Installation and Operation Manual
TFTN 085-199
64
Table 12-2 Low Voltage Wiring
(Listed in order from left to right)
Connection
Description
T-STAT #1
R
THERMOSTAT INPUT (ZONE 1)
–
closure of R to W circuit initiates a zone 1 CH demand, activating
the
ZONE 1
output. R = 24VAC Output; W = 24VAC Input; C = Common. Circuit is protected with a
2 Amp blade style fuse, located on the low voltage connection PCB.
NOTE
: For two-wire devices connect only to R and W (do NOT connect to C).
W
C
T-STAT #2
R
THERMOSTAT INPUT (ZONE 2)
–
closure of R to W circuit initiates a zone 2 CH demand, activating
the
ZONE 2
output. R = 24VAC Output; W = 24VAC Input; C = Common. Circuit is protected with a
2 Amp blade style fuse, located on the low voltage connection PCB.
NOTE
: For two-wire devices connect only to R and W (do NOT connect to C).
W
C
T-STAT #3
R
THERMOSTAT INPUT (ZONE 3)
–
closure of R to W circuit initiates a zone 3 CH demand, activating
the
ZONE 3
output. R = 24VAC Output; W = 24VAC Input; C = Common. Circuit is protected with a
2 Amp blade style fuse, located on the low voltage connection PCB.
NOTE
: For two-wire devices connect only to R and W (do NOT connect to C).
W
C
ALRM
ALARM CONTACTS (NO)
–
Contacts close during a lockout or other alarm condition. May be
connected to a BMS. Maximum capacity of contacts = 2 Amps at 24VAC.
AUX LIMIT
AUXILIARY LIMIT (SAFETY LIMIT INPUT)
–
circuit can be used to connect an external limit device if
required by the AHJ. Boiler will produce an a volatile (Auto Reset) safety lockout when circuit is
open. Circuit comes factory wired with a jumper
–
remove jumper if installing an external limit.
NOTE: Lockout can be set as Manual Reset
“
Safety lock non-volatile
”
via parameter 24.6.5.
0-10V IN
+
EXTERNAL MODULATION CONTROL (0-10V INPUT)
–
allows an external control to directly
modulate the burner firing rate or adjust the active set point. To activate this input, set
option Control Mode (42.0.0) to the desired control mode, i.e., Voltage Power for firing
rate control or Voltage Temp for setpoint control.
-
0-10V OUT
+
BURNER POWER OUTPUT SIGNAL (0-10V OUTPUT)
–
outputs a 0-10V output signal proportional to
the operating power of the burner.
-
VAR. PUMP
+
VARIABLE SPEED PUMP CONTROL
–
the boiler can control a variable speed BOILER PUMP via 0-10V
or PWM output signal. For 0-10V control connect to
the “+” and “return” (in arrow) terminals. For
PWM control connect to the “
-
”, “return” and “out” (out arrow) t
erminals. Select the type of
pump speed control from Pump Configuration option Boiler Pump Speed Control Signal.
-
DHW
SWITCH/NTC
DHW TANK SENSOR OR AQUASTAT
–
input for a tank sensor or tank thermostat (Aquastat)
installed in an Indirect Water Heater (IWH). Tank sensor must be 10k beta = 3977 NTC. A tank
sensor is available from NTI (P/N 84632).
OD NTC
OUTDOOR SENSOR
–
input for factory supplied outdoor sensor. Reading provides pertinent
information to the boiler for automatic temperature adjustment. Alternatively, the outdoor
temperature can be sourced from the Internet, if the boiler is connecting to WiFi.
AUX1 NTC
AUX1 SENSOR INPUT
–
function is determined by the setting of
Auxiliary Sensor 1 (24.6.1):
•
System Sensor
–
input for optional system supply temperature sensor, so that the boiler can
directly control the system supply temperature.
•
Buffer Tank
–
input for optional buffer tank temperature sensor, so that the boiler can directly
control the temperature of an external buffer tank.
Sensor must be 10k beta = 3977 NTC; an optional strap-on System Sensor is available from NTI
(P/N 84010).
(Continued…)
0
-10
V
PWM
