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6) 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 this
low water cutoff have a manual reset function. The low water cutoff may be a float type or probe type, but must be
designed for use in a hot-water system. The low water cutoff should be piped into the boiler supply just above the boiler
with no intervening valves between it and the boiler.
Use a low water cutoff that breaks the 120 VAC supply to the boiler. Do not attempt to wire a 24-volt low water cutoff
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 the manual reset
high limit as far above the operating limit setting as possible, but not over 240°F. Wire the control to break the 120
VAC electrical supply to the boiler.
8) Flow Control Valve (Required under some conditions) - The flow control valve prevents flow through the system unless
the circulator is operating. A flow control valve may be necessary on converted gravity systems to prevent gravity
circulation. Flow control valves are also used to prevent “ghost flows” in circulator zone systems through zones that are
not calling for heat.
9) Isolation Valves (Optional) - Isolation valves are useful if the boiler must be drained, as they will eliminate having to
drain and refill the entire system.
10) Drain Valve - The drain valve is shipped in the boiler parts bag. Install it in the tee under the circulator as shown in
Figure 1.
Piping for Special Situations
Certain types of heating systems have additional requirements. Some of the more common variations follow:
1) Indirect Water Heaters - Figure 12 shows typical indirect water heater piping. Boiler piping is the same as for any two-
zone system. Figure 12 shows circulator zoning, which is usually preferred for indirect water heaters. Size the
circulator and indirect water heater piping to obtain the boiler water flow through the indirect water heater called for by
the indirect water heater manufacturer.
FIGURE 11: STANDARD BOILER PIPING
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