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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 fl ow 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 satisfi ed, 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 and 3-2 using a GB142 wall hung
boiler.
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 3-3 illustrates typical circulator zone piping
with a fl oor standing G115WS, G125BE, GB125BE, or
G215 boiler.
.
Pressure Drop Values
Water
Model
Inlet
(IN)
SST150-40
1
SST250-65
1.5
SST300-80
1.5
SST450-119
1.5
8 |
Water
Coil
Outlet
Connection
(IN)
(IN)
1
1
1.5
1
1.5
1
1.5
1
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 fl ow) through the
coil of each tank. The boiler manifold piping must be sized
so that each coil has the fl ow rate called for in Table 3B.
Because the pressure drop through tank coils varies from
size to size, it is hard to predict the fl ow 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. A sample system is shown in FIG.
3-4.
Pressure Drop Chart
12
10
8
6
4
2
0
0
5
Coil
Surface
Length
area
(FT)
(SQ-FT)
GPM
30.8
10.0
0.41
41.5
13.5
0.61
41.5
13.5
0.61
67.3
22.0
0.73
Indirect Fired Water Heaters Installation and Operating Manual
Table 3A
8
12
16
Flow Rate
Table 3B
Pressure Drop (FT/HD)
5
8
12
16
GPM
GPM
GPM
1.04
2.34
4.16
1.57
3.53
6.27
1.57
3.53
6.27
1.87
4.22
7.50
SST450-119
SST250-65/
SST300-80
SST150-40
20
20
GPM
6.49
9.80
9.80
11.71
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