View Full Version : 2 Compressor in 1 system
skhan855
14-10-2020, 07:54 PM
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:
15689
Regards
Salman
skhan855
15-10-2020, 09:18 AM
Hi
Would appreciate follow up
Josip
15-10-2020, 12:39 PM
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
15-10-2020, 12:53 PM
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
15-10-2020, 09:07 PM
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:
15689
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/DOC230286438497/DOC230286438497.pdf
skhan855
15-10-2020, 09:42 PM
Thanks Ranger1, this means 1 NRV to each Compressor on discharge side and no NRV on sunction side?
RANGER1
15-10-2020, 09:50 PM
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/DOC148786422181/DOC148786422181.pdf
skhan855
16-10-2020, 02:20 PM
Yes, I think so, as stops condensed liquid on compressor head.
Another Danfoss paper, maybe a bit better.
https://assets.danfoss.com/documents/DOC148786422181/DOC148786422181.pdf
Thanks, it really helps
Yes, I think so, as stops condensed liquid on compressor head.
Another Danfoss paper, maybe a bit better.
https://assets.danfoss.com/documents/DOC148786422181/DOC148786422181.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
19-10-2020, 08:08 AM
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
19-10-2020, 08:19 AM
Hi i would say your thinking is good . go for this
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.
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
23-10-2020, 06:00 PM
you need to control both compressors to stop it freezing when the load is low
skhan855
01-11-2020, 11:15 AM
Thanks for all suggestions
Ninini
05-02-2021, 12:57 AM
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.
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