Alto-Shaam CT Express Combi Error Code E100: Board Version Mismatch
E100 means the display board (DB) and the relay board (RB) run different software versions, and the display board raised the alarm. Perform the software update again, and check the ribbon cable, compact flash card and connectors.
High: mismatched software can stop the oven from starting.
- Code
- E100
- Maker
- Alto-Shaam
- Equipment
- Combi ovens
- Applies to
- Combitherm CT Express / ESi / CCi (older 4-10 and 4.10 units; boiler or generator electric/gas)
What does Alto-Shaam error code E100 mean?
The CT Express has a display board (DB) and a relay board (RB), and their software must be the same version to work together. When the display board checks and finds a different version on the relay board, it posts E100 DB version is not equal to RB version. Error generated by DB. The usual cause is a software update that did not finish on both boards, which the manual lists first as a failed software update. The other causes are a defective ribbon cable, a defective compact flash card, and defective board connectors. The compact flash card carries the update, so a bad card can leave one board updated and the other not. The manual's remedy is to perform the software update again. This is the display board's report of the mismatch; E101 is the same mismatch reported by the relay board. On the CT PROformance and CT Classic ovens, E100 means a timed-out maintenance reminder, a different message.
Affected models and control systems
Combitherm CT Express ovens only (4-10ESi, 4-10ESiVH, 4-10CCi, CTX4-10E, CTX4-10EC, CTX4-10EVH). Other Combitherm series use E100 for a different message.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- E100 board version message on the display
- Oven not starting normally after a software update
- Message returning at start-up
Possible causes
Listed in Alto-Shaam's documentation
- Failed software update
- Ribbon cable defective
- Compact flash card defective
- Board connectors defective
Other likely causes — what usually sits behind error code E100 on this control. A technician confirms which one it is before any part is replaced.
- An update interrupted by a power dip while the oven was updating
- A compact flash card removed too soon after the update
Safe checks before calling for service
- Turn the oven off and on once.
- Do not remove the compact flash card or open the control panel.
- Note whether a software update was done recently and by whom.
- Tell the technician the date of the update and whether E101 also appears.
How a technician diagnoses error code E100
- Read the code and check whether E101 appears too.
- Confirm the software versions on both boards.
- Repeat the software update with a known-good compact flash card.
- Inspect the ribbon cable and board connectors.
- Replace the card or cable if the update fails again.
- Software updates need the right files, a compatible card and a stable supply.
- The connectors sit behind the panel near live voltage.
- An interrupted update can leave a board unable to start.
How error code E100 differs from similar codes
E101 reports the same mismatch from the relay board; on PROformance and Classic ovens E100 is a maintenance reminder.
Technical reference
- Maker documentation
- Alto-Shaam owner support
- Edition
- MN-36008 (Rev. 9) 03/16
- Models / control
- Combitherm CT Express / ESi / CCi (older 4-10 and 4.10 units; boiler or generator electric/gas)
- Section
- Section C, Error Codes, pp. C-3 to C-8
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
Related Alto-Shaam combi oven error codes
Is E100 the same as E101?
They describe the same mismatch, reported by different boards.
What does failed software update mean?
One board may have been updated and the other not.
Can I update it myself?
The update needs the right files and card, so a technician should do it.
Need help with Alto-Shaam error code E100?
A technician confirms the cause on site and gives you the price in writing before any work starts.