8J48A
Relay-Hot Water Control
For use with 24 VAC or Self-Generating Gas Valve
WHITE-RODGERS
(Suitable for External Zone Valve Load)
INSTALLATION INSTRUCTIONS
Operator: Save these instructions for future use!
FAILURE TO READ AND FOLLOW ALL INSTRUCTIONS CAREFULLY
BEFORE INSTALLING OR OPERATING THIS CONTROL COULD CAUSE
PERSONAL INJURY AND/OR PROPERTY DAMAGE.
DESCRIPTION
These relay-hot water controls combine a high limit control, a
transformer, a circulator relay, and wiring terminals into a single
unit. They are suitable for use on boilers equipped with a 24 volt
or millivolt gas valve.
These controls are designed primarily for use on boilers that do
not supply domestic hot water. (However, they are equipped
with an extra terminal to permit them to be used on boilers with
a tankless domestic coil by the addition of a separate SPDT low
limit-circulator control on systems using a 24 volt gas valve.)
The internal transformer supplies power for operating a gas
valveaswellastherelaycoil. Onsystemszoneswithmotorized
water valves, the internal transformer may also be used for
powering some (or all) of the water valves.
PRECAUTIONS
If in doubt about whether your wiring is millivolt, line, or low
voltage, have it inspected by a qualified heating and air condi-
tioning contractor, electrician, or someone familiar with basic
electricity and wiring.
CAUTION
!
To prevent electrical shock and/or equipment damage,
disconnect electric power to system, at main fuse or
circuit breaker box, until installation is complete.
Do not exceed the specification ratings.
All wiring must conform to local and national electrical codes
and ordinances.
WARNING
!
This control is a precision instrument, and should be handled
carefully.Roughhandlingordistortingcomponentscouldcause
the control to malfunction.
Do not use on circuits exceeding specified voltage.
Higher voltage will damage control and could cause
shock or fire hazard.
Do not short out terminals on gas valve or primary
control to test. Short or incorrect wiring will burn out
heat anticipator. Personal injury and/or property dam-
age may result from shorted or incorrect wiring.
SPECIFICATIONS
ELECTRICAL RATINGS
ROOM THERMOSTAT
Input Voltage: 120 VAC, 60 Hz
Circulator Motor: 8.0 Amps Full Load Current (120 VAC)
Set adjustable heater (anticipator) at 0.25, or use a fixed heater
with a 0.25 Amp rating.
48.0AmpsLockedRotorCurrent(120VAC) HOT WATER CONTROLS
Gas Valve: 24.0 VAC, 0.65 Amp OR
Millivolt Systems (0.25 to 1.0 VDC, 0.25 Amp)
Combined Load of Zone Valves:
Range: High Limit – 140° to 240°F. (Some models have a
Preset Dial Stop. Adjustments should be made by
authorized service personnel only.)
Internal transformer (terminals TV and Z) may be used for Differential: High Limit – 8°F Fixed
supplying power to four W-R Type 1311 or three Type 1361 Switch Action: High Limit – Open on rise
zone Valves. (For other zone valves, total zone valve load is not
to exceed 1.2 Amp.)
WHITE-RODGERS DIVISION
EMERSON ELECTRIC CO.
9797 REAVIS ROAD
PART NO. 37-4013C
Printed in U.S.A.
Replaces 37-4013B
9522
ST. LOUIS, MISSOURI 63123-5398
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WIRING AND OPERATION
All wiring should be installed according to local and national electrical codes and ordinances.
Figure4showswiringconnectionsforatypicalinstallationusing
the 8J48A with a 36C03 or a 36C53 24V manifold gas valve.
Figure 5 shows wiring connections for the 8J48A with a 36C03U
or 36C53U self-generating gas valve. Operation is as follows:
AUTO/MANUAL SWITCH
NOTE
For manual operation of self-generating millivolt systems
only.
As the room thermostat contacts close, the relay coil is ener-
gized and closes its two sets of relay contacts. The manifold gas
valveopensastheno.1relaycontactsclose,whilethecirculator
motor starts as the no. 2 relay contacts close.
The manual switch, located on the outside of the controls case,
allows operation of the burner during power failures. When the
switch is set to MANUAL, the burner will operate continuously
until the high limit temperature is reached. The circulator, which
requires line voltage to operate, will not function in MANUAL
mode. When power is restored, reset the switch to AUTO to
resume automatic operation.
When the room thermostat opens its contacts, the manifold gas
valve closes and the circulator motor stops.
If the boiler temperature exceeds the setting of the high limit
whilethethermostatiscallingforheat,thehighlimitwillclosethe
gas valve but permit the circulator to run as long as the
thermostat is calling for heat.
Factory-
installed installed
Jumper Jumper
Field-
Manual
Switch
High
Limit
Transformer
Z
W
TP
B
No. 2 Relay
Contacts
No. 1 Relay
Contacts
C1
Hot
120 VAC
Neutral
Low Voltage
Room Thermostat
L1
L2
36C
Gas Valve
T
TH TH-TR TR
C2
TV
B2
B3
B1
INTERNAL WIRING
Line Voltage
Circulator
Motor
Low Voltage
EXTERNAL WIRING
Line Voltage
Low Voltage
Figure 4. 24 Volt AC Gas Valve
Factory-
installed
Jumper
Manual
Switch
High
Limit
Transformer
Z
W
TP
B
No. 2 Relay
Contacts
No. 1 Relay
Contacts
C1
Hot
120 VAC
Neutral
Low Voltage
Room Thermostat
L1
L2
To 750 MV
Thermopile
36C
Gas Valve
T
TH TH-PG PG
C2
TV
B3 B2
B1
INTERNAL WIRING
Line Voltage
Circulator
Motor
Low Voltage
EXTERNAL WIRING
Line Voltage
Low Voltage
Figure 5. Millivolt Gas Valve
3
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WIRING AND OPERATION (cont’d)
Thermostat
Z
R
B
Low Limit
Circulator
Control
8J48A
BL
W
2
W-R
1361
Zone
TV
Z
T
W
1
3
Valves
NOTE: Remove external jumper
between W and Z terminals
C1
L1
C2
L2
Circulator
Motor
B1 B3
Figure 7. Alternate Connections for using Separate
Low Limit-Circulator Control on
Boiler with Tankless Domestic Coil
24V
Gas
Valve
Hot Neutral
LINE
Figure 6. Typical Connections for
Zoning with 2-Wire Zone Valves
Thermostat
Zone 1
Thermostat
Zone 2
Thermostat
Zone 3
Field-
Installed
Jumper
Field-
Installed
Jumper
829A
Relay
829A
Relay
5
6
3
4
1
2
5
6
3
4
1
2
8J48A
Factory-
Installed
Jumper
T
W
Z
TV
B
TP
C1 C2
Line Voltage
Low Voltage
Circulator
Zone 1
Circulator
Zone 2
Circulator
Zone 3
B1 B2 B3 L1 L2
Neutral
120 V
36C Series
Gas Valve
Hot
TR TH-TR TH
Figure 8. 8J48A - 24 Volt Systems Zoned with Circulators
Thermostat
Zone 1
Thermostat
Zone 2
Thermostat
Zone 3
Field-
Installed
Jumper
Field-
Installed
Jumper
829A
Relay
829A
Relay
5
6
3
4
1
2
5
6
3
4
1
2
8J48A
Factory-
Installed
Jumper
T
W
Z
TV
B
TP
C1 C2
Line Voltage
Low Voltage
Circulator
Zone 1
Circulator
Zone 2
Circulator
Zone 3
B1 B2 B3 L1 L2
Neutral
To 750 MV
Thermopile
120 V
Hot
36C Series
Gas Valve
PG TH-PG TH
Figure 9. 8J48A - Millivolt Systems Zoned with Circulators
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