Bryant 394 Gas - Manual (Page 6)

LINE-TO-LINE WIRING DIAGRAMS THERMOSTAT CONNECTIONS-HEATING ONLY
Figure 6 - Units without Heat-Cool Relay (HL Drive)
Figure 7 - Units with Heat-Cool Relay (M & E Drives)
Figure 8 - Units without Cooling Relay (B Drive)
Figure 9 - Units with Cooling Relay (C & X Drives)
1 A—Transformer
2A—Cooling Relay-SPST
2C—Heat-Cool Relay-SPDT
2G —Heating Relay-SPST
(Heat Motor Operated)
3A —Blower Motor
3D —Blower Motor
5A—Automatic Gas Valve
6A—Pilot Switch
(None on Propane)
7H —Limit Control-SPST
(On Counterflow Only)
7K —Limit Control-SPDT
Factory Line Voltage
Factory Low Voltage
Field Line Voltage
THERMOSTAT 34427D35 (NO -
TERM\WAL CODE). ALSO MODELS
883-P/N 344270030 OR 884-
P/N 34427003» THERMOSTAT 4
SUS BASE.
note : remove \ nter -
NAL JUMPER SETWIEM
1 W ^ J TERMtHALS.
I-
—1
1
OM-OFF FAN, MODEL 885
P/K| 34427033 TtiEFMOSTAT
t SUB-BASE OR THERMOSTOT
MODEL SBS P/ n 344i76
BASE P/M 34427034.
A68372
SEQUENCE OF OPERATING-HEATING
When the thermostat calls for heat, the control circuit
is closed between terminals (4 and W). Power from trans­
former (lA) energizes automatic gas valve coU (5A) and
heating relay coil (2G) simultaneously. After a short time
delay, automatic gas valve (5A) opens, permitting gas to
flow to the burners where it is ignited by the gas pilot. After
another delay, the heating relay switches its contacts (2G),
starting blower motor (3A or 3D) on its heating speed.
When the thermostat is satisfied, the circuit between
terminals (4 and W) is broken, de-energizing automatic
gas valve coil (5A) and heating relay coil (2G). After a
few seconds, automatic gas valve (5A) closes, stopping
the flow of gas to the main burners. After a longer delay,
heating relay (2G) opens its contacts to stop blower motor
(3A or 3D).
If the furnace overheats for any reason, limit control (7K)
will switch, breaking the circuit to automatic gas valve coil
(5A) and making a circuit to heating relay coil (2G). After
a short delay, the gas valve closes, shutting off the flow of
gas through the main burners. After an additional period of
time, heating relay (2G) closes its contacts, energizing
blower motor (3A or 3D) (if it is not already operating)
on heating speed. It continues to cycle until the fault is
corrected.
On counterflow furnaces, additional limit control (7H)
protects against overheating also. Should this control sense
a high temperature, it opens its contacts, de-energizing
automatic gas valve coil (5A) which, in turn, shuts off the
flow of gas to the main burners. After limit control (7H)
has cooled, its contacts close, automatically energizing
automatic gas valve coil (5A). After a short delay, the valve
opens, permitting gas to flow to the burners where it is
ignited by the pilot. Furnace blower motor (3A or 3D) may
or may not be operating, since it is independent of additional
limit control (7H).
SEQUENCE OF OPERATION-COOLING
When the thermostat calls for cooling, power from trans­
former (lA) energizes cooling relay coil (2C), closing its
contacts, and energizing blower motor (3A or 3D) on its
cooling speed. It continues to operate until the thermostat
is satisfied.
When the thermostat is satisfied, the circuit to terminal (G)
is broken, de-energizing cooling relay coil (2C) which, in
turn, opens its contacts, stopping blower motor (3 A or 3D).
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