Alto-Shaam CT Express Combi Error Code E98: Unit Mismatch
E98 RB is in Celsius and DB is in Fahrenheit means the relay board is set to Celsius while the display board is set to Fahrenheit. Change the unit configuration in the setup menu so both agree.
Low: a configuration mismatch that an operator can usually correct from the setup menu.
- Code
- E98
- 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 E98 mean?
The CT Express keeps a temperature unit setting on both the relay board (RB) and the display board (DB), and they must match. At start-up the boards compare them. If the relay board is in Celsius and the display board in Fahrenheit, the control posts E98 RB is in Celsius and DB is in Fahrenheit. The manual's remedy is a configuration change: change the unit configuration in the setup menu. This is the one E-code in the list that an operator can often clear with a setting. If it persists after the unit is changed, the manual points to hardware: a defective ribbon cable, a defective relay board connector or a defective display board connector. The listed causes also include a control programming issue, which is the mismatch itself. E99 is the same message with the units the other way around.
Affected models and control systems
CT Express combis: 4-10ESi, 4-10ESiVH, 4-10CCi, CTX4-10E, CTX4-10EC and CTX4-10EVH.
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
- E98 RB is in Celsius and DB is in Fahrenheit on the display
- Message after a settings change or board replacement
- Temperatures displayed in the wrong unit
Possible causes
Listed in Alto-Shaam's documentation
- Control programming issue (unit setting mismatch)
- Ribbon cable defective
- Relay board connector defective
- Display board connector defective
Other likely causes — what usually sits behind error code E98 on this control. A technician confirms which one it is before any part is replaced.
- A replacement board shipped set to the other temperature unit
- A settings reset that returned only one board to its factory setting
Safe checks before calling for service
- Open the setup menu and look at the unit configuration.
- Set the unit to the one you want, Celsius or Fahrenheit, and save.
- Turn the oven off and on to check that E98 is gone.
- If E98 persists, tell the technician which unit you chose.
How a technician diagnoses error code E98
- Read the code and check the unit setting on both boards.
- Set the unit configuration to a single value and restart.
- If the message remains, inspect the ribbon cable between display and relay boards.
- Check the board connectors for corrosion or looseness.
- Replace the cable or board only after the settings are consistent.
- Persistent mismatch can mean a ribbon cable or connector problem behind the panel.
- Board connectors are near live voltage.
- Replacing a board needs the oven's settings reloaded.
How error code E98 differs from similar codes
E99 is the same mismatch reversed: relay board in Fahrenheit and display board in Celsius.
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
Which unit should I pick?
Either; the point is that both boards use the same one.
Is E98 a hardware problem?
Usually it is a setting, unless it persists.
What if I did not change anything?
A board replacement or reset can leave the units different.
Need help with Alto-Shaam error code E98?
A technician confirms the cause on site and gives you the price in writing before any work starts.