Burnham K2WTC - Page 75

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IX. System Piping (continued)
Example – A 135MBH model is to be connected to a heating system as shown in Figure 9.5. A total of 20 ft of straight pipe
will be installed between the boiler and the system loop.
Count all ttings in the boiler loop (shaded in Figure 9.5):
4 90° Elbows
2 Turn in Tee
2 Isolation Valves
Note: Unions, Secondary Connection Tees, and factory supplied ttings are ignored.
Calculate total equivalent length from Table 9.3:
20 ft 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 60 ft, ow through boiler loop meets requirements in Table 9.1.
3) Hydraulic Separators – Hydraulic separators serve the same purpose as the closely spaced tees connecting the boiler and
system loops in Figure 9.2. 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 Figure 9.2. When a hydraulic separator is used in place of the tees, the 60 ft equivalent length limitation still
applies.Selectahydraulicseparatorhaving1”orlargerboilerconnectionsthatisdesignedfortheboilerowratesshownin
Table 9.1.
Table 9.3: 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. 7 ft equivalent length
may be assumed for strainers having a published Cv greater than 20.
Table 9.4a: Flow Available with Boiler Loop
Equivalent Length of 30 ft or Less
Table 9.4b: Flow Available with Boiler Loop
Equivalent Length of 60 ft or Less
Boiler Model
Approx. Flow
(GPM)
Approx. Rise (°F)
Boiler Model
Approx. Flow
(GPM)
Approx. Rise
(°F)
135 8.6 25 135 8.3 26
150 11.8 23 150 11.1 24
180 11.8 28 180 11.1 29