H.01-.08 Boiler Fault Code: What It Means on Every Brand

The H.01-.08 fault code appears on 2 boiler brands — Baxi and Remeha — and on all of them it points to the same kind of problem. The details still differ by brand (thresholds, sub-codes, reset procedure), so use the table below to jump to the page for your boiler.

Engineer may be needed 2 brands use this code

Which brand is your boiler?

The brand is printed on the front casing. Tap your brand for the full causes, fixes and repair costs.

Brand	What H.01-.08 means	Severity	DIY?
BBaxi	The H.01–.08 code is a temporary self-protection status on Baxi boilers, meaning the boiler has detected that the flow temperature in heating mode is climbing faster than expected. Full guide →	Engineer may be needed	Some checks
RRemehashown as H.01.08	The H.01.08 code appears on Remeha boilers — most notably the Quinta Ace range — when the central heating flow temperature is climbing far more rapidly than the control system expects. Full guide →	Engineer may be needed	No

H.01-.08 brand by brand

Baxi H.01-.08

The H.01–.08 code is a temporary self-protection status on Baxi boilers, meaning the boiler has detected that the flow temperature in heating mode is climbing faster than expected. Rather than locking out completely, the boiler pauses operation for roughly 10 minutes to let things settle, then attempts to restart automatically. It points to either insufficient or absent water circulation through the primary circuit, or a flow temperature sensor that is misreading. It is worth knowing where this sits within the wider H.01 family: H.01–.05 triggers when the difference between flow and return temperatures exceeds the permitted maximum, H.01–.08 (this code) fires when the flow temperature itself rises too rapidly in heating mode, and H.01–.18 indicates a temporary loss of circulation. All three share the same root causes but the boiler's internal logic distinguishes them by which threshold has been crossed.

Causes, fixes & costs for Baxi H.01-.08 → · All Baxi codes

Remeha H.01.08

The H.01.08 code appears on Remeha boilers — most notably the Quinta Ace range — when the central heating flow temperature is climbing far more rapidly than the control system expects. The boiler labels this condition 'CH Temp Grad. Level3', meaning the temperature rise rate has breached the third and most serious internal threshold. Because heat is building up in the heat exchanger faster than circulating water can carry it away, the boiler enters a blocking state: it suspends operation temporarily as a precaution rather than performing a full lockout. The underlying message is almost always the same — water is not flowing through the system at the rate it should be, whether due to a pump problem, low pressure, trapped air, or a physical blockage.

Causes, fixes & costs for Remeha H.01.08 → · All Remeha codes

Frequently asked questions

Is the H.01-.08 fault code the same on every boiler?

Broadly, yes — on Baxi and Remeha the H.01-.08 code points to the same class of fault, and the recommended response is similar. Model-specific details such as sub-codes and reset procedures still vary, so follow the page for your own brand.

Can I fix a H.01-.08 fault myself?

On some brands there are safe homeowner checks first — typically system pressure, the condensate pipe in cold weather, and a single reset. The underlying repair usually needs a registered engineer. Never open the boiler casing yourself.

Who should I call about a H.01-.08 fault?

For gas boilers, a Gas Safe registered engineer — it is a legal requirement for any work on the appliance. If you smell gas at any point, leave the property and call the National Gas Emergency line on 0800 111 999.

General guidance only — not a substitute for professional advice, and not certified by a registered engineer. Any work on a gas appliance must be carried out by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.