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Tas
25-04-2008, 05:05 PM
Hi there

I have a marine refrigeration system that is not cooling as well as it used to.

The system is Frigoboat and I believe is 12 years old. It has worked flawlessly for the last 4 years (since I bought this boat). It is a fully copper piped system with a sealed electric (12v) compressor.

The symptoms are:

compressor runs constantly (or very long periods)
evaporator forms thin layer of frost but not much more
condenser and compressor don't seem to be very warm
fridge doesn't get particularly cold!

The evaporator fan runs and the condenser is free from dust etc and the ambient temperature has not changed appreciably since this started happening.

Before I dismantle it all, is this a symptom of low refrigerant gas?

p_p
25-04-2008, 05:19 PM
It sounds like it is short of gas from the information supplied but could do with a bit more info if poss, like system standing & operating pressures etc.
Is it a capillary or exp valve.
Check for signs of any oil on pipework.

Regards

PP

Tas
25-04-2008, 05:59 PM
Hi P_P - thx for a quick reply!!

It is capillary and I don't know about the pressures as I have not had time to connect a guage set on to it yet (the compressor lives in a grubby cupboard.... :( )

There are no obvious signs of oil on the pipework but as much of this disappears behind bits of boat it's tricky to check it along the length. The bits I can see seem "clean".

From what I know (which isn't very much - I'm more mechanical and electrical boat systems) copper systems don't tend to loose gas even after 10+ years, unless you know different? The only possible weak points I can see are a couple of connections where the compressor is connected to the rest of the pipework via screwed couplings with rubber sealing washers. From what little experience I have these are usually reliable but after 10 odd years??? I don't know.

I don't want to take these apart yet but I will check for oil now you have said it!

I would guess the system is filled with R12 (from it's age) - can I top it up with RS-24 or does it all have to be purged and refilled completely (assuming I find the leak or it is just low on gas)?

Your help is much appreciated - suprisingly, refrigeration people are not common here in the Greek islands....and gas? Forget it...that's why I'm loathe to undo bits as yet!

Brian_UK
25-04-2008, 08:41 PM
Hi Tas and welcome to the forum.

Screwed joints with rubber washers are not a good means of sealing refrigerant systems.

You can't normally mix refrigerants so, especially if it is R12, you will have to recover the existing charge for safe disposal before doing any further work on the system.

With that age I would suggest a pressure test before anything else is decided.

Mayball
28-04-2008, 06:03 AM
Hi Tas
If your Frigoboat system is low on refrigerant, it will not be frosted on the entire surface of the evaporator. The thickness of the frost is more a function of the seals on the door, but the extent of the frost is a function of the amount of refrigerant charge.
Don

jure
28-04-2008, 06:49 PM
Hi TAS
I think the first thing you should do is to recover refrigerant and do the pressure test
Everything you wrote shoves insufficient refrigerant

nike123
28-04-2008, 07:24 PM
Hi TAS
I think the first thing you should do is to recover refrigerant and do the pressure test
Everything you wrote shoves insufficient refrigerant


First ting he should do is to check airflow/water flow, filter cleanliness and then check superheat and subcooling or sight-glass state. Then we could talk little more scientific and be little less prophets.
He didn't gave any superheat and subcooling or empty sight glass reading to contribute to theory on low refrigerant charge.

expat
28-04-2008, 08:49 PM
Look for leaks where the copper is unprotected and especially where it is in contact with other metals. Your problem is likely to be electrolysis.:(

PaulZ
29-04-2008, 04:21 AM
I agree with nike we don't know the operating pressures yet. These symptoms could also point to an inefficient compressor or several other faults.
Tas, get some gauges on the system and do the checks nike suggested and then come back with the info.
Paul

Tas
08-05-2008, 06:30 AM
Hi all,

Been busy with other problems.

Thanks for all the suggestions.

I will be getting a guage set soon and will post the results when I have them.

The fridge is still working albeit with limited cooling (which hasn't got any worse). This suggests to me no or tiny leak as surely all the gas would have leaked out by now??

I should re-iterate that the system has been working fine for probably 14 years(!!); there are no sight glasses to check refrigerant flow; cooling fins and fan on the compressor and condenser are clean and in good order.

The guage test will show the problem I'm sure!

powell
08-05-2008, 03:29 PM
Tas,

Just a thought but it would be cheaper to find a local refrigeration engineer to check out the system. You're going to need to purchase a few tools, which he/she will already have, to do the job yourself. Such as guages, leak dectectors, torches, refrigerant etc etc etc.

Regards.............. Powell