Specifications

Part number 550-142-120/0113
WM97+ gas-fired water boiler — Boiler Manual
– 60 –
Suggested DHW
boiler-side pipe
sizing
(for max 0.04
feet head loss per foot of
total equivalent length,
TEL)
Flow rate Size Flow rate Size
1 – 3.9 gpm ¾” 24 – 45 gpm 2”
3.9 – 7.1 gpm 1” 45 – 75 gpm 2½”
7.1 – 16 gpm 1¼” 75 - 140 gpm 3”
16 – 24 gpm 1½” 140 – 290 gpm 4”
Multiple boiler installations (continued)
Legend — Figure 69
The boiler internal primary/secondary by-pass valve must be CLOSED for multiple boiler installations piped
as shown in this manual. This allows the boiler internal circulator to circulator water to and from the manifolds.
1 Flow/check valve (integral to each
boiler internal circulator)
2 Isolation valves (when used)
3 Caps
4 Easy-Fit® Manifold (supply) — layout
and size per page 57
5 Easy-Fit® Manifold (return) — layout
and size per page 57
6 Primary circulator
7 Expansion tank (diaphragm type)
8 System air eliminator
9 System automatic air vent
13 Cold water supply
17 Boiler circulator — circulates water
between boiler and Easy-Fit® Mani-
folds
18 System supply
19 System return
20 Boiler relief valve and discharge
piping, installed per WM97+ 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 DHW boiler water supply, typical
23 DHW boiler water return, typical
24 DHW boiler-side circulators
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 mani-
folded. If DHW heaters supply separate DHW circuits, provide an
individual circulator for each water heater, and control each circula-
tor by its water heater’s aquastat.
32 Drain valves for DHW boiler water piping
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 prior-
ity by disabling the heating system circulator any
time there is a DHW call for heat. The boiler circula-
tors, 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.
Figure 69 Piping layout — typical piping for multiple WM97+ boilers,
with DHW storage heaters (4-boiler system)
(shown using WM97+155 boilers — adjust boiler
connections as required for other boiler models)