DX Geothermal Pond 4 ton Heat Pump

[MEMPHIS91]

Jeff, I am in the middle of redoing a lot insulation and fixes that the house needed when built. It was built in 1986, with R13 walls with Styrofoam and weather wrap. The ceiling are blown fiberglass, and about to be reblown to R39ish. But I have about 500 square feet of 17 feet tall vaulted ceiling where there is only about R22 on the slopped part of the ceiling (almost impossible to fix without TONS of work). The house is a total of 2,300 SQF with 300 SQF added on and 440 SQF in the upstairs.
I am adding radiant barrier to all the rafters and radiant double bubble to the knee walls upstairs and on the vault. I have been cutting down on air leaks (built on a slab) and will do a air exchange test when I'm done. I got the thermal seek camera to help locate cold/hot spots and have found a few. Like the chimney, about 100 SQF was toally uninsulated. The windows are old but I put rigid foam on the back bedrooms that we do not use during the winter and have put reflective film on all the windows that get summer sun. So though things will be better insulated BUT there was an extra 300 SQF added on (enclosed garage), so I really think that 3-4 tons is in the ball park.

[MEMPHIS91]

Looking into proper sizing of things, I will for sure have sight glasses in lots of places to be sure my charge is just right.
This is a good article
Analyzing Refrigerant Flow Problems

Looking at the waterfurnace stuff now.

[jeff5may]

Duh, I should have known that already. Now that you mention it, I have read posts you made about it elsewhere in the forum. Please forgive me, I'm an idiot.

Since you are considering the Emerson pots for your heat pump, here's a curveball for you to catch. They have two main types of variable-capacity scroll compressors: the ultra and the digital. Neither one needs a vfd to do its job.

The ultra scroll has two stages of capacity: high and low. The compression scroll has two suction ports and one discharge port inside the shell. One suction port is located at the outside edge of the scroll, and is open all the time. The second port is located between the first suction port and the discharge port. It has a "swing plate" that normally uncovers the port. When activated, it covers the port, which enables the whole scroll and increases pumping capacity. These models follow the ZPS*K5 naming, where the * is the high speed rating.

The digital scroll is continuously variable between 10 and 100 percent output. This is accomplished mechanically by allowing the top scroll to float slightly away from the bottom scroll. When this happens, the seal between the scrolls is lost, pumping stops immediately, and the motor is unloaded. Capacity is varied by duty cycle, by energizing an internal solenoid valve. When energized, the solenoid valve uses the compressor's own suction pressure to disengage the valves from each other. When released, the scroll goes right back to full output.These models follow the ZPD*KSE naming.

Both of these lines have been out since the 90's, so there should be some out there somewhere. I imagine they do what they should pretty well. Much too expensive for my modest systems, though.

[MEMPHIS91]

HAHAHA, YOU an idiot? Yeah ok sure, and I'm running for president.

Awesome info and really what I'm looking for. Sure I can make this thing work well with fewest parts possible, but if I'm going to live here for I don't know how long, I want this to be something I designed to run the best it can.
Heck why not digital control of the metering device like a mini split. I would love to control the compressor, the water pump, and the txvs! But that just might be a dream......
Hard to find the ZPD so far but a couple of hits for the ZPS came up, all for 410a of course so I could either use 410a or just know I need a larger compressor to get the same btus out of propane.
Here as an article on the ZPD, I would be a cool project to try a solenoid on a rotary compressor tied back into the suction side with a super fast on/off cycle to see if you could cut back on displacement with out messing something up. lol How Copeland Scroll Digital
Thanks Jeff
New in Box Copeland 4 Ton R 410A Scroll Compressor Model ZPS49K4E PFV 830 | eBay
Rheem Ruud 55 23156 34S Copeland Scroll Two Stage R410A ZPS49K5EPFV830 | eBay

[jeff5may]

In Europe, they are in the process of developing new lines of compressors that use brushless dc motors and inverter drives to run them. Check out these leaflets:

http://www.emersonclimate.com/europe...-EN-1410_1.pdf

Copeland Scroll

It looks like they are putting most of their eggs in the r-410a basket, at least for the larger-than-a-fridge range.
Copeland Scroll Variable Speed Technology

[MEMPHIS91]

Those look amazing! The ZPV038 would be a nice fit for my house I think. But getting my hands on one would be basically impossible and extremely expensive.
So I guess my options are.
-Buy a 3.5-4 ton R22 single phase single stage compressor and just design it the best way I can. This is the cheapest option but with the lowest COP.
-Buy a 4-5 ton single phase two stage compressor made for 410a and swap it over to R22. This will be pretty expensive ($650-800)
-Wait until the VPS comes to the US and still have to swap it to R22 (or keep it 410a) Still pretty expensive This would probably be the most expensive.
-Buy a 3 phase compressor made for R22 and a vfd to match. This is the very expensive ($800-1000), but considering that it gives me the control I want, I am still confused as to why this is not a good option. This 7.5kw is a close match to what I would need. 7 5KW 10HP 34A 220VAC Single Phase Variable Frequency Drive Inverter VSD VFD | eBay
-I could get 2 ton R22 single phase compressors and only use one on light loads and have both come on when needed. Finding a couple 2 ton compressors would not be very hard. Or a 2 and a 4 ton. http://hvac-talk.com/vbb/showthread....sor-vs-2-Stage

I will be on the lookout of a 2 stage compressor locally.
Thanks for all your help and advise as I try to really consider all the options I have.

[Fordguy64]

You could get two 2 ton two stage units. Would theoretically give you 4 stages depending on how it was all put together

[jeff5may]

Today's deal near you:
4 ton goodman AC condenser

[MEMPHIS91]

That does look like a good deal, Jeff! Thanks!

Ford, thanks for the idea, im still looking into dual compressors and if I need a 2 ton and a 4 ton, and only run one at a time, or I need 2 2 tons and run both when 4 tons are needed.

[superlen]

Memphis,

Regarding staging vs variable speed, watch out for oil return issues when using multiple compressors. I have visited three different Geothermal manufacturers over the last 10 years and while visiting with their engineers, (electronics side, not thermodynamics side), two of the three had mentioned field reliability issues with some of their multiple compressor designs regarding oil return. All three were migrating towards variable speed designs and away from multiple compressors. Production designs always have to meet a certain cost constraint so they may have just been trying to stay too close to the edge, or maybe they didn't get enough test/validation time before they had to go to market. Any number of possibilities exist.


For larger systems, I think VS has been the norm for some time now. It's just now making it's way down into the 5T and smaller systems as found in residential. What's interesting is that it skipped around the 3-5T systems with the minisplits leading the way now.

My prefs if I wanted variable capacity would be in order:
1. VS VFD or brushless DC either one
2. Two stage scroll compressor
3. Multiple compressor

Being a hacker, I would do what you're doing, keep a lookout for the perfect choice, and play with what you can scrounge up easily for not too much money.

One question I would ask is unless you have all the components, evap/cond/both txv settings, charge, water flow, air flow, ect. tweaked in perfectly, how much more efficient will a true variable speed compressor be over say just a simple two-stage unit? I don't know the answer to that.

Len