High Concentration Limit; Low Concentration Limit; High-Stage Generator Level Limit; Before Initial Start-Up - Carrier 16JT Series Start Up & Operation Manual

Pneumatic Valve Actuator (Fig. 18) — The proportional mil-
liamp output signal from the controller is converted to a pro-
portional pneumatic signal in the current/pneumatic (I/P)
transducer mounted on the valve operator. When safety de-
vice relay (4X) is deenergized in a chiller shutdown condi-
tion, its contacts remain open so that the transducer sees a
''0'' amp signal. The pneumatic control signal is therefore
bled off, so the actuator sees a ''0'' psig signal and remains
closed.
When the load limiter relay (LIX) is deenergized during
chiller startup or Cycle-Guard™ operation, the current lim-
iter is in control and provides a preset control signal to hold
the actuator at a mid-open position for a preset time delay
period.
LEGEND
Wiring Terminals
Air Tubing Provided
Air Tubing to be Done at Site by Contractor
NOTE: See Fig. 10 for Control Circuit Connections.
Fig. 18 — Pneumatic Valve Actuator
High Concentration Limit —
eration, some abnormal conditions can cause the concentra-
tion of the lithium bromide solution to increase above nor-
mal. When this happens, the Cycle-Guard valve opens to transfer
a small amount of refrigerant into the solution circuit to limit
the concentration. This is necessary to keep the strong so-
lution concentration from crystallizing.
The Cycle-Guard valve is controlled by the evaporator re-
frigerant level, which has a direct relationship to solution
concentration. As the concentration increases (the solution
has less water), so does the refrigerant level. And, because
solution crystallization is also related to temperature, a so-
lution thermostat is used with two evaporator refrigerant level
switches to provide stepped control of the Cycle-Guard valve
with varying condensing water temperatures.
With normal condensing water temperatures, the Cycle-
Guard valve is controlled by the higher level switch (33RH)
through the refrigerant level relay (33RHX). But with lower
condensing water temperatures, and with corresponding lower
solution temperatures, thermoswitch (26SH) contacts close
to control the Cycle-Guard valve at the lower level switch
(33RM) and, therefore, at a slightly lower solution concen-
tration. A High Refrigerant Level light (WL2) goes on when
the 33RHX level relay energizes for Cycle-Guard operation.
Also, 33RHX relay contacts open to drive the capacity con-
trol valve to a mid-open position (LIX), to reduce heat sup-
ply to the generator until the high level has been corrected.
The concentrations at which the Cycle-Guard valve is ac-
tivated are determined by the amount of refrigerant that is
charged into the machine. This charge should be trimmed at
start-up, and should be checked periodically during opera-
tion for correct Cycle-Guard operation.
Low Concentration Limit —
tion with low condensing water temperatures, the normal di-
lution of the solution lowers the refrigerant level in the
evaporator. Before the level becomes low enough to cause
pump cavitation and damage to the hermetic pump motor,
the evaporator low-level switch (33RL) opens to deenergize
62T2, which, temporarily stops the refrigerant pump. This
will happen only when the condensing water temperature falls
below the design limit. When the refrigerant level subse-
quently rises enough to close the low-level switch, the re-
frigerant pump start-delay timer (62T2) is energized. After
about 5 minutes, the timer contacts close to start the refrig-
erant pump and resume normal operation.
High-Stage Generator Level Limit —
trode with a level relay (33W) monitors the solution level in
the high-stage generator. If the level is too high, 33W relay
contacts stop the solution pump(s), which allow solution to
drain normally from the generator. When the solution level
drops below the electrode level, the relay restarts the solu-
tion pump(s).

BEFORE INITIAL START-UP

Job Data and Tools Required

1. Job specifications and job sheets, including list of ap-
plicable design temperatures and pressures
2. Machine assembly and field layout drawings
3. Controls and wiring drawings
4. 16JT Installation Instructions
5. Mechanic's hand tools
6. Absolute pressure gage or water-filled wet-bulb vacuum
indicator graduated with 0.1-in. (2 mm) of mercury in-
crements. Do not use manometer or gage containing
mercury.
19
During high load op-
During low-load opera-
A sensing elec-