Stiebel Eltron Water Heater Not Turning On
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The Short Answer: A Stiebel Eltron electric tankless heater only switches on when enough water flows through it and every one of its circuits has power. If it stays cold, check that all of its breakers are on, open a high-flow tap such as a tub spout, and look at the display or indicator light. A repeat breaker trip, or power and flow with no heat, needs a technician.
Which Stiebel Eltron do you have?
Stiebel Eltron makes small point-of-use heaters for a single sink, larger whole-house units such as the Tempra and Tempra Plus series, and separate heat pump tank models. This page covers the electric tankless units. The rating plate inside or on the side of the cover shows the voltage, kilowatts, and number of circuits. Whole-house models usually need two or more dedicated 240-volt circuits; small sink units may need one.
Three things must all be true for it to heat
- Power on every circuit. On multi-circuit models, the display or controls can stay alive while a heating circuit is off, so a heater that “looks on” may still produce cold water.
- Flow above the switch-on point. The heater senses flow and does nothing until it passes a minimum. A partly closed valve, a clogged inlet screen, or a very low-flow faucet or shower head can stay below it. Stiebel’s Tempra specifications (opens in a new tab) also show how much temperature rise each model can deliver at a given flow.
- No safety limit tripped. These heaters have overheat protection that cuts power if the heating chamber gets too hot, for example after a run with air in the chamber.
Match the symptom
| What you see | Likely direction | Next step |
|---|---|---|
| No display or light at all | No power to the unit | Check breakers and any disconnect |
| Display on, water cold at every tap | One heating circuit off, low flow, or a tripped limit | Check all breakers; test at a tub spout |
| Works at the tub, not at a sink | That faucet is below the switch-on flow | Clean the aerator; see below |
| Warm, not hot, in winter | Cold incoming water exceeds the model’s temperature rise | Lower the flow; see sizing |
| Worked until plumbing work or a water shut-off | Air in the heating chamber, or debris in the inlet screen | Run hot taps; call if no change |
| A breaker trips | Short or ground fault in the heater or wiring | Leave it off; call |
What you can check safely
- Every breaker for the heater. Look for any that sit in the middle position. Reset a tripped breaker once. If it trips again, leave it off.
- Flow at a large fixture. Open the tub spout fully on hot. If the heater activates there but not at the kitchen faucet, the faucet’s aerator may be clogged or too restrictive; clean it.
- Valves. Make sure any shut-off valves near the heater are fully open.
- After plumbing work, run hot water at several taps to clear air before expecting heat. An electric tankless heater should be full of water before it heats.
Do not open the cover to reach the inlet screen, limit switch, or wiring. On these units, those parts sit next to high-current terminals.
What the technician will check
An electrician or a technician familiar with electric tankless units will check voltage at each circuit, the condition of the heating elements and their insulation, the flow sensor, and the safety limit. They will also confirm the wire size and breaker rating match the installation instructions; upsizing a breaker to stop trips is never the answer. Flow sensors, limit switches, and heating elements are replaceable on many models; a heater with a cracked or leaking chamber is usually replaced.
For related symptoms, see electric tankless water heater goes cold after a few minutes and tankless water heater keeps tripping the breaker.
Frequently Asked Questions
Q: Why does my shower stay cold while the kitchen tap gets hot? A: The shower may be a low-flow head, or its mixing valve may draw so little hot water that flow through the heater stays under the switch-on point. Test with the shower set to full hot for a moment; if it heats, the fixture is the limit.
Q: Can the inlet screen stop the heater from turning on? A: Yes. A clogged screen reduces flow below the activation point. On most models it sits under the cover, so have a technician clean it.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- Stiebel Eltron: technical documents (opens in a new tab)Product-specific manuals and specifications.
- Stiebel Eltron: Tempra engineering specifications (opens in a new tab)Flow, temperature-rise and power relationship; product ratings apply only to the named Tempra models.
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