Another refridgeration question

[Bajansailor]

Following on from my loose knees post re my pals' Vancouver 32 in Greece, they also have a query re their reefer system on board.

Andy wrote :
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Apart from loose knees our radar wasn't working after we returned in Sept. (VERY hot summer) & last week the fridge went on the blink - it just stopped being cold/the ice disappeared from around the O-type evaporating plate, though this was still slightly cold when the compressor was running. (Karin thought I'd defrosted it!).
A repair guy from the marina looked at it & tried filling it with gas - twice. It's now a steady 8-9 degrees C - not ideal, but better than at first. I tried speaking to a lad (he sounded about 12!) at the Isotherm agent in England, but we still don't know what the problem is!
He seemed to think it was unlikely to be the compressor - they usually work forever according to him, with 1 in 1000 failing at some point (well we could be the unlucky 1!).
The repair guy thinks it might be the compressor - he said he found muck when he drew a vacuum before re-filling the system.
However, it seems odd that it's working better now, though not properly! We still aren't sure whether all the gas leaks out quickly or takes its time if the problem IS a leak - the repair guy doesn't have a gas sniffer!
It's been working now for 5 days with no loss of efficiency, so a leak seems unlikely.
Could there be air in the system?
Can the gas lose its efficiency or 'vanish' without there being a leak?
The compressor seems to be making the same noise it's always made, but it is working all the time now, as the thermostat temperatures are never reached - it used to run around 12hrs out of 24 - which would keep the evaporating plate frozen.

If you know anyone with basic fridge knowledge (our boat electrical systems 'bible' doesn't help & I've tried the soapy water test), then we'd love to know if they have any ideas.
We could wait until we're back in GB, but we're almost certainly not allowed to take a compressor or whole unit back by plane because of the compressed gas.
We bought this unit 6 years ago at the London Boat Show (2002) & had intended to carry it in our hold luggage (hadn't really thought about any implications), but it didn't arrive in time & was sent to Spain by the suppliers, where we fitted it ourselves.
It's only air cooled, but we've been very happy with it - Isotherm Classic compact with a Danfoss compressor BD35F.

We can get a new compressor or whole unit in Athens if required, but obviously don't want to go down that route if it's not necessary. We are hoping to find an email contact at Danfoss, in which case we'll send them the details also.
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I know nothing about refridgeration systems, but I am sure that some forumites have had similar experiences to the above, and can comment?

 

[2Tizwoz]

The 'repair guy' doesn't have a leak detector! /forums/images/graemlins/smile.gif

There will be a filter/drier in the system which if it is dirty will restrict the gas flow and should probably be changed. It sounds as if the system has been regassed, badly, by someone who isn't competent and may still be short of gas. As there is a leak, it should be found. A maintenance routine would also involve cleaning the condenser periodically.

 

[Bajansailor]

TNX for this, am sure that my pals will be along soon and take note.

 

[FullCircle]

Agree that it sounds like the gas charge is not correct. Also that the orifice may well be contaminated.
Recommend a full vac and refill, ensuring the vac is perfect. Leave the vac on and check for leaks. Refill with correct refrigerant.
If the syastem works consistently poorly, it sounds like no lreal leak, but could be very slow.

 

[Heckler]

the usual reason for semi cold evaporator is lack of gas, the man says he saw muck when he vacuumed, where? did he have a glass or plastic/liquid collector? if he saw debris then the compressor is on the way out. but really the filter water trap should have collected this, was he bull shitting? need to get a set of guages on it and check the pressures, the only way to tell really.
stu

 

[Bajansailor]

I shall ask the owners of this recalcitrant fridge to respond, either here or via me, to all the questions above.
It might take a little while though, as I dont think they are wified where they are at the moment, hence have to resort to internet cafes.

 

[Pete735]

As Stu implies, sounds like you need a more competent refrigeration guy. Evap not being cold and compressor running is sure sign of low refrigerant levels. A sniffer is essential for leak detection, soapy water is a waste of time on slow leaks, some leaks are so slow they can take a year + to loose refrigerant.

I do not understand remark about muck when vacuuming, refrig man should have removed refrigerant still in system into a recovery unit before vacuuming and this is a closed system, there's nothing to see other than a couple of gauges to watch.

Correct procedure is to remove refrigerant and check weight of refrigerant removed, pressure test with nitrogen, then if no leak detected vacuum and weigh in correct weight of refrigerant, manufacturer will tell you wt of refrigrant and type if its not on compressor. Refrig engineer should have all the kit for this as it's basic a/c stuff. Hope this helps and good luck.

 

[Bajansailor]

Received an email this morning from the Cresswells - here are their thoughts re the fridge issue. They are very grateful for all the comments and suggestions above!

They said :
"As far as the fridge is concerned we have come to the conclusion that there is a partial blockage in the compressor.
After I rattled it vigorously on its flexible mountings (same principle as bashing an old telly on the top!), it began to work more efficiently, actually producing frost on the evaporator plate.
It is still not quite as good as it used to be, but quite adequate while we have shore power.
We are waiting for a reply to an e-mail we sent to a guy we have been in contact with at Danfoss UK to see if it is economically viable to clean it out.
The problem here is that we have very limited choice of repair men. The one we have used so far is expensive and we are not sure that he knows what he is doing.
We feel perhaps it might be better to cut our losses and start again with a totally new system which we could fit ourselves.

 

[Pete735]

A blockage in compressor is almost impossible, if compressor was being impeded in some way then muck was in there when system was built, given it's been running that's v v unlikely and if muck was present, I think compressor would have failed very quickly. Danfoss compressors are hermetically sealed, so you can forget about cleaning them, it's a bin and replace job.

More likely are a poor electrical connection or depending upon the control system a sticking valve controlling refrigerant flow into evap. ( if system has one - some of systems I work on have them and some do not). Think I'd check all electrical connections, assuming refrigerant level is right ( I know that's a big assumption given previous posts!)