Gas/Propane Basics
The Gas Side
Wiring direct to the thermostat...could also be used
for a steam system by adding a Low Water Cut-Off and
Pressuretrol in place of the limit switch...
Figure 5
SV9510/SV9520 Typical Boiler Wiring Diagram
wiring from the DATA to “R” wire. Pay particular
attention to the triangle notes 1–6 in Figure 6.
In the next article we will discuss troubleshooting
the SmartValve Third Generation. ICM
Figure 6
SV9510/SV9520 Typical Boiler Wiring Connection
Direct to the System Thermostat
compatibility with power-stealing thermostats.
Many of the control boards cannot be used with
power-stealing thermostats unless there is an isolating
relay used or a 100 ohm 10 watt resistor placed
across W and C.
Figure 5 shows a typical wiring diagram with a
Forced Hot Water System using a R8285D Honeywell
Control Center. With this setup, the 120 VAC
is fed direct from the junction box to C3-2 (Hot)/C3-4
(Neutral); in this case, the 24 VAC is interrupted.
L1 Hot is also fed to Pin 3 on the R8285; also, 24
VAC is fed to Pin 4. On a call for heat from the thermostat,
24 VAC is fed from “R” through the thermostat
to “G,” then to the relay coil and back to “C.”
This brings in the two sets of relay contacts—1–3
sends 120 VAC to the circulator; 4–6 takes 24
VAC from “R” to “Y” through the aquastat control
(high limit) to the R and DATA wire C1-7 and C1-4
(DATA). The sequence after that is the same as the
sequence for Figure 3.
Figure 6 is an example of wiring direct to the
thermostat. This setup could also be used for a
steam system by adding a Low Water Cut-Off and
Pressuretrol in place of the limit switch.
The 24 VAC is again interrupted and the 120 VAC
is fed direct to C3-2 and C3-4. In many instances,
a jumper from C1-4 to C1-7 may accomplish the
22 ICM/November/December 2022