37
Operational Checkout
After the system has been charged and has operated for at least
2 hours at normal operating conditions without any indication
of malfunction, it should be allowed to operate overnight on
automatic controls. A thorough recheck of the entire system
operation should be made as follows:
(a) Check compressor discharge and suction
pressures. If not within system design limits,
determine why and take corrective action.
(b) Check liquid line sight glass and expansion
valve operation. If there are indications that more
refrigerant is required, leak test all connections and
system components and repair any leaks before
adding refrigerant.
(c) Using suitable instruments, carefully check line
voltage and amperage at the compressor termi-
nals. Voltage must be within 10% of that indicated
on the condensing unit nameplate. If high or low
voltage is indicated, notify the power company.
If amperage draw is excessive, immediately deter-
mine the cause and take corrective action. On 3
phase motor compressors, check to see that a
balanced load is drawn by each phase.
(d) The maximum approved settings for high pres-
sure controls on Bohn/Heatcraft air cooled con-
densing equipment is 400 psig. On air cooled
systems, check as follows:
`• Disconnect the fan motors or block the condenser
inlet air.
• Watch high pressure gauge for cutout point.
• Recheck all safety & operating controls for proper
operation and adjust if necessary.
(e) Check head pressure controls for pressure setting.
(f) Check crankcase heater operation if used.
(g) Install instruction card and control system diagram
for use of building manager or owner.
Check-Out & Start-Up
After the installation has been completed, the following points
should be covered before the system is placed in operation:
(a) Check all electrical and refrigerant connections.
Be sure they are all correct and tight.
(b) Check voltage taps on transformer. The transform-
er is shipped wired to 240 voltage tap/connection.
If your supply voltage is 208 volt systems, change
to 208 voltage tap.
(c) Check setting of time delay relay for low pressure
switch in condensing unit. It should be set at one
minute (the second marker).
(d) Check high and low pressure controls, pressure
regulating valves, oil pressure safety controls, and all
other safety controls and adjust them, if necessary.
(e) On freezers only, check the low pressure switch
setting. It must be set to 0 PSIG cut out, 10 PSIG cut
in, to allow start and operation, especially in cold
ambients.
(f) Liquid line should always be insulated.
(g) Wiring diagrams, instruction bulletins, etc. attached
to the condensing units should be read and led for
future reference.
(h) All fan motors on air cooled condensers, evapora-
tors, etc. should be checked for proper rotation.
Fan motor mounts should be carefully checked for
tightness and proper alignment.
(i) Observe system pressures during charging and
initial operation. Do not add oil while the system is
short of refrigerant unless oil level is dangerously
low.
(j) Continue charging until system has sufcient refriger-
ant for proper operation. Do not overcharge. Re-
member that bubbles in a sight glass may be caused
by a restriction as well as a shortage of refrigerant.
(k) Do not leave unit unattended until the system has
reached normal operating conditions and the oil
charge has been properly adjusted to maintain the
oil level at the center of the sight glass.
(l) At initial start-up, the system may cycle off at 2 min-
utes and display a low superheat error, then restart
itself. This cycle may be repeated a few times. Do
not shut the system off. Let the system run, as it may
take a few cycles for the electric expansion valve to
attain the correct setting for the desired superheat.
CAUTION: Extreme care must be taken in starting
compressors for the rst time after system charging. At
this time, all of the oil and most of the refrigerant might be
in the compressor creating a condition which could cause
compressor damage due to slugging. Activating the crank-
case heater for 24 hours prior to start-up is recommended.
If no crankcase heater is present, then directing a 500 watt
heat lamp or other safe heat source on the lower shell of
the compressor for approximately thirty minutes will be
benecial in eliminating this condition which might never
reoccur.
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