RACA Journal May 2023 | Page 46

Support

• When pliers or a valve are used , make sure they are properly adjusted for the tube size , and make sure that if a rubber seal is needed , it is correctly located and is in good condition .

• To vent the HC safely , follow the procedure outlined below :

• Run the compressor , if possible , before venting refrigerant – this heats up the compressor oil so that less refrigerant will be dissolved in it .

• Do not open the system in an enclosed area – work in a wellventilated area with windows and doors open and / or fan running , or outside and not underground .

• The vented refrigerant must not be drawn into a building or underground area . R600a is heavier than air .

• Before you use the piercing pliers or valve to open the system , put the other end of the hose outside or in a well-ventilated area . The area where you are releasing the refrigerant must not have any ignition sources such as flames and sparking electrical components .

• Pierce the process tube : take care to ensure that the pliers or valve are adjusted so they clamp firmly onto the process tube and that refrigerant does not leak from this connection .

• It can take up to 15 minutes for the refrigerant to be vented from an appliance in this way . Check that no more of the refrigerant is coming out of the hose before proceeding further , for example by putting the end of the hose in a container of water and looking for bubbles . Most of the refrigerant will be vented by this procedure , but some will remain in the oil and the system .

• Connect a vacuum pump and draw vacuum on system . The remainder of the refrigerant will be removed by the vacuum pump . Use a service line on the pump outlet to vent outdoors if needed .

• Your vacuum pump probably has an on / off switch which can spark when used . Do not use this switch when you use the pump to evacuate an HC system . Switch it on and off at the mains .

• You may assume at this point that all the HC refrigerant has been removed from the system . But if a blockage has occurred in the beginning of the capillary tube the entire high side of the system will contain HC refrigerant .

• Should you feel that the system has no HC refrigerant you may decide to remove the drier using an oxy acetylene flame . Stop !! Before doing so consider : If the capillary tube is blocked would you expect to find refrigerant in the pencil drier ? Well , in reality the drier will be full of liquid HC refrigerant .

Piercing Pliers

• Should you at this point try to remove the drier by heating up the drier with a flame the pressure inside the drier will rapidly increase and the drier will explode , spraying desiccant , copper

Supplied pieces and highly flammable burning HC refrigerant close to your face . Yes , this is very dangerous .

• Rather first pierce or cut a hole in the drier . Trapped refrigerant will be released and as you are in a ventilated area the refrigerant will disperse , causing no damage or injuries .

• The piercing pliers or valve do not usually give a good enough seal for evacuation and charging , so they are removed at this point .

• If the process tube is not long enough to fit a valve , you will need to braze on an extension tube – remember to have drawn a vacuum to remove refrigerant absorbed in the oil . You can make a flare at the end of the process tube and connect a valve to it .

REPLACING SYSTEM COMPONENTS You must use the correct electrical components if you need to replace these items , and you must replace them in the correct way .

In most HC appliances :

• The compressor relay is solid-state and the overload protector is a sealed device , to prevent sparking .

• The thermostat is either located in a sealed electrical box or a solid state / sealed type is used , to prevent sparking .

• On / off and door switches are sealed types , although usually they are not fitted .

• Standard capacitors and induction type fan motors are safe to use with HCs as they do not spark .

If you need to replace a sealed or solid-state device , use the correct safe type . If you need to replace devices which are mounted inside a sealed enclosure , make sure you put them again inside the electrical box and seal it properly , including the cable entries . Make sure any wiring connections cannot work loose – loose wires can cause sparks .

Margaret , in the next issue I will continue with pressure testing , leak testing evacuation and charging R600a systems .

Thank you for the question , Margaret . Let us understand hydrocarbons , they are the future . Thanks to everybody for the overwhelming response . Looking forward to hearing from you . RACA

Grant Laidlaw

Thank you for all for your interesting questions . Send your problems ( and sometimes your creative solutions ) to acra @ netactive . co . za with ‘ Solutions Page ’ in the subject line . You may include pictures .

RACA Journal I May 2023 www . refrigerationandaircon . co . za