Smith Cast Iron Boilers GB250 SERIES - Manual (Page 11)

11
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.
RISER TO OTHER
APPLIANCES BEAM
PIPE CLAMP
GAS
METER
GAS
VALVE
UNION
SEDIMENT
TRAP
MANUAL MAIN
SHUT OFF
VALVE
FIGURE 2.11
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 2.18.
GB250-8 and GB250-9 natural gas standing pilot units
have a secondary pressuretrol (located to the right of
the primary pressuretrol when facing the front of the
boiler). Connect wiring assemblies (provided on boiler)
from the low water cut-off or transformer to the primary
pressure control and from the gas valve to the
secondary pressure control as shown in Fig. 2.12. 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.
FOR FIELD
CONNECTION
TO PRIMARY
PRESSURE
CONTROL
(ON THE LEFT) FOR FIELD
CONNECTION
TO SECONDARY
PRESSURE
CONTROL
(ON THE RIGHT)
WIRE
ASS'Y. WIRE
ASS'Y.
GAS
VALVE GAS
VALVE
TRANSFORMER TRANSFORMER
400 SERIES
OR M & M
PS804 LWCO
FOR FIELD
CONNECTION
TO PRIMARY
PRESSURE
CONTROL
(ON THE LEFT) FOR FIELD
CONNECTION
TO SECONDARY
PRESSURE
CONTROL
(ON THE RIGHT)
WIRE
ASS'Y.
WIRE
ASS'Y.
} } } }
FOR BOILERS EQUIPPED WITH
MCDONNELL-MILLER LWCO FOR BOILERS EQUIPPED WITH
400 SERIES OR M&M PS804
FOR BOILERS EQUIPPED WITH
MCDONNELL-MILLER LWCO
FOR BOILERS EQUIPPED
400 SERIES OR M & M PS804 LWCO
FIGURE 2.12
DANGER: Before placing gas piping into service,
carefully test it to assure every joint is gas tight.
Bubble test all joints with a soap solution. NEVER
TEST WITH AN OPEN FLAME AS FIRE OR
EXPLOSION WILL RESULT.
WARNING: Turn off electrical power supply before
servicing. Contact with live electric components can
cause electric shock or death.