MG3P Installation Manual

24
Installation Example
Elevation: ...........................................................5,000 feet
Type of Gas: ................................................... Natural Gas
Local Heating Value of Gas: ....................................... 750
Determine which natural gas table to use. From Table 16, find 750
and follow down the column, stop at the 5,000 feet row. The heating
value listed is LOW. Table 18 will be used to determine orifice size
and manifold pressure.
in the usual way, by clocking the gas meter and using the local
gas heating value. See Verifying and Adjusting the Input Rate
(page 30).
IMPORTANT NOTE:
Observe the action of the burners to make sure there is no
yellowing, lifting or flashback of the flame.
Conversion to LP/Propane
WARNING:
This furnace was shipped from the factory
equipped to operate on natural gas. Conversion
to LP/propane gas must be performed by qualified
service personnel using factory supplied
conversion parts. Failure to use the proper
conversion kit can cause fire, explosion, property
damage, carbon monoxide poisoning, personal
injury, or death.
This furnace can be converted from factory-equipped natural
gas to Liquid Propane gas. Conversion of this valve requires
replacement of the burner orifices on the manifold assembly and
flipping the regulator cap to the side marked LP. See Figure 36
below. The orifices required for conversion are supplied with
the furnace.
For altitudes between 0 and 1,999 feet, only the orifice is
changed. Altitudes between 2,000 and 10,000 feet require both
the orifice and regulator pressure to be changed. See Table 19
(page 48) to determine the correct orifice size and manifold
pressure to use at different altitudes.
WARNING:
Shut off the gas supply at the manual gas shutoff
valve, before disconnecting the electrical power.
A fire or explosion may result causing property
damage, personal injury or loss of life. Failure to
follow the safety warnings exactly could result in
serious injury, death or property damage.
WARNING:
To avoid electric shock, personal injury, or death,
turn off the electric power at the disconnect or the
main service panel before making any electrical
connections.
the main gas valve, emergency shutoff valve and flexible gas
connectors (if applicable). The soap and water solution can be
applied on each joint or union using a small paintbrush. If any
bubbling is observed, the connection is not sealed adequately
and must be retightened. Repeat the tightening and soap check
process until bubbling ceases.
IMPORTANT NOTE:
When pressure testing gas supply lines at pressures
greater than 1/2 psig (14 inch W.C.), the gas supply piping
system must be disconnected from the furnace to prevent
damage to the gas control valve. If the test pressure is less
than or equal to 1/2 psig (14 inch W.C.), close the manual
shut-off valve.
High Altitude Application
High altitude conversion with this furnace depends on the
installation altitude and the heating value of the gas. The
installation of this furnace at altitudes above 2,000 feet must
meet the requirements of the National Fuel Gas Code or local
jurisdiction. In Canada, the requirements for high altitude are
different and governed by CGA B149.1. Always consult your
local code authority.
WARNING:
The reduction of input rating necessary for high
altitude installation may only be accomplished
with factory supplied orifices. Do not attempt to
drill out orifices in the field. Improperly drilled
orifices may cause fire, explosion, carbon
monoxide poisoning, personal injury or death.
This furnace is shipped from the factory with orifices and gas
regulator settings for natural gas operation at sea level altitudes.
At 2000 feet, the NFGC requires that this appliance be derated
4% for each 1000 feet of altitude. For example, the input needs
to be reduced 8% at 2,000 feet, 12% at 3,000 feet and etc. This
deration is in reference to the input rate and gas heating value
at sea level.
To derate the furnace requires knowing the heating value of the
gas at the installation site. Heating values at particular job sites
vary for two reasons:
1. The chemical mixture of the gas varies from region to region
and is expressed as the “sea level heating value”.
2. The heating value varies by altitude. For this reason, especially
in high altitude areas, the local gas utility specifies the heating
value at the residence’s gas meter as the “local value”.
For added flexibility, two tables have been provided for natural
gas installations with high or low heating values at sea level.
Table 17 (page 48) & Table 18 (page 48) contain the
manifold pressure and orifice sizes to use at various altitudes.
Table 17 (HIGH) is for natural gas installations with a heating
value of more than 1,000 Btu per cubic foot and Table 18 (LOW)
is for less than 1,000 Btu per cubic foot. To determine which
table to use:
1. Consult the local utility for the local heating value at your
installation site.
2. From Table 16 (page 48), find your local heating value as
supplied by the utility company. Follow down the column and
stop at your altitude level.
3. If your sea level heating value is HIGH, use Table 17 or if it’s
LOW, use Table 18. See example.
After changing the regulator pressure or the orifices, it is required
that you measure the gas input rate. This may be accomplished