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3
Boiler Side Piping (SDT models)
Figures 3-1 thru 3-4 show typical boiler side piping for
several common situations. Regardless of which system is
used it is imperative that the flow rates called for in Table
3C are developed through the coil. This requires properly
sized piping and a properly sized pump.
The systems shown in FIG's 3-1 thru 3-4 are described
below:
Zone with Circulator to Aquastat
This system is like the circulator zone system on a straight
heat job except that one of the zones goes to the tank
instead of radiation. As on any circulator zone system
check valves should be installed in each zone to prevent
unwanted circulation through zones which are not calling
for heat. Figure 3-1 on page 8 illustrates typical circulator
zone piping.
Zone with Valve to Aquastat
As with the circulator zone system, this system is just like a
standard heating zone system except that one of the zones is
connected to the tank coil as shown in FIG. 3-2 on page 9.
The system circulator must be large enough to move boiler
water through the coil regardless of the flow rate required
through the heating zones.
DHW Prioritization
This piping system is designed to provide direct hot water
priority over the other zones in the heating system. When
there is a Domestic Hot Water (DHW) call for heat, the
Knight control will shut off the boiler circulator and
activate the domestic hot water circulator. Once the DHW
demand is satisfied, the boiler circulator will be readjusted
as demand requires. The circulator must be large enough
to move the boiler water through the coil in the tank,
and it must meet the minimum boiler flow requirments.
The recommended piping for a DHW priority system is
depicted in FIG. 3-3 on page 10.
6
SDT/SET Installation & Operation Manual
Multiple Tank Connections (Boiler Side)
Multiple tank installations must be done in the "reverse-return"
manner. The reason for this is to create the same pressure drop
(and therefore, the same flow) through the coil of each tank.
The boiler manifold piping must be sized so that each coil has
the flow rate called for in Table 3B.
Because the pressure drop through tank coils varies from size
to size, it is hard to predict the flow rate that will be developed
through each coil when two tanks of different sizes are placed in
the same manifold. For this reason it is best not to mix tanks of
different sizes in the same zone if their recovery is critical.
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