REFRIGERATION SYSTEM CHECKS
Ensure the hold-down bolts on the compressor are secure and have not vibrated loose during shipment. Check that vi- bration grommets have been installed. Visually check all pip- ing and clamps. The entire refrigeration system has been factory charged and tested, making it unnecessary to field charge. Factory charges are shown in Appendix C and on the unit nameplate.
Install service manifold hoses. Gauges should read satura- tion pressure corresponding to ambient temperature. Charge should be checked to obtain 12° to 15° of sub-cooling per system (i.e. compressor circuits).
START-UP PROCEDURE AND CHECKLIST
Begin with power turned off at all disconnects.
1.Turn thermostat system switch to “Cool,” and fan switch to “Auto” and turn temperature setting as high as it will go.
2.Inspect all registers and set them to the normal open position.
3.Turn on the electrical supply at the disconnect.
4.Turn the fan switch to the “ON” position. The blower should operate after a 7-second delay.
5.Turn the fan switch to “Auto” position. The blower should stop after a 65 second delay.
6.Slowly lower the cooling temperature until first stage COOL (LOW COOL) starts. The blower, both fans, and first stage compressor should now be operating. Allow the unit to run 10 minutes, make sure cool air is being supplied by the unit.
7.Lower the cooling temperature further until second stage COOL (HIGH COOL) starts. The blower, both fans, and both compressors should now be operating. Allow the unit to run 10 minutes, make sure cool air is being supplied by the unit.
8.Turn the temperature setting to the highest position, stopping the unit. The indoor blower will continue to run for 65 seconds.
9.Turn the thermostat system switch to “OFF” and disconnect all power when servicing the unit.
WARNING
HIGH VOLTAGE!
DISCONNECT ALL POWER BEFORE SERVICING OR INSTALLING THIS UNIT. MULTIPLE POWER SOURCES MAY BE PRESENT. FAILURE TO DO SO MAY CAUSE PROPERTY DAMAGE, PERSONAL INJURY OR DEATH.
FINAL SYSTEM CHECKS
10.Check to see if all supply and return air grilles are adjusted and the air distribution system is balanced for the best compromise between heating and cooling.
11.Check for air leaks in the ductwork. See Sections on
Air Flow Adjustments.
12.Make sure the unit is free of “rattles”, and the tubing in the unit is free from excessive vibration. Also make sure tubes or lines are not rubbing against each other or sheet metal surfaces or edges. If so, correct the trouble.
13.Set the thermostat at the appropriate setting for cooling and heating or automatic change over for normal use.
14.Be sure the Owner is instructed on the unit operation, filter, servicing, correct thermostat operation, etc.
REFRIGERATION PERFORMANCE CHECK
Under normal summertime (full load) operating conditions, superheat should be between 8°F and 12°F and sub-cooling measured at the condenser outlet should be 15°F (nominal). A 25°F to 35°F temperature difference should exist between the entering condenser air and the temperature correspond- ing to the compressor saturated discharge pressure. Check that compressor RLA corresponds to values shown in Ap- pendix C. RLA draw can be much lower than values listed at low load conditions and low ambient condensing tempera- tures. Values in Appendix C can slightly exceed at high load conditions and high ambient condensing temperatures.
AIR FLOW ADJUSTMENTS
The drive on the supply fan is typically set in the middle of the RPM range. The drive motor sheave pitch diameter is field adjustable for the required airflow. Refer to “Drive Adjustments” section below.
When the final adjustments are complete, the current draw of the motor should be checked and compared to the full load current rating of the motor. The amperage must not ex- ceed the service factor stamped on the motor nameplate. The total airflow must not be less than that required for op- eration of the electric heaters or the furnace.
If an economizer is installed, check the unit operating bal- ance with the economizer at full outside air and at minimum outside air. Upon completion of the air flow balancing, we recommend replacing the variable pitched motor sheave with a properly-sized fixed sheave. A matching fixed sheave will provide longer belt and bearing life and vibration free opera- tion. Initially, it is best to have a variable pitched motor sheave for the purpose of airflow balancing, but once the balance has been achieved, fixed sheaves maintain alignment and minimize vibration more effectively. For direct drive units, move green wire for fan.
NOTE: Never run CFM below 350 CFM per ton, evaporator freezing or poor unit performance is possible.
