Weil-McLain WM97+70 Specifications download pdf (Page 38)

Part number 550-142-120/0113

WM97+ gas-fired water boiler — Boiler Manual

– 38 –

Head loss through boiler internal

piping

Top boiler connections (internal by-pass valve OPEN)

1. See Figure 39 for the head loss through boiler internal piping

for boiler top connections. This data is based on primary/

secondary piping (boiler internal by-pass valve OPEN).

2. For the special case of direct connection of WM97+70 or 110

boilers, see the information on page 44.

Figure 39 Head loss through boiler internal piping for top

boiler connections

WM97+70 or 110 WM97+155

Flow rate

(GPM)

Head loss

(Feet W. C.)

Flow rate

(GPM)

Head loss

(Feet W. C.)

0.0

2.2

1.2

2.7

1.4

3.3

1.5

4.0

1.7

4.8

2.3

5.9

Bottom boiler connections

1. See Figure 40 for the head loss through boiler internal piping

for boiler bottom connections.

Figure 40 Head loss through boiler internal piping for

bottom connections

WM97+70 or 110 WM97+155

Flow rate

(GPM)

Head loss

(Feet W. C.)

Flow rate

(GPM)

Head loss

(Feet W. C.)

0.0

1.3

0.3

2.1

0.6

3.0

1.2

4.2

2.3

5.5

2.9

7.1

Boiler circulator

1. The boiler circulator is factory-installed in the boiler as shown

in this manual. The boiler circulator is selected to ensure

adequate ﬂow through the WM97+ boiler.

DO NOT relocate or use the boiler circulator in any

way other than shown in this manual.

Failure to comply could result in unreliable perfor-

mance and nuisance shutdowns from insufﬁcient

ﬂow.

System circulators and zone

circulators

1. Install a system circulator or zone circulators as shown in the

piping diagrams in this manual. These circulators must be

supplied by the installer.

System or zone circulator ﬂow rate

1. Size circulators based on the ﬂow rate required to achieve the

temperature change needed.

2. You can closely estimate temperature rise (or drop) through a

circuit by using the following formula, where TD is tempera-

ture rise (or drop), FLOW is ﬂow rate (in gpm), and BTUH

is the heat load for the circuit:

FLOW =

BTUH

—–—–—–—–

TD x 500

Examples:

1. Consider a system loop for a system with total heating load

equal to 210,000 Btuh. The desired temperature drop through

the system piping is 20°F. Then the required ﬂow rate is:

FLOW =

210,000

—–—–—–—–

20 x 500

= 21 gpm

SIMPLIFIED:

For 20° temperature drop, FLOW = MBH / 10.

System or zone circulator head requirement

1. The circulator must be capable of delivering the required ﬂow

against the head loss that will occur in the piping.

2. Determine the pipe size needed and the resultant head loss

using accepted engineering methods.

3. The simpliﬁed pipe sizing here is limited to residential sys-

tems, and does not include systems with fan coil units or

radiant tubing.

The following simplified method for pipe and

circulator sizing must be limited to residential ap-

plications using baseboard (ﬁnned or cast iron),

cast iron radiators or convectors. DO NOT apply

for radiant heating, fan coil units or commercial

installations.

Install water piping (continued)

1 2 ... 33 34 35 36 37 38 39 40 41 42 43 ... 135 136

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Weil-McLain WM97+70 Specifications Page 38

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