Low
F4 on Alpha Intec 50CS

Your boiler is simply performing a routine safety clear-out to remove any remaining exhaust gases after finishing a heating or hot water cycle.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Post ventilation in progress. Fan in function after a request for domestic hot water or central heating in order to evacuate residual fumes.

Shared across the Alpha Intec² range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Wait for a few minutes to allow the fan to finish its cooling cycleMonitor the display to see if the code clears and the boiler resumes normal standby modeEnsure there are no obstructions to the external flue terminal

Find a Gas Safe engineer
Search the official register →
Boiler cover options

Avoid the next call-out bill

Monthly cover means no unexpected bills when your boiler breaks down.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

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

Related fault codes

F3View →

All 61 fault codes on the Intec 50CS

Seeing a different code? Every code this model can display, in one place.

010203040506081012151620232425272931323435363738434445464751596061627273747778798084878889909192939495969899CEE03E38E62E72STOP

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on a combi.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →