Re: [Amel Yacht Owners] Frigoboat re-charging


Ian Shepherd
 

Hi Paul,

I have been servicing my fridge/freezers on Crusader for some years now, and also the unit in my flat. From what you say, I would suspect a blockage in the evaporator, most likely caused by ice forming due to moisture getting into the system. I would suggest that you add two items to your kit. A vacuum pump and an infra-red temperature measuring gun.

Experience has shown me that it is generally a waste of time and gas re-gassing without evacuating the system for a minimum of 30 minutes on a low pressure system such as the SM Frigaboat equipment. High pressure systems need maybe 15-25 minutes longer if you have added one to you boat, such as a ice making machine. Vacuum pumps are available at a reasonable cost and well worth having.

I had a symptom similar to yours on my Scholte fridge freezer in my flat recently. After about 20 minutes of evacuating there was a sudden plop and the obstruction came free. Again I suspect it was caused by ice.

When it comes to re-gassing, I have read of many ways, some even measuring the current taken by the compressor. However, this is what I do:

1/ Vacuum pump for 30 minutes. Close the manifold valves and switch off the pump. Monitor the vacuum pressure for about 20 minutes. If it starts to decrease , you have a leak. Then I think you do need an expert to come find it and fix it.

2/ Let your R134a into the system for about 5 seconds only, then switch on the fridge with the thermostat turned fully up. The compressor has an outlet pipe called the liquid line, and a return pipe called the suction line. The connector that you attach your blue hose to is usually close to the compressor on the suction line.

3/ Touch the liquid line with your fingers. It should get hot. If it does not, then add more gas a little at a time till it does.

4/ Once this is happening you have compressed refrigerant on its way to the condenser which removes some heat through the fan, before it travels to the evaporator chest, which doubles as the ice box on the Frigaboat fridge.

5/ Using an infra-red temperature gun, measure the temperature of the evaporator chest. It should be headed downwards so somewhere around -15C on the fridge and -25C in the under the salon seat freezer. Remember it does take time to achieve these temperatures. The temperature around the whole of the evaporator chest should be about the same. If it is not, then you need to add more gas a little at a time and wait before re-measuring. Patience is the key word.

6/ Finally feel the temperature of the suction line close to where it enters the compressor. It should feel no more than cool, with perhaps a wet feel to the pipe. If it ices up, it means too much gas and that liquid is returning to the compressor instead of heat carrying gas.

It does take a lot of patience to get the balance just right. I leave the bottle and manifold connected for a full day before I am satisfied that I have it about right. Usually I end up with a suction line pressure of around 5-6 psi, which corresponds with what I have read, 7 psi being the maximum that an R134a system should run, or so some say.

I hope that this helps Paul. It's a bit of an art to get it right and I have had some professionals make a complete mess of my refrigeration, and others that have done an excellent job. However, when you are 'out there' and it goes wrong, there is no money better spent in having the equipment on board to fix it whist under way.

A quick question. How did you measure the high pressure side of the compressor? Did you fit a line tap? Maybe there is a connector on the liquid line as standard on the 54?

Regards

Ian shepherd SM2K 414 (2003) Crusader

Herzliya Marina Israel


On 28/06/2018 01:16, sharongbrown@... [amelyachtowners] wrote:
 
Hi all once again!

I'd like to resume this thread having now acquired a gauge set and a cylinder of R134A. After lots of trawling the web, tI'm still not 100% sure about my diagnosis for my faulty freezer. After running for quite some time, the high pressure reading is 105 psi and the low is minus 10 in Hg. This leads me to believe that there is a blockage in the capilliary tube or the evaporator, as from what I have managed to find out the low pressure should be around 7-10psi. The high pressure tube frosts up to the point of entry to the evaporator but the evaporator remains cold but not frosted. I've tried heating it with a mini blow torch (as I've seen fridge techs do) but to no avail.

I would be interested if someone could confirm my diagnosis or correct it if it is wrong, and offer any further advice on how the remedy the problem. I understand it may require a vacuum in which case I'll have to get the experts in.

Cheres,
Paul
Ya Fohi - Amel 54 #98

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