Typical Control Sequence; Abnormal Stop - Carrier 16JT Series Start Up & Operation Manual

Typical Control Sequence, Abnormal Stop
(Fig. 10 and 16)
1. Abnormal shutdown occurs automatically when any of
the chiller safety devices sense a condition which might
be potentially damaging to the chiller. The safeties are
grouped in 4 categories, each with its own fault relay:
a. High-temperature generator problems (fault relay 63GX),
with shutdown dilution
b. Hermetic pump motor high-temperature or overloads
(fault relay 26MX), without shutdown dilution
c. Water system flow interlocks or low-chilled water
temperature (fault relay CWX), without shutdown
dilution
d. High absorber pressure (ABSX), without shutdown di-
lution
2. When a safety is activated, its contacts open to de-
energize the fault relay for its group. The fault relay's nor-
mally closed contacts illuminate the indicator light for groups
a, b, or c and normally open contacts deenergize the safety
device relay (4X) and timer 62T3. This deenergizes load
limiter relay LIX.
3. Normally open 4X contacts drive the capacity control valve
to the closed position.
GL
OL1 — Chilled and Cooling Water Fault Indicator Light
OL2 — Refrigerant and Solution Pumps Fault Indicator Light
OL3 — High-Stage Generator Fault Indicator Light
RL
WL1 — Dilution Light
Fig. 16 — Typical Control Sequence, Abnormal Stop
4. Normally closed 4X contacts energize shutdown alarm
relays (30X1 and 30X2), and energize the alarm buzzer.
These relays remain energized through 4Y self-latching
contacts.
5. The 30X1 contacts open to deenergize start relays (1X1
and 1X2). To begin the shutdown sequence, normally closed
1X1 contacts turn the Stop light (RL) on.
6. The 2X run relay remains energized, as does the Run light
(GL). If the chilled water pump is tied into the chiller
control circuit for auto. start/stop, the 2X relay will keep
it running unless it has stopped on its own safety.
7a. If there are problems with high absorber pressure (relay
ABSX) or with the hermetic pumps (relay 26MX) or with
the cooling or chilled water (relay CWX), interlock re-
lays 1Y1 and 1Y2 immediately deenergize. Normally open
1Y2 contacts immediately stop the solution and refrig-
erant pumps without shutdown dilution. If the cooling
water pump and cooling tower fan are tied into the chiller
control circuit for auto. start/stop, then other normally
open 1Y2 contacts also stop them.
b. For problems with the high-temperature generator (re-
lay 63GX), interlock relays (1Y1 and 1Y2) remain en-
ergized to keep all pumps operating. Normally closed
1X1 contacts start the shutdown dilution timer (62T1).
— Run Light
— Stop Light
17