Parallel compressors

[A.Mortezania]

Dear Guys,
I have a question.

We can parallel compressors to make rack systems, I have 2 question :

1 – Can we parallel for example 10 HP semi-hermetic compressor with 35 HP semi-hermetic compressor ?

2 – Can we for example parallel two different types of compressors ? for example 10 HP scroll type + 10 HP semi-hermetic type ? If we can not why ?

Sincerely yours.

[nike123]

Oil return is main issue with parallel systems and variable refrigerant flow systems. If you properly manage oil return from system to compressors and oil level maintenance in compressors, than you can use any compressor type or size ensuring that all compressors use the same oil in same refrigerant circuit.

That being said, in practice, it is hard to accomplish that.

[anesti]

Hello friends.
Can you help how is the principle of the return of oil and management level in two compressors?
in this case we have two drawal compressor that are tied to the cross, through two capillary tubes (approximately 2mL). I think that one side of the capillary tube is connected to a pump oil within the compressor. To pass oil into a such tube capilar need high pressure. M5AC 055CR it is mini chiller with two scroll compresor. One is burned
file:///C:/Documents%20and%20Settings/User/My%20Documents/Downloads/chiller.pdf

[nike123]

14627

This is where oil return is done. I am not sure how it is oil level balanced between two compressors! It looks similar as liquid cooling of compressor.

[anesti]

Hi nike123 (http://www.refrigeration-engineer.com/forums/member.php?13885-nike123)
I think that, the capilar of compresor N2, is return oil to the suction line of compressor N1. If the level of oil in comp2 reaches the level of the oil pump, then he sends it to the comp N1. There is no other logical , because oil requires considerable pressure, to passing in capilar tube. Compressor N1 is burn and should be replaced only with the same compressor system. Thanks