If your Main boiler shows E317 or 162, Baxi’s current fault-code information describes it as “Wrong power supply electrical frequency (Hz)”. The boiler has detected that the electrical supply it is reading does not match the frequency it expects, so it has stopped rather than continuing under an unacceptable condition.
This is an electrical-supply or signal-related code, not a statement that the gas supply has failed. It also does not identify one guaranteed faulty part. The safest response is to keep the boiler closed, record what happened and arrange the appropriate professional checks.
What does Main E317 or 162 mean?
Electricity changes direction many times each second. That rate is called frequency and is measured in hertz, written as Hz. UK mains electricity is generated at a nominal frequency of 50 Hz. The boiler’s controls are designed to operate with the expected supply characteristics.
When a relevant Main boiler displays E317 or 162, its controls believe the electrical frequency being received or interpreted is wrong. The appliance cannot assume that normal operation is safe or reliable, so it may lock out.
The code tells an engineer what type of condition the boiler has detected. It does not, by itself, prove whether the issue comes from the incoming supply, a connection, local electrical work, temporary power quality or the boiler’s own electronics. Tests are needed before any repair decision is made.
Which Main boilers can show E317?
Baxi’s official error-code table places E317 / 162 in the appliance group that includes:
- Main Eco Compact Combi
- Main Eco Compact System
Other Main boilers may use different controls and different code meanings. Check the full model name on the front, data label or paperwork rather than assuming all Main models share this code.
Main Eco Compact support now appears on Baxi’s website because the manufacturer has brought the established Main range under the Baxi name. That makes the current Baxi error-code table the relevant primary reference for these models.
Is E317 the same as low voltage?
No. Frequency and voltage are different electrical characteristics. Baxi lists E317 / 162 as wrong electrical frequency, while E385 / 165 is listed separately as undervoltage.
This distinction matters because the numbers should not be treated as interchangeable. Advice for topping up boiler pressure, restoring the gas supply or correcting a low-voltage code does not explain E317.
What can you safely check?
Keep your checks observational and external:
- Photograph the display and note whether it shows E317, 162 or alternates between them.
- Confirm the exact Main model and whether it is a combi or system boiler.
- Note whether the fault followed a power cut, a tripped circuit, electrical work or use of a temporary generator.
- Check whether other household appliances, lights or clocks behaved unusually at the same time.
- Record whether the code appeared immediately at power-up or only when heating or hot water was requested.
If the user guide for your exact model permits a reset, one careful reset may be reasonable after a brief, isolated interruption. Do not repeatedly reset a boiler that returns to E317. A repeated code needs proper attention, and repeated attempts do not correct an unstable supply or an internal electrical problem.
What should you not do?
Do not remove the boiler casing, test live terminals, alter wiring, open the consumer unit or measure the mains supply yourself. Do not fit an adaptor, extension lead or voltage device in an attempt to make the boiler run.
Never assume the printed circuit board needs replacing simply because E317 has appeared. The display reports what the boiler has detected; it does not provide enough evidence to select a part.
Could a power cut cause E317?
A disturbance around a power cut or restoration may coincide with the code. That does not mean every E317 is caused by the wider electricity network, and it does not confirm that the boiler is faulty. The timing is useful information, so write it down.
If several appliances are behaving abnormally, lights are repeatedly flickering, or power problems affect more than the boiler, tell the repairer and contact the appropriate electricity network or a qualified electrician as advised. If the issue is confined to the boiler, the appliance and its supply still need to be assessed methodically.
What will be checked during a repair?
The engineer will confirm the code, model and fault history, then consider the circumstances in which the problem started. Checks may cover the quality of the supply reaching the appliance, the boiler’s electrical connections and how the controls are interpreting the frequency.
The findings determine whether the next step concerns the boiler, the local electrical installation or the incoming supply. That evidence-led approach avoids guessing and helps prevent an unnecessary part replacement.
Can the boiler still provide heating or hot water?
If it has locked out, heating and hot water may stop until the condition is cleared and the underlying problem is resolved. Do not bypass the lockout or keep cycling the power.
Use temporary electric heaters only in accordance with their instructions. Keep them upright, away from curtains and furniture, and plug them directly into a suitable wall socket rather than overloading an extension lead.
When is it an emergency?
E317 is an electrical-frequency code, but any separate gas or carbon-monoxide warning must still be treated urgently. If you smell gas, suspect carbon monoxide, see scorching or anyone feels unwell with headache, dizziness, nausea or breathlessness, move to fresh air and call the National Gas Emergency Service on 0800 111 999. Seek medical help if someone is unwell.
What information helps when booking?
Have a photo of the display, the exact boiler model and a short timeline ready. Include any recent power interruption, electrical work, generator use or unusual behaviour elsewhere in the property. You do not need to open the boiler or consumer unit to provide useful information.
Get your Main boiler working reliably again.
Book a fixed-price boiler repair so the E317 fault can be checked properly and the correct route to fixing it can be taken.
Main E317 FAQs
Are E317 and 162 the same code?
On the applicable Main Eco Compact models in Baxi’s current table, E317 / 162 are paired as the wrong power-supply electrical frequency.
Does E317 mean the voltage is too low?
No. Baxi lists undervoltage separately as E385 / 165. E317 concerns electrical frequency.
Can I check the frequency myself?
No live electrical testing should be attempted by a homeowner. Record the display and any wider power symptoms, then arrange professional attention.
Will switching the boiler off fix E317?
It may change the display after a temporary disturbance, but it does not prove the condition is resolved. If the code returns, stop resetting and arrange a repair.