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Table 5. Water Flow Requirements and Temperature Rise
Water Flow Requirements
Electrical
Data
All Sizes
with
Low Loss Header
without
Low Loss Header
Voltage
120 V
120 V
FLA
.70 A
.20 A
MCA
.9 A
.25 A
MOP
15 A
15 A
Minimum Clearances
Left + Right Sides
Front
Flue and Rear
Top
Size
inches
cm
inches
cm
inches
cm
inches
cm
ALL
4
10
2
5
6
15
20
51
Minimum
Clearances
from
Adjacent
Construction
Temperature Rise
15°F
8°C
20°F
11°C
25°F
14°C
Size
Flow Rate
Headloss
Flow Rate
Headloss
Flow Rate
Headloss
gpm
l/s
ft
m
gpm
l/s
ft
m
gpm
l/s
ft
m
50
5.3
0.3
0.3
0.1
4.0
0.3
0.2
0.1
3.2
0.2
0.1
0.1
75
8.0
0.5
0.6
0.2
6.0
0.4
0.3
0.1
4.8
0.3
0.2
0.1
100
10.7
0.7
1.3
0.4
8.0
0.5
0.7
0.2
6.4
0.4
0.5
0.2
125
*
13.3
0.8
2.2
0.7
10.0
0.6
1.3
0.4
8.0
0.5
0.8
0.2
150
*
17.0
1.1
2.5
0.8
12.8
0.8
1.8
0.5
10.3
0.6
1.2
0.4
200
*
22.8
1.4
5.0
1.5
17.0
1.0
3.1
0.9
13.7
0.9
1.9
0.6
*
Models 125-200 ship with a low loss header with integral pump, so a separate boiler pump does not need to be sized or fi eld-supplied.
NOTES:
1. Shaded area represents typical temperature rise.
2. gpm = water fl ow in gallons per minute.
3. l/s = water fl ow in liters per second.
4. ft = pressure drop (headloss) through the boiler in feet of water.
5. m = pressure drop (headloss) through the boiler in meters of water.
Sizing
Data
Heating Capacity AFUE % Water Gas
Input
Nat Gas
Conn. Conn.
Size
MBTU/h
kW
MBTU/h
kW
%
in.
in.
50
50
14.7
42
12.6
84 1-1/4 3/4
75
75
22.0
63
18.8
84 1-1/4
3/4
100
100
29.3
84
24.9
84 1-1/4
3/4
125
125
36.6
105
31.1
84 1-1/4
3/4
150
150
44.0
126
37.2
84 1-1/4
3/4
200
199
58.3
168
49.2
84 1-1/4
3/4
SECTION 5
PUMP REQUIREMENTS
5.A Pump Sizing
Table 6. Equivalent Feet and Head Loss
Model
Size
GPM
Equivalent Feet
of
¾”
Type M
Copper
Feet of Head
Loss
50
5
75
4.9
100
6.5
75
7.5
75
10.3
100
13.8
100
10
75
17.6
100
23.5
M
INI-
T
HERM
JX
Residential Boilers
®
This boiler has a water tube design, and requires
correct water flow for proper operation and long life.
Models 125-200 are built with a low loss header with
integral pump that serves the boiler and ensures proper
water flow. Optional low loss header with integral pump
kits, or kits with just pumps, are offered for use with
models 50, 75 and 100. When neither of the optional
kits are used with models 50, 75 and 100, care must be
taken to choose pumps and in the design of the piping.
A typical residential pump can flow enough water for the
average, properly-designed, zone system for models 50
and 75. If a zone exceeds 100 equivalent feet of 3/4”
pipe, a pump may not be large enough to overcome the
resistance and ensure proper water flow through the
boiler.
Sizing the pump requires the headloss of the zone
piping combined with the heat exchanger headloss.
Use Table 5 and 6 to approximate the head loss for
each zone and ensure the pump selection is adequate.
Compare to the manufacturer's pump curve to ensure
sufficient flow for the boiler.
Primary/Secondary systems and boilers with LLH
systems can be used to avoid needing larger pumps.
The boiler pump will maintain the proper flow
through the boiler regardless of the flow through the
system. This means that the system flow is now
only critical to the building comfort not the boiler
safety. Headloss is only calculated through the
individual zones for sizing of the system pump(s).