BoilerFaultCodes.com
722 Medium Lockout

One of your secondary heating zones has reached a temperature that is too high, causing the system to stop as a safety precaution.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Overheating in zone 2

What causes this fault?

This fault occurs when the water temperature in your second heating zone exceeds safe limits, prompting the boiler to shut down to prevent damage. It is usually caused by a physical blockage in that specific part of the system, a failed zone valve that won't open, or a pump that isn't circulating the hot water away from the boiler quickly enough.

This issue often surfaces during the first cold spell of autumn when secondary heating zones are switched back on after being idle all summer.

Typical repair cost £100-280 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Protect yourself from future repair bills

A boiler cover plan would cover faults like 722 — no call-out fees, no surprises.

Top rated
OpenFix
Boiler & heating care plans
Get a quote →
Hometree
from £12.95/month
Get a quote →
HomeServe
from £8.00/month
Get a quote →

Affiliate links — we may earn a commission at no extra cost to you.

Related fault codes