Smith Cast Iron Boilers GVIOM-5R Installation & Operating Instructions Manual page 10

Page 10
INSTALLATION & OPERATING INSTRUCTIONS
System Bypass
For systems using a circulator on the return as either a single
zone, or multiple zones with zone valves, install a system bypass
line between the supply and return on the suction side of the
circulator, see FIG. NO. 6. Install a metering valve in this bypass
line to regulate the amount of flow that will be diverted to the
return. A plug valve offers the best control for this application.
Although other valves may be less expensive, a plug valve will
be easier to set accurately.
In the absence of a flow indicator, set the metering valve using
temperature as a guide. The accompanying diagram suggests
one scenario. This addition requires only two tees, a plug valve,
and a small amount of pipe and offers the simplest approach to
reliably control condensation. For this system and those that
follow, be aware that you are using a percentage of the pump
capacity to blend, but the friction loss for the entire pump flow
has been reduced. In most cases, the standard pump packaged
with the boiler has enough capacity to feed the baseboard
distribution system and the bypass line.
FIG. NO. 6
SUPPLY
50%
160° F
100%
160° F
GV100W BOILER
FIG. NO. 5 Heating System Piping
DISCHARGE PIPE
SIZE TO EQUAL
VALVE OUTLET.
DO NOT RESTRICT
FLOW.
DISCHARGE SO AS TO AVOID EXPOSURE OF PERSONS TO
HOT LIQUID OR VAPOR. L E A V E O P E N E N D V I S I B L E F O R
P E R I O D I C INSPECTION FOR SLOW LEAKAGE OR DRIPS.
RETURN
50%
120° F
50%
160° F
100%
140° F
SYSTEM
BYPASS
SUPPORT DISCHARGE PIPING
SO AS TO AVOID STRAIN ON
THE VALVE BODY.
FOR DISCHARGE
THROUGH ROOF
CONSULT THE
SMITH CO.
1" CLEARANCE MUST BE
MAINTAINED BETWEEN
HOT WATER PIPING
AND COMBUSTIBLE
CONSTRUCTION.
Pump Away Bypass
For systems that use a single circulator to pump away from the
boiler, the bypass should be installed on the discharge side of
the circulator, see FIG. NO. 7. Full temperature water supplies
the baseboard distribution system as before. Half of the
circulator's volume moves through the bypass, blending and
heating the cooler return water. Again, the cost of installing the
bypass is small and setting it by temperature can be
accomplished with a contact thermometer.
FIG. NO. 7
SUPPLY RETURN
50%
50%
120° F
160° F
50%
160° F
100%
100%
140° F
160° F
PUMP AWAY
BYPASS