Crown Boiler AWR070 Installation Instructions Manual page 18

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 flow 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 11b.
Certain types of heating systems have additional requirements. Some of the more common variations follow:
1) "Left Piped" Boilers – If necessary, the supply and return may be connected to the left side of the boiler by moving the
1-1/4" plug and the relief valve fittings from the tappings in the left side of the boiler to the corresponding tappings on the
right. Both the supply and return connections must be made on the same side of the boiler.
2) Indirect Water Heaters - Figure 8.4 shows typical indirect water heater piping. Boiler piping is the same as for any two-
zone system. Figure 8.4 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.
3) Large Water Volume Systems - The piping shown in Figure 8.5 will minimize the amount of time that the boiler operates
with return temperatures below 120°F on these systems. A bypass is installed as shown to divert some supply water
directly into the return water. The bypass pipe should be the same size as the supply. The two throttling valves shown are
adjusted so that the return temperature rises above 120°F during the first few minutes of operation. A three-way valve can
be substituted for the two throttling valves shown. If the circulator is mounted on the supply, the bypass must be on the
discharge side of the circulator.
FIGURE 8.4: INDIRECT WATER HEATER BOILER SIDE PIPING
Piping for Special Situations
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