System Superheat; System Subcooling - Trane RTAA-70 Installation & Maintenance Manual

RTAA-SVX01A-EN
Start-Up Procedures
• A shortage of refrigerant is indicated if operating pressures are low and
subcooling is also low. If the operating pressures, sight glass, superheat
and subcooling readings indicate a refrigerant shortage, gas-charge
refrigerant into each circuit, as required. With the unit running, add
refrigerant vapor by connecting the charging line to the suction service
valve and charging through the backseat port until operating conditions
become normal.
CAUTION
Overcharging the Circuit!
If both suction and discharge pressures are low but subcooling is
normal, a problem other than refrigerant shortage exists. Do not
add refrigerant, as this may result in overcharging the circuit.
CAUTION
Compressor Damage!
Use only refrigerants specified on the unit nameplate, to prevent
compressor damage and insure full system capacity.
WARNING
Contains Refrigerant!
System contains oil and refrigerant under high pressure. Recover
refrigerant to relieve pressure before opening the system. See
unit nameplate for refrigerant type. Do not use non-approved
refrigerants, refrigerant substitutes, or refrigerant additives.
Failure to follow proper procedures or the use of non-approved
refrigerants, refrigerant substitutes, or refrigerant additives could
result in death or serious injury or equipment damage.
• If operating conditions indicate a refrigerant overcharge, remove refriger-
ant at the liquid line service valve. Allow refrigerant to escape slowly, to
minimize oil loss. Do not discharge refrigerant into the atmosphere.

System Superheat

Normal suction superheat for each circuit is approximately 4 F at full operating
load. Superheat temperature can be expected to be moving around the 4 F
setpoint when the chiller is pulling down, the compressor slide valve is being
modulated, or the fans are staging on either the same or opposite circuits.
Superheat can be expected to settle out at approximately 4 F when the above
items stabilize.

System Subcooling

Normal subcooling for each circuit ranges from 11 F to 20 F , depending on the
unit. If superheat is normal but subcooling is not, contact a qualified service
technician.
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