START-UP
IMPORTANT: Energize crankcase heaters 24 hours prior to base unit
Unit Preparation Ð Make sure that unit has been in- stalled in accordance with these installation instructions and applicable codes.
Compressor Mounting Ð Compressors are inter- nally spring mounted. Do not loosen or remove compressor holddown bolts.
Internal Wiring Ð Check all electrical connections in unit control boxes; tighten as required.
Refrigerant Service Ports Ð Each refrigerant sys- tem has 3
Cooling Ð To start unit, turn on main power supply. Set system selector switch at COOL position and fan switch at AUTO. position. Adjust thermostat to a setting below room temperature. Compressor starts on closure of contactor.
Check unit charge. Refer to Refrigerant Charge section on page 20.
Reset thermostat at a position above room temperature. Compressor will shut off.
TO SHUT OFF UNIT Ð Set system selector switch at OFF position. Resetting thermostat at a position above room tem- perature shuts unit off temporarily until space temperature exceeds thermostat setting.
Heating Ð To start unit, turn on main power supply.
Set thermostat at HEAT position and a setting above room temperature, fan at AUTO. position.
First stage of thermostat energizes Compressor no. 1 and Compressor no. 2; second stage energizes the electric heat (where applicable). Check heating effects at air supply grille(s).
If unit does not energize, reset limit switch (located on
TO SHUT OFF UNIT Ð Set system selector switch at OFF position. Resetting heating selector lever below room tem- perature will shut unit off temporarily until the space tem- perature falls below thermostat setting.
Safety Relief Ð A
Ventilation (Continuous Fan) Ð Set fan and sys- tem selector switches at ON and OFF positions, respec- tively. Indoor fan operates continuously to provide constant air circulation.
Operating Sequence (See Fig. 20)
COOLING Ð With accessory economizer Ð Upon a re- quest for cooling from the space thermostat, terminals Y1 and G will be energized with 24 v. As a result, the
economizer damper blade will open to minimum position. Note that if the indoor fan is on when the space thermostat calls for cooling, terminal G is already energized and the economizer damper blade is at minimum position.
If the
If the thermostat calls for a second stage of cooling by supplying 24 v to Y2, the
When the thermostat is satis®ed, Y2 will be deenergized ®rst, which will deenergize the outdoor fan and Compressor no. 1. When the indoor fan is deenergized, the economizer will return to a fully closed position.
If the
Without accessory economizer Ð Upon a request for cool- ing from the space thermostat, terminals Y1 and G will be energized with 24 v. As a result, the
If the space thermostat calls for a second stage of cooling by supplying 24 v to Y2, Compressor contactor no. 2 (C2) will be energized, thus energizing Compressor no. 2.
When the space thermostat is satis®ed, Y2 will be de- energized ®rst, which will deenergize Compressor no. 2.
Upon a further drop in space temperature, Y1 will be de- energized which will deenergize Compressor no. 1, and the outdoor and indoor fans.
HEATING Ð Upon a request for heating from the space ther- mostat, terminal W1 will be energized with 24 v. On units with economizer, the economizer damper blade will move to minimum position regardless of the
If the space temperature continues to fall while W1 is en- ergized, W2 will be energized with 24 v, and the heater con- tactor(s) (HC) will be energized, which will energize the electric heater(s).
When the space thermostat is satis®ed, W2 will be de- energized ®rst, and the electric heater(s) will be deenergized.
Upon a further rise in space temperature, W1 will be de- energized, and the reversing valve solenoids (RVS1 and RVS2) will be energized. On units with economizer, the econo- mizer damper blade will move to the fully closed position.
DEFROST Ð When the temperature of the outdoor coil drops below 28 F as sensed by the defrost thermostat (DFT2) and the defrost timer is at the end of a timed period (adjustable at 30, 50 or 90 minutes). RVS1 and RVS2 are energized and the OFC is deenergized. This switches the
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