Thermostatic Expansion Valves; Electric, Steam And Hot Water Start-Up; Systems) - Trane IntelliPak WEHE Series Installation, Operation And Maintenance Manual

Figure 49. Fresh air & return air linkage adjustment
Top View
RETURN AIR
DAMPERS
3
4
1
5
2
6
FILTER
SECTION

Thermostatic Expansion Valves

The reliability and performance of the refrigeration system
is heavily dependent upon proper expansion valve
adjustment. Therefore, the importance of maintaining the
proper superheat cannot be over emphasized. Accurate
measurements of superheat will provide the following
information.
1. How well the expansion valve is controlling the
refrigerant flow.
2. The efficiency of the evaporator coil.
3. The amount of protection the compressor is receiving
against flooding or overheating. The expansion valves
shipped installed in this unit were factory set to control
between 14-18°F at the ARI full load rating conditions
(approximately 45°/125°F saturated suction/
discharge). At part load, expect a properly adjusted
expansion valve to control to 8-12°F superheat. In
typical applications, field adjustment should not be
required unless the valves are replaced or damaged.
Systems operating with lower superheat could cause
serious compressor damage due to refrigerant
floodback.
Systems operating with superheat exceeding 20°F:
– Could cause excessive compressor cycling on
internal winding thermostat which leads to
compressor motor failure.
– Lowers the efficiency of the evaporator by reducing
the heat transfer capability.
RT-SVX35H-EN
FRESH AIR
DAMPERS
8
7
Tables are based on outdoor ambient between 65°F &
105°F, relative humidity above 40 percent. Measuring the
operating pressures can be meaningless outside of these
ranges.
Measuring Superheat
1. Measure the suction pressure at the suction line gauge
access port located near the compressor.
2. Using a Refrigerant/Temperature chart, convert the
pressure reading to a corresponding saturated vapor
temperature.
3. Measured the suction line temperature as close to the
expansion valve bulb, as possible. Use a thermocouple
type probe for an accurate reading.
4. Subtract the saturated vapor temperature obtained in
step 2 from the actual suction line temperature
obtained in step 3. The difference between the two
temperatures is known as "superheat".
When adjusting superheat, recheck the system subcooling
before shutting the system "Off".

Electric, Steam and Hot Water Start-Up

(Constant Volume & Variable Air Volume

Systems)

1. Ensure that the "System" selection switch at the
remote panel is in the "Off" position.
.
WARNING
Hazardous Voltage!
HIGH VOLTAGE IS PRESENT AT TERMINAL BLOCK 1TB1
OR UNIT DISCONNECT SWITCH 1S14. Disconnect all
electric power, including remote disconnects before
servicing. Follow proper lockout/tagout procedures to
ensure the power can not be inadvertently energized.
Failure to disconnect power before servicing could
result in death or serious injury.
2. Close the disconnect switch or circuit protector switch
that provides the supply power to the unit's terminal
block 1TB1 or the unit mounted disconnect switch
1S14.
3. Turn the 115 volt control circuit switch 1S1 and the 24
volt control circuit switch 1S70 to the "On" position.
4. Open the Human Interface access door, located in the
unit control panel, and press the SERVICE MODE key to
display the first service screen. Refer to the latest
edition of RT-SVP04*-EN (VAV) or RT-SVP05*-EN (CV)
for the SERVICE TEST screens and programming
instructions.
5. Use Table 20, p. 75 to program the following system
components for operation by scrolling through the
Human Interface displays;
System Start-up
93