Natural Gas And Lpg Conversion; Fuel System Changeover Kits (Dual Fuel) - Kohler APM402 Operation

3.6.3

Natural Gas and LPG Conversion

Most gaseous-fueled models can be converted to operate on either natural gas or LPG fuel. The engine ECM has fuel tables
and spark advance curves programmed for both natural gas and LPG. To change the fuel type, change the electrical connections
between the fuel system and the engine ECM as shown in the following instructions and connection diagrams. A hang tag on
the fuel regulator may provide additional conversion setup information. Fuel conversion may decrease generator set output.
Refer to the respective generator set spec sheet for ratings based on fuel selection. Changing fuel does not alter the emissions
compliance of the generator set engine. Consult your local generator set distributor/dealer for additional information.
Note:
If a gaseous-fueled model has the fuel type changed (LPG to natural gas or natural gas to LPG), order a new nameplate from
an authorized distributor/ dealer with the updated ratings and attach to the generator set.
Be sure to review the respective wiring diagram for your specific model for possible special applications.
3.6.4

Fuel System Changeover Kits (Dual Fuel)

A changeover fuel system kit provides automatic changeover from natural gas to LPG vapor. The primary and backup fuels each
have a fuel solenoid valve. The primary fuel is natural gas; the backup fuel is LPG vapor. Before starting, both fuel solenoid
valves are closed. When the generator set starts, the primary fuel solenoid valve opens. The primary fuel line has a pressure
switch in series with a relay connected to the start/run circuit.
When the primary fuel pressure drops below 0.6 kPa (1.4 oz./in.2) or 6.4 cm (2.5 in.) water column, a relay opens the backup
fuel solenoid valve and closes the primary fuel solenoid valve. When the primary fuel pressure rises above 0.6 kPa (1.4 oz./in.2)
or 6.4 cm (2.5 in.) water column, the generator set uses the primary fuel. Contact an authorized service distributor/dealer for kit
availability.
Emissions certified models use a single electronic-controlled pressure regulator (EPR) or direct acting electronic pressure
regulator (DEPR) for both fuels. A tee fitting connects both fuels together upstream of the EPR or DEPR. During operation when
using the secondary fuel, it is normal for a small amount of secondary fuel to seep back through the primary fuel solenoid valve.
To counter this situation, one of two methods is used depending upon the generator set model: (1) a second solenoid valve
(identical to the primary fuel solenoid valve) is installed in a reverse configuration on the primary fuel side or (2) a small vent line
is installed between the primary fuel inlet and the air intake through a fuel solenoid valve.
Dual-fuel systems that include a fuel reset box allow an operator to switch back to the primary fuel. The system will change
automatically to the primary fuel when the secondary source runs low or when the generator set stops and restarts.
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