2 Compressors In A Single Stage?

[The Shooter]

Hi I have some questions. Has some one already build these "dual" single stages(any work logs)? Is it worth it? What would you say about a dual Danfoss FR7.5G, R507 setup?

[fatguy1992]

I think someone used two compressors in parallel in the 1st stage in a cascade. I haven't seen it done in an SS though.

[quintus]

http://www.xtremesystems.org/forums/...ghlight=tandem

It can be used only one bigger condenser.

[Shingoshi]

That'd be series, but I'd imagine you'd burn the compressor in front out with the hot discharge from the one doing most of the compressing, and you'd manage a lower low side pressure.

If you put a heat-exchanger between the two compressors, heat won't be an issue. But then I would have two HX. One after the second, and the other between them. If you really want to get overly dramatic, depending on which refrigerant you're using, you could put one before the first compressor as well.

Then I would suggest connecting the heat-exchangers in series from the processor back to the condenser. That way you're progressively cooling them in order from the coldest to the warmest refrigerant in line.

I'll have to read the rest of this now to see what anyone has said about oil management. Because with two compressors, you need to distribute the oil evenly between the two.

EDIT: You should see the new Sanyo two-stage compressors in one unit! Search google for them. I believe there are other companies now making them as well.

Shingoshi

[Shingoshi]

With reciprocating compressors you simply drill a hole in the bottom of the case and link the two compressors with 1/4" tubing. The oil levels will equalize during operation. With rotary compressors I guess you can do the same thing.

In that case, they used a reservoir for all of the compressors and used an oil leveler to make sure each unit was properly fed.

My only question is, how safe is it to do this? Do you need a diagram to know where to drill the oil lines? Otherwise, doing this blind could be problematic.

Shingoshi

[[486]]

If you put a heat-exchanger between the two compressors, heat won't be an issue.

Then you have liquid refrigerant going into the second compressor.

[tiborrr]

Two stage compression isn't that hard of a project, but you need a phase separator in order to prevent low stage compressor to suck in liquid refrigerant. Also the refrigerant of choice must be able to operate at high and low pressure. It's possible to achieve very low temperatures but cascade is a better solution though since you can choose refrigerant for each cycle separately.

So - if you have two appropriate compressors:
- for very low temperatures go with cascade
- for very high cooling capacity go for a tandem.

[Shingoshi]

Then you have liquid refrigerant going into the second compressor.

I meant a reservoir for the OIL. They used a COMMON OIL RESERVOIR connected to the oil sumps of each compressor. They then fed all compressors their oil from that reservoir, using an oil leveler.

I think I missed your point! Yes, if there were no separator used, you would get liquid instead of vapor going into the second compressor. I just didn't think that was necessary to be explicit, since I thought that should already be known. Sorry for the assumption.

Hope that clears up any confusion.

Shingoshi

[[XC] gomeler]

An oil leveler? When performing multi-stage compression the compressors will have different suction and discharge pressures. You can't simply pipe the oil dumps together as the pressure will equalize and shortcircuit your loop. 2 stage compression is best accomplished with a single multistage compressor.

Tandem compression is simple as the pressures are identical.

[[XC] gomeler]

A note, it may be possible to operate a multistage compression system with the sumps connected via a solenoid. Run the system for a few hours and then powerdown and equalize the oil. Not worth the trouble though, a cascade will dare I say be safer.

[gosmeyer]

Again! Why?? Because you can? use some logic

Still dont get the point.

Not worth the trouble though, a cascade will dare I say be safer.

Nuff Said!

I know I'm old and i don't like change, haven't been around for awhile (maybe for the best) but where has Phase forum gone??

[Shingoshi]

As I was searching Google for methods of using parallel compressors, this is one of the links I came across.
Parallel compressors single condenser
This is the link where the discussion of oil came into play:
A very effective oil return system is key to success
I hope this explains what I said and why.

Shingoshi

[sdumper]

Again! Why?? Because you can? use some logic





Nuff Said!

I know I'm old and i don't like change, haven't been around for awhile (maybe for the best) but where has Phase forum gone??

+1

Its been very slow lately...

I might start posting some SS bencher builds just to break the routine...

[tiborrr]

You do that, Scott. Hell, i've been posting chiller, auto-cascades, cascades, waterblock to evaporator modifications. It seems as I'm the only one left working on something in here.

It's rather sad and lonely

[sdumper]

You do that, Scott. Hell, i've been posting chiller, auto-cascades, cascades, waterblock to evaporator modifications. It seems as I'm the only one left working on something in here.

It's rather sad and lonely

I was just thinking that you were really the only one building anything cool lately.

Nice work on that autocascade!!

[ultralo1]

Hopefully this Fall and winter I will contribute a build. For now I must be content to play with chew toys

[[XC] gomeler]

LOL have your fun ultralo1. As for myself I'm financially broke beyond belief until my student loans come in. When that happens though I'll have a little fun.

[tiborrr]

Gom, stop tearing away the mobo sockets, it might help the budget :P (this is being told by a person who ruined two M4A78T-E in a three weeks)

[[XC] gomeler]

http://cgi.ebay.com/COPELAND-SCROLL-...d=p3286.c0.m14

Tandem Scroll Compressors. This is how you build a tandem compressor system. Notice the oil equalization piping at the bottom with the sightglass. Imagine building a gigantic autocascade with this setup

[Shingoshi]

http://cgi.ebay.com/COPELAND-SCROLL-...d=p3286.c0.m14

Tandem Scroll Compressors. This is how you build a tandem compressor system. Notice the oil equalization piping at the bottom with the sightglass. Imagine building a gigantic autocascade with this setup

And I'm wondering how well this layout would work for me? My compressors are 230v R-22 2-ton units.

Shingoshi

[wdrzal]

And I'm wondering how well this layout would work for me? My compressors are 230v R-22 2-ton units.

Shingoshi

Hey guys,just a reminder, don't forget R-22 starts it's phase out per "Montreal Protocal" Dec 31. remember how R-12 prices went ballistic.......... I don't have a crystal ball but quit a few extra pallets warehoused.

[[XC] gomeler]

Hey guys,just a reminder, don't forget R-22 starts it's phase out per "Montreal Protocal" Dec 31. remember how R-12 prices went ballistic.......... I don't have a crystal ball but quit a few extra pallets warehoused.

I've got 2 jugs in storage back home to resell later

[Shingoshi]

Hey guys,just a reminder, don't forget R-22 starts it's phase out per "Montreal Protocal" Dec 31. remember how R-12 prices went ballistic.......... I don't have a crystal ball but quit a few extra pallets warehoused.

Maybe you should have known about this!
ISCEON® MO99™ refrigerant

Google can be so kind if you ask it to!
Shingoshi

[[XC] gomeler]

Maybe you should have known about this!
ISCEON® MO99™ refrigerant

Google can be so kind if you ask it to!
Shingoshi

I'm not quite certain what Walt's angle was on that but I would be willing to bet he's looking to resell it, hence why he'd store a few pallets. Like any commodity, prices will spike once production has ceased and the man sitting on a pile of said commodity will have a nice pay day as demand won't stop for a while.

[mEsUsah1]

to eliminate the oil level issue on hermetic compressors in paralell; you simply drill a hole in the bottom of the shell, and drill a hole at the upper part of the compressor, or use the service pipes to equalise the gass pressure. By doing so the oil flows freely from one compressor to the other. If one compressor is not running, ther wil be no problem since the compressor high pressure valves are shut due to the pressure difference.