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Old 12-13-14, 08:54 PM   #21
Bicycle Bob
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Setting out to burn NG is likely to encourage fracking, but I love the idea otherwise. I'm appalled that we can't buy NG heat pumps based on free pistons, without all the extra parts. Electronic valve control is making it easier to opmimize, too. Having the waste heat to temper the intake should make things easy.

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Old 12-13-14, 09:27 PM   #22
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Quote:
Originally Posted by theoldwizard1 View Post
...Even though there are losses in the electric transmission line and some in the electric motor inside the compressor, it is not likely that a natural gas "powered" heat pump (compressor) will EVER be cost effective !...

It just makes me crazy, absolutely crazy, when old guys use bold print...

Feast your elderly eyes on this.

Sincerely,

-AC
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Old 12-14-14, 06:14 AM   #23
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Quote:
Originally Posted by AC_Hacker View Post
It just makes me crazy, absolutely crazy, when old guys use bold print...

Feast your elderly eyes on this.

Sincerely,

-AC
It's not just old guys AC, haha
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Old 12-14-14, 06:23 AM   #24
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Quote:
Originally Posted by AC_Hacker View Post
It just makes me crazy, absolutely crazy, when old guys use bold print...

Feast your elderly eyes on this.

Sincerely,

-AC
It's interesting. If you look at that report, they are using running temps well in excess of our needs in the resi environment. The COP is around 1.6 and while there are savings to be had, I think a resi gas HP switching between ASHP and propane or NG (when needed) could have a COP of 5 and eliminate the ground loops. Also note they don't even look at it running at ambient temps anywhere below freezing

I find a lot of engineering articles still use water temps and boilers running at what we would have seen 20-30 years ago. 80% efficient copper fin boilers, as though they have never heard of low temp radiation or condensing equipment before. So much for real energy reduction.
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Old 12-14-14, 06:36 AM   #25
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Disappointed it's only for hot water. Would have been nice if they also had chilled water output. The real key is sizing it down to a residential scale.
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Old 12-14-14, 08:07 AM   #26
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Quote:
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From Wikipedia




I actually worked alongside some guys trying to develop a Wankel engine to run the A/C compressor in the late 1980s. The engine would run on natural gas. It was aimed at small businesses (convenience stores, fast food restaurants, etc).

The system worked fine, but there were durability issues. When run continuously, the oil and spark plugs had to be changed every 2-4 weeks ! Also wear on the seals (Wankel equivalent to piston rings) was high.

The motivation was a predicted shortfall of electric power in the SE (check the population growth in GA from 1980 through 2010).
Must have been problems with that particular company's engine. In Mazda rotaries, seal life is well over a thousand hours at high power, as long as 2stroke oil is used for apex seal lube instead of crankcase oil. No issues with crankcase oil, either. They do need extremely cold plugs when run at high power, though. Worst thing should have been rpm issues. It's difficult to get decent power at less than 4-5K rpm.

Charlie
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Old 12-14-14, 09:36 AM   #27
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Quote:
Originally Posted by Servicetech View Post
Disappointed it's only for hot water. Would have been nice if they also had chilled water output. The real key is sizing it down to a residential scale.
I think that it mostly has to do with where you place the metering device.

With heat pump application, you get the added benefit of "wasted heat" from the engine & exhaust.

-AC
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Old 12-14-14, 10:10 PM   #28
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With 96% efficient natural gas furnaces I don't see there being much room for improvement for the complexity of running an engine to drive a compressor for the heat pump cycle. Gas furnaces are reliable because its a very simple concept, fire and hot air. It seems you are considering this more for cooling and reducing your electric usage or in lieu of electricity. It might make more sense to use a NG powered generator to run your hvac. And try to capture the exhaust heat into hot water. The york units had briggs and straton motors. I don't think these motors were considered efficient. From a technician's stand point I wouldn't want to repair a york triathlon, sounds very specialized and proprietary.
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Old 12-14-14, 10:32 PM   #29
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The problem with a 96% efficient gas furnace is in the method they are using to get the efficiency number, I fathom.

The heat loss threw the rear vent would need to be factored in to get a idea of its efficiency. I am not a pro on the subject I feel about 40% ? of the heat is being lost out the back vent. They do breath I am thinking a heat recovery unit off the vent would prove to improve the efficiency number to more of its true potential.
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Old 12-14-14, 10:51 PM   #30
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Generally the name plate ratings show input btu and output btu to derive the efficiency. I am curious about under what conditions and runtimes they do their tests. The usual testimony for 96% furnaces are the lukewarm to touch pvc flues. Cant imagine too much heat escaping through that lukewarm pipe.

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