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MHU200NG
MHU250NG
MHU300NG
MHU400NG
Gas supply
Connection
MHU200NG
MHU250NG
MHU300NG
MHU400NG
*Assumes an average heating value of 2500 BTU/SCF and a Specific Gravity of 1.53.
•
A sediment trap meeting the typical requirements of Figure 9 shall
be installed in the line to the gas valve.
•
A dedicated shutoff valve for the heater must be installed in the
gas supply line.
Refer to Table 5 for natural gas and Table 6 for propane to determine
the cubic feet per hour (CFH) required for the type of gas and size of
unit to be installed. To determine the proper pipe diameter, use the
CFH value and the length of pipe necessary. In the case where several
units are serviced by the same main gas line, the total capacity (CFH)
and length of main must be adequate to service all appliances down-
stream of this main.
•
All piping must be installed in accordance with the requirements
outlined in the National Fuel Gas Code ANSI/Z223.1 (latest
edition) or CSA-B149.1 and B149.2. Support all gas supply piping
with pipe hangers, metal strapping, or other suitable material. Do
not rely on the heater to support the gas pipe.
WARNING: Always use two (2) opposing wrenches to tighten
mating pipe connections to prevent excessive torque on the
gas valve and manifold pipe. Excessive torque can damage
the valve and/or misalign the orifice, resulting in fire,
explosion, serious injury, or death.
•
When connecting gas supply lines, the length of the piping run
from the gas meter to the heater must be considered in determin-
ing the pipe size to avoid excessive pressure drop.
•
A drip leg should be installed in the vertical pipe run to the unit.
In some localities, codes may require that a manual main shutoff
valve and union (furnished by installer) be installed external to the
unit. Union must be of the ground joint type. A drip leg should be
readily accessible to permit cleaning and emptying. See Figure 9.
Gas supply
Gas supply
Connection
Pressure min.
["]
[" W.C.]
1/2
7
1/2
7
1/2
7
3/4
7
TABLE 5: Natural Gas Consumption
*Assumes an average heating value of 1050 BTU/SCF and a Specific Gravity of 0.60.
Gas supply
Gas supply
Pressure min.
Pressure max.
["]
[" W.C.]
1/2
1 1
1/2
1 1
1/2
1 1
3/4
1 1
TABLE 6: Propane Gas Consumption
Large Unit Heater
Gas supply
Manifold
Pressure max.
Pressure
[" W.C.]
[" W.C.]
20
4.5
20
4.9
20
1.73
20
2.13
Manifold
Orifice Drill
Pressure
Size
[" W.C.]
[" W.C.]
["]
20
7.23
0.075
20
7.23
0.075
20
3.81
0.084
20
4.74
0.084
NOTICE: Leave a min of 4'' clearance to the electrical connections box
on the back of the heater to allow for access.
A 1/8" NPT plugged tap shall be installed immediately upstream of the
gas supply connection to the heater. The purpose of this is to be able
to check for proper gas pressure entering the heater.
1 1
Operating Instructions and Owner's Manual
Orifice Drill
# of
Consump-
Size
Orifices
tion
["]
[CFH]
0.1 10
6
190.5
0.1 10
7
238.1
0.138
9
285.7
0.138
11
380.9
# of
Consumption
Orifices
[CFH]
6
80.0
7
100.0
9
120.0
1 1
160.0
Gas Supply Connection
Manual
Main Shut-off Valve
(Furnished by Installer)
Grounded Joint Union
Drip Leg
Sediment Trap
FIGURE 9
[Gal/Hr.
Propane]
2.19
2.74
3.29
4.38
Gas Flow
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