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VIII System Piping
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 120F can cause severe heat exchanger corrosion
damage.
• Operation of this boiler in a system having signifi cant amounts of dissolved oxygen can cause severe heat exchanger
corrosion damage.
• Do not use toxic additives, such as automotive antifreeze, in a hydronic system.
A. Standard Piping
Figure 26 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
Berkely Heights, NJ. The components in this system and their purposes are as follows:
1) Relief valve (Required) – Install the relief valve in the 3/4” tapping on the left side of the boiler 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 setting of up to
the Maximum Allowable Working Pressure (MAWP) shown on the rating plate. If the valve is replaced, the replacement
must have a relief capacity in excess of the Minimum Relief Valve Capacity shown on the rating plate.
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 fl oor. 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.
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.
2) Circulator (Required) – Although the circulator is shipped on the boiler return, it can be installed on the boiler supply. If the
circulator is moved to the supply it should be positioned just downstream of the expansion tank as shown in Figure 26.
3) Expansion Tank (Required) – If this boiler is replacing an existing boiler with no other changes in the system, the old
expansion tank can generally be reused. If the expansion tank must be replaced, consult the expansion tank manufacturer’s
literature for proper sizing.
4) Fill Valve (Required) – Either a manual or automatic fi ll valve may be used. The ideal location for the fi ll is at the expansion
tank.
5) Automatic Air Vent (Required) – At least one automatic air vent is required. Manual vents will usually be required in other
parts of the system to remove air during initial fi ll.
6) Low Water Cut-Off (Required in some situations) – A low water cut-off is required when the boiler is installed above
radiation. In addition, some codes, such as ASME CSD-1, require low water cut-offs. Codes may also require that this low
water cut-off have a manual reset function. The low water cut-off may be a fl oat type or probe type but must be designed
for use in a hot-water system. The low water cut-off should be piped into the boiler supply just above the boiler with no
intervening valve between it and the boiler.
Use a low water cut-off that breaks the 120 VAC supply to the boiler. Do not attempt to connect a 24-volt low water
cut-off into the boiler factory wiring.
7) Manual Reset High Limit (Required by some codes) – This control is required by ASME CSD-1 and some other codes.
Install the high limit in the boiler supply piping just beyond the boiler with no intervening valves. Set manual reset high
limit as far above the operating limit setting as possible, but not over 240F. Wire the control to break the 120 VAC electrical
supply to the boiler.