Gas Connections - Modine Manufacturing DBS Installation And Service Manual

INSTALLATION - GAS CONNECTIONS

Gas Connections

WARNING
1. All field gas piping must be pressure/leak tested prior to
operation. Never use an open flame. Use a soap solution or
equivalent for testing.
2. Gas pressure to appliance controls must never exceed
14" W.C. (1/2 psi).
3. To reduce the opportunity for condensation, the minimum
sea level input to the appliance, as indicated on the serial
plate, must not be less than 5% below the rated input, or 5%
below the minimum rated input of dual rated units.
CAUTION
Purging of air from gas supply line should be performed as
described in ANSI Z223.1 - latest edition "National Fuel Gas
Code", or in Canada in CAN/CGA-B149 codes.
IMPORTANT
To prevent premature heat exchanger failure, the input to the
appliance, as indicated on the serial plate, must not exceed
the rated input by more than 5%.
1. Installation of piping must conform with local building codes,
or in the absence of local codes, with the National Fuel Gas
Code, ANSI Z223.1 (NFPA 54) - Latest Edition. In Canada,
installation must be in accordance with CAN/CGA-B149.1 for
natural gas units and CAN/CGA-B149.2 for propane units.
2. Piping to units should conform with local and national
requirements for type and volume of gas handled, and
pressure drop allowed in the line.
3. Refer to Model Digits 4-6 of the Model Nomenclature on
page 57 and the value on the unit Model ID plate (not
individual furnace serial plates) to determine the gas
heating capacity in Thousands of Btu/hr (MBH). The
Model ID plate is located on the blower section electrical
compartment door. See Figure 12.1 for an example Model
ID plate.
Figure 12.1 - Model ID Plate Example
DBS960SMRHN20F2IQ5DBA00
4. For the length of pipe necessary, determine the pipe
diameter from Tables 13.1 or 13.2 for the unit heating
capacity. Where several units are served by the same main,
the total capacity and length of main must be considered.
While the gas connection(s) on the unit may be smaller
than the required supply pipe diameter, do not use pipe
sizes smaller than what is required leading up to the unit.
At the unit, reduce the pipe size down to the appropriate
size (sizes 75-225 are 1/2" connections, 250-960 are 3/4"
connections). Avoid pipe sizes smaller than 1/2". The inlet
pressure to the unit must be 6-7" W.C. for natural gas and
11-14" W.C. for propane gas. When sizing the inlet gas
pipe diameter, be sure the unit supply pressure can be met
after the line pressure drop has been subtracted. If the line
pressure drop is too high, refer to NFPA 54 National Fuel
Gas Code for other gas pipe capacities.
12
5. The gas piping to the unit can enter the unit from the side of
the unit or from below. Install a ground joint union with brass
seat and a manual shut-off valve external of the unit casing,
and adjacent to the unit for emergency shut-off and easy
servicing of controls, including a 1/8" NPT plugged tapping
accessible for test gauge connection (See Figure 12.2).
Verify the manual shut-off valve is gas tight on an annual
basis.
6. Provide a sediment trap before each unit in the line where
low spots cannot be avoided. (See Figure 12.2).
Figure 12.2
Recommended Sediment Trap/Manual Shut-off Valve
Installation - Side or Bottom Gas Connection
GAS
SUPPLY LINE
GAS
SUPPLY LINE
3"
MIN.
SEDIMENT
TRAP
7. When Pressure/Leak testing, pressures above 14" W.C.
(1/2 psi), close the field installed shut-off valve, disconnect
the appliance and its combination gas control from the gas
supply line, and plug the supply line before testing. When
testing pressures 14" W.C. (1/2 psi) or below, close the
manual shut-off valve on the appliance before testing.
5-594.10
GROUND
JOINT
UNION
W/ BRASS
SEAT
MANUAL GAS
SHUT-OFF VALVE
j
TO
CONTROLS
PLUGGED
1/8" NPT TEST
GAGE CONNECTION
j M anual shut-off valve is in the "OFF" position
when handle is perpendicular to pipe.