BoilerFaultCodes.com
28 High Lockout

Your boiler has detected that the internal sensor responsible for monitoring the temperature of your heating system has developed a fault.

Call an engineer soon

Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Fault on Central Heating Sensor

What causes this fault?

This fault occurs when the boiler's control board loses communication with the temperature sensor or receives an incorrect reading. The most common reason is that the sensor has physically degraded over time or the electrical wire connecting it to the main system has become loose or corroded.

This fault often appears when the heating is first turned on after summer, as the sensor may struggle to respond correctly after a long period of inactivity.

Typical repair cost £90-160 (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 28 — 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.

Potterton Performa 28i is discontinued — time for a new one?

Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.

UK's #1 online installer
Boxt
Fixed-price online quotes. Next-day installation.
Get a free quote →
Heatable
Instant online boiler quotes from £1,499.
Get a free quote →
iHeat
Fast installation. Price match guarantee.
Get a free quote →

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

Related fault codes