Fridge / Compressor external pipes freezing

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KevinT1

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On holiday for 3 weeks in CI / Brittany and we have noticed that the return pipes from the fridge to the compressor are collecting a significant mount of ice - eg 5mm diam copper pipe has 12mm of ice build up.

This is outside of the fridge and on the return pipe from the plate to the compressor, the fridge is getting down to temperature. Boat is a Hallberg Rassy 36 from 1998, System is frigoboat with air cooling, fitted as standard by the manufacturer.

I've contacted the Refridgeration Engineer who serviced and regassed the fridge last Autumn and he says it's due to the warm / humid weather. Nigel Calders manual says it's a symptom of over gassing.

Any thoughts - does any body else get this icing outside of the fridge ?
 
I can definitely answer this one.

The suction pipe temperature should be a few degrees above the evaporator plate temperature e.g. evap -3 - 0oC, SP 3 - 6 oC, which in turn should be a couple of degrees below the desired cabinet temperature, 4 - 7oC..

The idea is that all the liquid refrigerant should have boiled just before the fluid exits the evaporator, so there is little heat left to absorb. The refrigerant fluid is now a pure gas, so has no more latent heat to absorb, and holds several degrees of superheat above the saturated evaporation temperature (e.g Superheat = 6 Kelvin - sad isn't it !!!)

So Calder's advice is likely correct, or possibly the wrong refrigerant. If you are using R134a i doubt the wrong gas has been used, but easy to overcharge a small fridge. Some of the R12 drop ins might perform differently so check what gas you are using. As your boat is 1998 I would be amazed if this were supplied on by then illegal R12.

The suggestion this is due to excessive humidity is, er, how do I describe it, oh yes that's it - bollocks.

Moisture will condense out on the cold pipe, but for a fridge (not a freezer) this should always be above 0oC, so forms a dew which drips off. Even on a freezer the refrigeration process finished inside the evaporator plate, so even then only a light ice layer will form. To form a hard ice layer as described twice the thickness of the tube itself means active evaporating refrigeration is still taking place inside the suction return pipe.

If this is allowed to continue you are endangering your compressor, which will not tolerate liquid refrigerant entering. Liken this to running your car engine with white spirit instead of oil in the sump.

A cowboy will vent it, and proper fridge engineer will recover the excess, although for a small fridge just venting the manifold hoses will likely correct the charge quantity. Charging a small system means adding gas until the suction pipe starts to sweat, but never to freeze.

I would finish that the suction pipe should be tightly insulated, but as said liquid refrigerant returning to your compressor will kill it.
 
superheat6k said:
I can definitely answer this one.

The suction pipe temperature should be a few degrees above the evaporator plate temperature e.g. evap -3 - 0oC, SP 3 - 6 oC, which in turn should be a couple of degrees below the desired cabinet temperature, 4 - 7oC..

The idea is that all the liquid refrigerant should have boiled just before the fluid exits the evaporator, so there is little heat left to absorb. The refrigerant fluid is now a pure gas, so has no more latent heat to absorb, and holds several degrees of superheat above the saturated evaporation temperature (e.g Superheat = 6 Kelvin - sad isn't it !!!)

So Calder's advice is likely correct, or possibly the wrong refrigerant. If you are using R134a i doubt the wrong gas has been used, but easy to overcharge a small fridge. Some of the R12 drop ins might perform differently so check what gas you are using. As your boat is 1998 I would be amazed if this were supplied on by then illegal R12.

The suggestion this is due to excessive humidity is, er, how do I describe it, oh yes that's it - bollocks.

Moisture will condense out on the cold pipe, but for a fridge (not a freezer) this should always be above 0oC, so forms a dew which drips off. Even on a freezer the refrigeration process finished inside the evaporator plate, so even then only a light ice layer will form. To form a hard ice layer as described twice the thickness of the tube itself means active evaporating refrigeration is still taking place inside the suction return pipe.

If this is allowed to continue you are endangering your compressor, which will not tolerate liquid refrigerant entering. Liken this to running your car engine with white spirit instead of oil in the sump.

A cowboy will vent it, and proper fridge engineer will recover the excess, although for a small fridge just venting the manifold hoses will likely correct the charge quantity. Charging a small system means adding gas until the suction pipe starts to sweat, but never to freeze.

I would finish that the suction pipe should be tightly insulated, but as said liquid refrigerant returning to your compressor will kill it.
Click to expand...
Nail on head, overgassed! but if it has run ok since last autumn? Being a cowboy and knowing where all the R12 that was recovered years ago went and so being a cynic! A quick finger nail on the gas valve would release some enough to stop it! Again the however, the OP being an amateur, woukd probably let too much out, so, going back to the beginning, if its run ok till now, wouldnt worry too much about it!
Stu
 
If there is only one Schrader valve it will be on the suction side of the system which could be running on a negative pressure so attempting to vent off excessive refrigerant without using a set of gauges with the compressor running could result in you drawing air into the system !
small amounts of liquid refrigerant entering the compressor will boil off into a vapour when coming into contact with the hot compressor oil before entering the compressor cylinder
But as already said sounds like it's been slightly over charged
Unless the evaporator is very heavily iced up or the evaporator fan motor has failed ( if there is one )
On the plus side it shows the system hasn't lost any refrigerant !!
 
Thanks all for the very helpful replies.

I can confirm it is R134a, as the system has labels to that effect and the Refridgeration Engineer confirmed that when he serviced it.

To clarify, the icing only occurs when the thermostat is set to 6 or 7 ( out of 7 ) and at that point the internal temperature of the fridge gets down to 2 or 3 c. And the compressor is running almost 100% of the time.
If set to 4 or 5 then fridge is running 50%, but the internal temp only gets to 7 or 8 c and I guess this means any ice that is formed melts off during the off periods.

Whilst being very practical, I don't feel competent to mess around with this, and if there is no risk to the compressor, will hold off until we get home and get the Engineer back again.

Thanks
Kevin.
 
KevinT1 said:
Thanks all for the very helpful replies.

I can confirm it is R134a, as the system has labels to that effect and the Refridgeration Engineer confirmed that when he serviced it.

To clarify, the icing only occurs when the thermostat is set to 6 or 7 ( out of 7 ) and at that point the internal temperature of the fridge gets down to 2 or 3 c. And the compressor is running almost 100% of the time.
If set to 4 or 5 then fridge is running 50%, but the internal temp only gets to 7 or 8 c and I guess this means any ice that is formed melts off during the off periods.

Whilst being very practical, I don't feel competent to mess around with this, and if there is no risk to the compressor, will hold off until we get home and get the Engineer back again.

Thanks
Kevin.
Click to expand...

To get it down to 2 or 3C and it is running 100% of the time? I would suspect that the fridge could benefit substantially from more insulation added from the outside. Mine will only run 20% of the time to be stable at that temp even when it is 40C. Thats 4 inches all round of insulation. So if you can add more it would take a lot of the stress off the batteries, especially in the recent hot weather in France.
 
KevinT1 said:
Thanks all for the very helpful replies.

I can confirm it is R134a, as the system has labels to that effect and the Refridgeration Engineer confirmed that when he serviced it.

To clarify, the icing only occurs when the thermostat is set to 6 or 7 ( out of 7 ) and at that point the internal temperature of the fridge gets down to 2 or 3 c. And the compressor is running almost 100% of the time.
If set to 4 or 5 then fridge is running 50%, but the internal temp only gets to 7 or 8 c and I guess this means any ice that is formed melts off during the off periods.

Whilst being very practical, I don't feel competent to mess around with this, and if there is no risk to the compressor, will hold off until we get home and get the Engineer back again.

Thanks
Kevin.
Click to expand...
I would expect that when the unit was charged the temp wasn't taken so low, so possibly only minor overcharge. I would avoid running it with the hard frost on the suction, as you are risking the compressor. 5- 6 oC cabinet temp is fine for most fridges. Good advice to increase the insulation, and pay attention to any small gaps as the heat gain at these points can be massive.
 
Adethefridge said:
If there is only one Schrader valve it will be on the suction side of the system which could be running on a negative pressure so attempting to vent off excessive refrigerant without using a set of gauges with the compressor running could result in you drawing air into the system !
small amounts of liquid refrigerant entering the compressor will boil off into a vapour when coming into contact with the hot compressor oil before entering the compressor cylinder
But as already said sounds like it's been slightly over charged
Unless the evaporator is very heavily iced up or the evaporator fan motor has failed ( if there is one )
On the plus side it shows the system hasn't lost any refrigerant !!
Click to expand...
On my Bene there is an access valve on both sides, std Waeco compressor
S
 
William_H said:
And once the problem is solved perhaps insulation on the pipes would improve efficiency of the system...
Click to expand...
My husband insulated the pipe that froze when our fridge was installed, but it had been running with the door open We don't understand how an off-the-shelf system could be "over-gassed", especially as some leaked out as the fittings were tightened.
 
William_H said:
And once the problem is solved perhaps insulation on the pipes would improve efficiency of the system. olewill
Click to expand...

When we got the boat my pipe leading to the fridge/freezer would be coated in a sleeve of ice after a week or so. I bought a metre of pipe insulation at B & Q and covered the whole pipe rather than just the bit near the compressor. After that the fridge part was freezing everything including the milk in a few hours so I turned the control down to almost its lowest setting. The freezer now freezes and the fridge keeps the milk in liquid form!

Richard
 
On my recent install I noticed that the pipes were very cold and a bit drippy, so made the assumption that a bit more lagging would only help, seemed to improve the efficiency a little too. As per RichardS - Wickes lagging to the rescue.
 
Following this thread, could any of those more experienced in refrigeration (probably most/all of you) advise me - Have a Waeco CU-55 compressor and appropriate plate which is 10 years old and no longer cooling much, if at all. I believe new cooling plates come filled and with sealed connectors - with the high call out costs of a fridge man would it not be best to just buy a new plate and connect it myself or is life not that simple...?
 
Lightwave395 said:
Following this thread, could any of those more experienced in refrigeration (probably most/all of you) advise me - Have a Waeco CU-55 compressor and appropriate plate which is 10 years old and no longer cooling much, if at all. I believe new cooling plates come filled and with sealed connectors - with the high call out costs of a fridge man would it not be best to just buy a new plate and connect it myself or is life not that simple...?
Click to expand...

Just bumping this up for you ... but you would have been best advised to start a new thread with a title relating to your question.

Welcome to the Forum. :)

Richard
 
Waeco connectors don't self-seal, so if you disconnect your plate all the gas will escape. When you get a new compressor and plate they are both gassed and sealed with a membrane which is spiked on assembly. Try getting it professionally re-charged, you night get another 10 years out of it.
 
superheat6k said:
I can definitely answer this one.

The suction pipe temperature should be a few degrees above the evaporator plate temperature e.g. evap -3 - 0oC, SP 3 - 6 oC, which in turn should be a couple of degrees below the desired cabinet temperature, 4 - 7oC..

The idea is that all the liquid refrigerant should have boiled just before the fluid exits the evaporator, so there is little heat left to absorb. The refrigerant fluid is now a pure gas, so has no more latent heat to absorb, and holds several degrees of superheat above the saturated evaporation temperature (e.g Superheat = 6 Kelvin - sad isn't it !!!)

So Calder's advice is likely correct, or possibly the wrong refrigerant. If you are using R134a i doubt the wrong gas has been used, but easy to overcharge a small fridge. Some of the R12 drop ins might perform differently so check what gas you are using. As your boat is 1998 I would be amazed if this were supplied on by then illegal R12.

The suggestion this is due to excessive humidity is, er, how do I describe it, oh yes that's it - bollocks.

Moisture will condense out on the cold pipe, but for a fridge (not a freezer) this should always be above 0oC, so forms a dew which drips off. Even on a freezer the refrigeration process finished inside the evaporator plate, so even then only a light ice layer will form. To form a hard ice layer as described twice the thickness of the tube itself means active evaporating refrigeration is still taking place inside the suction return pipe.

If this is allowed to continue you are endangering your compressor, which will not tolerate liquid refrigerant entering. Liken this to running your car engine with white spirit instead of oil in the sump.

A cowboy will vent it, and proper fridge engineer will recover the excess, although for a small fridge just venting the manifold hoses will likely correct the charge quantity. Charging a small system means adding gas until the suction pipe starts to sweat, but never to freeze.

I would finish that the suction pipe should be tightly insulated, but as said liquid refrigerant returning to your compressor will kill it.
Click to expand...

^^^THIS^^^ for sure slightly overcharged.
 
Billjratt said:
Waeco connectors don't self-seal, so if you disconnect your plate all the gas will escape. When you get a new compressor and plate they are both gassed and sealed with a membrane which is spiked on assembly. Try getting it professionally re-charged, you night get another 10 years out of it.
Click to expand...

The best thing to do if you do have it recharged is ask them to cut the fittings off and braze the pipes together. I know from hard learnt experience of selling these units that I had to do this on every one I sold. Otherwise I would have to spend loads of time recharging lost gas systems as they inevitably leak. some leak faster than others but they all leak. Solution braze the pipes together and then I could give a two year warranty.
 
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