Operating instructions

V. Piping
IMPORTANT
All First Hour Ratings shown in this manual are based on the, minimum boiler water, flow rates shown in
Table 1. Read this section for information on sizing piping and circulators for the water heater zone. Zone
Design
In designing the water heater zone piping system, the following points should be considered: 1) Circulator or
Zone Valve Zoning? - Circulator zones are usually a better choice. Zone valves have a relatively high
pressure, drop with respect to flow rate required through the water heater tank (see Table 1).
If zone valves are selected, use a zone valve with a minimal delay in opening, such as a motorized type.
a) Priority Zoning - Priority zoning is used to divert all boiler output to the water heater when its zone calls for
heat regardless of any simultaneous calls for heat from space heating zones
b) Priority zoning can be done using a 3-way zone valve, or by using a relay to de-energize the heating
zones when the water heater calls for heat. (See the piping and wiring sections for more information on these
zone systems).
Boiler Side Piping
Figures 4-9 show typical boiler side piping for several common situations. Regardless of which system is
used, it is imperative that the minimum boiler water flow rates called for in Table 1 are developed through
the tank. This requires properly sized piping and a properly sized pump. The systems shown in figures 4-
9 are described below:
Standard Circulator Zone
This system is just like the circulator zone system on a straight heat job except that one of the zones goes
to the water heater tank instead of radiation. As on any circulator zone system, appropriate controls should
be installed in each zone to prevent unwanted circulation through zones, which are not calling for heat.
Figure 4 illustrates typical circulator zone piping.
Zone Valve System
As with the circulator zone system, this system is just like a standard heating only zone valve system
except that one of the zones is connected to the tank. The circulator must be large enough to move the
boiler water through the tank at the minimum boiler water flow rate called for in Table 1, regardless of the
flow rate required through the heating zones. Figure 5 illustrates a typical zone valve system.
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