E2 = element / power fault. The control detects element resistance out of spec OR voltage out of range. Several distinct underlying causes.
Diagnostic sequence
1. Verify all breakers are on
Tempra Plus uses 2-3 high-amperage double-pole breakers. If any one tripped, control sees partial power and may flag E2. Reset all.
2. Verify voltage at unit terminals
- Multimeter on AC voltage
- 240V ± 5% on each leg
- Under 220V = supply voltage issue (utility, drop in main feeder, undersized wire)
- Imbalance between legs (one 240V, one 230V) = neutral problem upstream
3. Element resistance test
Power OFF at all breakers. Verify with voltage tester. Then:
- Remove front cover
- Disconnect each element\'s leads
- Multimeter on Ω
- Test resistance across each element
- Compare to spec sheet (Tempra Plus element specs vary by model)
| Tempra model | Element wattage | Expected resistance |
|---|---|---|
| Tempra 12 Plus | 7.2 kW each (2) | ~8 Ω each |
| Tempra 15 Plus | 7.2 kW each (2) | ~8 Ω each |
| Tempra 20 Plus | 9.6 kW each (2) | ~6 Ω each |
| Tempra 24 Plus | 8 kW each (3) | ~7.2 Ω each |
| Tempra 29 Plus | 9.6 kW each (3) | ~6 Ω each |
| Tempra 36 Plus | 12 kW each (3) | ~4.8 Ω each |
OL (open) = element burned out, replace. Near 0 Ω = shorted, replace. Out of spec by >20% = degraded, replace.
4. Element-to-ground test
With multimeter on Ω, test from each element terminal to the unit housing/ground. Should read OL. Continuity to ground = element shorted to sheath; replace and verify breakers haven\'t welded contactors.
5. Contactor / control board fault
If elements test good and voltage is correct, the issue may be the contactor (relay that switches element power) or the control board. This is contractor-level diagnosis.
Reset E2
- Address the underlying issue (element replacement, voltage correction)
- Power cycle: all breakers off 30 seconds, then on
- Open a hot tap; verify heating and stable output temperature
Bottom line
E2 = element or power. Element ohm test is the home diagnostic; voltage verification is essential. Stiebel Eltron elements are available through tech support — warranty replacement if under 7 years.