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SECTION 10: WIRING
47 of 71
For 4-20mA control of the heater(s) firing rate, the
following control conditions apply:
ON/OFF relay at the external controller or BMS must
be wired to R and W terminals on the heater control
board to turn the heater ON and OFF.
(Open Circuit = OFF, Closed Circuit = ON).
Minimum rated input at 1% of signal (0-4 mA).
Full rated input at 90% of signal (18 mA).
Input varies linearly between 4 mA and 18 mA.
BMS controllers often offer PID loop control that can
optimize output signal and rate of change of the
output signal. Common analog application is defined
as follows:
1. BMS sensors that monitor zone air
temperatures are located in the heating space.
2. Based on sensed temperatures, the BMS will
output an analog signal for the desired heater(s)
firing rate.
3. As heater(s) receive the analog signal from the
BMS, the heater(s) modulate to the correspond-
ing firing rate.
4. As sensed air temperature rises closer to the
desired temperature setpoint, the BMS will
reduce the output signal, in turn reducing heater
firing rate.
5. Upon satisfying temperature setpoint, the BMS
will either:
a. Tu
rn off the heater.
b. Reduce the signal so that the minimum
heater firing rate is maintained until the
sensed temperature rises above the
setpoint to a cut-off limit temperature when
the BMS turns off the heater.
FIGURE 27: Analog Control Signal Wiring Diagram
*OPTIONAL
SWITCH
SATELLITE HEATER CONTROL
FOR SATELITTE
CONTROLLERS, J9 JUMPER CAN BE
LEFT IN ORIGINAL POSITION
REGARDLESS OF CONTROL METHOD.
J10 JUMPER POSITION
SHOWS "SATELLITE" DESIGNATION.
MODULATION CONTROL WIRING
TO ADDITIONAL SATELLITE
HEATER CONTROL TERMINALS
T28 and T29.
ON/OFF SWITCH
REQUIRED
MODULATION CONTROL WIRING
TO SATELLITE HEATERS
CENTRAL HEATER CONTROL
REMOTE ANALOG
CONTROL
SIGNAL FROM SEPARATE
CONTROLLER
0-10Vdc OR 4-20mA
ANALOG INPUT CONTROL IS
USED TO SELECT ANALOG
SIGNAL TYPE 0-10Vdc OR 4-20mA
(4-20mA POSITION SHOWN).
J10 JUMPER POSITION
SHOWS "CENTRAL"
DESIGNATION AND
"ANALOG" CONTROL METHOD.
J10
J9
W
R
-+
-
+
-+
OUT
RATE
FIRING
IN
RATE
FIRING
EXT. POT
GND
WIPER
HIGH
GND
BAR
SLIDE
GND
THERMISTOR
INPUT
ANALOG
THERMOSTAT
T31
T29
T19
T18
T16
T14
T27
T25
T30
T28
T17
T15
T13
T26
T24
-
+
J10
J9
W
R
-+
-
+
-+
OUT
RATE
FIRING
IN
RATE
FIRING
EXT. POT
GND
WIPER
HIGH
GND
BAR
SLIDE
GND
THERMISTOR
INPUT
ANALOG
THERMOSTAT
T31
T29
T19
T18
T16
T14
T27
T25
T30
T28
T17
T15
T13
T26
T24
A B
A B
* Separate on/off switch is optional for "satellite" heaters (install at user level). On/Off switch is used to
disable heater operation or reset a heater that is in "lockout" mode. If on/off switch is not desired, leave
jumper wire between R and W terminals in place.