BoilerFaultCodes
Unical Boiler Fault Codes
66 fault codes across 2 Unical boiler models — explained in plain English.
Unical Alkon domestic condensing boilers.
Unical fault codes on this site
We document 66 fault codes across 2 Unical models, covering 33 distinct codes. Unical boilers use plain numeric codes such as 09, 14, 45. Codes for 2 of these models are taken directly from the manufacturer's own service or installation manual. Unical is a smaller name in the UK market, and if you own one this is likely one of the few places its fault codes are collected in one place.
Models covered: Alkon C 28 HE, Alkon R 28 HE.
Just want the most common Unical problems?
The top 8 faults across the whole Unical range — causes, DIY checks, repair costs.
High-severity Unical fault codes
14 45 21 15 22
Your boiler has temporarily stopped working because it cannot properly read the temperature of the water returning from your heating system.
Alkon C 28 HE
Your boiler has stopped working because the water pressure inside the system has risen dangerously high above the safe limit.
Alkon C 28 HE
Your boiler is temporarily stopping because water is not flowing properly through the system, which can cause it to overheat.
Alkon C 28 HE
Your boiler is getting too hot inside because water isn't flowing through the heating system properly, so it has safely shut down to prevent damage.
Alkon C 28 HE
Your boiler has detected that two internal temperature sensors have been wired up the wrong way around.
Alkon C 28 HE
All models
2 Unical boiler models
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