How to tell low refrigerant levels

[goboatingnow]

Hi I notice in recent months the top 40mm or so of the evaporator plate isn’t frosting over , the rest does and also ices over. Previously ( April may ) it would normally frost right to the top

The fridge seems to be working fine and Ice bags placed against the evaporator still freeze

Am I losing refrigerant. The problem doesn’t seem to be getting worse ( from what I can tell )

Refrigeration is something I’m going to get to grips with this winter and I’m buying a pump and gauge set and will set up a system at home to practice on.

Thanks
Dave

[Dockhead]

That's exactly how you see that you're low on refrigeration.


A member on here, Richard Kollman, helped me a lot with the same problem a number of years ago. I have a very slight leak in both my reefer systems and I top them off every year using the techniques I learned from Kollman's website and his advice on here.


I would go through the archives and try to find the thread. There are links, and details about the process of evaluating when you've added enough.



Our reefer systems use tiny amounts of refrigerant and one of the 12oz cans lasts me for years. Can you buy the 12oz cans with the tapping kit and gauge, in Ireland? I just exhausted mine and need to replace it. I brought it way back then from the States.

[goboatingnow]

Yes I can buy these in Greece which is where the boat is. I’m not yet familiar with the top up procedure
I’m have Richards book etc.

I read up over the winter and do it in the spring

[Richard Kollmann]

Originally Posted by goboatingnow

Hi I notice in recent months the top 40mm or so of the evaporator plate isn’t frosting over , the rest does and also ices over. Previously ( April may ) it would normally frost right to the top

The fridge seems to be working fine and Ice bags placed against the evaporator still freeze

Am I losing refrigerant. The problem doesn’t seem to be getting worse ( from what I can tell )

Refrigeration is something I’m going to get to grips with this winter and I’m buying a pump and gauge set and will set up a system at home to practice on.

Thanks
Dave

An evaporator plate showing a loss of frost 40 mm from top is not necessarily indicating a loss of refrigerant do to a leak. I would suggest you not buy servicing equipment at this time or allow anyone to connect a pressure gauge to this system without confirmation there really is a loss of refrigerant. You will not receive good advice without describing your system better DC or AC current, system manufacture, evaporator thin plate aluminum or heavy eutectic plate, and compressor size.

If this is a conventional evaporator see how long it takes for the 40mm to increase to 80 mm. if the evaporator is a eutectic plate and frost line drops to 80 mm all the way around there is a loss of eutectic solution and not refrigerant. If this is an AC or DC powered system the best and safest tool for you to buy is a clamp on power wire amp meter.

[goboatingnow]

Sorry Richard

It’s an isotherm air cooled dc BDxx Compressor , thin plate evaporator and manufacturer cold box ( Bavaria 36 )

The unit is an upgrade over the stock system.

[Richard Kollmann]

Originally Posted by goboatingnow

Sorry Richard

It’s an isotherm air cooled dc BDxx Compressor , thin plate evaporator and manufacturer cold box ( Bavaria 36 )

The unit is an upgrade over the stock system.

It might be only 20 grams low on refrigerant and on a capillary tube refrigerant flow control device that loss can appear with low ambient temperatures.
Monitor frost line over time to see if it gets less. You also may find the present frost cover is more energy efficient than full frost cover.

[goboatingnow]

Originally Posted by Richard Kollmann

It might be only 20 grams low on refrigerant and on a capillary tube refrigerant flow control device that loss can appear with low ambient temperatures.

Monitor frost line over time to see if it gets less. You also may find the present frost cover is more energy efficient than full frost cover.

I notice today the ice line ( as I have ice buildup ) has fallen down to 60mm from the top of the evaporator plate. The top 60 is cool but has no frost or ice buildup at all.

[OzeLouie]

Originally Posted by goboatingnow

I notice today the ice line ( as I have ice buildup ) has fallen down to 60mm from the top of the evaporator plate. The top 60 is cool but has no frost or ice buildup at all.

Unfortunately you have a gas leak. If you want to fix it properly, follow the industry recognised remedy, otherwise using short-cut methods may get your system back to 'normal' for now but long term it will not only fail again but you will introduce damage to the system. Do it once, do it properly and avoid 'canned R134a' that has any additives in it. (Like leak sealer, dyes etc) Suggest searching 'Fridge Assist' for correct procedure.

[s/v Jedi]

Originally Posted by goboatingnow

I notice today the ice line ( as I have ice buildup ) has fallen down to 60mm from the top of the evaporator plate. The top 60 is cool but has no frost or ice buildup at all.

Did your ambient temperature drop? If not, probably a leak. If it did, that will lower your ice line as well.

[goboatingnow]

Originally Posted by s/v Jedi

Did your ambient temperature drop? If not, probably a leak. If it did, that will lower your ice line as well.

Yes it has got colder , in June with around 35 degree C in the boat the frost /ice line was right to the top

Now the ambients around 18-19 degrees C.

The compressor is running about 2mins in every 7 at present.

[Richard Kollmann]

This sounds like a leak somewhere and now its time right now to find it by checking high pressure side for leak with compressor running from compressor to beginning of small cap tube. then stop compressor and allow the lowside pressure to warm up testing servicing fitting cap seal first then complete low side including evaporator to warm up. The best leak test for this small a leak is 50% liquid soap and 50% water. Apply mixture with a one inch paint brush stabbing the area to create foam, then watch each test area for 5 minutes. I have 5 electronic leak detectors but even these will not find this small a leak. This method takes time or you can pay a tech who may not find the leak. The refrigerant line connectors are the first locations where I would look. These Isotherm connectors have metal to metal seals if the leak is there tighten them 1/8 turn be sure to use two wrenches so not to twist tubing.

[chasfgr]

I'd suspect an air leak into the top of the plate.

[RaymondR]

I suspect that if you were pulling the box down from close to ambient you might find frosting all the way to the top of the plates because there would be a lot of vapor in the evaporator due to the rapid intake of heat by the liquid refrigerant leading to rapid boil off of liquid refrigerant.

As you pull the temperature in the box down and the boil off rate decreases, the ratio of liquid to vapor changes to increase the total mass of liquid in the evaporator and as the level of liquid refrigerant drops the level at which heat absorption occurs drops with it.

But then again my perception of what goes on within the refrigeration circuit could be completely screwed up.

[goboatingnow]

Thanks still trying to get my head around this. I’ll test for leaks. It could be damage to the evaporator plate.

[Richard Kollmann]

Jedi and Raymond were more to the point than I was earlier. At standard temperatures 70 degrees F (20 C) There is little liquid refrigerant in your Isotherm unit what is in unit at standard day temperature is mostly refrigerant gas vapor. Therefor on hot days capillary tube systems there can be too much liquid refrigerant causing less cooling and wasted energy. On cold days there is less cooling because there is less liquid refrigerant flow.
I live on the north south east coast waterway and today there are Hundreds of boats headed south to spend winter in a tropical climate south of Latitudes 25 N. With correct refrigerant charge up north during the summer these mobile refrigerators with cap tube refrigerant flow control in the typical Sun for the winter will have too much refrigerant and consume more energy. With too much refrigerant volume line leaving evaporator will have too much wasted energy frost headed towards compressor. A little less frost on evaporator is better than to much frost, Yes compressor will run a little more but at a lower current draw.
I hope you now understand why most engineers prefer TXVs over capillary tube on mobile refrigeration and eutectic evaporator systems.

Non Destructive Testing only. There are no industry Standers for these Icebox Conversion Refrigerators. If there is a problem deal with facts and not
Shotgun theories. Last keep it simple and always question advice as you will find salesman do not always provide good advice.