Code: 23🧺 Smeg Dishwasher

Smeg Dishwasher Error 23 (Er 23): Boiler Not Heating (Commercial Models)

Reviewed 2026-10-26 · Based on 3 manufacturer & service sources

What the code means

In Smeg's commercial dishwasher manuals the display fault table lists Er 23 as "Boiler does not heat up as expected" (for example the undercounter and hood-type manual on doc.smeg.it) and the newer SP5/SP6 manual lists 23 as "Boiler heating failure". The SP5/SP6 technician table explains the logic: the alarm is triggered if the boiler temperature has not risen by at least 2 degrees above the lowest temperature recorded during the time-out, which is 150 seconds on three-phase machines and 300 seconds on single-phase machines. It is only active while the boiler is in its heating phase. Smeg lists the possible causes as a boiler pressure switch fault, temperature probe fault, heating element fault, or a fault in the control unit or its control relay. The older manual adds that the problem can happen because water is continually entering the tank (the same causes as Er 05, the tank fill fault), and warns that a burnt-out boiler element is often the result of the element running with no water in the boiler because the boiler pressure switch is reporting full when the boiler is actually empty. In that case the boiler air trap and pressure switch should be checked and replaced if needed, or the new element will fail too. Er 24 (boiler probe), Er 25 (boiler fill) and Er 26 (boiler drain) are separate codes.

Likely causes

Safe DIY checks

⚠ Before you start

Turn off power at the furnace/HVAC service switch and the breaker before opening panels. Shut the gas valve before any work near the burners, and never disconnect or alter the gas line. If you smell gas, leave the house and call your gas utility.

  1. Switch the machine off at the main switch, wait a few minutes and switch it back on. Smeg's manuals say to restart first and follow the table only if the fault persists.
  2. Check the water supply tap is fully open and the inlet water filter is clean, since a fill problem can feed into a boiler heating fault.
  3. Look for clogged rinse nozzles on the rinse arms and clean them.
  4. If 23 comes back after a restart, stop there: Smeg's user table says to contact After-sales Service for 23. Element, thermostat, contactor and pressure-switch checks involve mains wiring and should be done by a qualified technician.

🛠 When to call a pro

  • Error 23 returns after a restart: Smeg's user table says to contact After-sales Service.
  • The boiler element has failed: the technician should also check the boiler pressure switch and air trap, or the new element can burn out too.
  • Rinse water is cold or the machine is stuck waiting for temperature during service.
  • The machine is three-phase or hard-wired, which needs an electrician or commercial dishwasher technician.

Parts that commonly fix it

Always match the part number to your exact model.

⚙

Dishwasher boiler heating element

Match the exact Smeg commercial model and voltage; have the pressure switch checked at the same time.

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Boiler pressure switch

If it reports full with an empty boiler, Smeg says to check and replace it along with the air trap.

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⚙

Boiler temperature probe

Only if testing shows a faulty or badly positioned probe.

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Sources

  1. Smeg commercial undercounter and hood-type dishwasher manual, malfunctions shown on the display (Er 23 boiler does not heat up as expected; causes and air trap/pressure switch warning)
  2. Smeg SP5/SP6 commercial dishwasher manual, technician fault table (23 boiler heating failure, 2 degree rise within 150 s three-phase / 300 s single-phase) and user table (contact After-sales Service)
  3. Smeg commercial dishwasher manual (same Er 23 table)

Last reviewed 2026-10-26. Always confirm against the manual for your exact model number.