# Modbus OPC UA connections **URL:** \ **Category:** Ignition\ **Tags:** ignition81\ **Created:** [December 4, 2023, 4:51pm UTC](https://forum.inductiveautomation.com/t/modbus-opc-ua-connections/82673 "2023-12-04T16:51:14Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Christopher\_Smith](https://avatars.discourse-cdn.com/v4/letter/c/ce7236/32.png) [@Christopher\_Smith](https://forum.inductiveautomation.com/u/Christopher_Smith)\ **Post date:** [December 4, 2023, 4:51pm UTC](https://forum.inductiveautomation.com/t/modbus-opc-ua-connections/82673/1 "2023-12-04T16:51:14Z")
I have an existing Modbus setup with a single PLC being used as a hub for the other PLCs (all information comes into one PLC to talk with Ignition). This is because the other PLCs are in remote locations over radio or cellular modem. To reduce cost of data the cellular modem is polled every 30 seconds unless the remote PLC is being written to. The customer is trying to add another PLC at a site and control it from the central PLC. My problem is I only have 6 more holding registers before I hit the 125 Holding register limit. Can I set up 2 connections to the same PLC to get 250 holding registers? I have to reference this central PLC no matter what because I need information that only it keeps about the other sites to control the new site. ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [December 4, 2023, 4:53pm UTC](https://forum.inductiveautomation.com/t/modbus-opc-ua-connections/82673/2 "2023-12-04T16:53:45Z")
> [@Christopher\_Smith](#): > > before I hit the 125 Holding register limit. What? This is only per request... and only if they are contiguous already. > [@Christopher\_Smith](#): > > Can I set up 2 connections to the same PLC to get 250 holding registers? This would just be 2 requests, on 2 connections instead of 1... ---
**Author:** ![Christopher\_Smith](https://avatars.discourse-cdn.com/v4/letter/c/ce7236/32.png) [@Christopher\_Smith](https://forum.inductiveautomation.com/u/Christopher_Smith)\ **Post date:** [December 4, 2023, 5:17pm UTC](https://forum.inductiveautomation.com/t/modbus-opc-ua-connections/82673/3 "2023-12-04T17:17:34Z")
So Ignition will just make a second request to read the other holding registers? ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [December 4, 2023, 5:25pm UTC](https://forum.inductiveautomation.com/t/modbus-opc-ua-connections/82673/4 "2023-12-04T17:25:28Z")
Yes. ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [December 4, 2023, 8:31pm UTC](https://forum.inductiveautomation.com/t/modbus-opc-ua-connections/82673/6 "2023-12-04T20:31:39Z")
> [@Jasper\_Monroe](#): > > plans for further expansion This makes no sense in this topic. The OP misunderstood the limitations of a single Ignition connection. Full stop.