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VIII System Piping
A. Standard Heating System Piping
1) Figure 18 shows typical boiler system connections on a single zone system. Additional information on hydronic
system design may be found in Installation of Residential Hydronic Systems (Pub. #200) published by the Hydronics
Institute in Berkeley Heights, NJ. The components in this system and their purposes are as follows:
a. Relief valve (Required) - Install a 3/4” NPT x 3-1/2” lg. nipple in tapping “C” located on the left side of the
boiler. Mount the relief valve on the end of the nipple as shown in Figure 1. The relief valve shipped with the
boiler is set to open at 30 psi. This valve may be replaced with one having a pressure up to the “MAWP, WATER”
shown on the rating plate. If the valve is replaced, the replacement must have a relief capacity in excess of the DOE
heating capacity for the boiler.
Pipe the discharge of the relief valve to a location where water or steam will not create a hazard or cause property
damage if the valve opens. The end of the discharge pipe must terminate in an unthreaded pipe. If the relief valve
discharge is not piped to a drain it must terminate at least 6 inches above the floor. Do not run relief valve discharge
piping through an area that is prone to freezing. The termination of the relief valve discharge piping must be in an
area where it is not likely to become plugged by debris.
b. Drain Valve (Required) - Install a 3/4” NPT x 3-1/2” nipple in tapping “G” located in the rear of the left end section
of the boiler. Attach a 3/4” NPT pipe coupling to the end of the nipple and attach the drain valve to the end of the
coupling.
c. Circulator (Required) - The best circulator location is usually on the supply piping just downstream of the expansion
tank as shown in Figure 18.
d. Expansion Tank (Required) - If the expansion tank must be replaced, consult the expansion tank manufacturer’s
literature for proper sizing.
e. Fill Valve (Required) - Either a manual or automatic fill valve may be used. The ideal location for the fill is at the
expansion tank. On large systems with an automatic fill valve, it is recommended that a small water meter be
installed in the make-up water line to monitor the amount of water added to the system.
f. Automatic Air Vent (Required) - At least one automatic air vent is required and should be located at the expansion
tank. Manual vents will usually be required in other parts of the system to remove air during initial fill.
g. Low Water Cut-Off (Required in some situations) - A low water cutoff is required when the boiler is installed above
radiation. In addition, some codes such as ASME CSD-1 require low water cutoffs. Codes may also require that
CAUTION
• INSTALL BOILER SO THAT THE GAS IGNITION SYSTEM COMPONENTS ARE PROTECTED
FROM WATER (DRIPPING, SPRAYING, RAIN, ETC.) DURING APPLIANCE OPERATION AND
SERVICE (CIRCULATOR REPLACEMENT, ETC.).
• OPERATION OF THIS BOILER WITH CONTINUOUS RETURN TEMPERATURES BELOW 120°F
CAN CAUSE SEVERE HEAT EXCHANGER CORROSION DAMAGE.
• OPERATION OF THIS BOILER IN A SYSTEM HAVING SIGNIFICANT AMOUNTS OF DISSOLVED
OXYGEN CAN CAUSE SEVERE HEAT EXCHANGER CORROSION DAMAGE.
• DO NOT USE TOXIC ADDITIVES, SUCH AS AUTOMOTIVE ANTIFREEZE, IN A HYDRONIC
SYSTEM.
DANGER
• PIPE RELIEF VALVE DISCHARGE TO A SAFE LOCATION.
• DO NOT INSTALL A VALVE IN THE RELIEF VALVE DISCHARGE LINE.
• DO NOT MOVE RELIEF VALVE FROM FACTORY LOCATION.
• DO NOT PLUG RELIEF VALVE DISCHARGE.
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