Carrier 16DF013-050 - Manual (Page 28)

Typical Control Sequence — Normal Cooling
Stop (Fig. 25)
1. The timed shutdown sequence begins when the Stop but-
ton is depressed or the capacity controller senses there is
insufficient load for continued operation. The status in-
dicator will display ‘‘dPP’’.
2. The burner control is given a signal to move to the low-
fire position, and, after 30 seconds, combustion is stopped
and the burner goes through its post-purge shutdown
sequence.
3. The refrigerant pump is stopped, and the dilution valve is
opened to drain refrigerant from the evaporator into the
absorber solution. The valve remains open until the shut-
down is complete, and the refrigerant flow continues un-
til the evaporator level reaches the level of the drain pipe.
4. Five minutes after the stop sequence is initiated, the so-
lution temperature is checked to be sure it is cool enough
to stop the cooling water flow. When it is, the cooling
tower fan and cooling water pump are stopped if
they are connected to the control circuit for automatic
operation.
5. Fifteen minutes after the stop sequence is initiated, the
solution pump is stopped, and the machine shutdown is
completed. The pump remains in operation during the di-
lution period to mix refrigerant through the solution.
6. If the chilled water pump is connected to the control cir-
cuit for automatic operation, and the shutdown was ini-
tiated by the capacity controller, the chilled water pump
will continue running to be ready for a restart, and the
status indicator will display ‘‘APO’’. With a manual stop,
the chilled water pump will be stopped and the status in-
dicator will display ‘‘000’’.
IMPORTANT: With manual pump control, the chilled
water pump must not be stopped until the shut-
down cycle has been completed.
Typical Control Sequence — Normal Heating
Stop (Fig. 25)
1. The timed shutdown sequence begins when the Stop but-
ton is depressed or the capacity controller senses there is
insufficient load for continued operation. The status in-
dicator will display ‘‘dPO’’.
2. The burner control is given a signal to move to the low-
fire position, and, after 30 seconds, combustion is stopped
and the burner goes through its post-purge shutdown
sequence.
3. Fifteen minutes after the stop sequence is initiated, the
solution pump is stopped, and the machine shutdown is
completed. The pump remains in operation during the shut-
down period to cool the solution and machine.
4. If the hot water pump is connected to the control circuit
for automatic operation, and the shutdown was initiated
by the capacity controller, the hot water pump will con-
tinue running to be ready for a restart, and the status in-
dicator will display ‘‘APO’’. With a manual stop, the hot
water pump will be stopped and the status indicator will
display ‘‘000’’.
IMPORTANT: With manual pump control, the hot
water pump must not be stopped until the shut-
down cycle has been completed.
Fig. 25 — Normal ‘‘Stop’’ Flow Chart
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