Alto-Shaam Combi Oven Error Code E13: Steam Generator Temperature High
E13 Steam Generator Temperature High means probe B4 in the steam generator read above 248 F (120 C) for over 25 seconds. Press the Start icon to acknowledge it, and plan a descale and element check with a technician.
Medium: steam cooking is at risk, and a stuck steam contactor could overheat the generator.
- Code
- E13
- Maker
- Alto-Shaam
- Equipment
- Combi ovens
- Applies to
- Combitherm CT PROformance (CTP) and CT Classic (CTC); Combitherm CT Express / ESi / CCi (older 4-10 and 4.10 units; boiler or generator electric/gas)
What does Alto-Shaam error code E13 mean?
A steam generator should never get much hotter than the boiling point of water, because the water inside absorbs the heat. Probe B4 watches its temperature. If B4 reads above 248 F (120 C) for more than 25 seconds, the control posts E13 Steam Generator Temperature High. The usual reason is that the heat is not being carried away: calcium build-up in the generator or on the water level probe insulates the element and lets the metal run hot, or the level probe reads wrong and the water is lower than it should be. The other two causes in the manual are a steam element contactor that is locked on, so the element never switches off, and a B4 probe that is giving a bad reading. Pressing Start acknowledges it and the oven tries to return to normal operation, but scale will bring the temperature right back at the next steam call.
Affected models and control systems
Six sizes of CT PROformance and CT Classic combi ovens, 6-10 to 20-20, both electric and gas. On the CT Express line the manual calls the same condition Boiler Temperature High.
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
- E13 Steam Generator Temperature High on the display
- Steam output falling off in steam programs
- A rumbling or knocking sound from the generator in the days before
Possible causes
Listed in Alto-Shaam's documentation
- Calcium build-up on the water level probe
- Calcium build-up in the steam generator
- Steam element contactor locked on
- B4 probe malfunction
Other likely causes — what usually sits behind error code E13 on this control. A technician confirms which one it is before any part is replaced.
- Water treatment that has stopped working, letting hard water scale the generator quickly
- Descaling skipped for months in a high-volume kitchen
Safe checks before calling for service
- Press the Start icon once to acknowledge E13.
- Stop running steam programs and let the oven cool.
- Ask whoever maintains the water filter when its cartridge was last changed.
- Report how long it has been since the generator was descaled.
How a technician diagnoses error code E13
- Read the code and ask about the water treatment and descale history.
- Inspect the generator and the level probe for scale after the oven has cooled.
- Descale the generator and level probe as the manual directs.
- Check the steam element contactor for stuck contacts and the B4 probe with a meter.
- Replace the contactor or B4 only if it fails the test after descaling.
- Descaling uses acid solutions and a hot generator that can scald.
- The steam contactor and element carry live 208-240 V and high current.
- Choosing between scale, a bad probe and a stuck contactor means measuring each.
How error code E13 differs from similar codes
E13 is a steam side check; E11 watches the cavity probe N6 and E02 watches the relay board.
Technical reference
- Maker documentation
- Alto-Shaam owner support
- Edition
- MN-35949 Rev 08 03/22
- Models / control
- Combitherm CT PROformance (CTP) and CT Classic (CTC); Combitherm CT Express / ESi / CCi (older 4-10 and 4.10 units; boiler or generator electric/gas)
- Section
- Error Codes, pp. 25-31
- 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 E13 caused by hard water?
Calcium build-up in the generator and on its level probe is two of the four listed causes.
Will descaling fix it?
If scale was the cause, yes; if the contactor is stuck or B4 is bad, the temperature will return.
Can I use the oven without steam?
The oven tries to return to normal operation, but steam programs should be avoided until it is repaired.
Need help with Alto-Shaam error code E13?
A technician confirms the cause on site and gives you the price in writing before any work starts.