Note: Before charging a system with a new or replacement refrigerant check the fusible plug rating.
Condensers and receivers are fitted with fusible plugs. These are safety devices against excessive high side pressures developing in the event of a fire. (Excessive operating pressures are controlled by the high pressure cut-out switch) The plugs are normally brass studs with a 3 mm hole drilled through the centre, which is filled with a low melting point solder.
It is important that, when a replacement is fitted, the correct plug is selected. The following are the required melting points for various systems:
R12 1000 C (2100 F
R22 760 C (1700 F)
R502 760 C (1700 F)
R717 680 C(1550 F)