Alto-Shaam Combi Oven Error Code E51: No Water in Steam Generator
E51 No Water in Steam Generator means the lower level probe, B2, did not sense water within 5 minutes after fill valve Y1 opened on a roll-in oven. Press the Start icon to acknowledge it and check the water supply. If it returns, a technician should check the fill and drain parts.
Medium: steam cooking is affected until the generator can fill.
- Code
- E51
- 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 E51 mean?
The steam generator needs water before it can heat. After fill valve Y1 opens, the control watches the lower level probe, B2, and expects water to reach it quickly. If B2 is still dry after 5 minutes, the control posts E51 No Water in Steam Generator. This is a tougher test than E01, which waits for the upper probe, B1. The manual lists eight causes: the water supply is shut off, the pressure is low, calcium has built up on the probe, Y1 is not working, the drain pump elbow is leaking, the drain cap is missing, the drain pump is failing, or the relay board has failed. The manual's table applies this entry to roll-in models. Pressing Start acknowledges the message and the oven then tries to return to normal operation, but the next fill repeats the test, and the code returns if water still cannot build up in the generator.
Affected models and control systems
The roll-in CT PROformance and CT Classic combis. On the CT Express the manual shows this as No Water In Boiler and does not limit it to roll-in ovens.
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
- E51 No Water in Steam Generator on the display
- Steam programs not starting
- Fill valve clicking with no water level showing
Possible causes
Listed in Alto-Shaam's documentation
- Water supply shut off
- Water pressure low
- Calcium build-up on the level probe
- Fill solenoid Y1 malfunction
- Drain pump elbow leaking
- Drain cap missing
- Drain pump malfunction
- Relay board malfunction
Other likely causes — what usually sits behind error code E51 on this control. A technician confirms which one it is before any part is replaced.
- A fill line check valve stuck so water cannot reach the generator
- Water leaking out through the drain faster than the fill can raise the level
Safe checks before calling for service
- Press the Start icon once to acknowledge E51.
- Check that the water valve behind the oven is fully open and the hose is clear.
- Look for water on the floor that would suggest a drain leak.
- If E51 returns, note whether E01 appeared before it.
How a technician diagnoses error code E51
- Read the code and confirm the oven is a roll-in model.
- Measure water pressure at the oven inlet.
- Inspect drain cap, elbow and pump for leaks.
- Check the level probes for scale and test fill valve Y1.
- Test the relay board outputs; replace parts only after the tests.
- The generator and its drain sit at the bottom of the oven with live wiring beside hot water.
- Level probe and valve tests need a meter.
- A drain leak shows up only with the panels off.
How error code E51 differs from similar codes
E01 waits for the upper probe B1 and E51 for the lower probe B2; both follow a fill from valve Y1.
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
How is E51 different from E01?
E51 reports the lower probe B2 dry after 5 minutes; E01 reports the upper probe B1.
Does E51 always mean no water supply?
No, drain leaks and scale are on the list too.
Is E51 on table-top ovens?
The CTP and CTC table limits it to roll-in models.
Need help with Alto-Shaam error code E51?
A technician confirms the cause on site and gives you the price in writing before any work starts.