6" fiberglass. I ran the gas grill in the basement for 15 hours straight, 30,000 BTU/hr, about what the house will need on typical January days. In that time basement air temp went up 2 degrees, walls/floors 1 degree. (also bought and used a CO monitor). This seems to prove that the ground does control the basement temp, in the winter its about 10 degrees colder than now but this new info shows that I should not have an issue with it ever going below freezing. Of course I'm going to add more ceiling insulation too.

This has to work well to make sense where I live in CT since electricity is 18 cents per kwh here.

Comments appreciated.

Dave

Dave
i'd say it is a worthy experiment.
The unknown is how fast the basement will warm back up.
My idea would be to heat your favorite room or 2. Then it could cycle on and off giving the basement time to warm up.
BUT
the floor will need insulation like your freezer.
and fans might be needed to help draw heat off the basement floors and walls.
.
imo it will get colder than outside if it runs steady, all day. There are btu's to be found down there; i doubt anybody really knows the true supply. good luck and don't let the naysayers stop you.

Well, your experiment in thermodynamics is, unfortunately, somewhat flawed. Heat rises, cold does not.

I think its going to be difficult for you to get the answer your looking for without actually trying it. You have a giant basement so I would suspect it would work at some level. The real questions are how long will it take for your basement to reach freezing and if that happens how long will it take to recover from that temperature back to something usable.

Also based on the above I'd consider raising the HP off the floor a bit since that is where your coldest air is going to end up.

Not sure what your heat rises, cold does not reply has to do with anything. The temperature difference from a few inches off the floor to a few inches off the ceiling was always less than 2 degrees, I had a fan going to make sure. Also I don't understand your comment about raising the HP, the heat it is using will be coming in from the floor (from the ground), so the temps should stay quite uniform in the basement in the winter. However the temperature difference will be huge floor to ceiling in the summer when used for AC, then the HP definitely needs to be on the floor.

Well, your experiment in thermodynamics is, unfortunately, somewhat flawed. Heat rises, cold does not.

I think its going to be difficult for you to get the answer your looking for without actually trying it. You have a giant basement so I would suspect it would work at some level. The real questions are how long will it take for your basement to reach freezing and if that happens how long will it take to recover from that temperature back to something usable.

Also based on the above I'd consider raising the HP off the floor a bit since that is where your coldest air is going to end up.

Well, your experiment in thermodynamics is, unfortunately, somewhat flawed. Heat rises, cold does not.

Heat DOES NOT RISE! Heat travels equally well in all directions via radiant energy waves until something blocks the wave.

Further, there is no such entity as cold. Cold is merely the absence of heat.

I ran the gas grill in the basement for 15 hours straight, 30,000 BTU/hr, about what the house will need on typical January days. In that time basement air temp went up 2 degrees, walls/floors 1 degree. (also bought and used a CO monitor). This seems to prove that the ground does control the basement temp,...

This "proves" nothing. It is the mass of the floors and walls that are at a specific temperature and it will require that the HEAT, not temperature of these masses be raised or lowered before any significant temperature change will occur.

While your "little experiment" with adding roughly 450,000BTUs may have only raised the air temperature in the basement by 2 degrees it does not necessarily follow that you can (via heatpump) extract an average of 30,000BTUs per hour on a continuous basis during the heating season.

>>Heat DOES NOT RISE! Heat travels equally well in all directions via radiant energy waves until something blocks the wave.

Really? Are you serious? You are kidding right? You know we aren't talking about in a vacuum here right? This is a basement we're discussing.

Yes, I'm serious and no, I'm not kidding. HEAT does not rise. Heated AIR rises but HEAT travels equally in all directions.

That's probably the first thing you learn in thermodynamics.

I just completed an experiment to give me some idea if this will work. Initial average basement air temp 62, walls/floors 55, outside 60, house 66 so not much of a difference anywhere. Basement ceiling insulated with 6" fiberglass. I ran the gas grill in the basement for 15 hours straight, 30,000 BTU/hr, about what the house will need on typical January days. In that time basement air temp went up 2 degrees, walls/floors 1 degree. (also bought and used a CO monitor). This seems to prove that the ground does control the basement temp, in the winter its about 10 degrees colder than now but this new info shows that I should not have an issue with it ever going below freezing. Of course I'm going to add more ceiling insulation too.

This has to work well to make sense where I live in CT since electricity is 18 cents per kwh here.

Comments appreciated.

Dave



I have no idea on the question posed by the OP but have to mention this.

PLEASE DON'T BURN YOUR GAS GRILL INSIDE YOUR HOUSE!!!

You are asking for carbon monoxide poisoning. VERY bad thing!!!! People DIE from doing that every year.

looking at the previous posts, I am in agreement with the statement that the compressor might overheat if installed in the basement, but there may be a way around the problem.

My thoughts are these:

The condensing unit will naturally exhaust hot air from the top of the unit (in cooling mode), and this hot air would tend to heat-up the basement. However, if the hot air was ducted to the outside you should have the cool air in the basement for input and the hot air going outside. Further, if the hot air was used to somehow heat water for the water heater, then a double bonus. But... there would have to be some way of continuously bringing in fresh air. I think that is the sticking point. I have been thinking of this problem because the cost of Geo-thermal would take a big chunk out of my budget for my new house. I am going to build in 3 to 5 years, and I am doing the research and drawing plans for my new house.

Just a few thoughts.
Sonny1