Carrier 90MA/MF/MU manual Operation

CONTROL WIRING - On extended voltage (208/230-v) units, the control transformer is factory wired for 208-v usage. If unit is to be used on 230-v system, reconnect primary wiring on transformer. See Figure 13 (004/006 size) or Figure 15 (008/012 size).

On all units, the thermostat is factory installed. A sensing element is provided in the return air. To wire these units to a remote thermostat, or to a remote control switch and thermostat, refer to unit Wiring Diagram or contact your Carrier Transicold representative.

4.OPERATION

CAUTION

Compressor crankcase heater must be ener- gized for 24 hours prior to start up to prevent compressor bearing damage.

4.1To Start Unit

a. Thoroughly inspect exterior of unit. Clean and dust up debris, then wash with mild soap and water solu- tion.

b. On 008 & 012 size units, ensure compressor dis- charge, suction and liquid service valves are open. The valves are accessible from the front of the unit. To open valve, turn counterclockwise. After opening, replace and tighten valve cap to prevent leakage.

Check oil level in compressor sight glass. If level is below glass, add oil to bring level to approximately 1/4 glass. If level is above bottom of glass, do not re- move any oil until the crankcase heater has been ener- gized for at least twenty-four hours.

c.With selector switch in OFF position, turn main pow- er on. Leave power on for 24 hours so that crankcase heater can drive off accumulated refrigerant.

d.If desired, the selector switch may be placed in the FAN position during the crankcase warm-up period. On first start-up, check fan speed (Table 1 through Table 2) and rotation (Figure 1). If fan requires ad- justment, refer to paragraph 5.3.

e. Allow crankcase heater to remain energized (unit power on) for at least 24 hours. Open any valves in condenser cooling water supply lines and then set se- lector switch at COOL position. If room temperature is above thermostat setting compressor will start. On first start-up, set water regulating valve. (Refer to paragraph5.7.)

f. Set thermostat for comfort as desired.

4.2To Shut Down Unit

a.Turn selector switch to OFF position. Do not shut off main power except to service unit. The crankcase heater is operative only when main power is on. (Re- fer to paragraph 5.12).

b.If unit is to be used for winter heating, set selector switch at HEAT position and re-set thermostat at de- sired setting.

c.If unit may be exposed to freezing temperatures, drain water from condenser and water piping. Add a non- corrosive antifreeze to residual water in system.

4.3Sequence Of Operation

Unit operation is dependent on the position of the mode selector switch. (See note 3, Figure 14 or Figure 16.) Operation sequence for each switch position is provided in the following paragraphs.

OFF POSITION: With correct voltage supplied at the field power supply terminals, see Figure 13 or Figure 15 power flows through normally closed crankcase heater relay (CHR) contacts (CHR, 4/5) to energize the crankcase heater (CH).

TO PLACE THE UNIT IN THE FAN MODE: The switch (SW) is placed in the FAN position to supply 24 volt control power, to energize indoor fan contactor (IFC). Energizing IFC closes contacts (IFC, 11/21, 12/22 & 13/23) to energize the motor. Operation of the crankcase heater is maintained.

TO PLACE THE UNIT IN THE COOL MODE: The switch (SW) is placed in the COOL position. With thermostat (T-LOW) calling for cooling (closed to contacts R & W) control power flows from TRAN through T-LOW, SW and compressor lockout (CL) normally closed contacts to the discharge pressure switch (DPS). On 008/012 size units, flow continues through the compressor internal protector (IPC), compressor overloads (OLA & OLB) and the suction pressure switch (SPS), to energize CHR. On 004/006 size units, flow continues directly thorough the suction pressure switch to energize CHR.

Energizing CHR opens contacts CHR 4-5 to de-energize CH and closes contacts CHR 1-3 and energize the compressor contactor (CC). Energizing CC closes its contacts to start the compressor motor (C). Operation of the indoor fan motor (IFM) is maintained.

On 90MU units, power also flows from terminal TB1-5 to energize condenser fan relay (CFR). Energizing CFR closes its contacts to supply power to the field supplied condenser fan relay.

012 size units are fitted with a two stage cooling system. On these units, if thermostat switch T-HIGH is also calling for cooling, power flows through thermostat

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