Step 6: Wiring Boiler - HydroTherm VGAB Series Installation, Operation And Maintenance Manual

Testing Gas Piping
For any pressure testing in excess of 1/2 psi, the boiler
and its individual shutoff valve must be isolated from the
piping system by disconnecting them and capping the
outlet(s). For any pressure testing equal to or less than
1/2 psi, the boiler must be isolated from the piping
system by closing its manual shutoff valve.
Minimum pressure required at the gas valve inlet is 5"
W.C. for natural gas and 11" W.C. for propane.
Maximum pressure allowable at the gas valve inlet is 12"
W.C. If the gas pressure is above these limits, a
pressure regulator must be installed. If the gas pressure
is below these limits, contact the local utility.
STEP 6: WIRING THE BOILER
All electrical and control wiring must be installed in ac-
cordance with the codes listed in Section 1 of this
manual. Follow the wiring diagram for your particular
installation as shown in Figures 2.13 through 2.20.
For United States only, VGA-350B and 400B natural gas
standing pilot units have a secondary pressuretrol (lo-
cated to the right of the primary pressuretrol when fac-
ing the front of the boiler). Connect wiring assemblies
(provided on boiler) from the low water cut-off or trans-
former to the primary pressure control and from the gas
valve to the secondary pressure control as shown in Fig.
2.9. Do not readjust the secondary pressuretrol; its
purpose is to interrupt thermocouple power to the gas
valve in case the primary pressuretrol fails to function.
M&M #67
LWCO
FOR FIELD
CONNECTION
TO PRIMARY
PRESSURE
CONTROL
(ON THE LEFT)
TRANSFORMER !_:_=i o o i:
GAS
VALVE
FOR FIELD
CONNECTION
TO SECONDARY
PRESSURE
CONTROL
(ON THE RIGHT)
WIRE
ASS'Y.
400 SERIES
ORM&M
PS804 LWCO
FOR BOILERS EQUIPPED WITH
MCDONNELL-MILLER LWCO
FOR BOILERS EQUIPPED WITH
MCDONNELL-MILLER LWCO
FIGURE 2.12
FOR FIELD FOR FIELD
CONNECTION CONNECTION
TO PRIMARY TO SECONDARY
PRESSURE PRESSURE
CONTROL CONTROL
(ON THE LEFT) (ON THE RIGHT)
WIRE
ASS'Y.
I
FOR BOILERS EQUIPPED WITH
400 SERIES OR M&M PS804
FOR BOILERS EQUIPPED
400 SERIES OR M & M PS804 LWCO
11