Converting heat pump to make hot water? - Page 4

AC_Hacker · 04-04-14, 10:33 AM

Quote:

Originally Posted by NiHaoMike

A VFD is one solution.

Tell me everything you actually know about the efficiency of using a VFD that is designed to work with a three phase system, when it is used for a single phase compressor.

I already watched the YouTube videos... what do you actually know about the efficiency.

Don't guess.

-AC

jeff5may · 04-04-14, 05:34 PM

You can rig 2 legs of it and get whatever voltage and frequency of single phase power you want. As long as you don't overload the drive, it'll work. As for efficiency, it's a hack: I bet a transformer would be neck and neck with it at line frequency. But it's magic and can do back flips and stuff...so it's gotta be better.

The reason I mentioned a 3 phase drive was to run the heat pump if he only has single phase electric service. It is made for 460VAC, 3 phase power. However, with some tinkering, he may be able to slow the unit (somewhat) to match capacity or increase efficiency.

Then again, he may be able to just run a phase converter. Or buy a single phase heat pump.

NiHaoMike · 04-04-14, 07:51 PM

A rotary phase converter would be less efficient than a VFD (though possibly cheaper if you're buying it new), while a static phase converter is, for the most part, a VFD.

3 phase is pretty much standard in a commercial environment. He'll almost certainly have to have an electrician add a 3 phase circuit to use a 3 phase compressor, but a single phase compressor can just plug in if there's already an outlet with sufficient current capacity.

04-04-14, 05:34 PM	#32
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	You can rig 2 legs of it and get whatever voltage and frequency of single phase power you want. As long as you don't overload the drive, it'll work. As for efficiency, it's a hack: I bet a transformer would be neck and neck with it at line frequency. But it's magic and can do back flips and stuff...so it's gotta be better. The reason I mentioned a 3 phase drive was to run the heat pump if he only has single phase electric service. It is made for 460VAC, 3 phase power. However, with some tinkering, he may be able to slow the unit (somewhat) to match capacity or increase efficiency. Then again, he may be able to just run a phase converter. Or buy a single phase heat pump. Last edited by jeff5may; 04-04-14 at 05:40 PM.. Reason: comment

04-04-14, 07:51 PM	#33
NiHaoMike Supreme EcoRenovator Join Date: Oct 2008 Location: Austin, TX Posts: 1,154 Thanks: 14 Thanked 257 Times in 241 Posts	A rotary phase converter would be less efficient than a VFD (though possibly cheaper if you're buying it new), while a static phase converter is, for the most part, a VFD. 3 phase is pretty much standard in a commercial environment. He'll almost certainly have to have an electrician add a 3 phase circuit to use a 3 phase compressor, but a single phase compressor can just plug in if there's already an outlet with sufficient current capacity. __________________ To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her...