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Cummins ATS

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Electromatic

Electromatic

Senior Member
Location
Virginia
Occupation
Master Electrician
While waiting for a replacement permanent backup generator, I've been asked to wire a Cummins trailer-mount generator to an existing Cummins ATS. The genset terminal block (pictured) seemed simple enough--"Apply Ground to Activate", TB1-1 Remote Start. I tried jumping 20-22 to 1 but got nothing. I contacted Cummins and got a rather strange response to wire the ATS terminals directly to the genset starter (pictured response).
pwrcommand_tb.jpg cummins wiring.png

This doesn't seem right to me. Wouldn't the control wires between the ATS and the starter have to carry the full current to engage the starter? I asked if I should rather wire the B+ and GND to the matching terminals on TB1, but Cummins' response was that the manual says to go to the starter.

Any thoughts?
TIA
 
H

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
With Cummins, the transferswitch needs a constant DC hot, what they are needing is a battery positive, a battery negative, and a wire to the start input. They use three wires instead of two like Kohler. Kohler powers the electronics with source one, (AC) or source two (AC) Cummins powers the electronics of the generator battery.
 
qcroanoke

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Sorta retired........
hillbilly1 said:
With Cummins, the transferswitch needs a constant DC hot, what they are needing is a battery positive, a battery negative, and a wire to the start input. They use three wires instead of two like Kohler. Kohler powers the electronics with source one, (AC) or source two (AC) Cummins powers the electronics of the generator battery.
Click to expand...
Just make sure its an unswitched B plus.
Seems like we were told to start doing what they told you to do years ago. I havent been involved with an Onan Install in a long time.
 
Last edited:
Electromatic

Electromatic

Senior Member
Location
Virginia
Occupation
Master Electrician
The main thing I don't get is wiring directly to the starter. It seems like that is making the ATS terminals and the control wires carry the full starting current. Also, what would tell the genset to shut down on re-transfer to utility power?
 
B

Birken Vogt

Senior Member
Location
Grass Valley, Ca
They are just looking for a place to source battery (B+) and ground. Of course it needs a fuse if you do it that way.

The way the installation manual would have told you was to use B+ from the genset controller (pin 17) and ground (pins 20,21,22) along with RMT which is the start signal.

In recent years I have seen Cummins gensets come the other way, apply ground to RMT to get it to start rather than apply B+ to RMT.

The way to test for sure is to have the genset set to auto start. Then measure voltage on RMT, open circuit. Is it +12v, +8v, +5v or something? Then it is looking for ground, and grounding it should cause it to start. Or is it 0v? Then it is probably looking to have B+ applied to command a start.
 
H

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
Electromatic said:
The main thing I don't get is wiring directly to the starter. It seems like that is making the ATS terminals and the control wires carry the full starting current. Also, what would tell the genset to shut down on re-transfer to utility power?
Click to expand...
It doesn’t carry the start current, it is just an unswitched battery voltage, you can come directly off the battery if you wanted too for that voltage.
 
Electromatic

Electromatic

Senior Member
Location
Virginia
Occupation
Master Electrician
Thanks, all. I was thinking the ATS would close the B+ and/or GND terminals and directly trigger the starter. I see that the starter is just a place to source the B+ and GND.
I'm going to try it with wiring at the terminal strip and go to the starter only if that doesn't work.
 
B

Birken Vogt

Senior Member
Location
Grass Valley, Ca
Actually I see what might be a problem.

The sticker in the genset says "apply ground to activate" on terminals 1, 2, etc.

But in general, Cummins transfer switches used to apply B+ to call for generator start.

You might have to switch around the wires in the transfer switch or add an inverting relay to get this to work well together.

If the transfer switch is applying B+ to terminal 1, it is not going to make it start.
 
Electromatic

Electromatic

Senior Member
Location
Virginia
Occupation
Master Electrician
I initially tried jumping just at the genset terminal strip pins 20-22(GND) to pin 1 and got nothing. Why did that not work? I checked for a delayed start--there wasn't one programmed, and I jumped it for 30s or so.
 
B

Birken Vogt

Senior Member
Location
Grass Valley, Ca
Too hard to tell from here. What is generator model and serial? Got any manuals on the unit?

This is a bit like saying, I have a Ford car, I turned the ignition switch on why won't it start?
 
Electromatic

Electromatic

Senior Member
Location
Virginia
Occupation
Master Electrician
The generator is a Cummins DGCB. I don't have any paperwork for it. I've found the operator's manual online, but can't find much for the installation or wiring. I'm just trying to get as much info as I can before returning to the site.
Thanks again to all.
 
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