Baxi E317 fault codewhat it means and how to fix it
Mains 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.
Take care
Get a Gas Safe registered engineer to look at your Baxi E317
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 E317 means
E317 is one of the four codes Baxi's professional page lists with an alternative number: "E317 / 162 — Wrong power supply electrical frequency (Hz)". The board measures the mains it is fed and expects 50 Hz; if what it reads is outside its tolerance it shows E317 and stops, because the timing of several of its safety functions is derived from the supply frequency.
In a house on the public grid the frequency does not wander, so a Baxi showing E317 is nearly always misreading a good supply — a board fault, or a supply so noisy or distorted that the board cannot count it — rather than reporting a genuine grid problem. The two exceptions are worth ruling out first: a boiler fed from a small generator or an inverter during a power cut, whose frequency really can drift, and a boiler that has just been reconnected after electrical work.
E317 is not in the 600 and 800 manuals' list of codes that can be relit from the Reset button; it does not appear in their printed table at all, and this page rests on the professional page's listing for the family. It shows with the spanner symbol where it appears, so Baxi's user-guide instruction is to contact your installer, annual service provider or Baxi Customer Support. Switching the boiler off at the fused spur for a minute and back on is a reasonable single check, since it forces the board to re-measure; if E317 returns on a normal grid supply, the board is the suspect and an engineer should confirm the supply at the boiler terminals before condemning it.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| PCB frequency measurement fault | The most common cause on a grid-fed boiler. The board misreads a good 50 Hz supply and reports it out of range. Replaced as a unit. | Common |
| Generator or inverter supply | A boiler run from a portable generator or a battery inverter during an outage can genuinely see a frequency outside tolerance. The code clears when the mains returns. | Occasional |
| Noisy or distorted mains | Heavy switching loads on the same circuit, or a poor neutral, can distort the waveform enough that the board cannot count it cleanly. | Occasional |
| Wiring at the boiler | A loose neutral at the terminal strip or fused spur gives the board an unstable reference. Checked before the board is condemned. | Rare |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£80–£400
Time on site
45 minutes
Supply check and terminal tightening £80–£150. PCB £250–£400 fitted.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
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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
- E385Get it checkedUnder-voltage (shown on some boards as 165): the supply at the board dropped below what it will run on. Usually a house-wiring or supply problem the boiler is reporting, not causing.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 support portal
- Manufacturer technical and service documentation
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.