Carrier 90MA, 90MU Operation, Make Electrical Connections, To start unit, To Shut Down Unit

Step 12 - Make Electrical Connections

GENERAL - Provide an adequate fused disconnect switch within sight of the unit. Provision for locking switch open (OFF) is advisable to prevent power from being turned on when unit is being serviced.

POWER WIRING - Conduit opening for all units is on left side of unit near control box. Connect field power wires at the compressor contactor.

Supply voltage must be in accordance with nameplate voltage. Voltage between phases must be balanced within 2% and current within 10% with compressor running.

Correct improper voltage or phase imbalance. Unit failure as a result of operation on improper line voltage or excessive phase imbalance constitutes abuse and shall void the Carrier warranty. Use the following formula to determine the percent voltage imbalance.

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 12 (90MA*04/*06) or figure 14 (90MA*08/*12).

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.

OPERATION

CAUTION

Compressor crankcase heater must be energized for 24 hours prior to startup to prevent compressor bearing damage.

To start unit:

1.Thoroughly inspect exterior of unit. Clean and dust up debris, then wash with mild soap and water solution.

2.On 90MA*08 &*12 units, ensure compressor discharge, suction and liquid service valves are open. (Refer to “Operation - Service Valves.) 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 remove any oil until the crankcase heater has been energized for at least twenty-four hours.

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

4.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 (Tables 1A/B/C/2A/B/C) and rotation (Figure 1). If fan requires adjustment, refer to “Service, Evaporator-Fan Adjustment”.

5.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 selector switch at COOL position. If room temperature is above thermostat setting compressor will start. On first start-up, set water regulating valve. (Refer to “Service, Water Regulating Valve.)

6.Set thermostat for comfort as desired.

To Shut Down Unit:

1.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. (Refer to “Service, Crankcase Heater”).

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

3.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.

Service Valves - Always ensure that compressor suction, and discharge service valves and liquid service valve are open before operating unit.

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.

Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations

Printed in U.S.A. Pg 12 90MA-3SI SUPERCEDES FORM 62-02971-00 09-2009