Thoughts on this gshp

[Fordguy64]

So I was cruising Craigslist yesterday and ran across a 2 month old post so I'm thinking I could probably get it for less then 500

http://dayton.craigslist.org/mat/4279324219.html

I emailed the guy last night to see if he still had it and he does.. The only problem is that it's a 265v model. They sell boosters that go from 240 to 265 but I imagine that they are not 100% efficient.. So that brings me to the next question.. Buy it and change compressor to 240v and change the txvs to r22 and run on propane?

Or skip it all together..

[NiHaoMike]

Do the Davuluri Treatment (recover R410a, change TXVs and filter drier, put in R22 or similar) and it will run just fine on 240V. Much cheaper than buying a new compressor.

If it's inverter drive, it might just work as-is.

[Fordguy64]

I did a little research on the booster It would cost 200ish for on of those if it was needed.. Guess I need to do a heat load on my house to make sure that I need a 2.5 ton unit.. It has a 2.5 ton ac unit down that seems to be fine

[doug30293]

265V is the upper limit of a nominal 230V single phase compressor. You don't need a buck/boost transformer to run it.

The refrigeration industry uses nomenclature and conventions that are anything but conventional. Putting 265V on the nameplate of a residential condensing unit is just one example. Convoluted spaghetti wiring diagrams are another.

The unit you are looking at is probably precharged with refrigerant. Provide a water supply and it should be ready to go. $500 seems like a bargain.

[AC_Hacker]

Originally Posted by Fordguy64

...So that brings me to the next question.. Buy it and change compressor to 240v and change the txvs to r22 and run on propane?...

What path you take all depends on your level of experience, and willingness to take on some very serious learning and hacking.

I think that your quickest and most reliable path to success is as you first indicated, get some kind of step-up transformer or equivalent.

Your unit will already have some sensors (TXVs) and also some electronic sensors, which are already optimized for R410a. These will not be affected in any way by a step-up transformer of some kind. A GSHP will have very good efficiency, so some minor transformer losses won't matter much.

However, if you want to really get down and geeky, this unit would be an incredible learning opportunity, because you'll get to learn about a huge amount about GSHP machines, since you'll need to redesign almost all the sub-systems of the unit you have.

What ever you do, please keep us in the loop and take lots of photos.

This could be a very interesting project.

Best,

-AC_Hacker

[jeff5may]

If it fits your need, I would buy it, get the water loops going, and try it on 240VAC first. If it works, you're set for (hopefully) a long unit life at high savings potential. 10% droop on an AC line is not a real big deal to a unit that will only draw 2-3 KW. If it has trouble starting, put a hard start kit on it.

[NiHaoMike]

It lists 239V as the minimum voltage, so it might work but marginally. Get your multimeter, measure a 120V outlet, and you should be able to get by if it's actually 120V or more. It will not work if it's actually 2 phases of a 120/208 service, but that's generally only found in apartments and commercial buildings.

I suppose you could just install it and check the amps. Call it done if it stays within specifications even under worst case load, but if it goes over, time to add a transformer or mod the unit. Look for one with either a 120V or 240V primary and a 10-18V secondary with at least 25A continuous rating.

BTW, you might be able to find a usable transformer out of some discarded UPSes, probably one rated 500VA or more. Look for one that's heavy without the batteries - the light ones are switchmode and will not be useful here. (I suppose you could mod one into a VFD if it's big enough...) Find the high voltage winding and (for the more common 120V type) connect it from one hot to neutral. Then connect the low voltage winding in series with one of the hots going to the unit. If you end up with less voltage, reverse the connections to one of the windings. Depending on the transformer, you might need to only use half of the low voltage winding.

Another option is to modify two or more microwave oven transformers. Cut off the high voltage secondary and wind a low voltage secondary. You'll want to use two with the primaries and secondaries in series run on 120V, since the core is not designed with much margin to begin with. Aim for the same 10-18V secondary voltage as I mentioned before.

[Fordguy64]

ok i got some more info on the unit

http://www.docs.hvacpartners.com/idc...-811-50021.pdf

best i can tell from serial number the unit was built 41st week of 2010

it is a horizontal unit witch kind of sucks but i think i can make it work.

[AC_Hacker]

Originally Posted by Fordguy64

...it is a horizontal unit witch kind of sucks but i think i can make it work.

Go for it!

Please take lots of photos along the way.

Best,

-AC

[Fordguy64]

Well I'm supposed to go pick it up tomorrow.. I found a few similar units on eBay going for 1500-2000$