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14.6 P ressure sw itches and transducers
Transducers
Transducers that incorporate Schrader depressors will be supplied fitted directly to a port, those without will
include a valve for isolation purposes to allow for maintenance.
Pressure switches – Safety.
Pressure switches fitted to compressor bodies are pre-set cartridge type will NOT be fitted with Schrader valves;
this is to ensure that these safety switches are reacting to a definite pressure that cannot be influenced by
mechanical tolerances.
High Pressure switch testing
Periodically, as deemed by customer requirements, remove the high pressure switch from the system and apply
dry nitrogen pressure using a calibrated gauge of a suitable range and ensure that the switch breaks and resets in
line with the settings shown on the switch data sheet. Refit the switch, leak test and set the system back in
operation.
15 M ax im um refrigerant charge
When the unit is pumped down, the receiver must be capable to accommodate all the refrigerant charge (kg)
holding in the system. Also, it is really important to avoid to overcharge the system which can cause issues in
compressor operation and efficiency.
Consindering the above, the estimation of maximum refrigerant charge values are based on 80% capacity of the
receiver (assuming that the unit is pumped down from the receiver).
The maximum amount of refrigerant can be charged into the system is 9.27 kg (at 80% receiver capacity).
16 Estim ation of refrigerant and oil charge
The refrigerant charge shown below based on estimation that the receiver is fiilled up to 1
st
sight glass, different
pipework lengths and evaporator.
Copyright HPL March 2021
P4367 Rev 01
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