Unit Startup Procedures
34
CG-SVX038A-EN
Checking Operating Conditions
Once the unit has been operating for about 10 minutes and
the system has stabilized, check operating conditions and
complete the checkout procedures that follow.
•
Recheck evaporator water and condenser (CGWR)
water flows and pressure drops. These readings
should be stable at proper levels.
•
Check suction pressure and discharge pressure of the
unit.
Discharge pressures—take at Schrader fitting provided on
the discharge line. Normal discharge pressures are:
CCAR units:
315 psig to 500 psig
CGWR units:
275 psig to 430 psig
Suction pressures— take at Schrader fitting provided on
the suction line. Normal suction pressures are:
42°F–60°F LWT:
104–155 psig
15°F–39°F LWT:
60–103 psig
•
Check compressor oil levels. At full load, oil level
should be visible in the oil level sight glass on the
compressor. If it is not, add or remove oil as required.
•
Check the liquid line sight glasses. Refrigerant flow
past the sight glasses should be clear. Bubbles in the
liquid line indicate either low refrigerant charge or
excessive pressure drop in the liquid line. Such a
restriction can often be identified by a noticeable
temperature differential on either side of the restricted
area. Frost often forms on the outside of the liquid line
at this point also.
The system may not be properly charged although
the sight glass is clear. Also consider superheat,
sub-cooling and operating pressure.
•
Once oil level, amp draw and operating pressures have
stabilized, measure system suction superheat.
•
Measure system liquid line sub-cooling.
•
If operating pressure, sight glass, superheat and sub-
cooling readings indicate refrigerant shortage, charge
refrigerant into each circuit. Refrigerant shortage is
indicated if operating pressures are low and sub-
cooling is also low.
If suction and discharge pressures are low but sub-
cooling is normal, no refrigerant shortage exists.
Adding refrigerant, will result in overcharging.
Add refrigerant with the unit running by metering liquid
refrigerant through the Schrader valve between the
expansion valve and the evaporator refrigerant inlet until
operating conditions are normal.
System Superheat
Normal superheat for each circuit is 10°F–16°F at full load.
If superheat is not within this range, adjust expansion
valve superheat setting. Allow 5–10 minutes between
adjustments for the expansion valve to stabilize on each
new setting.
System Sub-cooling
Normal sub-cooling for each circuit is 5°F to 10°F at full
load where saturated discharge pressure and liquid line
temperature are measured at chiller liquid line.
NOTICE:
Evaporator/Condenser Damage!
Water (fluid) flow must be established in evaporator
and condenser before adding refrigerate, removing
refrigerate, or pulling vacuum, to protect heat
exchangers from freezing.
NOTICE:
Compressor Damage!
Do not allow liquid refrigerant to enter the suction line
as excessive liquid accumulation in the liquid lines
could result in compressor damage.
To prevent compressor damage and ensure full cooling
capacity, use refrigerants specified on the unit
nameplate only.
•
If operating conditions indicate an overcharge,
slowly (to minimize oil loss) remove refrigerant at the
liquid line Schrader fitting. Do not discharge
refrigerant into the atmosphere.
•
If the remote condenser (CCAR) is equipped with low
ambient dampers, check for proper actuator and
blade travel in relation to condensing pressure.
•
Once proper unit operation is confirmed, inspect for
debris, misplaced tools., etc. Secure control panel
doors in place.
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