What does the Baxi H.01 – .21 fault code mean?

Your boiler is heating up too quickly when you turn the tap on, which usually means water isn't flowing through the system fast enough to take the heat away.

How much does it cost to fix Baxi error code H.01 – .21?

Typical repair cost for the Baxi H.01 – .21 fault is £120-£350 including labour.

Baxi H.01 – .21 Fault Code: What It Means & How to Fix It

Technical description

Temporary error – flow temperature increasing too fast in domestic hot water (DHW) mode, insufficient circulation or sensor error.

What causes this fault?

This fault occurs when the water inside your boiler heats up much faster than the system expects, causing it to shut down to prevent overheating. The most common reasons are a blockage in the internal heat exchanger or a pump that isn't able to push the hot water away from the burner quickly enough. It can also be caused by a faulty sensor giving the boiler an incorrect temperature reading.

This fault is slightly more common in summer when the boiler has been idle for long periods, which can lead to the internal pump sticking or debris settling in the heat exchanger.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer

Search the official register →

Your boiler is heating up too quickly when you turn the tap on, which usually means water isn't flowing through the system fast enough to take the heat away.

Technical description

What causes this fault?

Engineer required

Related guides you might find useful

No hot water but heating works

Banging / kettling / whistling noise

Radiators cold at the bottom

Recently viewed