MK1 Fridge

[Daverw]

Halfords manage due to loop hole for car ac, this also has oil and dye in it which is often not compatible with the oil in your boat system. All R134a available now is recovered gas. You are correct that the handling regs are not universal between countries, this is the same for most certification, this is got round by most experience techs, as time served and proven competency then come into play, luckily I work mainly in industrial refrigeration which uses ammonia or CO2 which are a different level of certification due to high risk of death if you get it wrong.

The issue with servicing is the equipment needed for gas recovery, pressure testing and evacuation , if you look at the stuff a car garage uses and this is as basic as it comes, not easy to get it to your boat, I have a small vac pump which is quite power hungry and heavy, recovery unit which is about the size of a tool box, gas bottle, recovery bottle and bottle scales, don’t think I could keep all this on board. That’s why most who do this on the side don’t follow the rules

 

[lustyd]

I agree that to do it properly all that stuff is impractical on a boat. I'm not sure I'd call it not following the rules particularly (although, obviously it isn't following them), a lot of issues on a boat would result in the system starting from "empty" due to a leak so recovery becomes less of an issue. Anything that needs a full system emptying still ought to have a pro with the tools. I also think from a practical standpoint, the choice is fast becoming get a pro vs buy a new fridge kit for the average boater. Fridge kits with gas in them are a few hundred bucks and easy enough to fit but waste a whole working unit plus the gas will already have vented (or will vent during DIY replacement). I can't imagine most PBOs even bother enquiring about cost to fix.
It's not helpful that the new gas isn't compatible either. If what you say about r134a is right then some time soon we're all going to need a new fridge when it runs out which seems like madness. It also still seems to be cheaper than r1234yf which gives little motivation to change a system over outside of availability.

 

[Daverw]

Not sure that R1234yf is actually cheaper than R134a as R134a is doubling in cost each few months as phase out really starts to bite, many systems have already been moved away as availability is very sketchy.

The big thing I always suggest people deal with is the actual leak issue, this will not fix its self and most are not that difficult to find and fix, just a small bottle of oxygen free nitrogen (OFN), torch, soapy water and a bit of time

 

[lustyd]

Weird, from what I've seen R1234yf seems to be twice the price and that's before replacing the compressor. As before though, this is all quick Google compared to your experience. Funnily enough I'm reading a book written during the R12/r134a transition and seems like this is a similar situation, along with a similar Danfoss/Secop compressor update (the book was at the transition to bd35f/bd50).

Got some brazing rods ordered so fingers crossed for the next step!

 

[luke collins]

When you come to sizing the capillary you can use dancap software. Seems a lot of work when you can buy all the parts online and build a system. I would stick to 134a. The newer gases are flammable and you need to consider this within system design as well as pressures of the system. Pressure on the high side can be 20 bar so research how to joint the copper parts together by brazing and ensure socket joints with good brazing penetration. Good luck with your project.

 

[superheat6k]

A quick bit of Google. As a professional, what pressure in barg do you think the average r134a yacht fridge uses on the high side? I do understand that various factors come into play, but yacht fridges are extremely standard at this point so a lot of that is largely irrelevant. Please do post any relevant info/links here, it's very useful to have information from a professional.

We set our HP trips at 17 Bar. On a very hot day we rarely go above 15 bar.

 

[superheat6k]

Weird, from what I've seen R1234yf seems to be twice the price and that's before replacing the compressor. As before though, this is all quick Google compared to your experience. Funnily enough I'm reading a book written during the R12/r134a transition and seems like this is a similar situation, along with a similar Danfoss/Secop compressor update (the book was at the transition to bd35f/bd50).

Got some brazing rods ordered so fingers crossed for the next step!

R1234YF is mildly flammable and should not be used inside a boat for this reason. R513A is possible (a blend of R134a and R1234YF), but R134a remains widely available presently and right now is cheaper, and virgin product R134a remains available. I bought 1800 kg of the stuff last year in anticipation of substantial price rises. In 2018 the price went up by a factor of 7, and then dropped back to twice the 2017 price. A 50% rise is expected in the next few weeks (even then is is cheaper than R513A and much much cheaper than R1234YF), which for us is good news as we still have about 1000kg left. but we can't sell it to non qualified users and would get into serious trouble if we did do this, not least to our firm's reputation, so we simply do not countenance ever doing this. All the gas we buy is actually used (as in charged into systems) is by our own F Gas qualified staff as part of our own client projects on their Chillers.

A typical project might for us require up to 500 kg. The typical boat fridge holds ~ 100g or less.

 

[lustyd]

OK brazing rods arrived and had a go. As expected the inside of the pipe sooted up. Can anyone explain how you're achieving a clean joint without nitrogen in the pipe? I'm assuming "don't worry about soot in the pipes" isn't the answer ?

 

[Daverw]

I’m not sure what your doing different to what I normally do, I don’t have any soot issue unless there is a lot of oil in the pipe. What gas are you using and how hot are you getting the copper before putting rod on the joint?

 

[AntarcticPilot]

You could try building one of these: Einstein refrigerator - Wikipedia.

 

[luke collins]

OK brazing rods arrived and had a go. As expected the inside of the pipe sooted up. Can anyone explain how you're achieving a clean joint without nitrogen in the pipe? I'm assuming "don't worry about soot in the pipes" isn't the answer ?

. You really need nitrogen ran through the pipes while brazing. Try lower pipe temps when brazing it will help but not stop it. Cherry red temp is where you want to be in colour.

 

[lustyd]

You really need nitrogen ran through the pipes while brazing

Yes that was my conclusion when researching, but there were several posts above from experts claiming it wasn't necessary, I was using a standard torch with MAP gas and only got the pipe to the point where the rod melted so wasn't over heated.

 

[lustyd]

unless there is a lot of oil in the pipe

It's not oil, the soot is oxidised copper so regardless how clean you get the pipe it would still be a problem if there's oxygen present.

 

[luke collins]

there are lots that dont use nitrogen, it normally ends up trapped in the drier/filter or oil of the compressor. With what you are doing I would say 75% of engineers seen out and about fitting a replacement compressor do not use nitrogen, new installation/lots of brazes generally use nitrogen.

 

[lustyd]

Thanks, yes that makes sense and was wondering if it was just a case of ignore it in most instances. If I were remote and needing to fix my fridge it's certainly better than no fridge!

 

[vyv_cox]

I asked son Owen about the sooting. His reply:

Its best to blow nitrogen through yes. I often get away with it because we have a filter dryer in the system. But good practice would be to use nitrogen. I do when i need to.

Sometimes its impossible because you dont have a port at both ends of the line, usually if you do it with a clean flame very briefly its fine. Its just an experience thing. For beginners they end up oxidising it badly because they have not enough heat or take ages to do the braze. You do have to be very careful on reversing valves particularly because they have a plastic shuttle valve that can melt and block with scale. Very tricky.

 

[lustyd]

Thanks Vyv, very useful

 

[Daverw]

Just to add that I use oxy / acetylene and small joints take about 15 to 30 seconds to do, as said cherry red and add rod quickly.

 

[lustyd]

Yes only took me a few seconds with my torch. The problem isn’t time it’s temperature. Copper oxidises at a lower temperature than brazing rods melt at so there’s no free lunch here, the copper will oxidise. At over 400-700C the oxide will be thick and flaky.