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.

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.:mad:

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.

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

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

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.

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.

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.