Bryant 452W - Manual (Page 9)

IB
2B
2D
2J
Tapped Primary Transformer
Pump Heater Relay (SPST-NC)
Power Relay (DPST)
Circuit Breaker
(Lockout Relay)
Motor (Hydraulic Pump)
3A2 - Motor (Water Pump)
3C1 - Motor (Fan) (PSC)
3A1
3C2 - Motor (Fan) (PSC)
5B - Gas Valve (Magnetic)
6B - Pilot (Reignition)
7A - High-Pressure Limit Switch
(Auto. Reset) (SPST)
7H1 - Limit Switch (High-Temp
Cont) (SPST)
7H2 - Limit Switch (Sec, High-Temp.
Manual Reset) (SPST)
7L - Ambistat (Part Load Control)
(SPST)
7P - Pressure Switch (Pilot Gas) (SPST)
11A1 - Resistor
11A2 - Pump Heater
If any of the original wire, as supplied, must be
replaced, use the same or equivalent wire.
Figure 9 - Model 90-452W Wiring Diagram
Current also flows from chiller terminal Y, through
the high-temperature limit switch (7H1), the closed
contacts of the circuit breaker (2J), part load control
(7L), high-pressme switch (7A), secondary high-
temperature limit switch (7H2), the gas valve coil
(5B), and to chiller terminal F. The energized gas
valve coil opens the gas valve and supplies gas to the
generator burners.
Part Load Control
The part load control (7L) circuit is an automatic
recycling type of temperature sensitive switch. Con­
nected to the switch is a long capillary tube that is in­
serted in the chilled-water supply line. The part load
control switch contacts open when the chilled-water
supply temperature drops below 40±1°F. The
opening of the part load control switch contacts
deenergizes the gas valve and shuts off the gas supply
to the burners. The power relay (2D) remains
energized and the fan motors (3Cl & 3C2) hydraulic
prnnp motor (3A1), and the water pump motor (3A2)
will continue to run.
The part load control switch contacts will close again
when the chilled-water temperature rises to 42 ± 1 °F.
The magnetic gas valve will be reenergized and turn
the gas on again.
High-Temperature Cutoff
The high-temperature cutoff circuit includes a high-
temperature limit switch (7H1), located in the front of
the generator, plus a circuit breaker (2J) that is
located in the control box.
If the generator becomes overheated, the high-
temperature limit switch (7H1) will open, providing a
current path through the heater element of the circuit
breaker (2J). This current flow through the heater
causes the normally closed contacts of the circuit
breaker to open, removing the 24-volts potential from
the magnetic gas valve. The deenergized gas valve will
turn off the gas supply to the burners.
The control box cover must be removed to reset the
circuit breaker. Pressing the red “reset” button resets
the circuit breaker.
A secondary high-temperature limit switch (7H2) is
connected in the Y leg of the control circuit to insure
the closing of the gas valve in the event the generator
overheats and the high-temperatme limit switch
(7H1) does not open. The secondary high-temperature
limit switch is located on the generator header and
must be reset manually.
Hydraulic Pump Heater
Model 90-452W is equipped with a hydraulic pump
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