Typical Control Sequence, Normal Stop - Carrier 16JT Series Start Up & Operation Manual

Typical Control Sequence, Normal Stop

(Fig. 10 and 15)
1. If the Local Remote switch is in the remote position, the
shutdown sequence begins when the remote control con-
tacts open. The run relay (2X) deenergizes, and the Run
light (GL) is turned off, ready for auto restart. When the
machine Stop button is depressed, with the Local/Remote
switch in either position, the start relay (3X) and run re-
lay (2X) are deenergized, and the Run light (GL) is turned
off.
2. Start relays (1X1 and 1X2) deenergize to begin the shut-
down sequence, and alarm latching relay (4Y) de-energizes
to lock out the alarm shutdown relays (30X1 and 30X2).
Normally closed 1X1 contacts turn the Stop light (RL)
on.
3. Normally open 1X2 contacts deenergize the safety de-
vice relay (4X) and timer 62T3. This deenergizes LIX
and normally open 4X contacts drive the capacity control
valve to the closed position.
4. Other normally closed 1X1 contacts start the shutdown
dilution timer (62T1) and illuminate the Dilution light
*When chilled water, cooling water and/or cooling tower fan are not interlocked during auto. start-stop cycle, they must be manually stopped after
completion of the dilution cycle.
NOTE: Leave steam supply valve open during auto.-stop.
GL — Run Light
RL — Stop Light
Fig. 15 — Typical Control Sequence, Normal Stop
(WL1). When 4X relay deenergizes, its normally closed
contacts energize the Cycle-Guard™ valve to transfer re-
frigerant into the solution for dilution. The refrigerant
pump and Cycle-Guard valve continue to be energized
until the evaporator refrigerant drops to the dilution level
switch, which opens to deenergize the refrigerant pump
delay-start timer (62T2). The normally open timer con-
tacts then stop the Cycle-Guard valve and refrigerant pump.
(Normally open 1X1 contacts transferred control of the
62T2 timer from the evaporator low-level switch to the
dilution level switch when 1X1 was deenergized.)
5. When shutdown timer (62T1) times out after about 15
minutes, its contacts open to deenergize interlock relays
(1Y1 and 1Y2). Normally open 1Y1 and 1Y2 contacts
unlatch the relays to keep them open, and others open to
stop the solution pump(s), as well as the refrigerant pump
and Cycle-Guard if they have not already stopped. The
chilled water pump, cooling water pump, and cooling tower
fan stop if they are tied into the chiller control circuit for
auto. start/stop. When 62T1 times out, it also shuts off
the Dilution light.
WL1 — Dilution Light
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