Fridge capillary tube blocked intermittently - how to clear?

[Yngmar]

History part 1: My boat came with an old Frigoboat system, which I've spent some time on before, figured out the electronics unit on the compressor (Danfoss BD35F) was dead (seawater had gotten at the PCB) and swapped out that electronics unit for a matching one from eBay. The fridge worked fine for over a year and I've learnt all about diagnostic LEDs and stuff. I've also replaced the mechanical thermostat with an electronic one and added a circulation fan inside the fridge, which helped make things more efficient.

History part 2: Very occasionally at first, the fridge would not cool properly, despite the compressor running. The evaporator was only a bit cool and did not make the happy sound of boiling refrigerant. I learnt a lot about overcharged and undercharged refrigerant and capillary tubes and how a tiny tiny piece of debris (often just a bit of crumbled sealant from a connector) can block those tubes. The symptoms are pretty obvious - when switching the fridge off for 10-15 minutes and then back on again, relieving the pressure and causing the debris to fall down again, it usually started working absolutely fine again for many weeks at a time, until the piece of debris arrived at a chokepoint and blocked it again.

Current issue: Unfortunately it now seems to have finally gotten itself wedged in tight somewhere. Switching it off for any length of time does not reset the problem, only very occasionally evaporating sounds can be heard for a minute or two before it blocks again. Tried tapping on the refrigerant tubes as well in an attempt to dislodge the bit(s), but all to no avail.

Question: How do I get the crumbs out of the tubes? There are two Frigoboat self-sealing connectors which I could crack, plus a large Schrader type valve for recharging. There's a filter drier in the pressure line as well, which I assume after this time (10+ years I assume) is due for replacement, but appears to be brazed into the copper tube. How does one replace that?

Bonus Question #1: Is there are refrigeration engineer covering the Brighton area that actually understands how fridges work rather than just doing troubleshooting from a flowchart and charging me many pointless hours repeating things I've already tried? Must have some familiarity with boats (tricky access, Frigoboat connector adapters), which most domestic guys will probably lack.

Bonus Question #2: If I want to have a go at clearing the debris myself with the help of the compressor pump (as one guy on the Jeanneau forums has done), I will need to recharge the thing afterwards. Apparently car aircon (R134a) refill kits can be used for this, if the bottle is held upright so the oil stays in the bottle. But which fittings and adapters do I need to tap into that bottle and attach it to my Schrader valve (larger type than on a bicycle tire, 1/4" I read on this handy page)?

Note: I'm aware of the dangers of pressurized refrigerant and will try not to lose an eye and/or finger because I find having those quite useful myself.

 

[superheat6k]

The 1/4" flare schraeder fitting can be used to draw the gas out so it can be re-used, but you will need somewhere to hold it and a proper recovery unit. Venting of refrigerant is illegal and not particularly environmentally friendly either.

The drier is changed by sweating out the old and sweating in a new one, or it can be cut, the pipe ends flared and a flare fit drier inserted (don't forget to affix the flare nuts before flaring the tube ends), but these rarely need changing. Unless you are thinking of removing the system I would get rid of the instant connectors as these are the likely source of the dirt now plaguing you. Getting the crud out will be the difficult part because you will only know it is out when the job is complete and the problem has gone and stays away. I would cut the pipe just upstream of the capillary then blow it back from the schraeder fitting, which is normally on the low side, although assuming the drier is just upstream anyway then just removing the old then blowing back might suffice. I would place some clean white rag over the open pipe before blowing back so you can see what has been ejected.

Once the new drier is sweated into place the system will require evacuating for an hour or so before recharging with R134a.

There is a fridge wholesaler in Shoreham called SRW who can supply most of what you require, but may or may not sell you the gas. They will be well placed to suggest someone near you who could do all this work. If you are going to pay a professional make sure they properly degas with a recovery unit and cylinder and that they then evacuate with a vac pump, and do not simply purge through with fresh gas.

 

[ip485]

I had exactly the same problem and a drier is definitely the solution precisely as explained by superheat6k. I had an excellent engineer from Hayling Island do some work on my system, not least because as you say engineers that really know what they are doing are few and far between, but you will need to pay for travel. If you DIY the above sounds the perfect solution. There is one other possibility which is "just" some water vapour in the system which has frozen and blocked the capillary. A drier will solve this as well, but sometimes if you turn off the whole system and let it rest and thoroughly warm through it will work fine for a good while until the water freezes in the "wrong" place and perhaps blocks it again. I had the exact same thing as well and every so often the fridge would stop working, but start again when thoroughly defrosted and left off for a few days.

Touch wood since having had driers installed in both fridge, freezer and cool box and regassed not a single issue and all working perfectly.

 

[superheat6k]

I had exactly the same problem and a drier is definitely the solution precisely as explained by superheat6k. I had an excellent engineer from Hayling Island do some work on my system, not least because as you say engineers that really know what they are doing are few and far between, but you will need to pay for travel. If you DIY the above sounds the perfect solution. There is one other possibility which is "just" some water vapour in the system which has frozen and blocked the capillary. A drier will solve this as well, but sometimes if you turn off the whole system and let it rest and thoroughly warm through it will work fine for a good while until the water freezes in the "wrong" place and perhaps blocks it again. I had the exact same thing as well and every so often the fridge would stop working, but start again when thoroughly defrosted and left off for a few days.

Touch wood since having had driers installed in both fridge, freezer and cool box and regassed not a single issue and all working perfectly.

Moisture in the symptom could easily be the cause as suggested here. Another reason why I do not like instant connections for fridge systems - all air contains moisture and each time the instant connection is made a small quantity of air will enter the system, and the amount of moisture required to cause a water freeze in the tiny capillary tube is about the volume of a few grains of sugar. This is why proper evacuation is so crucial prior to charging. Dryness in fridge systems means utterly dry. It is possible the existing drier is simply saturated and cannot hold any more moisture / water.

 

[Daverw]

Just be little careful, what you have just done is illegal as your not FGas trained or registered., people have been prosecuted for doing this. Also just for your reference you should have pressure tested for leaks tightness as vac test will seat joints that may leak under pressure.

 

[crisjones]

We had a similar problem a few years ago on our fridge. Penguin recommended a commercial refrigeration engineer (N Wales) who came along to check it out. His diagnosis was that it was probably moisture in the system that was freezing and blocking the capillary tube (could also have been dirt). He brazed in a new filter drier unit, blew the system out with oxygen free nitrogen at a pretty high pressure for around 30mins, then he evacuated the system for a couple of hours before refilling with new refrigerant.
He was very thorough, explained everything he was doing and why so I understood why it took quite a long time. He said that the better the evacuation process is the more chance there is of a succesful solution. He obviously knew what he was doing because the fridge has worked perfectly for over 6 years of full time liveaboard use.
I would say that the above process is probably the only sure way of solving your problem and is not really a DIY proposition given the need for nitrogen, proper gauges, high vacuum pump, accurate scales etc. I will try DIY on anything and have regassed fridges in the past but this was a step too far.
The engineer was adamant that evacuating the system was the most important part and he insisted it would take at least a couple of hours to do it properly, he could have done it in 30mins andthe fridge would have worked but maybe not for six years or more. Just saying that you need to make sure any engineer you do find does it properly.
I think he charged about £250 but that included 2 x 50mile each way trips and around 5 hrs on the boat in total, as well as parts and gas etc, seemed a very fair price overall.

 

[littledancersadhu]

Is your fridge still working?