Dunham-Bush ACDX, Installation, Operation And Maintenance Instructions, Page: 21 / 44

Some packages may have logic that prevents 4.1.2. Manual Control
loading if the leaving water temperature is Screw compressors can be controlled
falling (negative derivative) at a certain rate. manually with the keypad. A compressor can
The desired leaving water temperature is control. When a compressor is controlled
typically stored in setpoint 1A. manually, it can be commanded to load, hold,
Calibrations of Amps Calculation at Full Load accept a load command.
The amps calculation is calibrated at the
factory and does not normally need to be
To place a compressor in manual control,
altered. If a compressor is replaced or which turns it on, the following procedure is
improper operation is observed, the amps used:
values can be calibrated as follows:
1. Check calibration of discharge pressure, 2. Address desired compressor (1, 4, 7, or 10
and amps. NOTE: Calibrate amps with control point).
potentiometer on filter board. 3. Press ENTER to modify status.
2. Manually load the compressor(s) to full
load. This can be done one compressor MAN.
at a time if necessary. 5. Press ENTER. The compressor will start
3. Locate the amps and full load amps
(FLA) analog locations from the analog 6. Press 0 to return to computer control, 1 to
input menu for the compressor being hold, 2 to load, 3 to unload. Note:
calibrated. Compressors will not load past amp limits.
4. When the compressor(s) are at full load
and conditions are close to design, data.
record the amps and FLA analog values.
5. If the values do not match within 2-3
amps, do the following calculation: operating manually, the compressor will
AMPS - FLA shutdown. To put all compressors back into
6. Locate the amps calculation A setpoint
for the compressor from the setpoint press RESET.
menu.
The setpoint is labeled FLA # CON,
where # is 1 through 4 for each compressor number. manual control. DO NOT start a compressor
7. Add the value obtained in step 5 to the
amps calculation A setpoint value from
step 6.
NOTE: All compressors will revert back to
8. Change the amps calculation setpoint to
the new value. a load, unload or hold command at least
9. Verify that amps and FLA now match
closely. repeated to meet the 15 minute requirement
10. Manually unload the compressor all for manual control.
the way.
11. Locate the percent full load capacity 4.2. Staging of Compressors
(%FLCP) for the compressor from the The staging of compressors is based on leaving
analog input menu and record the water temperature and the capacity calculations
value. mentioned in section 4.1. When the percent
12. If the value is 25% ±3%, no change capacity target gets up to full load and
is required. If the value is less than temperature is above deadband, a time delay of
22% or greater than 28%, locate the one or two minutes is initiated before starting
%FLA # CON setpoint B. If the the next compressor. When the capacity target
setpoint is equal to 25.0, change it to falls below a stored setpoint and temperature is
the value observed in step 11 and below the deadband, a compressor is turned
proceed to step 13. If the setpoint is off.
not equal to 25.0, change it to 25.0
and repeat steps 11 and 12.
The percent capacity values that the computer
13. Repeat this procedure for each is calculating can be displayed by addressing
compressor. the analog input menu.
be turned on, off, or placed in computer
or unload. If current limit is active, it will not
1. Log in for authorization.
4. Use up or down arrow keys to select ON
or continue to run in hold state.
7. Use menu key or arrows to access other
If a safety condition is exceeded while
computer control from a locked off state,
CAUTION: Anti-recycle timer is bypassed by
more than once every 15 minutes.
automatic control if the computer is not given
once every 15 minutes. A command can be
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