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Unified HMI tag limits

3/19/2025 10:05 AM	Rate (0)
megaball Advanced Member Joined: 10/10/2019 Last visit: 4/17/2025 Posts: 14 Rating: (1)	Hi, I’m looking for advice on how to properly implement projections with UDTs while ensuring I stay within tag limits. For this project, I’m using an MTP1900 Unified Comfort HMI, which will be connected to at least two PLCs. Each PLC uses different UDTs to control various devices. I’ve already prepared the data in the PLCs and am now starting HMI programming. However, I have some concerns regarding tag calculations. The MTP1900 supports up to 8000 tags per project, but after connecting the PLCs and transferring the required UDTs, TIA Portal is showing 9225 tags in the project. Does this mean I’ve already exceeded the tag limit? Are all 9225 tags counted towards the 8000-tag limit, or is there a distinction between used and total tags? Any insights or best practices for optimizing tag usage would be greatly appreciated. Thanks! https://cache.industry.siemens.com/dl/files/257/109773257/att_1019074/v1/hmi_unified_comfort_panels_operating_instructions_enUS_en-US.pdf

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3/19/2025 10:38 AM	Rate (1)
ElonksuM_SN_BN Regular Expert Joined: 5/6/2022 Last visit: 4/21/2025 Posts: 587 Rating: (122)	Hi megaball, Regarding the tag limit, please note that the compilation of the project takes into account all elements of UDTs, Arrays and Structs which have to be less than 8,000 (soft limit) or 16,000 (hard limit) respectively: "Unified Comfort Panels: Scope of functions with WinCC" In principle, it is generally recommended to stay within the system limits, since full functionality of the system cannot be guaranteed. However, if you do not have any problems with the operation of the panel that you are saturating it, you can work without any problems. As for optimization, there is no documentation as such to be able to offer you some examples of best practice, you would have to review the dimensions of the project before doing a project to be able to review which Siemens equipment is the most suitable for your case. I don't know if anyone in this regard will be able to help you. Best regards!
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