Velocity Shadow Series, Installation And Operating Instructions Manual

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Example – A 120MBH model is to be connected to a heating system as shown in Figure 9.2. A total of 20 ft of straight pipe
will be installed between the boiler and the system loop.
Count all fittings in the boiler loop (shaded in Figure 9.2):
4 90 Elbows
2 Turn in Tee (under boiler- primary-secondary tees not counted)
2 Isolation Valves
1 Y Strainer having a Cv of 30.
Note: Unions, Secondary Connection Tees, and factory supplied fittings are ignored.
Calculate total equivalent length from Table 9.4:
20ft Straight Pipe + 4 Elbows x 2.8 + 2 Turn in Tee x 5.5 + 2 Valves x 0.7 = 43.6 Equivalent Feet
Since the total equivalent length is less than 60ft, flow through boiler loop meets requirements in Table 9.1
3) Indirect Water Heater Loop Piping – If an indirect water heater is used, install it as shown in Figures 9.3a or 9.3b. Refer to
the indirect water heater installation manual for the proper sizing of the indirect water heater loop pump and piping.
4) Hydraulic Separators – Hydraulic separators serve the same purpose as the closely spaced tees connecting the boiler and
system loops in Figure 9.1. They also generally provide effective connection points for automatic air elimination devices
and an expansion tank. These separators are available from several sources and may be used in place of the closely spaced
tees shown in Figures 9.2, 9.3a or 9.3b. When a hydraulic separator is used in place of the tees, the 60ft equivalent length
limitation still applies. Select a hydraulic separator having 1” or larger boiler connections that is designed for the boiler flow
rates shown in Table 9.1.
Table 9.4: Equivalent Lengths for Selected Valves and Fittings
(May Be Used for Copper or Threaded Fittings)
Fitting Pipe Size Equivalent Length (ft)
90° Elbow 1” 2.8
45° Elbow 1” 1.4
90° Turn in Tee 1” 5.5
Run of Tee 1” 1.8
Gate Valve (Open) 1” 0.7
Full Port Ball Valve 1” 0.7
Y-Strainer* 1” 7.0
* Based on Cv of 20. Pressure drop through strainers varies widely. 7ft equivalent length may be
assumed for strainers having a published Cv greater than 20.
Table 9.5: Flow Available with Boiler Loop Equivalent Length of 60ft or Less*
Boiler Model
Approx. Flow
(GPM)
Approx. Rise (°F)
Circulator Model
Taco Grundfos
80MBH 6.4 23 009 26-64
100MBH 8.0 23 0013 26-99
120MBH 9.2 24 0013 26-99
150MBH 11.9 24 0013 26-99
180MBH 11.9 29 0013 26-99
* For multi-speed pumps, this table assumes pump is set to highest speed.