Any refrigeration engineers in?
Discussion
Obviously I’m guessing a bit as I’m not stood in front of it but the danger to the compressor is probably not immediate as the effect of running on when in pump down mode will be the lack of refrigerant flow over the motor which will over heat and burn it out eventually
It does sound like either wiring or a faulty LP control switch
Take a photo and post it up
It does sound like either wiring or a faulty LP control switch
Take a photo and post it up
Thanks, very helpful, I'll take some pictures tomorrow and post them up.
I'm curious if we might just not be giving a tired compressor enough time to engage the LPS, the quality control sticker from the unit is from 2015, I have no idea how long they are likely to last, it was probably in constant use for about 6-7 years before sitting for a year. Brand names on it are GEA Searle, Trenton and Marston, most parts seem to be Danfoss.
I've attached the pictures that the lad sent me of the LPS
I'm curious if we might just not be giving a tired compressor enough time to engage the LPS, the quality control sticker from the unit is from 2015, I have no idea how long they are likely to last, it was probably in constant use for about 6-7 years before sitting for a year. Brand names on it are GEA Searle, Trenton and Marston, most parts seem to be Danfoss.
I've attached the pictures that the lad sent me of the LPS
jmsgld said:
Many thanks for your input, yes I agree, would like to diagnose the problem. If I put up some photos would you be able to give me some pointers as to how to diagnose if it is the LPS or whatever you suggest?
Your welcome, I have reached the limit if my ability now though I am afraid. I am The maintenance manager in a factory making frozen products, we have a several dozen refrigeration systems in all sorts of capacities, gasses and function, etc
We actually use an external contractor to actually maintain it and for call out repairs.
While I have the understaning of the systems the parts, how it works and the refrigeration principles etc. I actually lack the experience of physically working on the kit.
But it looks like there is still some knowledgeable people in here that might be able to help you further.
Every day is a school day.
Can someone confirm; a cold store system stops the flow refrigerant flow, then the low pressure switch switches the compressor off?
Seems a strange way of doing it.
Not sure about UK/Europe, R404a refrigerant is sometimes used in cold stores - very very expensive in NZ (due to its global warming potential). Perfectly alright to recover and reuse of course - but you need all the equipment.
I’m a long way from fully up to speed on current systems/process, I learnt refrigeration theory as an apprentice for an air con company starting nearly 40 years ago and have been off the tools and remote from the trade (but not completely) for over 25 years. But if you are taught something properly, you never forget.
why pump down? As a general principle, not specifically related to cold stores which I didn’t do much work on anyway then the main reason is to avoid liquid refrigerant forming in the evaporator/compressor during shutdown
How does it work? I described it in my previous posts. My laptop has packed up and I’m typing this on a phone, I’m not doing all that again
why pump down? As a general principle, not specifically related to cold stores which I didn’t do much work on anyway then the main reason is to avoid liquid refrigerant forming in the evaporator/compressor during shutdown
How does it work? I described it in my previous posts. My laptop has packed up and I’m typing this on a phone, I’m not doing all that again
Edited by LastPoster on Saturday 29th June 07:51
caziques said:
Every day is a school day.
Can someone confirm; a cold store system stops the flow refrigerant flow, then the low pressure switch switches the compressor off?
Seems a strange way of doing it.
Not sure about UK/Europe, R404a refrigerant is sometimes used in cold stores - very very expensive in NZ (due to its global warming potential). Perfectly alright to recover and reuse of course - but you need all the equipment.
Yes they can, depends on the system normally on larger ones with more gas. Can someone confirm; a cold store system stops the flow refrigerant flow, then the low pressure switch switches the compressor off?
Seems a strange way of doing it.
Not sure about UK/Europe, R404a refrigerant is sometimes used in cold stores - very very expensive in NZ (due to its global warming potential). Perfectly alright to recover and reuse of course - but you need all the equipment.
In a cold store it should be -18 so there is potential for ice for form on the coils if the refrigerant is left constantly. The systems can pump down the coil and shut down. Or pump down do a defrost (either using using heaters or the warm gas in the system)
I wasnt aware they did it as part of the normal control cycle sometimes. (Though some of my work systems cool a huge freezer, and others have the compressors on inverters so they ramp down rather than off completely)
Yep of the top of my head we have R404, R449,R452 which were about £90/kg last time we had work
We also have Ammonia (R717) which is actually very cheap as a refrigerant seen it for £7/kg - it's the dangerous nature of it that complicates things!
Edited by Buzz84 on Saturday 29th June 08:32
It has a receiver and so should be a pump down system and in theory the LP switch should stop the compressor by breaking the line to the contactor coil.
But I’m not a fridge tech so can’t really say what’s causing this, it’s easy to blame the switch, but mechanically ithe system might not be doing what it’s supposed to.
It’s quite a crude control method in my opinion, I’m used to more complicated stuff.
But I’m not a fridge tech so can’t really say what’s causing this, it’s easy to blame the switch, but mechanically ithe system might not be doing what it’s supposed to.
It’s quite a crude control method in my opinion, I’m used to more complicated stuff.
jmsgld said:
The original piping for refrigerant was very long, and in this set up is very short. I don't know if that impacts the total amount of refrigerant or the pressure? Thanks
Pipe run length affects the amount of refrigerant required by the system, but not the running pressuresWhoever installed/commisioned it for you should have adjusted the charge correctly
Comment above about of having a receiver so must be a pump down system is not correct. Receivers are required to cope with varying load.
I note it’s a cold room ( big fridge) not a freezer so the comments about defrost cycles and timers aren’t relevant
In terms of what’s next, the system looks a little complex for your needs but you are where you are. When temperature is satisfactory at the controller ( you talked about hearing it click) then the solenoid should close. The change in note of the compressor suggests this is happening and after a bit the LP switch should open due to the fall in pressure. At this point the compressor contactor should lose the voltage to its coil and drop out. The compressor will then stop. If it doesn’t the contactor is stuck. If the voltage doesn’t go then it’s not opening the LP switch either because the switch is faulty or the compressor cannot pump it down. But you need gauges to check pressures to decide that.
It’s quite possible the diagnosis of a faulty switch is correct. There is nothing unique about the switch you just need a replacement with the correct pressure range. A refrigeration wholesaler such as Dean and Wood or HRP should be able to help. I think that 061F9010 is the part number
Edited by LastPoster on Saturday 29th June 10:33
Many years ago, our cold store had a faulty LP switch.
We came in the morning to find the fridge at about -10C. Everything frozen and ruined. A new switch was put in and it worked well until we replaced the whole compressor unit a few years later.
It was also the catalyst to installing a SMS alert system for low / hi temps. Been an absolute godsend.
We came in the morning to find the fridge at about -10C. Everything frozen and ruined. A new switch was put in and it worked well until we replaced the whole compressor unit a few years later.
It was also the catalyst to installing a SMS alert system for low / hi temps. Been an absolute godsend.
Many thanks LastPoster for all your help, much appreciated.
Yes, it is more complicated than we need, it was an ebay job, local commercial tenant needed it gone quickly so was only £100 for the whole thing.
I will test the electrical side of things as suggested and check with the lad whether he adjusted the amount of refrigerant, could it potentially cause this issue if there is too much refrigerant in there?
Cheers, James
Yes, it is more complicated than we need, it was an ebay job, local commercial tenant needed it gone quickly so was only £100 for the whole thing.
I will test the electrical side of things as suggested and check with the lad whether he adjusted the amount of refrigerant, could it potentially cause this issue if there is too much refrigerant in there?
Cheers, James
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