Unit Startup
108
RT-SVX24J-EN
Temperature Differential Setpoint minus 5°F but not the
Evaporator Temperature Differential Setpoint, an
information only, auto-reset, High Superheat diagnostic is
initiated. If the calculated superheat exceeds the
Evaporator Temperature Differential Setpoint, a manual
reset, low refrigerant charge diagnostic is initiated and all
compressors on the circuit are locked out.
Wet Heat Sequence of Operation
Electrical circuitry for units with steam or hot water heat is
limited to the connections associated with the modulating
valve actuator and the freezestat.
Like the furnaces described earlier, steam and hot water
heat control systems are wired to ensure that
simultaneous heating and cooling do not occur. The
supply fan will cycle “On” and “Off” with each call for heat
during both an occupied and unoccupied period.
Whenever there is a call for heat,
the relay on the heat
module
energizes. This allows a modulated voltage
signal to be sent to the “Wet” heat actuator. The value of
this signal regulates the flow of steam or hot water
through the coil by positioning the valve stem at some
point between fully closed (6 VDC) and fully open (8.5
VDC).
Freeze Protection
A freezestat is mounted inside the heat section of hot water
and steam heat units to prevent the “wet” heat coil from
freezing during the “Off” cycle.
If the temperature of the air leaving the heating coils falls
to 40 F, the freezestat normally open contacts close,
completing the heat fail circuit on the UCM. When this
occurs:
a. The supply fan is turned “Off”.
b. “Wet” heat actuator fully opens to allow hot water
or steam to pass through the heating coil and
prevent freeze-up.
c. A “Low Air Temperature Unit Trip” diagnostic is
displayed on the Human Interface LCD screen.
For heating control settings and time delay specifications,
refer to
Table 45, p. 156
.
Unit Startup Check List
Use the following checklist, in conjunction with the
“General Unit Requirement” checklist”, to ensure that the
unit is properly installed and ready for operation. Be sure
to complete all of the procedures described in this section
before starting the unit for the first time.
[ ]Turn the field supplied disconnect switch, located
upstream of the rooftop unit, to the “Off” position.
•
[ ] Turn the 115 volt control circuit switch 1S2 to the
“Off” position. It is located in the secondary of the 1T1
transformer.
•
[ ]Turn the 24 volt control circuit switch 1S3 to the “Off”
position. It is located in the secondary of the 1T2 - 1T5
transformers.
•
[ ] Turn the “System” selection switch (at the Remote
Panel) to the “Off” position and the “Fan” selection
switch (if Applicable) to the “Auto” or “Off” position.
•
[ ] Check all electrical connections for tightness and
“point of termination” accuracy.
•
[ ] Verify that the condenser airflow will be
unobstructed.
•
[ ] Check the compressor crankcase oil level. Oil should
be visible in the compressor oil sight glass. The oil
level should be 1/2 to 3/4 high in the sight glass with the
compressor “Off”.
•
[ ] Verify that all refrigerant service valves are back
seated on each circuit.
Do not start the unit in the cooling mode if the ambient
temperature is below the following minimum
recommended operating temperature:
Standard unit with or without HGBP-+45°F
•
[ ] Check the supply fan belts for proper tension and the
fan bearings for sufficient lubrication. If the belts
require adjustment, or if the bearings need lubricating,
refer to the Service/Maintenance section of this
manual for instructions.
•
[ ] Inspect the interior of the unit for tools and debris.
Install all panels in preparation for starting the unit.
Electrical Phasing
Scroll compressors are phase sensitive. Proper phasing of
the electrical supply to the unit is critical for proper
operation and reliability. The compressor motor is
WARNING
Hazardous Voltage!
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.
CAUTION
Compressor Damage!
Do not allow liquid refrigerant to enter the suction line.
Excessive liquid accumulation in the liquid lines could
result in compressor damage.Compressor service
valves must be fully opened before startup (suction,
discharge, liquid line, and oil line).
Содержание SEHJ090-162
Страница 40: ...Dimensional Data 40 RT SVX24J EN Figure 13 Evaporative condenser water connection locations RIGHT SIDE VIEW ...
Страница 48: ...Installation 48 RT SVX24J EN Figure 18 Ductwork conversion ...
Страница 58: ...Installation 58 RT SVX24J EN Figure 36 5 Connected tubes 6 install panels Connected tubes 5 6 ...
Страница 75: ...Installation RT SVX24J EN 75 Figure 51 Hot water coil piping Figure 52 Steam coil piping ...
Страница 87: ...Installation RT SVX24J EN 87 Figure 57 Typical field wiring diagram for 90 to 162 ton CV control options ...
Страница 89: ...Installation RT SVX24J EN 89 Figure 59 Typical field wiring diagram for 90 to 162 ton VAV control options ...