Breaking Vacuum; Refrigerant; Preparing Machine For Charging; Chiller Dehydration - Carrier 17DA Start-Up, Operation And Maintenance Instructions Manual

3/4-IN. INSULATION
EVACUATOR ASSEMBLY
BREAKING VACUUM — When breaking vacuum during
leak testing or other service work, always use dry refrigerant or
other form of dry gas; i.e., nitrogen or air.
The use of dry gas to break machine vacuum is especially
important in areas of high humidity to prevent corrosion dam-
age due to water condensing in refrigerant spaces within
machine.
PREPARING MACHINE FOR CHARGING REFRIGER-
ANT — After servicing machine and checking the leakage
rate, apply a vacuum pump and pull machine pressure down to
0.15 in. (4 mm) mercury absolute pressure or less. Valve off
and charge with refrigerant.
After the first few minutes of operation, residual air not re-
moved by the vacuum pump will collect in the condenser shell
where it will be pulled off by the purge sampling tube.
CHILLER DEHYDRATION — Dehydration is recommend-
ed if the chiller has been open for a considerable period of time,
if the chiller is known to contain moisture, or if there has been a
complete loss of chiller holding charge or refrigerant pressure.
a17-577
Fig. 6 — Purge Cycle Schematic Piping
PURGE SYSTEM
VALVE ASSEMBLY
1 — Purge Connection
2 — Shutoff Valves
3 — Strainer
4 — Orifice
5 — Condensing Chamber
6 — Condensing Chamber Pressure Gage
7 — Non-Condensable Vent Valve
8 — Cooling Coil
9 — Refrigerant Chamber and Purge Float Valve
10 — Refrigerant Sight Glass
11 — Water Chamber and Hand Drain Valve
12 — Water Sight Glass
Do not start or megohm-test the compressor motor or oil
pump motor, even for a rotation check, if the chiller is
under dehydration vacuum. Insulation breakdown and
severe damage may result.
Dehydration can be done at room temperatures. Using a
cold trap (Fig. 7) may substantially reduce the time required to
complete the dehydration. The higher the room temperature,
the faster dehydration takes place. At low room temperatures, a
very deep vacuum is required to boil off any moisture. If low
ambient temperatures are involved, contact a qualified service
representative for the dehydration techniques required.
Perform dehydration as follows:
1. Connect a high capacity vacuum pump (5 cfm [.002 m
or larger is recommended) to the refrigerant charging
valve (Fig. 4, item 10). Tubing from the pump to the chill-
er should be as short in length and as large in diameter as
possible to provide least resistance to gas flow.
2. Use an electronic vacuum indicator or a wet bulb vacuum
indicator to measure the vacuum. Open the shutoff valve
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LEGEND
CAUTION
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