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Indirect Fired Water Heaters Installation and Operating Manual
Installation & Operating Manual
3 Boiler Side Piping
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
3B are developed through the coil. This requires properly
sized piping and a properly sized pump. The system shown
in FIG’s 3-1 thru 3-4 are described below:
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
controller 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. 3-1
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 3-2 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. 3-3.
The system circulator must be large enough to move boiler
water through the coil regardless of the flow rate required
through the heating zones.
.
Pressure Drop Values Table 3B
Model
Water
Inlet
(IN)
Water
Outlet
(IN)
Coil
Connection
(IN)
Coil
Length
(FT)
Surface
area
(SQ-FT)
Pressure Drop (FT/HD)
5
GPM
8
GPM
12
GPM
16
GPM
20
GPM
SST150-40
1
1
1
30.8
10.0
0.41
1.04
2.34
4.16
6.49
SST250-65
1.5
1.5
1
41.5
13.5
0.61
1.57
3.53
6.27
9.80
SST300-80
1.5
1.5
1
41.5
13.5
0.61
1.57
3.53
6.27
9.80
SST450-119
1.5
1.5
1
67.3
22.0
0.73
1.87
4.22
7.50
11.71
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.
0
2
4
6
8
10
12
14
16
0
5
8
12
16
20
SST450-119
SST250-65/
SST300-80
SST150-40
Flow Rate
Head Loss (Ft. of Hd.)
Pressure Drop Chart
Table 3A
