Installation & Operation Manual
6
Boiler Side Piping
Figures 3-1 thru 3-3 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 3A
on page 6 are developed through the coil. This requires
properly sized piping and a properly sized pump.
The system shown in FIG’s 3-1 thru 3-3 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 7 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. The
circulator must be large enough to move boiler water
through the coil regardless of the flow rate required through
the heating zones.
3
Piping
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 coils.
The recommended piping for a DHW priority system is depicted
in FIG. 3-3 on page 8.
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 3A below. For example, if two
tanks are to be manifolded together, the circulator and zone
piping common to both tanks must be capable of moving
16 GPM (2 x 8 GPM), see FIG. 3-4 on page 9.
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
two different sizes in the same zone if their recovery is critical.
Table 3A
Pressure Drop Values
Model
Coil
Length (FT)
Tube
Diameter (IN)
Pressure Drop
(FT/HD)
8 GPM
12 GPM
16 GPM
20 GPM
SSS031
22.0
1 1/4
1.4
3.0
5.1
7.8
SSS041
27.6
1 1/4
1.7
4.0
6.4
9.8
SSS051
32.8
1 1/4
2.0
4.4
7.6
11.7
SSS081
49.2
1 1/4
N/A
6.3
10.9
16.7
SSS119
65.6
1 1/4
N/A
N/A
15.3
23.5
