Baxi H.02.09 status codewhat it means
Not a fault: a Baxi Combi 2 or 200/400 Combi has been told to stop by an external input, or frost protection is running. Baxi's remedy is to find and remove the external cause.
Before you start
What H.02.09 means
H.02.09 and its sibling H.02.10 are the Combi 2's way of saying the boiler has been stopped from outside. The manual defines H.02.09 as "partial stoppage of the boiler" with the cause "SIGNAL INDICATING BLOCKING INPUT ACTIVE OR FROST PROTECTION ACTIVE", and H.02.10 as "complete stoppage of the boiler — BLOCKING INPUT SIGNAL (WITHOUT FROST PROTECTION)"; Baxi's professional page words them as partial or total stoppage with the antifreeze function active or not.
The remedy for both is the same three lines: "external cause: remove the cause; parameter configuration error: check parameters; faulty wiring connection: check wiring". The blocking input is a pair of terminals on the board that an installer can wire to something that should be allowed to stop the boiler — a heat-pump controller in a hybrid system, a cylinder safety stat, a ventilation interlock — and when that contact opens the boiler shows H.02.09 (still protecting itself against frost) or H.02.10 (fully stopped) and waits. The H means it is a temporary fault: it "disappears when the error condition is removed", and no reset is needed or offered. The 200/400 Combi manual does not print these two codes; its blocking-input behaviour is undocumented in the UK manual, so this page is scoped to the Combi 2 and System 2 and mentions the 200/400 only for readers who arrive here from a similar display.
In a house with no such device wired, H.02.09 or H.02.10 on a boiler that has just been installed almost always means the blocking-input link or a parameter has been set wrongly at commissioning, and the installer is the person to call. In a house with a hybrid or an external control, the code is doing what it was set up to do, and the thing to look at is the device that asked the boiler to stop.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| External device asking the boiler to stop | A hybrid heat-pump controller, a cylinder stat or an interlock wired to the blocking input has opened its contact. Baxi's "external cause: remove the cause". | Common |
| Parameter set wrongly at commissioning | The blocking input function enabled in the installer menu on a boiler with nothing wired to it. Baxi's "parameter configuration error: check parameters". | Common |
| Wiring to the blocking input | A link wire missing or a connection loose at the terminals. Baxi's "faulty wiring connection: check wiring". | Occasional |
| Frost protection running | H.02.09 specifically includes the case where the boiler is protecting itself against frost while blocked. Normal behaviour in a cold spell on a boiler that has been stopped externally. | Occasional |
What to try yourself
If your boiler is part of a hybrid system or has an external controller, look there first: it has probably told the boiler to stop, and the code will clear when it releases it.
If nothing of the kind is fitted and the boiler is new, contact the installer. Baxi's remedy is to check the parameters and the wiring at the blocking input, which is inside the boiler.
No reset is needed. H codes clear by themselves when the condition is removed.
Get a Gas Safe registered engineer to look at your Baxi H.02.09
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What it costs to fix
Typical repair cost
£0–£120
Time on site
10 minutes
Nothing if the external device is the cause. A commissioning correction £80–£120 if the installer has to return.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Baxi / Potterton / Main main PCB
£150–£320Authorised Baxi parts distributor
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Baxi fault codes
- E168Get it checkedTrade lists call E168 a Baxi PCB lockout, but no Baxi UK manual or error-code page prints it. Treat it as a board fault: one power cycle, then an engineer.Related: electronics and power
- E83Usually simple to fixE83 to E87: the boiler has lost contact with a connected control — a room unit or programmer wired to the board. Check the control first; the boiler itself is usually fine.Related: electronics and power
- E103Get it checkedSafety Assist codes E103, E104 and E107: the battery-backed safety board on the 600 and 800 is exhausted, faulty or out of step with the main board. Contact your installer; there is no reset.Related: electronics and power
- E.02.47Usually simple to fix"Connection to external device unsuccessful": a Baxi 200/400 Combi or Combi 2 has lost a control it was paired with. Check the control and its wiring; Baxi's remedy is the auto-detect function.Related: electronics and power
- E55Get it checked"Calibration Required": the gas valve has not been set up to the board after a PCB or valve change. An engineer's combustion-analyser job, not a fault a householder can clear.Related: electronics and power
- E317Get it checkedMains frequency out of range (shown on some boards as 162). The boiler, not the supply, is almost always the odd one out. Check other appliances, then call an engineer.Related: electronics and power
Own a Baxi boiler? Save it and its codes come first next time.
Related guides
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
- Manufacturer support portal
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.