Onan Neutral Wiring

ATTENTION INSTALLERS!

Special Wiring Instructions for Installers of Cummins Standby Generators

The Cummins installation instructions supplied with some generators are not clear concerning where to terminate the field neutral cable at the generator.  And the terminal block was not marked in the past in the termination compartment.  The neutral cable MUST be connected properly or unpredictable floating voltages can result which can damage electrical loads.  This has been an issue for model 20GGDB vapor fueled generators and may also be applicable to other models.

Photos below are for a 20kW 20GGDB 120/240VAC single phase genset with 12-lead alternator.

Click thumbnail images below to enlarge and to print.
WRONG	CORRECT

Instructions

There should be two 4-post terminal blocks in the output box where the 12 generator leads are made up.  One of these blocks is already wired to the output circuit breaker where the hot leads should be connected.

The other 4-post block is where the neutral from the transfer switch must be connected. Two of the posts have two generator wires connected to them by the factory.  One of the other posts has 3 or 4 factory leads connected.  Land the neutral lug on top of that post.

The ground wire should be connected to the stud in the output box that has the white wires going to it. These white wires are NOT neutrals. They are simply an equipment grounding point that connects the box to the alternator.

After making the wiring changes start the generator and measure the voltages.  They should all be within normal ranges.  If they are not, do not transfer any load to the generator.  Contact the dealer that sold you the genset for further instructions.

 

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