Burnham FREEDOM FCM120 Page 34 Installation, Operating And Service Instructions Download

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Method 1: Primary/Secondary Piping

This method can be used in heat-only applications as shown in Figure 9.2 or with an indirect water heater as shown

in Figure 9.3. This method relies on primary/secondary pumping to ensure that the required

ow is always maintained

through the boiler. In this system, the

ow rate through the boiler is completely independent of the

ow rate through the

heating system. Use the following guidelines to ensure that the boiler will have the required

ow shown in Table 9.1

regardless of the

ow in the heating system.

1) Primary Loop Piping - Size the primary circulator and piping to obtain the design

ow rate through the heating system

as you would on any other heating system. All piping between the expansion tank and secondary connection tees must
be at least as large as that shown in Table 9.5, column (a). In order to keep the

ow rates in the primary and secondary

loops independent of each other, provide at least 8 diameters of straight pipe upstream of the

rst secondary tee and 4

diameters downstream of the second secondary tee. Keep the distance between the expansion tank and the

rst secondary

tee as short as practical.

2) Secondary Loop (“Boiler Loop”) Piping – All piping must be the size shown for the boiler in Table 9.5, column (a). To

size the circulator:
a) Select one of the boiler water

ow rates shown in Table 9.5, column (b) for the boiler being installed. When

selecting the required boiler

ow rate, keep in mind that if the

ow rate in the primary loop exceeds the

rate through the boiler, it will not be possible to obtain a 180F supply temperature in the primary loop. This is
because the supply water exiting the boiler will be mixed with cooler system return water before entering the
radiation.

b) Count all

ttings in the planned secondary loop (the secondary loop consists of the shaded piping in Figure

9.4a). In doing so, do not count the secondary connection tees, unions, or the

ttings supplied with the boiler

(these have already been accounted for).

Using Table 9.7,

nd the equivalent lengths of all

ttings in the secondary loop. Total these equivalent lengths

and add them to the total length of planned straight pipe in the secondary loop. The result is the total equivalent
length of the secondary loop.

d) Using Table 9.5,

nd the boiler size being installed and select a boiler secondary circulator that shows a

“maximum equivalent length” (column e) in excess of the total equivalent length calculated in Step (c).

3) Indirect Water Heater Loop Piping (If Indirect Water Heater is Used) – All piping must be the size shown in Table 9.6,

column (a). If the indirect water heater connections are smaller than the pipe size called for in column (a), reduce the
pipe size at the indirect water heater connections. To size the circulator:
a)

Count all

ttings in the planned Indirect Water Heater Loop (the indirect water heater loop consists of the

shaded piping in Figure 9.4b). In doing so, you will be counting some piping and

ttings which are common to

the heating system secondary (“boiler loop”) piping and which were counted in Step 2a above. Do not count the
elbows or

ttings supplied with the boiler.

b) Using Table 9.7,

nd the equivalent lengths of all

ttings in the indirect water heater loop. Total these equivalent

lengths and add them to the total length of planned straight pipe in the indirect water heater loop.

The result is the total equivalent length of the indirect water heater loop.
c)

Using Table 9.6,

nd the boiler size being installed and select an indirect water heater loop circulator that shows

a “maximum equivalent length” (column f) in excess of the total equivalent length calculated in Step b.

Example – Assume that a FCM120 is to be installed in a heating system along with an Alliance indirect water heater.

A total of 15 ft of straight pipe will be installed between the boiler and the primary loop. A total of 20 ft of straight
pipe will be installed between the boiler and the indirect water heater. Fittings are arranged as shown in Figure
9.3. A 9.0 GPM

ow is required in the boiler loop. The MS-40 requires a

ow rate of 8 GPM and has a head loss

of 3.0 ft.

Total

ttings in Secondary loop (“boiler loop”):

6 90 Elbows

  2 Runs of Tees
  1 Swing Check
  2 Isolation Valves
  Note: Unions, Secondary Connection Tees, and factory supplied

ttings are ignored.

Calculate total equivalent length from Table 9.7:

15ft Straight Pipe + 6 Elbows x 2.75 + 2 Runs of Tees x 1.75 + 1 Swing Check x 7 + 2 valves x 0.6 = 43.2

equivalent feet straight pipe. From Table 9.5, we see that a Taco 0014 will pump 9 GPM through a FCM120 with 61
equivalent feet of pipe, so the Taco 0014 is OK.