Two−Stage Modulation Compressors Checks
Use this checklist on page 42 to verify
TOOLS REQUIRED
SRefrigeration gauge set
SDigital volt/amp meter
SElectronic temperature thermometer
S
IMPORTANT
This performance check is ONLY valid on systems that have clean indoor and outdoor coils, proper airflow over coils, and correct system refrigerant charge. All components in the system must be functioning proper to correctly perform compressor modulation operational check. (Accurate measurements are critical to this test as indoor system loading and outdoor ambient can affect variations between low and high capacity readings).
PROCEDURE
NOTE − Block outdoor coil to maintain a minimum of 375 psig during testing).
1.Turn main power OFF to outdoor unit.
2.Adjust room thermostat set point 5ºF above the room temperature.
3.Remove control access panel. Install refrigeration gauges on unit. Attach the amp meter to the common (black wire) wire of the compressor harness. Attach thermometer to discharge line as close as possible to the compressor.
4.Turn toggle switch OFF and install switch in series with Y2 wire from room thermostat.
5.Cycle main power ON.
6.Allow pressures and temperatures to stabilize before taking measurements (may take up to 10 minutes).
7.Record all of the readings for the Y1 demand.
8.Close switch to energize Y2 demand. Verify power is going to compressor solenoid.
9.Allow pressures and temperatures to stabilize before taking measurements (may take up to 10 minutes).
10.Record all of the readings with the Y1 and Y2 demand.
11.If temperatures and pressures change in the direction noted in Two−Stage Modulation Compressor Field Operational Checklist on page 42, the compressor is properly modulating from low to high capacity. (If no amperage, pressures or temperature readings change when this test is performed, the compressor is not modulating between low and high capacity and replacement is necessary).
12. After testing is complete, return unit to original set up.
Maintenance
DEALER
Maintenance and service must be performed by a qualified installer or service agency. At the beginning of each cooling season, the system should be checked as follows:
Outdoor Unit
1.Clean and inspect outdoor coil (may be flushed with a water hose). Ensure power is off before cleaning.
2.Outdoor unit fan motor is pre−lubricated and sealed. No further lubrication is needed.
3.Visually inspect all connecting lines, joints and coils for evidence of oil leaks.
4.Check all wiring for loose connections.
5.Check for correct voltage at unit (unit operating).
6.Check amp draw on outdoor fan motor.
Motor Nameplate:_________ Actual:__________.
7.Inspect drain holes in coil compartment base and clean if necessary.
NOTE - If insufficient heating or cooling occurs, the unit should be gauged and refrigerant charge should be checked.
Outdoor Coil
It may be necessary to flush the outdoor coil more frequently if it is exposed to substances which are corrosive or which block airflow across the coil (e.g., pet urine, cottonwood seeds, fertilizers, fluids that may contain high levels of corrosive chemicals such as salts)
SOutdoor Coil door coil may be flushed with a water hose.
SOutdoor Coil (Sea Coast) air in ocean
locations can carry salt, which is corrosive to most metal. Units that are located near the ocean require frequent inspections and maintenance. These inspections will determine the necessary need to wash the unit including the outdoor coil. Consult your installing contractor for proper intervals/procedures for your geographic area or service contract.
Indoor Unit
1.Clean or change filters.
2.Lennox blower motors are prelubricated and permanently sealed. No more lubrication is needed.
3.Adjust blower speed for cooling. Measure the pressure drop over the coil to determine the correct blower CFM. Refer to the unit information service manual for pressure drop tables and procedure.
4.Belt Drive Blowers − Check belt for wear and proper tension.
5.Check all wiring for loose connections.
6.Check for correct voltage at unit. (blower operating)
7.Check amp draw on blower motor.
Motor Nameplate:_________ Actual:__________.
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