Johnson Controls York VERSECON YSWD 012, Installation Operation & Maintenance

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JOHNSON CONTROLS
FORM 145.05-NOM1 (708)
4. Allow the compressor to run a short time, being
ready to stop it immediately if any unusual noise
or adverse conditions develop.
5. Check the system operating parameters by checking
evaporator superheat and condensing subcooling.
The leaving condenser water temperature should
be between 85.0° F and 95.0° F when checking
subcooling. Connect a gauge manifold set to the
Schrader service valve connections on the suction
and liquid lines of the refrigerant system to be
checked. After the system is running and the pres-
sures have stabilized, measure the temperature of
the liquid line between the liquid line drier and the
expansion valve and the suction line temperature
on the suction line leaving the evaporator coil.
Calculate the evaporator superheat and the con-
densing subcooling. The evaporator superheat
should be between 6 and 12° F. The condenser
subcooling should be between 6 and 10° F. Refer to
the next section for information on how to calculate
evaporator superheat and condenser subcooling.
Repeat the above process for each of the refrigerant
systems.
6. With an ammeter, verify that each phase of the
supply fan motor and compressors are within the
RLA/FLA as listed on the unit data plate.
Refrigerant Charge
The Versecon unit comes fully charged from the factory
with Refrigerant R-22. Table 11 is a Temperature/
Pressure chart for R-22.
Subcooling
The subcooling temperature of each system can be
calculated by recording the temperature of the liquid
line between the filter drier and the expansion valve and
subtracting it from the liquid line saturation temperature
at the liquid line service port
.
Example:
202 psig Liquid Line 102° F
(Converted to Saturation Temp)
Minus Liquid Line Temp
92° F
Liquid Line Subcooling 10° F
The subcooling should be adjusted to 6 to 10° F at
design conditions.
If the subcooling is low, check the temperature of
the liquid line on the entering and leaving side of the
filter drier. If the temperature drop across the drier is
greater than 3.0° F the drier is restricted and must be
replaced.
If the filter drier is okay add refrigerant to increase
the subcooling and recover refrigerant to decrease the
subcooling.
After the subcooling is verified, the evaporator superheat
should be checked. The evaporator superheat should
be checked only after steady state operation of the unit
has been established, and the unit is running in a fully
loaded condition.
Superheat (R-22)
The evaporator superheat is calculated as the difference
between the actual temperature of the refrigerant
gas leaving the evaporator coil and the temperature
corresponding to the suction pressure as shown in a
standard Temperature/Pressure chart in Table 11.
Example:
Suction Temperature 46° F
Minus 60 psig Suction Press
Converted to Saturation Temp
34° F
Evaporator Superheat 12° F
When adjusting the expansion valve, the adjusting
screw should be turned not more than one turn at a time,
allowing sufficient time (approximately 15 minutes)
between adjustments for the system and the thermal
expansion valve to respond and stabilize.
Assure the evaporator superheat is set between 6 and
12° F.
Leak Checking
Leak check compressors, fittings, and piping to assure
no leaks. Verify the evaporator distributor tubes do not
have bare copper touching each other or are against a
sheet metal edge.
If the unit is functioning satisfactorily during the
initial operating period, no safety trips and the unit
controls are functioning properly, the unit is ready
to be placed into operation.