air source water heater using HT gear heat? - AVS Forum
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post #1 of 8 Old 06-06-2012, 06:25 AM - Thread Starter
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We're going to tear down our existing home and build a new one in it's place.

I'm interested in being energy efficient when possible. HT and computer gear can produce a lot of heat. Has anyone considered or used an air source hot water heater to take advantage of the waste heat?

They basically work by taking heat out of the ambient air and using that as a reverse cycle air conditioner. Seeing as how all my computer and HT gear cranks out a fair amount of heat it occurs to me it might be worth finding a way to utilize it.

I've got a totally blank slate to work with with regard to placement of the theater and utility equipment. So putting them near each other isn't a problem. It'd also be easy to place proper drains to avoid problems from potential tank failures later.

Anyone used an air source water heater?
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post #2 of 8 Old 06-06-2012, 12:29 PM
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Quote:
Originally Posted by wkearney99 View Post

We're going to tear down our existing home and build a new one in it's place.
I'm interested in being energy efficient when possible. HT and computer gear can produce a lot of heat. Has anyone considered or used an air source hot water heater to take advantage of the waste heat?
They basically work by taking heat out of the ambient air and using that as a reverse cycle air conditioner. Seeing as how all my computer and HT gear cranks out a fair amount of heat it occurs to me it might be worth finding a way to utilize it.
I've got a totally blank slate to work with with regard to placement of the theater and utility equipment. So putting them near each other isn't a problem. It'd also be easy to place proper drains to avoid problems from potential tank failures later.
Anyone used an air source water heater?

far more efficient transfer of energy to just use solar water heater if it really means that much to you.

consider that electric WH elements are ~5000 watts. I strongly doubt all of your equipment together is losing 5kw of heat (in reality, probably your WHOLE house, including lights are not losing 5kw of heat), then you would need 100% efficiency to even make use of that.

solar water heater is a pump, can use a standard tank conversion, and black pipes/basin and the water will be hot enough to burn you on a summer day.....and may be able to avoid pump if water pressure adequate and installation allows efficient use of gravity.
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post #3 of 8 Old 06-07-2012, 01:54 PM - Thread Starter
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Originally Posted by longtimelurker View Post

far more efficient transfer of energy to just use solar water heater if it really means that much to you. .

The point isn't to just get hot water, the point is to consider recovering the heat that's being generated and otherwise wasted.

Yes, a roof solar array is arguably a great way to collect heat for household water. But that's not my primary need. I'm interested in dealing with the heat all my gear cranks out. No, it's certainly not making 5kw worth of heat, but it's enough that added HVAC cooling is necessary for it in the summer months. And in the winter it heats enough of the surrounding area to allow closing off heat into the surrounding space.

So the question remains, has anyone else here used an air-sourced water heater in their house?
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post #4 of 8 Old 06-07-2012, 06:39 PM
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Interesting concept!

Would you otherwise use a conventional electric water heater or is gas available where you are? If you have gas I'd guess your total energy budget may be lower using an indirect fired hot water system (from your heating boiler) and cooling the gear with the central AC. Modern condensing boilers will hit 95% efficiency.

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post #5 of 8 Old 06-08-2012, 08:59 AM - Thread Starter
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Gas is available, we use it now for the water heater, furnace (forced air ducting) and backup AC generator. But all that gets ripped out (by a recycler) when the place is demolished. What I'm doing is weighing my options on what goes into the new structure. We're going to be insulating the hell out of the whole house. So just about anything we go with will almost certainly be less expensive to operate, as the current structure has barely any insulation in the 1" firred walls and air leaks like a proverbial sieve.

But meanwhile I've got a bunch of computer and AV gear that cranks out of a lot of heat. Heat that is either dealt with by the air handler (as part of all the other ducted HVAC) or through an air-source water heater. But since those are electric they might be more expensive to operate than is practical, at least when compared to gas. But if we go with geothermal and a desuperheater it might be advantageous to look at this kind of water heater for backup along with a storage tank.
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post #6 of 8 Old 06-08-2012, 10:17 AM
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I have a coworker that had an air source water heater installed in his basement...he said it works well and cools his basement down pretty good! I happen to think that it would work pretty well.

If there are rebates available from my local utility company, I might consider doing it when my water heater is due for replacement. In my scenario, I have all my equipment in an A/V room, and I have a bathroom exhaust fan that is controlled off a line-voltage thermostat. That exhaust fan sucks air past the rack and blows it into my storage room (that houses my furnace and water heater). It cant work much better than that.

I havent done much research yet, but one thing to think about is if you are using a bunch of hot water, you probably are not down in the theater rejecting heat from your electronics. I suppose a dishwasher or a washing machine could be running while you are watching movies, etc. What I am getting at is I dont know how much $ savings you would see, so it would be hard to calculate a payback. If your utility company gives you a rebate though, it could help it be financially feasible.
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post #7 of 8 Old 06-10-2012, 08:44 AM - Thread Starter
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Thanks Brian. I'm having a local HVAC guy work up some numbers for me on this and I'll report back.

As for overlapping use, I believe the idea is the water heater will recover what it can to keep the contents hot all the time. I have a fair amount of gear that I use for working at home. It'll be able to recover heat from more than just the AV gear. A bunch of it runs 24x7. Maybe not 'enough' for the heater to heat all of the water, but perhaps enough to offset the amount of AC that would be necessary to cool the room otherwise.

Since this is all new construction I have a lot of flexibility in where stuff gets located. Thus I'd be able to put the water heater potentially right in the same location as the equipment. Taking account for access, draining and the like, of course.
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post #8 of 8 Old 06-11-2012, 04:20 AM
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We replaced our gas water heater with a GE Geospring (heat pump) water heater about 6 months ago. We really like the unit, and it uses the heat is the surrounding room via the heat pump to heat the water in the water heater. In eco mode (only uses heat pump) it uses minimal energy and heats just as hot as our gas unit did. The recovery time is longer, but it hasn't been a big issue yet. As and added bonus, it cools and conditions the air in the room when it is running. Ours is installed in the same room as our furnace, and it really puts that extra heat to work. I could see doing the same with heat from HT equipment.

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