Air Source Heat Pump Outside Unit Location

cholcombe · 01-21-11, 10:55 AM

This might sound a little crazy but I was wondering. Would it be possible or even advisable to place the outside of unit of a heat pump in your unheated attic? I figure you're losing heat through there anyways so maybe you'd be able to recapture some of it. I'd also imagine that the temp in the attic is slightly warmer than the surrounding outside air. What do you guys think about this? Just a crazy thought.

Piwoslaw · 01-22-11, 04:16 AM

More insulation will be much more cost effective.
Once the heat pump starts sucking heat from the attic, it will get cold in there, colder than outside, so in effect it won't be more efficient than placing it outside.

cholcombe · 01-22-11, 08:45 AM

mm yeah that's a good point! I didn't think of that. Thanks Piwoslaw

Xringer · 01-23-11, 08:49 AM

Quote:

Originally Posted by Piwoslaw

More insulation will be much more cost effective.
Once the heat pump starts sucking heat from the attic, it will get cold in there, colder than outside, so in effect it won't be more efficient than placing it outside.

I agree.. It's 13.6 °F here right now, but if you measure the cold air
coming off the Sanyo, it's going to be Much colder. And, there is a LOT of it.

The Sanyo needs a LARGE supply of outdoor air to work.
You would need to install large fans to suck the cold air out of your attic.

However, if you were using a small BTU mini-split inside a very large attic
which is always hot, due to solar heating of the roof (no snow blockage), it might work okay.

The biggest bummer is, summer cooling would be about impossible during the day time..

Right now, it's so cold here, we are in multi-heat mode.
1. Oil heat is in flow-through mode.
2. Sanyo is using 690w (10,000 BTUs maybe).
3. South facing windows are letting in some free solar heat!
4. Electric oil-filled heater is keeping the den from frosting over.
5. 400w PV is warming the oil burner storage water.
6. I'm drinking hot INKA drinks!

cholcombe · 01-23-11, 09:11 AM

Xringer: Yeah I know it's pretty brutal outside now. We're burning up oil like crazy. I think I might set the daytime temps down to 65. It's 68 right now and it's kinda tough maintaining that. I agree, putting the sanyo in the attic is probably a dumb idea. Just thought I'd throw it out there and see what people think. The whole mini split heat pump concept is a little new to me. I majored in computer science in college

I've been online reading how heat pumps work. It's fascinating stuff. I most likely will be buying one when I get my tax return money in. The only problem is where to indoor handling unit. It seems you and a few others have mentioned that convection currents do a good job of moving heat through the house. That could be very helpful.

Xringer · 01-23-11, 10:11 AM

Just take a look at this fan.. It moves a large volume of air..
(The leading edge of the blades are razor sharp).

Some people have used fans to move warm air around their home.
I think someone had a small array of muffin fans on the ceiling in a hallway.

I don't mind the bedroom being 2 or 3 degrees colder.. Nicer sleeping..
Just keeping the main parts of the house at 21C all the time seems to be keeping me in my comfort zone.

Those leaking basement windows are killing the geo heat off the floor slab..
In one corner, it was 44F this morning. But most of the slab is now at 60F.
Shot a sump-pump hole and it was 65F down there.

New casement windows is on my bucket list..

~~~
Anyways, your post had got me thinking about all that heat in the attic..
(When there is not 3 feet of snow on the shingles).

If I could install an attic vent fan that fed warm air into a PVC downspout
that ran down the side of my house, with the exhaust centered behind the Sanyo...
That might save some power on sunny days..

Recycling:
And, like you said, some of the heat inside the house escapes to the attic..
So, why not return that heat to where it can be re-used..

Thanks for the idea!

I have already found a cheap 48v fan..
48 Volt Patriot Fan

AC_Hacker · 01-26-11, 10:51 AM

Quote:

Originally Posted by cholcombe

...to place the outside of unit of a heat pump in your unheated attic? I figure you're losing heat through there anyways so maybe you'd be able to recapture some of it...

Thought I'd weigh in on this one...

Quote:

Originally Posted by Piwoslaw

Once the heat pump starts sucking heat from the attic, it will get cold in there, colder than outside, so in effect it won't be more efficient than placing it outside.

This could be worked to your advantage... If you had no insulation between the roof and the inside of the attic, AND had some really excellent insulation in the attic floor (like maybe R-60 ridgid foam + radiant reflector on top), it would be different. Then your heat pump would greatly benefit from the trapped warmth in the attic (in this case you would want a black roof). But still, the exhaust from the mini-split would be best vented outside.

In the summer, if you could bring in fresh air straight into the mini-split and still exhaust the minisplit to the outside, it would work out.

But Xringer is right, in the winter, the minisplit put out huge quantities of very cold air. If you had your mini-split in the mud-room, you'd best change its name to 'The Deep Freeze' (in all seriousness).

Locally there is a house called 'The Rose House' that has PV on the roof and channels the hot air that is coming off the back of the PV panels to feed the input of the mini-split. It improves the efficiency of the mini-split and the PV panels.

-AC_Hacker

basketclam · 09-23-11, 12:41 PM

Hey guys, just joined this forum so I could follow up on this question. Do you suppose it would work to put a heat pump in an unheated area in a subterranean basement? I was thinking about maybe an excavation under your garage. With venting to the outdoors. My thinking is that you'd essentially be able to benefit from the steady underground temperature in the summer AND winter. Am I just chasing pipe dreams here, or is there any merit to this?

Xringer · 09-23-11, 12:59 PM

If you had the amount of ventilation needed for the ASHP, (At 2-tons, it's a LOT).
During cold weather, the system would still be at the mercy of the outdoor air temps..

If the air temp is -15C, your ASHP is going to quickly be sucking in -15C air,
trying it's best to suck some heat out of it.

During the summer, it's going to be cooler under there, in the shade.
So, it will use a bit less power to cool the house.

If the outdoor unit was down in a 20 foot pit, cool air settles and cooling
would work better. (Heating, not so good).

For the winter, I really like the idea of pulling the intake air through a long green house.
The air would pick up some solar heating and drop power cost.
During the summer, the intake air would have to directly vented from the outdoors..
Unless the green house was then shaded and cool inside...

01-21-11, 10:55 AM	#1
cholcombe Helper EcoRenovator Join Date: Oct 2009 Location: Portland, OR Posts: 56 Thanks: 13 Thanked 1 Time in 1 Post	Air Source Heat Pump Outside Unit Location This might sound a little crazy but I was wondering. Would it be possible or even advisable to place the outside of unit of a heat pump in your unheated attic? I figure you're losing heat through there anyways so maybe you'd be able to recapture some of it. I'd also imagine that the temp in the attic is slightly warmer than the surrounding outside air. What do you guys think about this? Just a crazy thought.

01-22-11, 04:16 AM	#2
Piwoslaw Super Moderator Join Date: May 2009 Location: Warsaw, Poland Posts: 961 Thanks: 188 Thanked 110 Times in 86 Posts	More insulation will be much more cost effective. Once the heat pump starts sucking heat from the attic, it will get cold in there, colder than outside, so in effect it won't be more efficient than placing it outside. __________________ Ecorenovation - the bottomless piggy bank that tries to tame the energy hog. Last edited by Piwoslaw; 01-22-11 at 11:31 AM..

01-23-11, 10:11 AM	#6
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	Just take a look at this fan.. It moves a large volume of air.. (The leading edge of the blades are razor sharp). Some people have used fans to move warm air around their home. I think someone had a small array of muffin fans on the ceiling in a hallway. I don't mind the bedroom being 2 or 3 degrees colder.. Nicer sleeping.. Just keeping the main parts of the house at 21C all the time seems to be keeping me in my comfort zone. Those leaking basement windows are killing the geo heat off the floor slab.. In one corner, it was 44F this morning. But most of the slab is now at 60F. Shot a sump-pump hole and it was 65F down there. New casement windows is on my bucket list.. ~~~ Anyways, your post had got me thinking about all that heat in the attic.. (When there is not 3 feet of snow on the shingles). If I could install an attic vent fan that fed warm air into a PVC downspout that ran down the side of my house, with the exhaust centered behind the Sanyo... That might save some power on sunny days.. Recycling: And, like you said, some of the heat inside the house escapes to the attic.. So, why not return that heat to where it can be re-used.. Thanks for the idea! I have already found a cheap 48v fan.. 48 Volt Patriot Fan Last edited by Xringer; 01-23-11 at 10:30 AM.. Reason: found a 48v fan..

01-22-11, 08:45 AM	#3
cholcombe Helper EcoRenovator Join Date: Oct 2009 Location: Portland, OR Posts: 56 Thanks: 13 Thanked 1 Time in 1 Post	mm yeah that's a good point! I didn't think of that. Thanks Piwoslaw

01-23-11, 09:11 AM	#5
cholcombe Helper EcoRenovator Join Date: Oct 2009 Location: Portland, OR Posts: 56 Thanks: 13 Thanked 1 Time in 1 Post	Xringer: Yeah I know it's pretty brutal outside now. We're burning up oil like crazy. I think I might set the daytime temps down to 65. It's 68 right now and it's kinda tough maintaining that. I agree, putting the sanyo in the attic is probably a dumb idea. Just thought I'd throw it out there and see what people think. The whole mini split heat pump concept is a little new to me. I majored in computer science in college I've been online reading how heat pumps work. It's fascinating stuff. I most likely will be buying one when I get my tax return money in. The only problem is where to indoor handling unit. It seems you and a few others have mentioned that convection currents do a good job of moving heat through the house. That could be very helpful.

09-23-11, 12:41 PM	#8
basketclam Lurking Renovator Join Date: Sep 2011 Location: Canada Posts: 1 Thanks: 0 Thanked 0 Times in 0 Posts	Hey guys, just joined this forum so I could follow up on this question. Do you suppose it would work to put a heat pump in an unheated area in a subterranean basement? I was thinking about maybe an excavation under your garage. With venting to the outdoors. My thinking is that you'd essentially be able to benefit from the steady underground temperature in the summer AND winter. Am I just chasing pipe dreams here, or is there any merit to this?

09-23-11, 12:59 PM	#9
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	If you had the amount of ventilation needed for the ASHP, (At 2-tons, it's a LOT). During cold weather, the system would still be at the mercy of the outdoor air temps.. If the air temp is -15C, your ASHP is going to quickly be sucking in -15C air, trying it's best to suck some heat out of it. During the summer, it's going to be cooler under there, in the shade. So, it will use a bit less power to cool the house. If the outdoor unit was down in a 20 foot pit, cool air settles and cooling would work better. (Heating, not so good). For the winter, I really like the idea of pulling the intake air through a long green house. The air would pick up some solar heating and drop power cost. During the summer, the intake air would have to directly vented from the outdoors.. Unless the green house was then shaded and cool inside...