Cummins LT100 Transfer Switch 1

[Hawkas]

Does anyone have any experience with this LT100 range of transfer switches. When the system is powered up the mains contactor does not energise, and the emergency contactor remains de-energized as well. The only indication on the control board is the red "Start" LED which lights up but nothing else. I have spoken to Cummins who can't seem to help, and it took nearly six months to locate a replacement manual. There is no toubleshooting guide in the manual so I'm hoping someone will be able to steer me in the right direction. The unit has been installed and inspected, so electrically it is correct, just doesn't do anything. If I put the generator in "Remote" mode then it fires up straight away, which leads me to hope that it is just a settings problem on the control board.

 

[catserveng]

Does the controller have the correct Normal source voltage at it's sesning terminals?

When the generator starts and runs, does the Emergency source contactor energize?

Been awhile since I've worked on one of those switches, as memory serves, they were built with 120 VAC sensing to the controller, and used VT's to sense line voltage. What is rated voltage and frequency of your ATS?

Doesn't the controller also have LED's for Normal and Emergency source voltage indication?

If you can provide some more details of the ATS I might be able to dig up some info to help.

 

[Hawkas]

No the emergency contactor does not energize.
The ATS is an LT100, 415VAC, Three Phase Three Wire, with Control Package B.
The LED indicators from top to bottom are "Stop Timing", "XFR Timing", "Re-XFR Timing", "XFR", "Re-XFR", "Norm Avail", "Emer Avail", & "Start"

 

[catserveng]

With Normal source energized is the "Norm Avail" LED on? If you start and run the emergency generator at rated voltage and frequency does the "Emer Avail" LED come on?

I was not able to find any info at home last night on this ATS, do you have a wiring diagram? If so, locate the controller inputs for normal and emergency source voltage and make sure the board is seeing the voltages. If the LED's don't come on with it's associated source available, then check the controller power supply.

Is the "Start" LED on? If so, the controller may be working but not seeing normal source.

Sorry, didn't do many of these and hard to work from memory.

 

[Hawkas]

The only LED that comes on is the "Start" LED, no matter what source is connected. The customer lost his manuals and we just got a replacement installation manual from Cummins (which took about two months!!). There are no drawings of the control board in the manual, I guess we needed a service manual rather than an installation manual.
When I put the genrato in remote mode it does start up, I'm guessing because the "Start" condition is present. So it's pointing to being the pot settings on the control board ie. normal dropout, normal pickup, emergency dropout and emergency pickup, and perhaps also emergency and normal calibration pots??

 

[catserveng]

Start LED is coming on because controller is not seeing the Normal source, usually utility, and then if generator starts and runs, and gets to rated voltage and frequency, the Emergency available LED should come on, and then the Xfer Timing LED, after the transfer delay times out, the ATS shold shift to the Emergency position, if it doesn't, then controller is also not seeing the generator voltage.

So it appears you have a problem with the voltage sensing circuits on both sources based on your info so far. It is possible the controller has a fault also.

To go further in troubleshooting you'll at least need a connection drawing, or see if you can find a technician with experience with that controller and ATS.

 

[Hawkas]

Thanks for that, the installation manual is reasonably clear about setting the pots, so I will go to site next week and look at those things you mentioned, thanks a lot for the help.