BoilerFaultCodesYour boiler has detected that the floor thermostat or external safety circuit has been triggered, often to protect your underfloor heating system from overheating.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: All Combi and System Boilers
What causes this fault?
This fault occurs when an external safety device, usually connected to an underfloor heating system, detects that the water temperature has become high enough to potentially damage your floors. The boiler shuts down immediately as a protective measure because a sensor has tripped or a connection in that safety circuit has been broken. The most common reasons are a pump failure within the underfloor manifold or a faulty external limit thermostat sending a false signal.
This code is more frequent during the first cold spells of autumn and winter when underfloor heating systems are switched back on after being idle for several months.
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 116 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
Affiliate links — we may earn a commission at no extra cost to you.