Cummins LT100 Transfer Switch
Cummins LT100 Transfer Switch
(OP)
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.





RE: Cummins LT100 Transfer Switch
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.
RE: Cummins LT100 Transfer Switch
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"
RE: Cummins LT100 Transfer Switch
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.
RE: Cummins LT100 Transfer Switch
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??
RE: Cummins LT100 Transfer Switch
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.
RE: Cummins LT100 Transfer Switch