F.1008 on a Viessmann One Base: Number of supported devices on main control unit exceeded
Short answer
On a Viessmann heat pump, F.1008 means: Number of supported devices on main control unit exceeded. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Number of supported devices on main control unit exceeded.
Part involved: Number of supported devices on main control unit exceeded.
When it shows: System characteristics: The CAN bus subscriber connected last is not recognised by the (lead) heat pump (main appliance).
Likely causes:
- The max. number of 15 additional CAN bus subscribers (e.g. lag heat pump and/or other appliances) has been exceeded.
- Further messages: I.96, I.97, I.98.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: Not stated per code in Viessmann document 6199893 GB 01/2026 (VSA00009).
Manual reset: User may acknowledge via HMI after noting the code (6249162 p.57); the message returns if the cause persists.
What you can check
- On the HMI, tap the message and "?" to read the system characteristics and Viessmann's user tips; note the code (e.g. F.xxx) and text for your contractor (operating instructions 6249162 p.57).
- Acknowledge the message once via the HMI; do not acknowledge fault messages several times in quick succession (6249162 p.58) - notify your contractor.
What the engineer will check
- Check the number of additional CAN bus subscribers (e.g. lag heat pump and/or other appliances).
- Disconnect the unsupported CAN bus subscriber from the CAN bus system.
- Check whether this disconnected CAN bus subscriber can be connected to a main appliance in another CAN bus system.
Who to ask for: Viessmann-trained heat pump installer/service engineer.
Sources
- Service instructions for contractors: Heat pumps in monoblock design incl. hybrid – System configuration and diagnostics (Vitocal 150-A/151-A/250-A/252-A, IDU-A, AWMOF-151/251, AquaSnap 30AWH, BI-BLOC R290) (6199893 GB 01/2026) ↗ · 6199893 GB 01/2026 (VSA00009) · page 177 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026