Fridges, can someone explain to me about re-gassing them please?

Bobc

Bobc

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I have a Waeco CU55 unit with a plate in the fridge box ?(top loading thing), and only one small corner of the plate is getting cold. So I am assuming that it has lost its gas.

When I spoke to the guy at Penguin at the boat show, he said about taking it to them for re-gassing.

I assumed that the gas runs through the pipes from the condensor unit up to the plate and back round in a closed loop. If this is the case, how can I take the unit out to be re-gassed?

I must be missing something regarding where the gas lives or the way they work. I've search T'internet for clues, but with no success.

Can someone shed some light on this please.

Ta
 
Hi

if you look at your installation you will find there are quick connector couplings in the pipework - these can be undone and self seal - you can then remove the fridge and send it to them
the other alternative is to get a fridge man to the boat and do it in without removal - I know which i would do
 
dnickj said:
Hi

if you look at your installation you will find there are quick connector couplings in the pipework - these can be undone and self seal - you can then remove the fridge and send it to them
the other alternative is to get a fridge man to the boat and do it in without removal - I know which i would do
Click to expand...

I would get a "Fridge" man to the boat he can then check for leaks on your system. Just in case your gas has done a runner!
 
Indeed the question is 'where has the refrigerant gone?'.

It's important to have the correct amount of refrigerant and oil in the system. If you take part of it off, how do you know what is left?

Correct way is to vac out everything, charge with nitrogen to leak check, vac out and recharge with oil and refrigerant.

It is so much better to get it done in situ.

If you are in the Solent area, I can recommend a chap who is brilliant!

Tony.
 
Jabs said:
It is so much better to get it done in situ.
Click to expand...

Can he/she reliably find a leak? Getting someone to the boat to fix it is going to be > £100? And if they don't detect the leak it could be another trip + replacement parts? Could easily exceed the cost of a new unit.

I've fitted one of these myself. I've never really understood how the system coped with the air in the plate. I presume only the compressor is charged with gas?
 
We've just had a fridge man out to sort out our fridge. He had a complex set of gauges which he connected to the compressor via what looked like a factory sealed widget on the end of a single pipe sticking out of the unit. In fact, on removing the plastic capsule sealing it, a valve is revealed to which the magic valve and gauge set is connected.

He checked the unit over, added some gas, sucked his teeth and watched for a bit...... Eventually he said we needed a new evaporator plate, the compressor needed a through digging out and some new cooling fans and the system then needed regassing. I asked why not replace the compressor but he was adamant that it wasn't needed and his dig out should see it lasting another ten years or more.....

I'd priced up a new compressor and plate already, his quote came in at about 2/3 of that plus he could do the job by the following day, so we went with that. I have to say the difference in performance is enormous. Whereas the thing was running for more than 60% of the time and only delivering marginal cooling, it now runs for about 15% of the time and is COLD for the first time in years.

Unfortunately, whilst I'd happily recommend our fridge man, he works out of Lefkas ....... You may well be able to get hold of a new compressor and plate for less than you'd pay a fridge man in UK, as they seem to be both more available there and somewhat cheaper.

As to the plate and compressor, they come with sealed fittings. I think both have the correct level of refrigerant in them and you simply join the connectors, which are a once only seal.
 
We had a problem (Frigoboat fridge/freeer on a 1998 Beneteau) and our local ( Florida) Fridge fellah charged us just $150 to visit the boat. He put a vacuum pump on it to remove any remaining gas, then had a special 'bomb' (his words) that put a mix of gas and special sealant in after which he pressure tested it to 400 psi and told us to leave it running for a few days to test it. so far, several weeks later it has all been OK. I left it running 3 days , we have shorepower connected, natch, with a water bottle in the evsaporator which froze solid quickly. I then left it not running a day or two in case it might leak when not pressurised by the compressor but it still worked fine and refroze my testwater bottle again when turned on for an hour or two and the temp in the bottom of the otherwise empty box was around 0.5 deg C with only another water bottle in there ( I have an infra red temp measuring gun) This is a large fridge freezer box and normally we would put some pre frozen at home cold packs ( the things sold for chilling cold boxes) stacked on the bottom floor to reduce it's size a bit and the current consumed when away from shorepower.
 
.
Bobc said:
I have a Waeco CU55 unit with a plate in the fridge box ?(top loading thing), and only one small corner of the plate is getting cold. So I am assuming that it has lost its gas.

When I spoke to the guy at Penguin at the boat show, he said about taking it to them for re-gassing.

I assumed that the gas runs through the pipes from the condensor unit up to the plate and back round in a closed loop. If this is the case, how can I take the unit out to be re-gassed?

I must be missing something regarding where the gas lives or the way they work. I've search T'internet for clues, but with no success.

Can someone shed some light on this please.

Ta
Click to expand...
The important thing is, where has the gas escaped from it? Has someone defrosted it with a sharp knife and puntured the plate? Or is it leaking slightly from the quick connects? Check those with a brush and some soapy water.
S
 
skipper_stu said:
.
The important thing is, where has the gas escaped from it? Has someone defrosted it with a sharp knife and puntured the plate? Or is it leaking slightly from the quick connects? Check those with a brush and some soapy water.
S
Click to expand...

Just look for oil!

The refrigerant contains oil which lubricates the compressor.

The gas evaporates and the oil stains where it escapes.

Some frig systems put dye in the gas to make it easier to find leaks.

You can buy the gauges for not much money, but you also need a vac pump and scales to weigh the charge.



Tony.
 
This is how a fridge works. It isn't black magic, its thermodynamics, just like your engine, your kettle, fridges just use a differing position in the cycle of hot and cold.

The first thing to understand is that different liquids boil at different pressures and temperature. Fridges use fluids (liquid / gas compunds) that boil at a conveniently low temperature at a low but manageable pressure, say 2 bar and -10oC, but when the pressure is raised to say 10 Bar will boil at a higher temperature, say +40oC.

The next point is the boiling point where the liquid turns to gas is the same as the condensing point where the gas changes to liquid.

There is a major beneficial phenonemon that occurs as the fluid as a liquid boils to gas or gas condenses to a liquid - latent heat. This is extra energy given up when condensing, or absorbed when evaporating, that is the major reason fridges work with an efficiency above 1. This means with a fridge for every 1 kW of energy you put in, you can get 3 or even 4 kW of useful energy movement out. This is not heat energy being created, but being 'Pumped'. All fridges are heat pumps.

So now back to your simple fridge, but jst before we go there, a simple example of refrigeration most peple might have directly experienced: Filling a gas lighter - the cylinder of butane contains a liquified gas, this is squirted into the base of the inverted lighter. When the nozzle is withdrawn a small amount of the liquified gas remains in the nozzle. This spills out and immediately evaporates as the atmospheric pressure is far lower, so the liquid boils. If it lands on your hand it feels very very cold, this is becuase the evaporation absorbs heat to enable it to evaporate.

Your fridge has four major parts, indeed any fridge no matter how big or small that uses a compressor. Thse are the compressor, the condenser, the control device and the evapoirator. The refrigerant fluid circulates around these four components.

Firstly to work the system must have no air at all within it. This is routinely achieved using a low vacuum pump to suck all air out. Secondly it must be compeltely sealed so once in the refrigerant gas cannot leak out.

So if you have lost gas this means it has leaked out. If the hole through which it leaked is not sealed it wil leakout again. Moreover if the gas leaks out, air wil leak in. Fridges will not work with air within. This Thread is too short to explain why, so please just accept this as a given.

Now back to the four parts. Let's start at the suction entry to the compressor. A cold gas is drawn in, then it is compressed and discharged. When any gas is compressed its molecules get squeezed into a smaller space. This makes the gas feel hot, its pressure also rises.

This hot high pressure gas leaves the compressor and is fed to the Condenser. The refrigerant used is chosen because it will evaporate and condense at convenient pressures and tenperatures. So as the hot gas passes through the condenser it gives up its heat and as it cools it condenses. Notably it gives up its latent heat as it condenses into a liquid. This is a major transfer of heat, the compressor only imparts a small amount of energy, mostly required for the gas to move arund the system.

When the fluid leaves the condenser it is all liquid, but at high pressure. It is then passed to the control device, which on small fridges is simply a long narrow tube, this means the higher pressure liquid loses its pressure, so when it leaves the 'capillary' tube its pressure has reduced close to the original compressor inlet or suction pressure.

This liquid wants to evaporate, but to do so it has to absorb heat, mostly latent heat, to do so. So it is passed to the evaporator, which is the grid like part inside the fridge that actually gets cold. The evaporator, a plate like device with tubes formed within, absorbs heat, to absorb heat it must become colder then the surroundings, so it becomes very cold, and effectively cools the fridge itself.

The fluid leaving the evaporator is by now a low pressure cold gas again. This passes back to he compressor and the cycle repeats. In action the system is a continuous process.

I hope tis exlains in simple terms how your fridge works. Temperature control is provided by a thermostatic switch that starts and stops the compressor as the temperastue rises and falls.
 
Jabs said:
Indeed the question is 'where has the refrigerant gone?'.

It's important to have the correct amount of refrigerant and oil in the system. If you take part of it off, how do you know what is left?

Correct way is to vac out everything, charge with nitrogen to leak check, vac out and recharge with oil and refrigerant.

It is so much better to get it done in situ.

If you are in the Solent area, I can recommend a chap who is brilliant!

Tony.
Click to expand...

Yes please Tony. recommendation greatly appreciated.
 
superheat6k said:
This is how a fridge works. It isn't black magic, its thermodynamics, just like your engine, your kettle, fridges just use a differing position in the cycle of hot and cold.

The first thing to understand is that different liquids boil at different pressures and temperature. Fridges use fluids (liquid / gas compunds) that boil at a conveniently low temperature at a low but manageable pressure, say 2 bar and -10oC, but when the pressure is raised to say 10 Bar will boil at a higher temperature, say +40oC.

The next point is the boiling point where the liquid turns to gas is the same as the condensing point where the gas changes to liquid.

There is a major beneficial phenonemon that occurs as the fluid as a liquid boils to gas or gas condenses to a liquid - latent heat. This is extra energy given up when condensing, or absorbed when evaporating, that is the major reason fridges work with an efficiency above 1. This means with a fridge for every 1 kW of energy you put in, you can get 3 or even 4 kW of useful energy movement out. This is not heat energy being created, but being 'Pumped'. All fridges are heat pumps.

So now back to your simple fridge, but jst before we go there, a simple example of refrigeration most peple might have directly experienced: Filling a gas lighter - the cylinder of butane contains a liquified gas, this is squirted into the base of the inverted lighter. When the nozzle is withdrawn a small amount of the liquified gas remains in the nozzle. This spills out and immediately evaporates as the atmospheric pressure is far lower, so the liquid boils. If it lands on your hand it feels very very cold, this is becuase the evaporation absorbs heat to enable it to evaporate.

Your fridge has four major parts, indeed any fridge no matter how big or small that uses a compressor. Thse are the compressor, the condenser, the control device and the evapoirator. The refrigerant fluid circulates around these four components.

Firstly to work the system must have no air at all within it. This is routinely achieved using a low vacuum pump to suck all air out. Secondly it must be compeltely sealed so once in the refrigerant gas cannot leak out.

So if you have lost gas this means it has leaked out. If the hole through which it leaked is not sealed it wil leakout again. Moreover if the gas leaks out, air wil leak in. Fridges will not work with air within. This Thread is too short to explain why, so please just accept this as a given.

Now back to the four parts. Let's start at the suction entry to the compressor. A cold gas is drawn in, then it is compressed and discharged. When any gas is compressed its molecules get squeezed into a smaller space. This makes the gas feel hot, its pressure also rises.

This hot high pressure gas leaves the compressor and is fed to the Condenser. The refrigerant used is chosen because it will evaporate and condense at convenient pressures and tenperatures. So as the hot gas passes through the condenser it gives up its heat and as it cools it condenses. Notably it gives up its latent heat as it condenses into a liquid. This is a major transfer of heat, the compressor only imparts a small amount of energy, mostly required for the gas to move arund the system.

When the fluid leaves the condenser it is all liquid, but at high pressure. It is then passed to the control device, which on small fridges is simply a long narrow tube, this means the higher pressure liquid loses its pressure, so when it leaves the 'capillary' tube its pressure has reduced close to the original compressor inlet or suction pressure.

This liquid wants to evaporate, but to do so it has to absorb heat, mostly latent heat, to do so. So it is passed to the evaporator, which is the grid like part inside the fridge that actually gets cold. The evaporator, a plate like device with tubes formed within, absorbs heat, to absorb heat it must become colder then the surroundings, so it becomes very cold, and effectively cools the fridge itself.

The fluid leaving the evaporator is by now a low pressure cold gas again. This passes back to he compressor and the cycle repeats. In action the system is a continuous process.

I hope tis exlains in simple terms how your fridge works. Temperature control is provided by a thermostatic switch that starts and stops the compressor as the temperastue rises and falls.
Click to expand...

Really useful response, thank you.
 
Bobc said:
Really useful response, thank you.
Click to expand...

Bottom line, find the leak! If it is still cooling slightly it will more than likely be coming from a "variable" leak. If it was a hole all of the gas would have leaked out. So I would be concentrating on the unions where the quick connects are. Also if it is still cooling, there is still gas in it therefore highly unlikely (positive pressure) to have air in it.
S
 
If you go on vyv cox web site he has full details on how to DIY regass your fridge. I have done this on a waeco coolbox conversion .You may need to purchase a filler adaptor and a can of recharge gas £20 all in.
 
TSB240 said:
If you go on vyv cox web site he has full details on how to DIY regass your fridge. I have done this on a waeco coolbox conversion .You may need to purchase a filler adaptor and a can of recharge gas £20 all in.
Click to expand...

My son Owen, who wrote the piece on the website, knows fridges and air conditioning systems very well indeed, having had his own company installing, maintaining and repairing them. He says that the quick connect fittings always leak a little. On systems he has built he cuts them out and brazes the joint up.
 
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