Crown Boiler FWZ Series, Installation Instructions Manual

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19
VIII System Piping
WARNING
• Install boiler so that the electrical 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 135°f can cause severe
boiler or chimney damage.
• Do not operate this boiler at a flow rate less than the minimum shown in Table 8.0, Column
(a).
• 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.
• Pipe relief valve discharge to a safe location. The relief valve may discharge scalding hot
water.
• 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. Blocking the relief valve may result in boiler explosion.
A. Standard Piping
Figure 8.2 shows typical boiler system connections on a single zone system. Additional information on hydronic system design
may be found in the I=B=R Guide RHH published by the Air-Conditioning, Heating and Refrigeration Institute (AHRI). The
components in this system and their purposes are as follows:
1) Relief valve (Required) - Mount the relief valve on the rear of the boiler as shown in Figure 8.1 using the fittings provided.
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 “Maximum Allowable Working Pressure” shown on the rating plate. If the valve is replaced, the replacement must have a
relief capacity in excess of the 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.
2) Return Injector Pipe - The return injector distributes water evenly throughout the heat exchanger and also helps to minimize
the possibility of thermal shock. Install it in the upper-rear tapping as shown in Figure 8.1. The 2 x 1-1/2” reducing elbow can
be oriented in any direction.
3) Circulator (Required) - Figure 8.2 shows the ideal location of the circulator which is in the supply piping immediately
downstream of the expansion tank. A less ideal, but acceptable, location for most residential circulators is in the return. The
circulator/s and connected piping should be sized so that the temperature rise across the boiler is 20F. Burner operation while
the flow through the boiler is less than that shown in Table 8.0, column (a) could result in problems regulating the supply
temperature. If the system is zoned, the flow rate through the boiler should be greater than that shown in Table 8.0 when only
the zone having the lowest flow rate is on. If this requirement cannot otherwise be met, use a bypass, or primary-secondary
piping. Boiler head loss data at the minimum flow and the flow corresponding to a 20F rise are shown in Table 8.0.
4) 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.