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0 commissioning and startup (cont'd) – Reznor RECC Unit Installation Manual User Manual

Page 66

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Form I-MAPSIII&IV, Page 66

Power Supply Voltage Phasing

Blower Rotation - If blower rotation is not correct, reverse by interchanging two wires

on the 3-phase supply connection to the blower motor.

Compressors

Connect refrigerant pressure gauges to the suction and discharge lines of the

compressors and an electric meter to the power supply.

CAUTION: Be sure to connect pressure gauges to the suction

and discharge lines before system startup so that compressor

rotation can be checked immediately. Scroll compressors

will be destroyed if allowed to operate in the wrong direction.

Record the ambient temperature. Adjust the system controller so that a call for

cooling exists.

N

OTE: Outdoor ambient lockouts may prevent mechanical cooling. Temporarily

override lockouts by lowering the cooling setpoint. When testing is complete, reset

the controller.

Because it is possible to unknowingly connect 3-phase power in such a way

as to cause the scroll compressor or blower to rotate in reverse, it is very

important to check this on startup. See below and Paragraph 7.2.3.
Check Compressors - Immediately at startup, observe the gauges. If the

suction pressure rises and discharge pressure drops, the compressor is

operating in reverse and must be shut down. Turn off the power and switch

the 3-phase line voltage wiring connections before restarting the unit.

(Important NOTE: If allowed to operate for several minutes in reverse, the

compressor’s internal protector will trip. If a compressor is repeatedly allowed to

restart and run in reverse, the compressor will be permanently damaged.)

10.0 Commissioning and Startup (cont'd)

10.3 Checklist Prior

to Startup

(cont'd)

10.3.1 Gas Heat

Checklist Prior to

Startup (cont'd)

Check the subcooling and superheat.

Subcooling is the measurement of liquid refrigerant stored in the condenser coil.

Too much subcooling indicates a system overcharge. Too little indicates a system

undercharge and may not provide the thermal expansion valve with a full column

of liquid refrigerant for proper operation.

Superheat is the verification that the evaporator coil is properly using the

refrigerant supplied. Too much superheat indicates that the coil is undercharged.

Too little superheat indicates that the coil is overcharged and potentially flooding

liquid refrigerant to the compressor.

Two important requirements before checking subcooling & superheat:

1) Each circuit

MUST be isolated before measuring its temperature. Another

active circuit will influence the reading and make it impossible to determine

accurate superheat and subcooling.

2) If the circuit is equipped with an optional hot gas bypass valve, the valve must

be disabled before measuring subcooling and superheat. Disable the hot gas

bypass valve by removing the cover and adjusting the spring tension.

Count and

record the number of counterclockwise turns until the spring tension is relieved.

(When you can return the bypass valve to its original setting, turn the spring the

same number of turns clockwise.) To check setting, see Paragraph 7.7.

Instructions for Checking and Adjusting the Subcooling of an Isolated

Circuit:

Measure and record temperature and pressure of the liquid line at the condenser

coil outlet. At initial startup, fill out the "Startup Form" (See page 70.)

STEP 1) Record Measurements: Temperature =

________°F (°C) and Pressure = ________ psig

IMPORTANT:

All refrigeration

checks must

be made by a

qualified R-410A

refrigeration

technician.