Error messages: 2xEP500P Split Phase Mode

I received my two EP500 Pros last week. The goal is to use the Fusion box to be able to utilize split phase. However, whenever I connect the communications cable I get various error messages on either of the units. One thing I thought was odd is the communications cable did not have the blueish ring that threads to secure the cable. I have tried many times, rebooted them, etc. Still cannot get them to the point to set one as master. Attached are pictures of the errors on both units.

I have emailed support many times and called, no answer. As of now I cannot use them as intended as my connection to my transfer switch needs split phase. Pretty frustrating.

Anyone have a suggestion? Thanks!

If it is like the AC300 then the AC output needs to be off.
You will get errors when you first set it up as the units complain about the other guy.
Clear the errors and then you should be good to go

I had the AC/DC output off, many attempts including all but the communications cable connected to rule out any conflicts. Cleared alarms many times and almost like clockwork, when I plugged in the communications cables alarms starting going off.

Thanks for the response!

I had the same problem and found out that the cable is not plugged in far enough, so I twisted the cable and it went in farther and the errors when away. It is working fine in master/slave mode.

Hi @bharris , According to your situation, we have the following information that you need to reconfirm.

  1. Can you confirm that the communication cables are connected? Is it plugged in properly?
  2. Has the networking been set up?

Yes, the cables are secure. The errors start as soon as I plug in the second cable. For “networking” I cannot get past the Master/Slave selection screen. Both have MASTER selected and no option to select SLAVE. All this while alarms are going off that will not clear.

Attached is the picture of the cable, no logos or matching the color scheme of the others.

Hi @bharris ,
Thank you very much for the description and the picture provided. But could you please take a video of the operation? Start with the connection, make sure the cable is 100% plugged in place and tightened. Then check the screen settings.
I am sending you this document “How to connect two EP500 Pro to the utility power for 240 Volt Circuits” and you can try it again and see if the machine still reports errors. If it still reports errors, please send us a video. That way we can see more visually what the problem is. Thank you in advance for your kind cooperation.

I followed the instructions and I have a public Google Drive link with the video. I have two formats due to the size. I had a second Fusion Box Pro and still had issues. Not sure what I am doing wrong. As well attached the errors messages again.


Hi @bharris , thank you so much for sharing the operation video.
We have submitted your video to the relevant technical support department.

We see from the video that you are connected to the communication cable with the power on. You need to keep the machine off and then connect the communication cable, then turn it on and see if the error is still reported?

OK. I was able to get it to finally work. However, the instructions are far from clear and also maybe I was lucky.

I powered off the units with communications and fusion box connected. Powered up one unit first, cleared alarms and selected MASTER. THEN powered up the second cleared alarms and finally was able to select the SLAVE setting.

This is very clunky and does not match the instructions. If both units are on it does not work.

Also the draw from the units is quite uneven, when both were at 100%. With such little draw on both it is setting off two of my APC UPS units with a power failure/restore before the events were suppressed. Log file is on the the Google Drive that is shared. Please keep this open as I cannot be the only one that will encounter this. Thank you.

@bharris , Thank you so much for your cooperation!
Your troubleshooting ideas are very clear and the steps are excellent. Even our professional engineers are praising you. Feel free to contact us if you have any follow-up questions. Have fun using it :smiley:

Thank you. My concern is uneven power distribution, even it is tripping the UPS units. Also, if you would update the documentation as this was very frustrating and clunky to clear alarms and etc.


Hi @bharris , The following are suggestions from engineers.
Before you begin installing your Reliance Controls transfer switch system, you need to create a plan for the appliances you choose to run during a power outage. In setting up a transfer switch to get the most power from your two power stations in split phase power system, it is desirable to “balance the load” between the two phases of your transfer switch. Each side should be distributed evenly, not more than 3000W per phase. Devices which will consume the most of the two power stations’ wattage should be divided between the two.

Thank you very much for your suggestion, we have forwarded it to the relevant departments. Have a nice day!

“Devices which will consume the most of the two power stations’ wattage should be divided between the two.”
What you are saying is that to balance the load on each phase (each EP500Pro) the wattage drawn while in use needs to be as balanced as possible. Ex. two deep freezers and two tv’s should be wired into the panel on two circuits, each consisting of one freezer and one tv. (assuming the wattage draw is comparable for each appliance pair).

Hi @MikeD , It means to make the total power of the load in both phases as equal and close as possible