Part number 550-101-232/0703
11
GAS
-
FIRED
WATER
BOILER
—
Installation Manual — Multiple-boiler Systems
Figure 10
Typical piping for multiple Ultra boilers, Weil-McLain Easy-Fit
®
Manifolds, and indirect water heaters
1
Flow/check valve (each boiler)
2
Isolation valves (when used)
3
Caps
4
Easy-Fit
®
Manifold (supply), sized per Fig. 1
or Fig. 2, page 6
5
Easy-Fit
®
Manifold (return), sized per Fig. 1
or Fig. 2, page 6
6
Primary circulator
7
Expansion tank (diaphragm type)
8
System air eliminator
9
System automatic air vent
13
Cold water supply
17
Boiler circulator (each boiler)
18
System supply
19
System return
20
Boiler relief valve and discharge piping,
installed per Ultra Boiler Manual
21
Indirect-fired storage water heaters (Weil-
McLain PLUS Line shown) — Example is
shown with reverse-return boiler-side piping
using a single circulator. Alternate: each water
heater could have its own circulator.
22
Boiler water inlet
23
Boiler water outlet
24
DHW boiler-side circulator
25
DHW boiler-side supply Easy-Fit
®
Manifold
26
DHW boiler-side return Easy-Fit
®
Manifold
27
Flow/check valves (to prevent induced or
gravity flow in heating system or DHW piping)
28
Check valve to prevent heat migration in
heating system
29
See water heater manual for DHW piping —
The DHW piping must also be manifolded
together since the boiler-side piping is
manifolded. If DHW heaters supply separate
DHW circuits, provide an individual circulator
for each water heater, and control each
circulator by its water heater’s aquastat.
This piping is suggested only. The layout above should be controlled with a boiler sequencing panel that provides DHW operation as
well. Wire the heating system circulator to operate only on call for heat. Alternatively, use the boiler sequencing panel to provide
domestic priority by disabling the heating system circulator any time there is a DHW call for heat. The boiler circulators, item 17, must
operate on any call for heat, whether heating system or DHW. Offset the DHW boiler-side supply and return manifolds as shown so
the total run of pipe and fittings to each of the water heaters is approximately equal.
Suggested DHW boiler-side pipe sizing (based
on 500 milinch per foot head loss in piping):
0 – 7 gpm .......................... 1 inch
7 – 16 gpm ........................ 1¼ inch
16 – 24 gpm ...................... 1½ inch
24 – 45 gpm ...................... 2 inch
45 – 75 gpm ...................... 2½ inch
75 –140 gpm ..................... 3 inch
140 – 290 gpm .................. 4 inch
