Gas Headers (Natural Gas)
1. Determine cubic feet of gas per hour for each bank of
modules, using the following formula:
Module Bank Btuh Input
= Cubic Feet Per Hour
NG Heating Value
2. Determine length of the header, which is typically
dependent on length of the bank of modules which it
serves (see Figure B2). In most cases, the header is
straight pipe only.
3. In Figure B3, find the appropriate pipe length in the
upper portion of the table under "Length of Pipe, Feet"
heading.
4. Move down the column; match the cubic feet per hour
(from Step 1). Higher capacity selection is acceptable.
5. Move across to the left-hand column "Nominal Iron
Pipe Size, Inches" and read required pipe size.
Gas Main (Natural Gas)
1. Determine the cubic feet of gas per hour for the total
heating plant, using the following formula:
Heating Plant Btuh Input
= Cubic Feet Per Hour
NG Heating Value
Figure B1 provides recommended gas header and gas
main pipe sizes for Multi-Temp heating plants. For accu-
rate size selection, be sure to use total equivalent pipe
length; that is, the equivalent foot-length of all fittings,
such as elbows, tees and valves, used in the gas pipe
run (which can be determined from National Fuel Gas
Code tables), added to the straight length of pipe.
Considering gas pipe sizing involves selecting the prop-
er diameter, for the initial determination only, as a rule of
thumb add 20% for the fittings to the straight length of
piping to get a total equivalent length. However, once a
diameter has been selected, the total equivalent length
must be verified.
CALCULATING GAS PIPE SIZING
If the information provided in Figure B1 is not sufficient
for your application situation, then you can easily calcu-
late the gas pipe diameter. You need to know:
1. Total Btuh input of all modules in the heating plant.
2. Heating value (Btu per cubic foot) of the natural gas
(not required for propane), which can be obtained
from the local gas utility.
3. Total equivalent lengths of the gas main and the gas
headers which must be sized separately.
Figures B3 and B4 are pipe sizing table for natural gas
and propane gas piping. They apply for sizing black iron
pipe only and are based on total equivalent pipe length
and maximum capacity of the pipe (in cubic feet of gas
per hour for natural gas or in thousands of Btu per hour
for propane). Natural gas sizing table assumes a 1000
Btu/cu.ft. heating value for natural gas.
BOILER
MODEL
MR-360C 3’6”
MR-420C 3’6”
MR-500C 3’6”
MR-600B 3’6”
MR-750C 5’4”
LGTH
APPENDIX B: GAS PIPE SIZING
24
FIGURE B2
BOILER
MODEL
MR-180B 10’7”
MR-2100B 12’4”
MR-2400B 14’1”
LGTH
BOILER
MODEL
MR-840C 7’1”
MR-900B 5’4”
MR-1000C 7’1”
MR-1200B 7’1”
MR-1500B 8’10
”
LGTH
FIGURE B1
MR-360C
MR-420C
MR-500C
MR-600B
MR-750C
MR-840C
MR-900B
MR-1000C
MR-1200B
MR-1500B
MR-1800B
MR-2100B
MR-2400B
BOILER
MODEL
NO. OF
MODS.
GAS
HEADER
PIPE SIZE
(IN.)
GAS MAIN PIPE SIZE (INS.)
LENGTH OF MAIN FROM METER (FT.)
40 60 80 100 125 150
175
200
NG LP NG
LP
NG
LP
NG
LP
NG
LP
NG
LP
NG
LP
3
1-1/4”
2”
1-1/4”
2”
1-1/2”
2”
1-1/2”
2
1-1/2” 2-1/2” 1-1/2 2-1/2”
2”
2-1/2” 2-1/2”
4
1-1/4”
2”
1-1/4”
2”
1-1/2”
2”
1-1/2”
2
1-1/2” 2-1/2” 1-1/2 2-1/2”
2”
2-1/2” 2-1/2”
3
1-1/4”
2”
1-1/4”
2”
1-1/2”
2”
1-1/2”
2
1-1/2” 2-1/2” 1-1/2 2-1/2”
2”
2-1/2” 2-1/2”
5
1-1/2”
2”
1-1/2” 1-1/2”
2”
2-1/2”
2”
2-1/2”
2”
3”
2”
3”
2”
3”
3”
6
2”
2-1/2”
2”
2-1/2”
2”
3”
2”
3”
2”
3”
—
3”
—
3”
4”
7
2”
2-1/2”
2”
3”
2”
3”
2”
3”
—
3”
—
3”
—
4”
4”
8
2”
3”
2”
3”
3”
—
3”
—
—
—
—
—
—
—
—
4
1-1/2”
2”
1-1/2”
2”
1-1/2” 2-1/2”
2”
2-1/2”
2”
2-1/2”
2”
3”
2”
3”
3”
2
1-1/4”
1-1/2” 1-1/4” 1-1/2” 1-1/4”
2”
1-1/4”
2”
1-1/4”
2”
1-1/4”
2”
1-1/2”
2”
2”
PRESS.
DROP
(W.C.)
0.3
Summary of Contents for MultiTemp MR Series
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