Crankcase Heater; Compressor Operation; Figure 40 Adjusting Compressor Delays; Figure 41 Verifying Compressor Output Status - Bard MEGA-TEC W180B Service Instructions Manual

Crankcase Heater

All units covered in this manual are provided with
compressor crankcase heat.
This crankcase heater is a band-type heater located
around the bottom of the compressor. This heater is
controlled by the crankcase heater relay. The heater is
only energized when the compressor is not running.
Crankcase heat is essential to prevent liquid refrigerant
from migrating to the compressor, preventing oil pump
out on compressor start-up and possible bearing or
scroll vane failure due to compressing a liquid.
IMPORTANT: The following procedure must be followed
at initial start-up and at any time power has been
removed for 12 hours or longer.
To prevent compressor damage which may result from
the presence of liquid refrigerant in the compressor
crankcase:
1. Make certain the room thermostat is in the "off"
position (the compressor is not to operate).
2. Apply power by closing the system disconnect
switch. This energizes the compressor heater which
evaporates the liquid refrigerant in the crankcase.
3. Allow 4 hours or 60 minutes per pound of
refrigerant in the system as noted on the unit
rating plate, whichever is greater.
4. After properly elapsed time, the thermostat may be
set to operate the compressor.
5. Do not open system disconnect switch except as
required for safety while servicing.

Compressor Operation

The compressor will be enabled when the unit (in orphan
mode) or LC provide a cooling call. The compressor call
from the controller has several delays that may affect
the start or stop time of the compressor in regards to
the cooling demand. The compressor has a minimum
on time of 180 seconds to prevent short cycling the
compressor. The compressor also has a minimum off
time of 120 seconds to prevent start ups before the
pressure in the refrigeration system equalizes. When
the second stage is engaged, it also has a minimum run
time of 120 seconds to allow the system to stabilize
before returning to single stage or shutting down.
These delays can be changed by:
1. Press MENU key to go to the Main Menu screen.
2. Press UP or DOWN keys and ENTER key to enter
TECHNICIAN password 1313.
3. Press UP or DOWN keys to scroll to Adv System
Config; press ENTER key.
4. Press UP or DOWN keys to scroll to Comp. Safety
B2; press ENTER key.
Manual 2100-749
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5. Press ENTER key to scroll to Min On Time or Min
Off Time (see Figure 40).
6. Press UP or DOWN keys to change the value.
7. Press ENTER key to save value and move the
cursor to next parameter or top of screen.
8. Press ESCAPE key several times to return to Main
Menu screen.
FIGURE 40
Adjusting Compressor Delays
To view the status of the compressor outputs:
1. Press MENU key to go to the Main Menu screen.
2. Press UP or DOWN keys and ENTER key to enter
TECHNICIAN password 1313.
3. Press UP or DOWN keys to scroll to I/O Config;
press ENTER key.
4. Press UP or DOWN keys to scroll to Digital
Outputs; press ENTER key.
5. Press UP or DOWN keys to scroll to Digital Outputs
C2-1.
6. The status is displayed next to Compressor 1,
Comp 1 Full and Compressor 2 (see Figure 41).
FIGURE 41
Verifying Compressor Output Status
The compressor outputs can be put into override to aid
in troubleshooting. The override will only stay active for
5 minutes.
To override the compressor outputs:
1. Press MENU key to go to the Main Menu screen.