# Kohler RXT ATS question



## Dan M (May 1, 2021)

I have a fairly complex power system consisting of grid, solar a generator (Kohler 20RESCL) and two ATS's, an RXT that came with the 20RESCL that is the primary ATS (grid for normal and solar for emergency) and a Generac RXSC100A3 that provides power from grid or generator to charge the solar batteries when sun energy is unavailable. 
What I need to know is how to disable the generator auto-start feature on the RXT without losing the automatic switching functionality when normal (grid) power goes down. The emergency side of the RXT is energized at all times from the solar power inverters/batteries. 
The reason is that I want the auto-start to be controlled by my inverter and only turn the generator (terminals 3/4) on when the batteries reach a pre-determined state of discharge and then shut off the generator when fully charged. As it is now, if the grid goes down, the generator is commanded to start by the RXT and remains running until grid power is restored which is a waste of fuel that's very difficult to get delivered, and undeliverable in the winter months.
If more info is needed I can provide it, I just didn't want to make this request too lengthy. I live in a very remote area in NE Washington so I have to do all of this on my own.
Thanks to any and all that can offer assistance. This is the last piece of this complex puzzle and the solution is proving to be very elusive.


----------



## iowagold (Jan 22, 2020)

just use another relay in line with the generator call to autostart sense so it will not call for gen run till the solar batteries needs charged.
easy to do.


----------



## Maggedon (May 13, 2021)

Dan, Some inverters have built in programmable relays to start a 2 wire (Terminals 3 and 4 on your Kohler) the old Trace/Xantrex SW model inverters and most Outbacks have relays that can do this. 
Also, do some checking.... if you jumper across terminals 3 and 4 on your RESCL does it actually try to start when in auto? if so a simple relay may be all you need. (you may have to disconnect the other RBUS start wires from the ATS to test this removing the ATS control from the picture for the test).

If Terminals 3 and 4 actually start your genset and you have inverters that can control it, then you can actually take the ATS RXT out of the equation and just let the inverters control the entire scenario genset, Grid, solar, all of it. Unfortunately not all inverter types can do this level of control.

So what inverters do you have?


----------



## Dan M (May 1, 2021)

Maggedon said:


> Dan, Some inverters have built in programmable relays to start a 2 wire (Terminals 3 and 4 on your Kohler) the old Trace/Xantrex SW model inverters and most Outbacks have relays that can do this.
> Also, do some checking.... if you jumper across terminals 3 and 4 on your RESCL does it actually try to start when in auto? if so a simple relay may be all you need. (you may have to disconnect the other RBUS start wires from the ATS to test this removing the ATS control from the picture for the test).
> 
> If Terminals 3 and 4 actually start your genset and you have inverters that can control it, then you can actually take the ATS RXT out of the equation and just let the inverters control the entire scenario genset, Grid, solar, all of it. Unfortunately not all inverter types can do this level of control.
> ...


My apologies for the delay and thank you for your response. I have Outback inverters and charge controller and the master inverter is already set up to auto start/stop the generator via the 3/4 terminals. The problem is that when grid power goes down the RXT automatically starts the generator, as would be correct in a normal situation, but, for me, my backup power is my solar power system and batteries and I want to use the generator to charge these batteries as needed when sunlight is unavailable (much of the winter months). If I disconnect the P13 connection on the RXT, I do disable the auto-start/stop but I also lose automatic switching when the grid goes down requiring me to go outside to manually switch the RXT to the "emergency" position, a pain at -15F and 2' of snow. So, I just need to disable the auto-start/stop from the RXT (ATS) but maintain auto switching during an outage. Prior to having grid power everything worked just as needed but I had the solar power output wired to the "normal" side and the generator to the "emergency" side and set up to both supply power to the house and/or charge the batteries depending on my power needs (solar is limited to 5000w / 30a). I've found a PSP KTWS-1 that converts from 4 wire start/stop to 2 wire (RXT Two Wire Start Converter - PSP Products ). I was thinking maybe I could get that and then put a relay on the start stop leads to "fool" the ATS? I had an initial issue with my Generac RXSC100A3 ATS that I use for battery charging (normal side from grid, emergency side from generator) not switching when the grid was down but I added a transformer (120v/12v) to the terminal 23 and ground lugs and that solved the problem. I'm hoping for something similar for the RXT otherwise, my only option seems to be to purchase another RXSC100A3 ATS. I'm so close to having the perfect system but this one thing is blocking me. Thanks in advance for your advice.
Dan


----------



## Dan M (May 1, 2021)

Maggedon said:


> Dan, Some inverters have built in programmable relays to start a 2 wire (Terminals 3 and 4 on your Kohler) the old Trace/Xantrex SW model inverters and most Outbacks have relays that can do this.
> Also, do some checking.... if you jumper across terminals 3 and 4 on your RESCL does it actually try to start when in auto? if so a simple relay may be all you need. (you may have to disconnect the other RBUS start wires from the ATS to test this removing the ATS control from the picture for the test).
> 
> If Terminals 3 and 4 actually start your genset and you have inverters that can control it, then you can actually take the ATS RXT out of the equation and just let the inverters control the entire scenario genset, Grid, solar, all of it. Unfortunately not all inverter types can do this level of control.
> ...


Maggedon, one quick clarification, I said P13 I meant P10 on the controller interface. I've also enquired with Kohler and they were of absolutely no help.


----------



## SolarSean (11 mo ago)

We are having a similar issue trying to have the RXT ATS switch from Grid to Gen but not start the Gen. I wonder if you found a solution. Did you try the PSP KTWS-1? It looks like it would be a good solution.


----------



## Ground Fault (Jun 9, 2020)

You lost me at _fairly complex._


----------

