1. Overview of WinCC V7 Station Models
Siemens SIMATIC WinCC V7 (current line: V7.5 / V7.4 SP1) supports three fundamentally different HMI station roles inside a single PCS 7 or S7-based plant. The role a PC plays is selected on the ES, written into the project type, and enforced at runtime by the WinCC Explorer together with the license keys on the corresponding WinCC license USB stick / Automation License Manager:
- Single-User Station – A standalone OS that connects directly to one or more PLCs, owns its own project on its own hard drive, and cannot publish data to any other WinCC client.
- Server (Multi-User Server) – An OS that owns the master project, holds all tags, archives, alarms, and connections to the PLCs, and serves those data via TCP/IP to attached clients.
- Client – An OS that has no PLC connection of its own, instead displays the project that is loaded on the server (or on one of two redundant servers).
A Engineering Station (ES) is a separate, fourth role: it is the PC that runs SIMATIC Manager (or PCS 7 Engineering) and WinCC Explorer in configuration mode. The ES is the only station from which a Multi-User project can be edited and downloaded. In a redundant 2 × Server + n × Client architecture, the ES is usually configured as a Single-User station, or it is connected as an additional WinCC Client with RC license against the active server.
2. Why Single-User is NOT a Server
A common misunderstanding is that a Single-User station is "just a small server." It is not. The WinCC project type is set on the ES by right-clicking the OS object and choosing Properties > Type:
- Single-User project – Cannot host a client. There is no WinCC server service listening on TCP port 0 (or whatever is configured in the client/server channel).
- Multi-User project (Client / Server) – The server channel is published; clients attach to it.
This means four single-user stations + one PLC means four independent S7 connections are opened from four different PCs against one S7-414-5H. Each station fetches its own data, owns its own archive, and the PLC is loaded with four times the communication load. By contrast, one server + four clients opens only one set of S7 connections (or two sets if the servers are redundant) and the four clients receive the already-acquired data over the LAN.
3. Reference Architecture: 1 × ES, 2 × Server (redundant), 4 × Client
The reference for this guide is the architecture requested in the field report:
- 1 × S7-414-5H redundant controller pair, MLFB example
6ES7414-5HM06-0AB0(Firmware V6.x), with two sync modules and a PROFINET / Industrial Ethernet CP, e.g.6GK7443-1EX30-0XE0(CP 443-1). - 1 × Engineering Station running SIMATIC Manager / STEP 7 V5.7 (or TIA V18 for non-PCS 7 use cases) plus WinCC V7.5.
- 2 × OS Servers in redundant configuration with WinCC Redundancy.
- 4 × OS Clients (operator stations), each licensed with RC128 or Runtime Client.
The redundant pair is required for the S7-414-5H H-CPU: the OS servers perform the redundant partner switchover in lockstep with the CPU's H-system switchover so that operators never see a black screen when the primary controller goes to STOP.
4. WinCC V7 License Catalog and Per-Station Mapping
The license model for WinCC V7.5 licensing is built around four axes: tag count, server / client / single role, redundancy, and optional packages. The following table consolidates the required licenses for each PC in the reference architecture.
| Station | Required Licenses | Notes |
|---|---|---|
| OS Server #1 (Master) | WinCC RT 512 / 1024 / 2048 (per tag count) + Server license + Redundancy license | Tag count = total internal + process tags. Archive Tag Logging up to 512 tags is included; above this an Archive license is required. |
| OS Server #2 (Standby) | WinCC RT (same size as Server #1) + Redundancy license | Only ONE Server license is needed for the pair; the redundancy license covers both. |
| OS Client 1–4 | WinCC RC128 or WinCC Runtime Client | RC128 is sufficient for the number of internal tags displayed; RC Client is unlimited. |
| Engineering Station | WinCC Configuration (size matched to project) + Server license + Redundancy license if the ES is used to compile and download the multi-user server project | If the ES is only a configuration tool and runs no Runtime, the configuration license alone is enough. |
Tag-count license tiers (per the official WinCC V7.5 price list) are: 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 100 000, 150 000, 256 000. The runtime cost grows stepwise, so it is a real engineering decision whether to design a project with 1024 or 2048 tags.
5. SIMATIC NET Connection Limits and S7-414-5H Sizing
Each OS server connects to the S7-414-5H through SIMATIC NET. The default bundle is SOFTNET-IE S7 (single PLC connection) or SOFTNET-IE S7 Extended, while for chassis-mounted industrial PCs the CP 1623 or CP 1628 with HARDNET-IE S7 is preferred for OPC UA and S7 redundancy.
Connection limits per channel:
- SOFTNET-IE S7: 1 S7 connection (per license).
- SOFTNET-IE S7 Extended: up to 8 S7 connections.
- SOFTNET-IE S7 V16+ Powerpack: 16 / 64 / 128 / 256 S7 connections.
- CP 1623 / CP 1628 (HARDNET-IE S7): up to 128 S7 connections per CP.
For the S7-414-5H in this example, two OS servers + one ES = 3 S7 connections to the H-CPU. Because H-CPUs only expose a single logical connection per partner, each partner (OS server) must be set up as a separate passive connection in the H-CPU's NetPro configuration. A SOFTNET-IE S7 Extended license per server is more than enough; the CP 1613 / 1623 is only needed if you also have non-S7 (e.g. PROFINET CBA, OPC) traffic.
6. Performance & Cost Comparison: 4 × Single-User vs 1 × Server + 4 × Client
| Criterion | 4 × Single-User | 1 × Server + 4 × Client |
|---|---|---|
| Number of S7 connections to PLC | 4 (one per station) | 1 (server only) |
| PLC cycle / communication load | 4× | 1× |
| Archive redundancy | None (each PC has its own) | Automatic via WinCC Redundancy |
| Client simultaneous updates | 4 independent update cycles | Server multicasts updated data once |
| License cost (approximate relative) | 4 × RT(512) = high | 1 × RT(512) + 4 × RC128 = lower |
| Engineering complexity | 4 separate projects, 4 downloads | 1 server project, clients thin |
The conclusion is unambiguous: the Client / Server model is both more cost-effective and more performant for any plant with more than one operator station. The single-user model only makes sense for small standalone machines, service laptops, or sandbox/training stations.
7. Configuring the Engineering Station
The ES is the only station that owns the project source. To configure a redundant 2-Server / 4-Client / 1-ES WinCC V7 project:
- Install STEP 7 V5.7 (or PCS 7 V9.x), WinCC V7.5, and SIMATIC NET V16+ on the ES. Use the same language (default English) on every PC to avoid text database mismatches.
- In SIMATIC Manager, create an S7 project and add the H-station S7-414-5H with both racks and the two CP 443-1 modules.
- Insert an OS object in the plant view, change its Type from "Single-User" to "Multi-User (Server)", and assign a target computer name, e.g.
OS_SERVER_1. - Insert a second OS, set the same project type, target computer
OS_SERVER_2, and tick Redundant in the OS object properties. - Insert 4 × OS objects, change each type to Client, and enter the preferred server name in Server Assignment (WinCC Explorer > Computer > Properties > Server).
- Configure the S7 connections: in NetPro on the ES, open the H-station and create three passive S7 connections (one each from SERVER_1, SERVER_2, and ES).
- Compile the OS, download the server project to OS_SERVER_1, then to OS_SERVER_2. The redundancy license on each server is verified at first Runtime start.
- Activate the project on the servers. The clients should now auto-locate the active server (default = OS_SERVER_1) and start their picture tree.
The ES itself should be set to a Single-User project in its own right so that engineers do not inadvertently affect the live server. To make configuration-only changes to the server project, the engineer opens it on the ES, edits, recompiles, and performs a Delta Download to the standby server first, then the master.
8. Tag, Archive, and Optional License Mapping
The default archive (Tag Logging) supports up to 512 archive tags per server. Above that you need a separate Archive license. If you also use User Archives (recipe sets, batch records, parameter sets) you need the optional User Archive license. If you use Audit for FDA / 21 CFR Part 11 trails, you also need the WinCC/Audit option.
| Function | Built-in | Additional license needed when… |
|---|---|---|
| Internal + process tags | Up to 128 (smallest RT128) | Tag count exceeds RT tier |
| Tag Logging archives | ≤ 512 tags / server | > 512 → "Archive" license |
| Alarm Logging | Included in RT | n/a |
| User Archives | Not included | Always optional license |
| Redundancy | Not included | Always (per server pair) |
| SIMATIC NET S7 connections | 1 (SOFTNET-IE S7) | > 8 → HARDNET-IE S7 or Powerpack |
| Server (multi-user publish) | Not included in RT | Always if the OS is a server |
9. Project Type, Default Behavior, and the "Demo Mode" Pitfall
An OS inserted from the SIMATIC Manager component library is by default a Multi-User / Server project. If you do not own a Server license, WinCC Runtime will start in Demo Mode and stop after one hour with the explicit license error License missing: WinCC Server. The same applies to the Redundancy license, the Archive license, and any of the optional packages.
To force a project to behave like a single-user one (and therefore avoid the Server license requirement) you edit the OS object property Type = Single-User on the ES, recompile, and re-download. After that change, the OS has no listening server channel and any attempt to attach a WinCC client will fail with Connection to server refused at the WinCC channel DLL layer.
10. Commissioning and Verification Steps
- On each server, run Automation License Manager, confirm that the Server, Redundancy, and RT license keys are present and bound to the correct Volume Serial Number.
- From the ES, in WinCC Explorer, open the project on
OS_SERVER_1, right-click Server > Status, and confirm that the H-CPU connection is "OK" and that redundancy status is "Master". - Repeat on
OS_SERVER_2. It should report "Standby". - Power down
OS_SERVER_1. Within ~5 s the clients should reattach toOS_SERVER_2and the alarm line should display "Redundancy: Server 1 failure". - Trigger an S7-414-5H H-system switchover (e.g. by stopping the primary CPU). The OS servers should follow within a few seconds; no client should freeze.
- Check the WinCC channel diagnostics in WinCC Explorer > Tools > Channel Diagnosis. S7 connection diagnostic value =
1(OK) on every active connection.
11. Troubleshooting Matrix
| Symptom | Likely root cause | Fix |
|---|---|---|
| Runtime stops after 1 h with "missing Server license" | OS is a Multi-User project but no Server license key on the PC | Install Server license, OR change OS type to Single-User |
| Clients show "no connection to server" | Server service not started, or different WinCC versions, or firewall blocking TCP 0/0 (default) | Verify WinCC Server service started, equal WinCC build numbers, allow WinCC.exe and CCEServer.exe through the firewall |
| One client shows picture, others stay black | Client license tier exceeded, or archive tag limit on that client | Upgrade RC128 → RC Client, or remove redundant client connections |
| Redundancy does not switch | Redundant partner path not set, or both servers on the same physical NIC | Use a dedicated crossover cable / second NIC for redundancy heartbeat (default port 0) |
| S7-414-5H connection stays in "Disconnect" | Wrong connection resource on the H-CPU, or CP 443-1 IP mismatch | Open NetPro on the ES and verify that each server's passive connection slot is unique, and that the CP 443-1 IP is reachable from the server VLAN |
| ES cannot edit the server project | ES is a Client with RC, not the original SIMATIC Manager ES | Recompile the master project only on the SIMATIC Manager ES, not on a remote RC client |
12. FAQ
Is a Single-User station implicitly a server?
No. A Single-User WinCC station has no listening server channel and cannot host a WinCC client. It connects to the PLC on its own and displays its locally stored project. Only a Multi-User OS with the Server license can publish data to clients.
Which is cheaper for four operator stations, four Single-User OS or one Server + four Clients?
One Server + four Clients is cheaper on licenses, more efficient on PLC communication (one set of S7 connections instead of four), and is the only configuration that supports redundant archiving. Four Single-User OSs are only justified for independent islands or service stations.
What licenses does the Engineering Station need in a 2-Server / 4-Client / 1-ES WinCC V7 project?
The ES needs a WinCC Configuration license matching the project's tag count, a Server license, and a Redundancy license if you compile the multi-user server project on the ES. If the ES is a pure configuration PC and never runs the WinCC Server service, the configuration license alone is enough.
How many SIMATIC NET S7 connections does a 2-Server + ES system need against an S7-414-5H?
Three S7 connections (one from each of OS Server 1, OS Server 2, and the ES). On each server, a SOFTNET-IE S7 Extended (up to 8 connections) is more than sufficient; HARDNET-IE S7 is only required when the same PC also serves OPC UA / PROFINET traffic or when more than 8 PLC connections are needed.
Can an RC Client be used as the Engineering Station?
No. An RC Client can open the project that lives on the server and edit pictures, scripts, and tags, but it cannot run SIMATIC Manager, cannot create or modify integrated PLC + WinCC projects, and cannot download to the PLC. The ES must be a true STEP 7 / WinCC engineering PC with a Configuration license.
What happens if I run a Multi-User server without the Server or Redundancy license?
WinCC Runtime starts in Demo Mode and stops after one hour. The system log shows "License missing: WinCC Server" (or "WinCC Redundancy"). To clear the alarm, install the missing license on the affected PC and restart the WinCC Runtime.