Verified boiler fault code

Warmflow E12 Fault Code (Agentis Boilers (B-Series, I-Series and E-Series))

Tank-control NTC error.

Safety disclaimer

Boiler repair help from Aza & Sons Services

Fault code summary

Manufacturer: Warmflow
Fault code: E12
Fault type: Hot water, Temperature sensor
Severity: medium
Reset: The manual directs the user to a service engineer; no user repair or reset is specified.
Applicable models: B21, B26, B33, I21, I26, I33, I44, I21PRO, I26PRO, I33PRO, I44PRO, I21P/PRO, I26P/PRO, I33P/PRO, I44P, I21S/PRO, I26S/PRO, I33S/PRO, I21C/PRO, I26C/PRO, I33C/PRO, E21, E26, E33, E44, E21PRO, E26PRO, E33PRO, E44PRO, E21P/PRO, E26P/PRO, E33P/PRO, E44P, E21S/PRO, E26S/PRO, E33S/PRO, E21C/PRO, E26C/PRO, E33C/PRO

Quick answer

Tank-control NTC error.

What does this fault code mean?

Tank-control NTC error.

Common causes

Tank-control NTC temperature sensor short circuit or disconnection

Symptoms

E12 displayed on the LCD

What can the homeowner safely check?

Record the code and do not disconnect or test the NTC sensor.

Boiler reset information

The manual directs the user to a service engineer; no user repair or reset is specified.

When should I call an engineer?

Contact a suitably qualified heating engineer when the fault persists, the boiler locks out, or the manufacturer instructions do not resolve it. For gas appliance work in the UK, use a Gas Safe registered engineer.

Engineer diagnosis

A qualified engineer should inspect the tank-control NTC sensor, wiring and control board.

Applicable boiler models

Related fault codes

Manufacturer documentation

Warmflow Agentis Boiler Manual 6572 G

Last verified

2026-09-12

Frequently asked questions

What does Warmflow E12 mean?

Tank-control NTC error.

Can I reset a Warmflow E12 fault?

The manual directs the user to a service engineer; no user repair or reset is specified.