Stiebel Eltron Water Heater Not Heating

Common Symptoms

• Tempra: water flow from hot taps is lower than expected (AFC reducing flow — may be normal)
• Tempra: cold water from hot taps after an E1 or E2 fault code display
• Tempra: no power — LED display is blank
• SHC/SH: storage tank produces cold water even after full recovery time
• SHC/SH: water temperature cannot reach the thermostat set point
• DHC: point-of-use unit produces no heat at a single sink or fixture
• Any model: hot water is lukewarm but not reaching set temperature

Most Likely Causes

1. 1

   Advanced Flow Control (AFC) Reducing Flow — Tempra Normal Operation

   The Tempra's AFC system continuously monitors the heating element's ability to raise inlet water to the set temperature. When flow demand exceeds heating capacity (high flow rate, cold inlet water, or high temperature set point), AFC automatically reduces flow rather than delivering lukewarm or cold water. This is a designed feature — not a fault. No reset is needed. To increase flow: lower the temperature set point, reduce simultaneous fixture use, or upgrade to a higher-kW Tempra model.

2. 2

   E1/E2 Overheat Fault — Tempra

   E1 (upper heating module overheat) and E2 (lower heating module overheat) indicate the thermal cutout tripped due to overheating. Common causes: hard water scale coating the heating modules (reduces heat transfer, causes local overheating), inadequate water flow to the unit (inlet supply valve not fully open), or a failed thermostat. The thermal cutout can be reset with the red reset button on the unit. If E1/E2 recurs, descale the heating modules.

3. 3

   Incorrect or Undersized Breaker — Tempra

   Tempra models require dedicated 240V double-pole breakers ranging from 60A (Tempra 12) to 150A (Tempra 36 Plus). Connecting a Tempra to an undersized breaker will cause the breaker to trip under load, the unit to operate at reduced capacity, or the wire to overheat. Wire gauge must match — Tempra 24 requires minimum 6 AWG; Tempra 36 requires minimum 3/0 AWG. Verify breaker size against the data label on the unit and Stiebel Eltron's installation manual.

4. 4

   Heating Element Failure — SHC/SH Storage Tank

   SHC/SH storage tank elements can fail due to age, hard water scale, or sediment buildup. A healthy element tests 12–16Ω with a multimeter (open circuit = failed). The SHC/SH also has an ECO (energy cutoff) thermostat — a separate high-limit safety device with its own red reset button. If the ECO has tripped, the tank will not heat even if the main thermostat is functional.

5. 5

   Internal Flow Switch Failure — DHC Point-of-Use

   DHC point-of-use units use an internal flow switch to activate heating when water moves through the unit. If the flow switch fails, the unit will not heat regardless of flow rate. DHC units run on 120V or 240V depending on the model — verify the correct circuit voltage is present at the outlet or junction box before suspecting the flow switch.

Quick DIY Checks

1. 1Step 1 — Identify your Stiebel Eltron model: check the data label on the unit. Tempra models are electric tankless with an LED display (e.g., Tempra 12, Tempra 20, Tempra 24 Plus, Tempra 36 Plus). SHC/SH models are storage tanks with a thermostat dial on the outside of the tank. DHC models are compact point-of-use units typically installed under a sink or near a shower. The troubleshooting path differs significantly between series.
2. 2Step 2 — Tempra: check for E1 or E2 fault code on the LED display. If E1 or E2 is displayed, locate the red reset button on the unit (typically behind a small cover on the front panel). Press and release the reset button. Restore flow and check if hot water returns. If E1/E2 clears but returns after a short operating period, the heating module has scale buildup — proceed to descale (Step 5). If the display is blank (no power), go to Step 3.
3. 3Step 3 — Tempra: no display / no power. Go to the electrical panel and locate the dedicated double-pole breaker for the Tempra. Verify the breaker amperage against the unit's data label: Tempra 12 = 60A; Tempra 15 = 60A; Tempra 20 = 100A; Tempra 24 = 100A; Tempra 24 Plus = 100A; Tempra 29 Plus = 125A; Tempra 36 Plus = 150A. A tripped breaker will be in the middle position — push fully to OFF then back to ON. If the breaker trips again immediately under load, stop — do not reset repeatedly. An electrician must inspect the wiring and heating modules for a short.

1. 4Step 4 — Tempra: AFC reducing flow (no error code, but reduced water pressure at hot taps). This is Advanced Flow Control operating normally — the heating element is at capacity for the current conditions. Calculate the temperature rise: subtract the cold inlet water temperature from your target set temperature. Example: target 110°F minus 50°F inlet = 60°F rise needed. At 60°F temperature rise, a Tempra 20 (19.2 kW) can only supply approximately 1.0 GPM. Reduce the temperature set point, close off one fixture, or accept the reduced flow. AFC is not an error — no reset is needed.
2. 5Step 5 — Tempra: descale procedure (if E1/E2 recurs or unit has been in hard water service). Turn off the dedicated breaker. Close the cold water supply valve to the unit. Connect a submersible pump, two hoses, and a bucket filled with undiluted white vinegar or CLR. Stiebel Eltron offers a descale kit (part 234584) designed for Tempra units. Circulate the descaling solution through the unit for 45–60 minutes following the procedure in the Tempra installation manual. Flush with clean water for 10 minutes after descaling. Restore supply and breaker.
3. 6Step 6 — SHC/SH storage tank: ECO thermostat reset. Locate the access panel on the side of the storage tank (typically two panels — upper and lower). Remove the insulation pad behind the panel to expose the thermostat and element assembly. Look for the red ECO (energy cutoff) reset button above the thermostat dial. Press and release it firmly — you may hear or feel a click. Replace the insulation and panel. Restore power and allow 45–60 minutes for full recovery. If the ECO trips again after reset, the element has failed or the thermostat is set too high.
4. 7Step 7 — SHC/SH: element resistance test. With the dedicated breaker off and verified off with a non-contact voltage tester: remove the access panel and insulation. Disconnect the two wires from the element terminals. Set a multimeter to resistance (Ω) mode. Touch the probes to the two element terminals. A good element reads 12–16Ω (the exact resistance depends on element wattage — lower resistance = higher wattage). An open circuit (OL on the multimeter display) means the element has burned out and must be replaced. Also check for continuity between either terminal and the tank body — continuity here means the element has shorted to ground and must be replaced.
5. 8Step 8 — DHC point-of-use: verify circuit voltage and flow switch. Confirm the correct voltage is present at the DHC unit's circuit: DHC-E models use 240V; DHC 3-1/3-2 models use 120V. If no voltage is present at the outlet or junction box, trace the circuit to the breaker panel. If correct voltage is present, open a hot tap fully and confirm water flows through the DHC unit. If the DHC unit receives flow and voltage but produces no heat, the internal flow switch has likely failed — the DHC unit must be replaced as the flow switch is not a user-serviceable component.

Repair vs Replace

Recommended Tools & Parts

• Stiebel Eltron Descale Kit (Part 234584)

  Stiebel Eltron's proprietary descale kit for Tempra electric tankless units, including the circulation pump adapter and recommended descaling procedure. Use in hard water areas when E1/E2 codes recur or the unit has not been descaled in 2+ years.

  $40–$60

  Buy on Amazon →

• Replacement Heating Element for SHC/SH Storage Tank

  Replacement 240V heating element for Stiebel Eltron SHC/SH storage water heater. Order by model number — SHC 6 and SHC 10 use different element specs. A good element tests 12–16Ω; open circuit = failed.

  $25–$60

  Buy on Amazon →

• Digital Multimeter

  Required for resistance testing SHC/SH heating elements (12–16Ω spec) and verifying 240V power at the Tempra's terminal block before any internal work.

  $15–$35

  Buy on Amazon →

• Non-Contact Voltage Tester

  Mandatory safety tool for confirming all 240V power is off at the Tempra or SHC/SH before opening any panel or touching wiring.

  $15–$30

  Buy on Amazon →

Links are Amazon affiliate links (tag: fixitfastai-20). Prices are estimates.

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