New 13kw Cummins Gen with older Generac Transfer Switch

Cummins/Onan Air Cooled & Liquid Cooled standby generator troubleshooting and repair questions
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RickGaud
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Looking for some help, we just replaced a 19 year old Generac Home Standby Generator with a new 13kw Cummins Generator and wanted to keep the 2012 Generac Transfer switch. There doesn’t appear to be a model number on the Generac Switch, it has an issue number of C-3680, SN 7062695 and Assembly OH6382A. We need some assistance in wiring the new Cummins Generator to this older Generac Transfer Switch. There are 5 control cables to and from the Generator location to the switch. I will attach some images…. Unfortunately we cannot seem to find any schematic diagrams on the Generac Transfer Switch. Any help anyone can offer would be greatly appreciated. Thanks
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RickGaud
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A few more images….
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nrp3
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Without knowing what the Cummins needs for control wiring, it's hard to tell you what to do with the transfer switch.
Birken Vogt
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Assuming it is like the (very few) I have had to deal with.

Refer to your installation manual.

Cummins uses a simple relay to close a contact and tell the generator it's time to start. I suppose a Generac voltage monitor relay would do for this, but installed as an isolated set of NC contacts instead of the NO it usually has. This site can sell you that kit.

It also looks like the transfer switch control is a +12VDC output instead of a switched ground, so you would have to do a little rework of the Generac arrangement for that to work.

Hard to describe over the internet. Refer to Cummins A053X172 for the generator inst. and A046S594 for the transfer switch they were expecting it to have.
grsthegreat
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I too have only worked on a few cummins over the years, but as i recall there were some telemetry involved between the units, which cannot be handled by generac switch (if i recall correctly). Also, the cummins transfer switch handled all the cool down and warm up programming and the exercise function, which the generac switch does not. I know PSP Products makes a conversion unit to switch a generac switch to a 2 wire start unit, but i dont know if this would work on a cummins genset. I suppose you could contact them.
Birken Vogt
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See my above reply and check out the manuals referenced. No telemetry on this Cummins unit, and the transfer switch has a simple relay across N1/N2 that when it drops, closes a contact that starts the genset, then the genset sends a 12VDC signal to make the switch transfer, same/similar to Generac. All this needs is a voltage monitor to close the contact and some understanding as to how it all works, I know it confused me in the field last time, and it confused me this morning again but I finally remembered how it works.
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