STARTUP AND SHUTDOWN
PRE-STARTUP
1.
2.
3.
4.
5.
6.
1.
6.
1.
2.
3.
With all electric disconnects open, check all screw or lug
type electrical connections to be sure they are tight for
good electrical contact. Check all compressor valve con-
nections for tightness to avoid refrigerant loss at start-
up. Although all factory connections are tight before ship-
ment, some loosening may have resulted from shipping
vibration.
On chilled water installations, check to see that all water
piping is properly connected.
Check the compressor oil level. Prior to startup, the oil
level should cover at least one-third of the oil sightglass.
Check the voltage of the unit power supply and see that
it is within the
*
10% tolerance that is allowed. Phase
voltage unbalance must be within
&20/o.
Check the unit power supply wiring for adequate
ampaci-
ty and a minimum insulation temperature rating of 75C.
Verify that all mechanical and electrical inspections have
been completed per local codes.
10.
CAUTION: Most relays and terminals in the unit control center
are hot with
S1
and the control circuit disconnect on. Do not
close
S1
until startup.
See that all auxiliary control equipment is operative and
that an adequate cooling load is available for initial
startup.
Open the compressor suction and discharge shutoff
valves until backseated. Always replace valve seal caps.
Making sure control stop switch
S1
is open (off) and
pumpdown
switches
PS1
and PS2 are on “manual
pumpdown,” throw the main power and control discon-
nect switches to “on.” This will energize crankcase
heaters. Wait a minimum of 12 hours before starting up
unit.
Open all water flow valves and start the chilled water
pump. Check all piping for leaks and vent the air from
the evaporator as well as from the system piping to ob-
tain clean, non-corrosive water in the evaporator circuit.
INITIAL STARTUP
Double check that the compressor suction and discharge
shutoff valves are backseated. Always replace valve seal
caps.
Open the manual liquid line shutoff valve at the outlet of
the subcooler.
Adjust the dial on temperature controller
CP1
to the
desired chilled water or leaving air temperature.
Start the auxiliary equipment for the installation.
Check to see that
pumpdown
switches PSI and PS2 are
in the “manual pumpdown” (open) position. Throw the
emergency stop switch
S1
to the “on” position. If
pressures on the low side of the system are above 60 psig,
the unit will start and pump down.
After the compressor lockout timer
TD1
has timed out, start
7.
8.
9.
the system by moving
pumpdown
switches PS1 and PS2
to the “auto pumpdown” position.
After running the unit for a short time, check the oil level
in each compressor crankcase, rotation of condenser fans,
and check for flashing in the refrigerant sightglass (see
“Maintenance”, page 49).
Superheat should be adjusted to maintain between 8 and
12 degrees F.
After system performance has stabilized, it is
necesary
that
the “Compressorized Equipment Warranty Form” (Form
No. 415415Y) be completed to obtain full warranty
benefits. This form is shipped with the unit, and after com-
pletion should be returned to McQuay’s Service Depart-
ment through your sales representative.
TEMPORARY SHUTDOWN
Move
pumpdown
switches PS1 and PS2 to the “manual pumpdown” position. After
the compressors have pumped down, turn off the chilled water pump or evaporator
fan. It is especially important on chilled water installations that the compressors pump
down before the water flow to the evaporator is interrupted to avoid freeze-up.
CAUTION: With the unit left in this condition, it is capable of recycling pumpdown
operation. To defeat this mode of operation, move control stop switch
S1
to the “off”
position.
STARTUP AFTER TEMPORARY SHUTDOWN
1. Start the chilled water pump.
2. With emergency stop switch
S1
in the “on” position, move
pumpdown
switches
PS1 and PS2 to the “auto pumpdown” position.
3. Observe the unit operation for a short time to be sure that the compressors do
not cut out on low oil pressure.
EXTENDED SHUTDOWN
(For startup after extended shutdown, refer to applicable “Initial Startup” steps.)
Close the manual liquid line shutoff valves.
After the compressors have pumped down, turn off the
chilled water pump or evaporator fan.
Turn off all power to the unit and to the auxiliary
equipment.
4.
5.
6.
Move the control stop switch
S1
to the “off” position.
Close the compressor suction and discharge valves.
Tag all opened disconnect switches to warn against start-
up before opening the compressor suction and discharge
valves.
Page 48 I IM 269
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