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Emergency refrigeration repair

Mar 28, 2013

Patching a system until you can get to an HVAC technician

A refrigeration repair kit.

A refrigeration repair kit.

If your refrigerator/freezer quits while you are in U.S. waters, only a properly licensed refrigeration technician who has the required equipment (refrigerant recovery system, vacuum pump, etc.) may legally service your system. However, if you are offshore or in foreign waters far from a licensed technician, your best and perhaps only hope is to do the job yourself.

This means planning ahead and placing a few extra items in your spare parts kit (see sidebar). Almost all refrigeration units built in the last 10 years use the environmentally friendly HF-134a refrigerant, but confirm the type of refrigerant used by your refrigeration system before proceeding. These items are available at most auto parts stores worldwide.
 

Diagnosing the problem

If you happen to notice that your refrigeration system is cycling more frequently than normal or is running constantly, act quickly to identify the problem. You will save more of your refrigerated food and less damage will occur to the refrigeration system. Most of the world’s 12- and 24-volt refrigeration systems are based on a hermetically-sealed compressor manufactured by Danfoss. This is a highly reliable device and it very rarely fails. However, if it does fail, it cannot be repaired and must be replaced. So, the following is based on the assumption that the compressor still runs, the problem (at worst) is loss of refrigerant, and you have the necessary repair materials at hand.
 

Do the easy things first

• Inspect the evaporator (the cold part in the freezer/refrigerator) carefully. If it is still cold enough to form frost, then note the frost level on the outside of the evaporator. It should be within a half-inch or so of the top of the evaporator. If much lower or no frost level is visible, then refrigerant loss is most probable.

A low refrigerant level is indicated by the low frost line on the evaporator, indicating the need for recharging.

Using a brush and soapy water on the evaporator to locate the leak.

• Have a look at the compressor/condenser and ensure that the unit has an unobstructed source of cooling air and that the fan is working. Clean or replace the air filter and clean the condenser fins as best you can. Take care as they are very thin and are easily damaged. If your condenser is water cooled, make sure that the water pump is delivering adequate cooling water.

• Looking at the compressor, place your fingers on the two refrigerant tubes connected to the compressor. The smaller of the two is the liquid line and should be quite warm, much warmer than the larger line which is the gas or return line. If you can detect no temperature difference while the compressor is running, then almost certainly the problem is loss of refrigerant.

• Make arrangements to move your perishables and all remaining ice to a picnic cooler as you will need access to the evaporator for a day or two. A friendly fellow cruiser perhaps will store your perishables for you.

• If the refrigeration system is still cooling at all, then shut off the compressor to allow the refrigerant pressures to equalize. This will make any leaks in the low pressure side easier to locate. Make up a thick solution of dishwashing soap and water, and using a small paint brush carefully daub the soapy water on the surfaces of the evaporator and the refrigerant line which connects the evaporator to the compressor.

• Look carefully for any sign of an oily deposit along the refrigerant lines, as this is a sure sign of a leak. Pay particular attention to the point where the refrigerant line joins the evaporator as this is a notoriously troublesome area. Also look for any possible contact between the refrigerant line and the wall of the evaporator, as the evaporator wall is very thin and any contact with the refrigerant line will quickly wear through the thin wall. (A good preventative measure before you experience a failure is to slip a short length of soft plastic tubing over the refrigerant line to separate it from contact with the evaporator wall or any other surface.) Watch carefully for bubbles being formed by leaking refrigerant. This will require patience if the leak is very small.

• If the refrigeration system is not cooling at all, then you will have to add some refrigerant to be able to locate the leak with the bubble test.
 

Adding refrigerant to compressor

• DO NOT UNDER ANY CIRCUMSTANCES CONNECT A REFRIGERANT CONTAINER TO THE HIGH-PRESSURE SIDE OF THE COMPRESSOR NOR TO THE HIGH-PRESSURE OR LIQUID LINE. If you have any problem comprehending this, STOP NOW and go no further.

• Wear gloves and eye protection and use common sense during this entire procedure. Exert your best efforts to prevent any air or moisture from being introduced into the refrigeration system.

• Turn off the circuit breaker to the compressor. Locate the service valve on the compressor and using two wrenches to avoid twisting the tubing on the compressor, remove the dust cap by turning it counter-clockwise. Under the dust cap is a Schrader valve just like in your bicycle or car tire. Use a small screwdriver or punch to depress the valve to let out a puff of refrigerant. This will blow out any dust or moisture. Attach the can adapter to the can of refrigerant and attach the charging hose to the can adapter. Slowly turn the valve on the can adapter clockwise to puncture the refrigerant can and then turn the valve counter-clockwise to open the valve. With the hose aimed overboard and the refrigerant can held upright, vent some refrigerant gas through the hose to drive out any air and moisture. A five-second blast should do nicely.

• With a tiny amount of refrigerant gas flowing through the hose to keep out air and moisture, and the can held upright, connect the charging hose to the service valve on the compressor. Open the can valve a turn or two and start the compressor, all the while keeping the refrigerant can upright to ensure that only gas is admitted into the compressor. (Otherwise, liquid entering the compressor will cause permanent internal damage.)

• The refrigerant container will get very cold as the refrigerant evaporates, so keep your gloves on while handling the can.

• Add refrigerant for two minutes and then shut the can valve and remove the charging hose from the compressor. Replace the dust cap and cover the end of the charging hose with a piece of tape to keep out air and moisture.

• Shut off the compressor and perform the soap bubble test on the evaporator until the leak is located.

• If the leak cannot be located with the soap bubble test, then add the refrigerant containing the special ultra-violet (UV) dye. (Follow the instructions on the can of refrigerant if different from the following.) Turn off the circuit breaker for the compressor before beginning this procedure, as you do not want the compressor to run while you are adding liquid refrigerant. This time, and this time only, invert the refrigerant can to introduce liquid refrigerant into the system as the dye will not be transported by refrigerant in the gas phase. (I had to learn this the hard way.) A two-minute dose of liquid refrigerant and dye should be enough to find the leak. Disconnect the charging hose and replace the dust cap on the service valve. Run the compressor for a few minutes to distribute the UV dye and then shut it off to allow the pressures to equalize. Connect the UV LED to a nine-volt battery and a 370-ohm resistor or use your UV flashlight. Shine the UV LED on the evaporator and refrigerant lines to locate the leak. (Shine the LED on the charging hose to get an idea of what the illuminated dye looks like.) It may require a second addition of refrigerant and dye to locate the leak.
 

Connecting the charging hose to the compressor service valve. Make sure to wear gloves as the refrigerant container can get very cold as the gas flows.

Repairing the leak

While allowing the refrigerator/freezer to warm to ambient temperature, carefully and gently sand the area around the leak with 320-grit sandpaper just enough to brighten the metal and remove any paint. Clean the sanded area with acetone or MEK. If there is any refrigerant remaining in the system, vent it now by connecting the charging hose to the compressor service valve. Mix up some J-B Weld and apply a liberal amount to the area around the leak. Wrap the J-B Weld with kitchen film to hold it in place until the epoxy sets. If you notice a bubble being formed in the J-B Weld, vent the compressor again.

Allow the J-B Weld to cure for 24 hours and inspect it carefully for any evidence of a bubble. If one is found, sand the J-B Weld and apply a fresh layer and wait another 24 hours for the J-B Weld to cure.

Add a two-minute charge to the compressor and soap the repaired area again. If it is still leak-free, resume charging the system.
 

Charging the system    

If you were fortunate enough to notice the refrigeration failure before all of the refrigerant escaped, chances are that no damaging amount of moisture has entered the system and a successful repair can be effected by replacing the refrigerant. If moisture has entered the system, the proper procedure would be to evacuate the system with a vacuum pump for 24 hours to remove any moisture and non-condensable gases and have the drier replaced before recharging. (In the 15 years that we have been out cruising, I have met only one cruiser with a vacuum pump aboard, and he had no idea how to use it!) So here is an emergency procedure that usually works:

With the compressor switched off, add refrigerant for two minutes, keeping the refrigerant can upright all the while. Wait for 15 minutes and vent the refrigerant to the atmosphere. Ventilate the area thoroughly. Use a hose to get the refrigerant gas overboard. It is not toxic, but neither will it support life, and worse, if it comes into contact with a very hot surface or an open flame, extremely poisonous phosgene gas will be formed. Repeat the two-minute charge, 15-minute wait, then vent cycle two more times. This should purge the system sufficiently to allow operation.

Add refrigerant again for two minutes and turn on the compressor. The liquid line should warm up a bit and the evaporator should begin to cool slightly. Continue to add refrigerant in 10-second increments, waiting two minutes between charges. The evaporator should begin to frost by now. Continue this charge and wait cycle of adding refrigerant until the frost line on the evaporator is within a half-inch of the top of the evaporator. You may have to prop open the refrigerator door to keep the compressor running constantly. This is not exact, it doesn’t comply with the manufacturers’ instructions, and it probably voids your warranty. But, it certainly has a very good chance of returning your refrigeration system to operation, so you can celebrate with a cool beverage or two!

When you arrive at a location where competent refrigeration repair can be obtained, it is a good idea to have the system properly evacuated with a vacuum pump and have the drier replaced. If your evaporator is over five years old, it’s a good idea to replace it, as due to the extremely thin aluminum used in its construction, your evaporator is living on borrowed time.

Finally, it’s a good idea to leave your refrigerator/freezer running at all times, rather than shutting it down when you are away from your boat for extended periods. At ambient temperature, the evaporator will corrode more rapidly than when it is cold, so by keeping it cold, it will last much longer.

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Contributing editor Harry Hungate and his wife, Jane Lothrop, have been cruising on their Corbin 39 cutter, Cormorant, since 1997, and have had occasion to make emergency refrigeration repairs in exotic locations during their west-about circumnavigation. They plan to cruise the U.S. East Coast in 2013. Follow their adventures at harryjane.weebly.com.

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