# Thread: oil return system in parallel compressor rack

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## oil return system in parallel compressor rack

Dear fellows:
I´m trying to understand the theory of operation of the oil return system in a parallel compressor rack. It´s my understanding that the oil is taken out of the refrigerant at the oil separator located in the discharge manifold. From there, whenever there is enough oil in the separator to open the float valve, the oil travels to the oil reservoir. From there, the oil flows to each one of the oil level controls, located at each compressor, and from there into the crankcases. What I cannot understand yet is how is the oil reservoir kept at a slighty higher pressure than the crankcases in order to keep the oil flowing. As far as I can see in this rack, whenever the oil separator float valve cracks open, the pressure in the whole oil return system must be that of the discharge line, not just a few pounds above the crankcase pressure. How is this high pressure not allowed to get into the crankcases and suction manifold ? Any comments welcomed.

2. Originally Posted by coldkeeper1
Dear fellows:
I´m trying to understand the theory of operation of the oil return system in a parallel compressor rack. It´s my understanding that the oil is taken out of the refrigerant at the oil separator located in the discharge manifold. From there, whenever there is enough oil in the separator to open the float valve, the oil travels to the oil reservoir. From there, the oil flows to each one of the oil level controls, located at each compressor, and from there into the crankcases. What I cannot understand yet is how is the oil reservoir kept at a slighty higher pressure than the crankcases in order to keep the oil flowing. As far as I can see in this rack, whenever the oil separator float valve cracks open, the pressure in the whole oil return system must be that of the discharge line, not just a few pounds above the crankcase pressure. How is this high pressure not allowed to get into the crankcases and suction manifold ? Any comments welcomed.
It's done with a check valve on top of the oil reservoir ie a 20 lb ckeck valve
would keep 20 pis in the res above suction psi.

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Originally Posted by crackertech
It's done with a check valve on top of the oil reservoir ie a 20 lb ckeck valve
would keep 20 pis in the res above suction psi.
Yep.

Beat me to it, cracker.

It is also very important to maintain a proper level in the reservoir. If it is too full, it will cause problems and, if it is empty, well that's obvious.

4. If its a Hussmann rack then there is a differential valve on the oil return line. I can't remember the part 3 but I believe it starts with a Y. This valve looks like a TXV without the sensing bulb. This valves work alot like a TXV creating a pressure differential.

5. Originally Posted by CE-TECH
If its a Hussmann rack then there is a differential valve on the oil return line. I can't remember the part 3 but I believe it starts with a Y. This valve looks like a TXV without the sensing bulb. This valves work alot like a TXV creating a pressure differential.
I have only seen that on hussman 2 stage low temp racks.

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Originally Posted by crackertech
I have only seen that on hussman 2 stage low temp racks.
I see that valve on all of my Hussmann racks.

It actually took me a little longer to catch on the the typical separator/reservoir system when I finally ran into it.

7. Originally Posted by crackertech
I have only seen that on hussman 2 stage low temp racks.
I have seen it on many hussman racks. I always called it a Y valve and URI would know what I wanted.

8. "Y valve" is slang

The valve is a Y-825-2 valve. It is made by sporlan, but good luck on finding information on that specific valve because it was designed by sporlan for Hussmann. And Sporlan never documented any literature on it.

You will find a little info in some Hussmann Racks Manuals http://www.hussmann.com/Discontinued...SS_Rack_im.pdf page 106.

however it functions the same as sporlans Y1236-C http://sporlan.jandrewschoen.com/110-10_012008.pdf

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you have a hi presure oil system here made by hussman and temp rites are the same set up with a valve that is and work on the same princple

High Pressure System
If your system has an oil separator with a built-in oil reservoir, you will need one of two models depending on your system; either an A-7, a constant-output valve, or an Y1236C, a variable-output valve.

A-7
The A-7 is a constant output valve. The majority of Temprite 920R Series coalescent oil separators monitor the oil back to the oil level control via the A-7 pressure-reducing valve set to the desired pressure.
NOTE: If you are using a split suction header, i.e., +20°F, -20°F, you will need two (2) A-7 valves per system.
See schematic: High Pressure Oil System with Split Suction

Y1236C
The Y1236C valve is a variable output pressure-reducing valve that tracks suction pressure. It is designed for high-pressure oil return systems, or other situations where a differential pressure regulator is required. Set the output as needed for the system and the Y1236C adjusts the flow to maintain the desired output pressure.
See schematics: High Pressure Oil System with Split Suction and High Pressure Oil System with Pressure-Reducing Valves

NOTE: A TraxOil electronic oil level control does not require a pressure-reducing valve.

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Originally Posted by dirtyboy103us

NOTE: A TraxOil electronic oil level control does not require a pressure-reducing valve.
TraxOil R.I.P. Emerson OMB valves, now. Exactly same thing only much better with no magnets to collect crap to and fail.

11. I put this together some time ago for our shop training program.
Hope it clears up some confusion.

12. Originally Posted by bryan l
I put this together some time ago for our shop training program.
Hope it clears up some confusion.
bryan would mind if we put this up in the EF

13. Feel free.

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