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View Full Version : can l.b.p. unit replace h.b.p. unit on a cold room?







jammy
15-05-2009, 11:19 PM
Just looked at small cold room in a restaurant where the evaporator and expansion valve were changed about 4 months ago. When i visited the condenser fan motor had siezed, i changed it and tested ok. The next day i received a call to say the r.c.d. device was tripping when the unit was switched on, turned out the compressor had gone. I decided to change the condenser unit (ELECTROLUX MR 18 TB). I requested a price for 18cc h.b.p. r404a unit and was told by supplier that a cmx 18 l.b.p. unit would achieve a temperature of -3c. The room was run at +1c so i accepted this as it was considerably cheaper. I fitted it late on tonight and found that it was very slow coming down to temp. I left to go back and see how things are tomorrow as it was getting late. Any thoughts?!

nike123
16-05-2009, 09:34 AM
It is not clear what replacement compressor make is. Is it Danfoss SC 18 CMX?

jammy
16-05-2009, 06:01 PM
Electrolux (acc). Does it matter what make it is, isn't it only relevant that it is 18cc and l.b.p.? Hope that dosen't sound confrontational, if it does it's not meant to. I would really appreciate comments from someone like yourself.

nike123
16-05-2009, 07:45 PM
Electrolux (acc). Does it matter what make it is, isn't it only relevant that it is 18cc and l.b.p.? Hope that dosen't sound confrontational, if it does it's not meant to. I would really appreciate comments from someone like yourself.

It does matter since every compressor manufacturer gives operation envelope and if you are out of that envelope, you could expect premature death of compressor.
There are some compressors which could work as LBP and MBP compressors. Therefore I asked what is make!
For example that Danfoss I mentioned could work with highest evaporation temperature of -5C.
Some other LBP could not work higher than -10C.
If your case temperature is 1C, that could mean that evaporation temperature is -7C and for that Danfoss it is within operation envelope and for some other it could mean that is outside operation envelope.

multisync
16-05-2009, 11:31 PM
I remember seeing two indentical unite hermatique condensing units
First one on R12 doing the cold room and the second one on R502 doing the freezer. Both chugging away quite happily :eek::eek::eek::eek::eek::eek:

jammy
19-05-2009, 12:37 PM
Supplier told me that it evapoates at -10c and can achieve -3c. Despite adjusting valve and everything else in system being right i cannot get it to condense. My conclusion is that it needs to be h.b.p.

nike123
19-05-2009, 12:54 PM
Supplier told me that it evapoates at -10c and can achieve -3c. Despite adjusting valve and everything else in system being right i cannot get it to condense. My conclusion is that it needs to be h.b.p.

If it started and runs then it must achieve its duty.
What is superheat, subcooling saturation temperatures air in and out temperatures?

jammy
19-05-2009, 11:47 PM
Superheat was 24f! Decanted refrigerant, changed drier, vacuumed and re-charged. Coming down much quicker now.

D.D.KORANNE
20-05-2009, 10:47 AM
difference betwen lbp & hbp is the motor rating . lbp compressor hence will konk off on hbp application ; hence need to check among other things such as operating envelop of
compressor

jammy
25-05-2009, 12:21 PM
Thanks for taking time to give me the advice you did, i appreciate it.