Multiple Boiler Water Piping - Williamson-Thermoflo GWC-070 Manual

GWC -
gas fired water boiler

Multiple boiler water piping

Secondary header piping installation
1. Main header and secondary header pipe sizing.
a. New system — See page 15.
b. Replacing boilers in an existing system — Without reducing
size, connect system supply and return lines. Install tees or
crosses for secondary headers as shown in Figure 30 or Fig-
ure 31. Size headers to handle total connected boiler output
as shown.
2. Provide connections in main header for secondary headers as close
as possible to the midpoint of multiple boilers.
a. Use tees for four or less boilers, as in Figure 30.
b. Use either tees (Figure 30) or crosses (Figure 31) for five or
more boilers.
3. Secondary header placement:
a. To alternate spacing for supply and return lines to boilers,
reverse the short-end and long-end of the headers as shown
in Figure 30 and Figure 31.
b. Return header must be on the return side of the main and sup-
ply header must be on the supply side of the main. Drawings
in this manual show flow in system main from right to left.
For system flowing left to right, reverse the locations of the
manifolds accordingly.
4. Connect from secondary header branches to boiler supply and
return connections using copper or steel pipe, sized for the re-
quired flow rate.
5. Provide a flow/check valve in the supply piping of each boiler as
shown in piping diagrams in this manual. Install an isolation valve
on the supply and return of each boiler as shown. Some local codes
may require the use of individual water level controls and limits
on each boiler when isolation valves are installed.
6. Install main system air eliminator and primary circulator in sup-
ply piping as shown in piping diagrams. Place expansion tank on
suction side of system circulator as shown.
7. Install system accessories as shown in drawings.
8. Piping recommendation drawings:
a. Figure 30 and Figure 31 show details of secondary headers.
b. Figure 32, page 25 is a schematic piping drawing showing the
locations of typical boiler piping and system piping, including
limits and other devices often required by local codes.
c. Figure 33, page 26 and Figure 34, page 27 are three-dimensional
piping drawings of typical multiple boiler installation.
d. Figure 35, page 28 shows recommended piping when an isolat-
ing heat exchanger is needed.
9. If desired, other primary/secondary piping arrangements can be
used.
When using isolation valves on each boiler, some codes
may require providing a low water control and additional
limit for each boiler. Consult local codes to determine
if omission of the individual boiler isolation valves may
allow the use of a single water level control and additional
limit for the entire multiple boiler system.
24
— Boiler Manual
Figure 30
Figure 31
Maximum connected load per header:
2-inch header —
3-inch header — 1400 MBH
4-inch header — 2900 MBH
Single-sided secondary header, typical
Double-sided secondary header, typical
Part number 550-142-056/0411
450 MBH