Munchkin 399M User Manual
Page 9
9
GAS CONNECTION
A. GAS CONNECTION
The gas supply shall have a maximum inlet
pressure of less than 14" water column (350
mm), ½ pound pressure (3.5 kPa), and a
minimum of 7" water column. The entire
piping system, gas meter and regulator must
be sized properly to prevent pressure drop
greater than 0.5" as stated in the National Fuel
Gas Code. This information is listed on the
rating plate. It is very important that you are
connected to the type of gas as noted on the
rating plate. "LP" for liquefied petroleum,
propane gas or, "Nat" natural or city gas. All
gas connections must be approved by the local gas supplier, or utility in addition to the governing
authority, prior to turning the gas supply on. The nipple provided is 1¼" and it is mandatory that a 1 x
1¼" reducing coupling (provided) is used, threaded into the branch of a 1¼" tee, and a drip leg
fabricated, as per the National Fuel Gas code. You must ensure that the entire gas line to the
connection at the Munchkin is no smaller than 1¼". Once all the inspections have been performed,
the piping must be leak tested. If the leak test requirement is a higher test pressure than the maximum
inlet pressure, you must isolate the Munchkin from the gas line. In order to do this, you must shut the
gas off using factory and field-installed gas cocks (following the lighting instructions in Part 6 Section
B.) This will prevent high pressure. Failure to do so may damage the gas valve. In the event the gas
valve is exposed to a pressure greater than ½ PSI, 14" water column, the gas valve must be replaced.
Never use an open flame (match, lighter, etc.) to check gas connections.
B. GAS PIPING
1. Run the gas supply line in accordance with all applicable codes.
2. Locate and install manual shutoff valves in accordance with state and local requirements.
C. GAS TABLE
Refer to Table (1) to size the supply piping to minimize pressure drop between meter or regulator
and unit.
Maximum Capacity of Pipe in Cubic Feet of Gas per Hour for Gas Pressures of 0.5 psi or Less and a
Pressure Drop of 0.3 Inch water Column
(TABLE 1)
(Based on a 0.60 Specific Gravity Gas)
It is recommended that a soapy solution be used to detect leaks. Bubbles will appear on the pipe to
indicate a leak is present. The gas piping must be sized for the proper flow and length of pipe, to
avoid pressure drop. Both the gas meter and the gas regulator must be properly sized for the total
gas load. If you experience a pressure drop greater than 1" WC, the meter, regulator or gas line is
undersized or in need of service. You can attach a manometer to the incoming gas drip leg, by
Nominal
Iron Pipe Internal
Length of Pipe (Feet)
Size
Diameter
(inches)
(inches) 10
20
30
40
50
60
70
80
90
100
125
150
175
200.
3/4
.824
278
190
152 130 115
105
96
90
84
79
72
64
59
55}
BTU'S
1
1.049
520
350
285 245 215
195 180
170
160
150
130
120
110
100}
PER
1 1/4
1.380
1,050
730
590 500 440
400 370
350
320
305
275
250
225
210}
HOUR
1 1/2
1.610
1,600
1,100
890 760 670
610 560
530
490
460
410
380
350
320}
X 1,000