# Issue facing connection with node-red-contrib-s7 node while connecting siemens s7 200 plc

**URL:** <https://discourse.nodered.org/t/issue-facing-connection-with-node-red-contrib-s7-node-while-connecting-siemens-s7-200-plc/100233>\
**Category:** Industrial\
**Created:** [24 January 2026 07:42 UTC](https://discourse.nodered.org/t/issue-facing-connection-with-node-red-contrib-s7-node-while-connecting-siemens-s7-200-plc/100233 "2026-01-24T07:42:40Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Nilava1992](https://avatars.discourse-cdn.com/v4/letter/n/34f0e0/32.png) [@Nilava1992](https://discourse.nodered.org/u/Nilava1992)\
**Post date:** [24 January 2026 07:42 UTC](https://discourse.nodered.org/t/issue-facing-connection-with-node-red-contrib-s7-node-while-connecting-siemens-s7-200-plc/100233/1 "2026-01-24T07:42:40Z")

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Hi,  
I’m facing a strange issue in **Node-RED** related to **Siemens S7-200 communication**.

I have an existing Node-RED flow with S7 nodes that connects properly to a Siemens S7-200 PLC. As long as I **don’t modify the flow** , the connection remains stable.

However, **as soon as I make any change** to that flow—such as:

- adding another S7 node
- adding or modifying an S7 variable
- or editing the existing S7 configuration

the **S7 connection gets closed / disconnected** immediately.

Important points:

- The problem occurs only on an **ELPRO industrial panel PC** running **Windows 10 Pro**.
- The **same modified flow works perfectly fine on another PC**.
- The original (unchanged) flow also works fine on the ELPRO PC until any modification is made.

Has anyone faced a similar issue on industrial PCs or Windows 10 systems?  
Any ideas on what could cause Node-RED to drop the S7 connection only after flow changes?  
[node-red flow which is running.json](https://discourse.nodered.org/uploads/short-url/iu8orVgXCCh6I5NSSvMRoyDo2KC.json) (6.4 MB)  
[node-red flow which to be run.json](https://discourse.nodered.org/uploads/short-url/9LpfNiw7Fy1JyDGaayoZoWvffJo.json) (7.7 MB)

Thank you

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**Author:** ![Steve-Mcl](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/steve-mcl/32/4826_2.png) [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)\
**Post date:** [24 January 2026 08:14 UTC](https://discourse.nodered.org/t/issue-facing-connection-with-node-red-contrib-s7-node-while-connecting-siemens-s7-200-plc/100233/2 "2026-01-24T08:14:52Z")

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What kind of deploy are you using? Full? Flows? Nodes?

I recommend using changed nodes only deploy mode when networked connections are used (to avoid destroying and reconnecting) It won't solve all issues but will reduce friction until you figure out the real issue.

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**Author:** ![Nilava1992](https://avatars.discourse-cdn.com/v4/letter/n/34f0e0/32.png) [@Nilava1992](https://discourse.nodered.org/u/Nilava1992)\
**Post date:** [24 January 2026 09:03 UTC](https://discourse.nodered.org/t/issue-facing-connection-with-node-red-contrib-s7-node-while-connecting-siemens-s7-200-plc/100233/3 "2026-01-24T09:03:44Z")

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I was using **Full Deploy**.

To isolate the issue, I also tried bypassing deploy completely by **manually replacing the `flows.json` file** in the `.node-red` folder with the other flow and then restarting Node-RED. In this case as well:

- the **old flow connects successfully** to the PLC
- the **other (modified) flow fails to connect**, even though no deploy action is involved

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**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [25 March 2026 09:04 UTC](https://discourse.nodered.org/t/issue-facing-connection-with-node-red-contrib-s7-node-while-connecting-siemens-s7-200-plc/100233/4 "2026-03-25T09:04:33Z")

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