Hoshizaki TM-500AAE, Service Manual

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7) Evacuation, Vacuum Pump and Refrigerant Charge [R404A]
Never allow the oil in the vacuum pump to flow backward. The vacuum level and vacuum
pump may be the same as those for the current refrigerants. However, the rubber hose and
gauge manifold to be used for evacuation and refrigerant charge should be exclusively for
R404A.
8) Refrigerant Leak Check
Refrigerant leaks can be detected by charging the unit with a little refrigerant, raising the
pressure with nitrogen and using an electronic detector. Do not use air or oxygen instead of
nitrogen for this purpose, or rise in pressure as well as in temperature may cause R404A to
suddenly react with oxygen and explode. Be sure to use nitrogen to prevent explosion.
[b] REFRIGERANT RECOVERY
The refrigerant must be recovered if required by an applicable law. A Low-side Access
Valve is provided in the unit. Recover the refrigerant from the Access Valve, and store it in a
proper container. Do not discharge the refrigerant into the atmosphere.
When replacing the Drier, take the opportunity to also fit a High-side Access Valve for ease
of charging liquid refrigerant.
[c] EVACUATION AND RECHARGE
1) Attach Charging Hoses, Service Manifold and Vacuum Pump to the Low-side and High-
side (to be fitted by servicer) Access Valves. If possible, use Quick Release Connectors
onto the Access Valves (especially on the high side).
2) Turn on the Vacuum Pump.
3) Allow the Vacuum Pump to pull down to a 760 mmHg vacuum. Evacuating period depends
on the pump capacity.
4) Close the Low-side and High-side Valves on the Service Manifold.
5) Disconnect the Vacuum Pump, and attach a Refrigerant Charging Cylinder to accurately
weigh in the liquid charge. Remember to purge any air from the Charging Hose. See the
Nameplate for the required refrigerant charge.
6) Open the High-side Valve on the Gauge Manifold, and accurately measure in the liquid
charge. Close the valve on the Charging Cylinder before closing the High-side Manifold
Valve. Any remaining liquid in the line can be charged into the low side.
Note: Always charge in the liquid stage, as many refrigerants are blends and vapour
charging will affect the blend consistency (eg. R404A).