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PRE-START-UP
IMPORTANT: Before beginning Pre-Start-Up or Start-
Up, review Start-Up Checklist at the center of this
publication. The Checklist assures proper start-up of a
unit and provides a record of unit condition, applica-
tion requirements, system information, and operation
at initial start-up.
Do not attempt to start the air-conditioning system until
following checks have been completed.
System Check
1. Check the outside air hoods to ensure the hoods are fully
opened and secure, with filters in place.
2. Check the supply fan and exhaust fan suspension brack-
ets. Shipping spacers should be removed and sleds
levelled to specification.
3. Check compressor suspension. On 48/50MP62L units
snubber washers can be moved with finger pressure. On
all other units, rails allow compressors to float freely on
compressor rail springs.
4. Electrical power source must agree with unit
nameplate.
5. Check tightness of all electrical connections.
Failure to open discharge service valve prior to start-
ing compressor can result in damage to or failure
of the compressor.
6. Backseat (open) compressor suction and discharge shut-
off valves. Close valves one turn to allow refrigerant pres-
sure to reach the test gages.
7. Open liquid line service valves.
8. Oil should be visible in the compressor sight glasses.
See Fig. 44. An acceptable oil level in the compressor
is from
3
⁄
8
to
1
⁄
8
of sight glass (06E-299 compressors are
1
⁄
8
of sight glass).Adjust the oil level as required. No oil
should be removed unless the crankcase heater has been
energized for at least 24 hours. Oil Charge section on
page 49 for Carrier-approved oils.
9. Perform leak test. Be sure there are no refrigerant leaks.
All units are shipped with a complete operating charge
of R-22 and should be under sufficient pressure for leak
testing after installation. If there is no system pressure,
add refrigerant until a pressure is observed and check
for leaks. After leaks are repaired, remove and recover
refrigerant from system. For leak testing procedures, see
GTAC 2, Module 5, Charging, Recovery, Recycling and
Reclamation section. Do not use the system compres-
sors to remove refrigerant from the system.
10. Crankcase heaters must be firmly locked into compres-
sors, and must be on for 24 hours prior to start-up.
Crankcase heaters on all units are wired into the
control circuit, so they are always operable as long
as the main power supply disconnect is on (closed),
even if any safety device is open. Compressor heat-
ers must be on for 24 hours prior to the start-up of
any compressor.
Fig. 41 — Compressor Mounting —
48/50MP62L Units
Fig. 42 — Front View of Compressor Mounting
Rail Assembly — 48/50MP70M-10R Units
NUT
COMPRESSOR MOUNTING FOOT
COMPRESSOR MOUNTING RAIL
Fig. 43 — Rear View of Compressor Mounting
Rail Assembly — 48/50MP70M-10R Units
28