2 Compressor in 1 system

[skhan855]

Hi,
I am making a chiller for injection molding and plan to install 2 compressor in a system being 1 primary and 1 secondary.
Primary would be running at all times while secondary would be used when temperature from primary could not be attained and need extra power for extra load.

I am confused with 2 question and need expert advice.

1) If I install 2 compressors than should I place NRV on both compressors on both suction and discharge side?

2) one of local compressor was advising me to drill a liner horizontal pipe between 2 compressor for compressor oil of both compressors to be equal at all times, according to him if I don't do this then oil on compressor will not be balanced.

Diagram below:
2ndcompressor.jpg

Regards
Salman

[skhan855]

Hi
Would appreciate follow up

[Josip]

Hi, skhan855

Hi
Would appreciate follow up

after maybe only 24 hours without reply to your request
this is not necessary ...
we all are here voluntary

(our daily bread we have doing our normal jobs)

someone will give you some advice when get a
free time for it ....

Maybe I sound rude, but we have to respect everyone
who is spending own free time here to help someone ...
so, no need to push .....

Best regards, Josip

[skhan855]

Ofcourse, thats why I asked initially asked advice in a respected manner. I really appreciate contribution of members on this forum as it helped me earlier in lot of cases.

[RANGER1]

Hi,
I am making a chiller for injection molding and plan to install 2 compressor in a system being 1 primary and 1 secondary.
Primary would be running at all times while secondary would be used when temperature from primary could not be attained and need extra power for extra load.

I am confused with 2 question and need expert advice.

1) If I install 2 compressors than should I place NRV on both compressors on both suction and discharge side?

2) one of local compressor was advising me to drill a liner horizontal pipe between 2 compressor for compressor oil of both compressors to be equal at all times, according to him if I don't do this then oil on compressor will not be balanced.

Diagram below:
2ndcompressor.jpg

Regards
Salman

Salman,
Yes advice is correct, but only require check valve in compressor discharge.
Pipe so oil cannot accumulate in its discharge pipework if off for extended periods.

Yes also need to balance/equalise compressor sumps, usually compressor has to be designed for this when purchased.

https://assets.danfoss.com/documents...0286438497.pdf

[skhan855]

Thanks Ranger1, this means 1 NRV to each Compressor on discharge side and no NRV on sunction side?

[RANGER1]

Thanks Ranger1, this means 1 NRV to each Compressor on discharge side and no NRV on sunction side?

Yes, I think so, as stops condensed liquid on compressor head.
Another Danfoss paper, maybe a bit better.

https://assets.danfoss.com/documents...8786422181.pdf

[skhan855]

Yes, I think so, as stops condensed liquid on compressor head.
Another Danfoss paper, maybe a bit better.

https://assets.danfoss.com/documents...8786422181.pdf

Thanks, it really helps

[mbc]

Yes, I think so, as stops condensed liquid on compressor head.
Another Danfoss paper, maybe a bit better.

https://assets.danfoss.com/documents...8786422181.pdf

Hi
Yes this a 1 reason
Another important reason
if on of the discharge valve plate is brocked.
Provent gas goes to suction side in rack system.

In rack system also blanceing of oil should have good attention with oil filter and insulate valves.

[CoolKiwi]

Oil balance line required, discharge check valves (nrv) recommended.
Also, oil balance lines require careful installation as separate compressors can twist and break connections.
Scrolls are especially bad, but solid mounting eliminates this issue. (Noise not too bad with scrolls) recips, just make sure you have a couple 90 elbows between comps.
Avoid flare connections where possible.
How do you intend to control the comps?
If using lp switch, I suggest a delay timer on 2nd comp. Digital control, set a delay.
Good luck and have fun..

[ramesh]

Hi i would say your thinking is good . go for this

[Aik]

Oil balance line required, discharge check valves (nrv) recommended.

For discharge valve better use nrvh - with stronger spring.
For oil equalization you need two tubes - one for oil, another - for union suction chambers of compressors. Or one big tube which one half for oil equalization, another half for gas equalization.
As regurds me, I prefer classic oil return system with oil separator, oil reciver and oil regulators on each compressors.

[mbc]

Hi Aik
you recommend for to use classic oil return is very good
when one of the compressor damaged and burnouts and oil carbonated
it doesn't effict other compressor oils.

[martinw58]

you need to control both compressors to stop it freezing when the load is low

[skhan855]

Thanks for all suggestions

[Ninini]

Yeah, i also think the person-located's suggestion is right, if not , the balance will not be keep.And aslo,Maybe you should learn something about the one-way valve and check valve which can provide you help.