Ideal F7 fault code: why your boiler has stopped, and who you actually need to ring

What does the Ideal F7 fault code mean?

Ideal F7 means your boiler has detected that the 230V mains electricity reaching it is too low to run safely, so it has stopped. The fault is in the electrical supply, not usually the boiler. You cannot fix it yourself. Reset once, and if F7 returns, Ideal's own instruction is to call a qualified electrician or your electricity provider.

Ideal's own words, from the fault codes table in the Logic Combi user guide bound into the official Logic Combi installation and servicing manual: "Low Mains Voltage ... Contact a qualified electrician or your electricty provider." The spelling of "electricty" is Ideal's, not ours. The installer's fault finding chart in the same document puts it more bluntly still: "ALTERNATING `F' and `7' ... LOW MAINS VOLTAGE CONTACT ELECTRICITY PROVIDER".

Here is the detail that tells you how Ideal itself treats this code. Almost every entry in that installer fault finding chart sends the engineer off to a numbered diagnostic frame to test something. In the copy of the chart we read, F7 has none. The chart goes straight from the code to "CONTACT ELECTRICITY PROVIDER".

F7 does appear on Ideal's public consumer fault code FAQ, which describes it as "Voltage to the boiler may be too low. Contact a local electrician to inspect the electrics of your property". One wrinkle is worth flagging, because it causes confusion: that page labels the code "Low Mains Volume", while every Ideal manual we checked says "Low Mains Voltage". Voltage is the correct word.

One number worth having before you start. If the whole house or the street is affected, ring 105. It is the free national power cut number, it is answered day or night including weekends, and it puts you through to the electricity network operator for your area rather than to the company that bills you. It is the right first call for a power cut or a supply problem outside your home.

A safety note before you go further. F7 is an electrical supply fault, not a gas escape. But whatever is on the display, if you smell gas or your carbon monoxide alarm sounds, put this page down and ring the National Gas Emergency Service on 0800 111 999 straight away.

Key facts

Seven things worth knowing before you spend money on the wrong trade.

• What F7 means: low mains voltage. The boiler has measured the electricity supply arriving at it, found it below what it needs, and shut down rather than run on it.
• Can I fix it myself? No, beyond a single reset. Everything else needs a meter on live terminals, which is qualified electrician work.
• When it becomes somebody else's job: as soon as F7 returns after that one reset. Ideal's own route is a qualified electrician or your electricity provider, and 105 if the whole street is affected. A Gas Safe registered engineer only enters the picture if an electrician has proved the supply at the boiler is healthy and F7 still shows.
• Which boilers show it: F7 is confirmed in the official Ideal Logic Combi installation and servicing manual for the Logic Combi 24, 30 and 35, and in the matching Logic Combi user guide. Ideal's brand-wide fault code FAQ lists it for its boilers generally, and Ideal's official Logic Code Combi ESP1 page covers the 26, 33 and 38kW models. If your model is not among those, check your own Ideal user guide rather than a third-party list.
• The number nobody can give you: Ideal publishes no voltage threshold for F7. Other sites quote a specific cut-off figure, but no Ideal document we read states one, so we will not repeat a number Ideal has not published. The manual states only the supply the boiler requires, "230 V ~ 50 Hz" with 3 amp fusing.
• Do not keep resetting. Five resets inside 15 minutes puts an Ideal boiler into L5, a second lockout on top of the first. Clearing L5 means switching the power off and on at the fused spur, and on an F7 the spur is one of the parts under suspicion, so if you get that far, leave the boiler off and wait for the electrician.
• If you would rather a boiler breakdown was handled for you next time: a Smart Plan boiler and central heating module covers parts and labour up to £500 per 12-month period if your boiler is under 7 years old, or up to £200 if it is over 7. A new plan covers future faults, not a fault your boiler already has, so it is not the answer to tonight's F7. It is a service plan, not insurance. A £95 call-out fee, paid in advance, applies in your first 30 days, for faults the plan does not cover, if the engineer cannot get access, and for early annual-service requests. Cover-plan call-outs run Monday to Friday, 08:00 to 18:00. Outside those hours you are only seen sooner for a genuine emergency breakdown, so a Saturday fault may wait until Monday. Using a module starts a 12-month agreement period the first time you use a service. There is a 14-day cooling-off period, which ends the moment a service is carried out, and leaving early after that costs the remaining months or 75% of the outstanding balance.

Why is my Ideal boiler showing F7?

Because something between the street and the boiler's terminal block is letting the voltage sag. That could be the incoming supply to the whole property, or it could be one tired connection in the final run of cable before the boiler. The two look identical on the display and are told apart by what else in the house is misbehaving.

So the useful question is not "what is wrong with my boiler", it is "how far back does this go". If the whole house is flickering, the answer is upstream and possibly not even on your side of the meter. If nothing else in the house has noticed, the boiler's own supply is the more likely place to look: the fused spur, the cable, or the connections at either end. Only a meter at the boiler proves which it is.

One thing to be straight about. Ideal publishes no cause list for F7, only the instruction to contact your electricity provider. The causes in the table below are general electrical-supply reasoning, not an Ideal document. What the table does give you is the symptom that separates each one, so you can describe it accurately when you ring. None of them are homeowner jobs.

Which of these matches what is happening in my home?

Can I fix an Ideal F7 myself?

No, and this is a short section for a reason. Measuring the mains voltage at the boiler's live terminals is the check Ideal's own fault finding chart calls for, and it is not a homeowner job. Neither is opening, rewiring or working on the fused spur, the supply cable or the terminal block.

What follows is not a repair list. It is the small set of safe observations that tell you, and then the electrician, where the problem sits. Doing them properly can turn a vague call-out into a targeted one.

1. Check whether the rest of the home has power. Are lights, sockets and other appliances working normally, and are the lights dimming or flickering? Flickering points away from your boiler and towards the supply.

2. Ask a neighbour whether their supply is affected too. If it is, the problem is street-side rather than anything in your home, so ring 105, the free national power cut number, which connects you to your local electricity network operator.

3. Look at the boiler and its fused spur switch for obvious external damage, scorching or a burnt smell. Look only. Do not open the boiler casing and do not unscrew anything.

4. Reset the boiler once, following the reset instructions in your Ideal user guide.

5. If F7 returns after that single reset, stop resetting and follow Ideal's own advice: contact a qualified electrician or your electricity provider.

That is the whole safe list. Radiator bleeding and pressure top-ups have nothing to do with F7, so they are not on it.

Everything else belongs to a qualified electrician: measuring the voltage at the L and N terminals inside the boiler, inspecting, tightening or rewiring the fused spur, supply cable and terminal block, testing the stability of the incoming supply, and escalating to the local electricity network operator. Testing or replacing the boiler's PCB, and any work at all that involves removing the casing, is Gas Safe registered engineer territory.

While you wait, leaving the boiler switched off is safe, but it does mean no heating and no hot water. If it is freezing outside, keep one room warm by another means and keep an eye on any exposed pipes.

If anyone in your home is elderly, unwell or disabled, or you have young children, say so when you ring your electricity supplier or 105. Suppliers and network operators run a free Priority Services Register, and being on it puts your household higher up the list during a power cut.

Is F7 the same as F6, F9, or the F.7 I have seen on other boilers?

No to all three, and the last one catches people out most. Ideal writes this code as F7, with no decimal point. A code written "F.7", with a dot, is another manufacturer's format, so if that is what is on your display you are reading advice for the wrong boiler. Check the badge on the front panel before you act on anything.

F6 is the code directly before F7 in Ideal's list, and it is the one most often muddled with it. It is a completely different fault: outside sensor failure. Ideal's action there is to reset the appliance and, if it still fails, contact Ideal under warranty or a Gas Safe registered engineer. That one is a boiler fault, so it goes to a heating engineer, not an electrician.

F9 is unconfigured PCB. The installer chart's action is blunt: PCB FAULT, REPLACE PCB. Engineer or Ideal only. F9 and F7 both point at electronics in a loose sense, which is why they get muddled, but F7 is about the electricity going in and F9 is about the board itself.

The rest of the F block is sensor and combustion territory and none of it involves an electrician. F5 is a return thermistor fault and F4 is a flow thermistor fault, both reset once then engineer. F3 is a fan fault, same route. F2 is flame loss, where it is worth checking your other gas appliances work and that the meter is on or has credit before you call. F0 is no water flow thermistor, reset once then engineer. F1 is low water pressure, the one code on this list with a real homeowner action: check the gauge reads between 1 and 1.5 bar and re-pressurise following your manual.

L5 is the one you can create yourself while chasing F7. Resetting more than once will not clear F7, and five resets inside 15 minutes locks an Ideal boiler out with L5 on top of it. Clearing L5 means switching the power off and on at the fused spur, and the spur is one of the parts an F7 puts in doubt, so if you have already reached L5, leave the boiler off and let the electrician sort both. That is why we keep saying reset once, not repeatedly.

When should I call an electrician, and when do I need a Gas Safe engineer?

Call an electrician or your electricity provider as soon as one reset has failed to clear F7. That is not our opinion, it is Ideal's instruction in its own user guide: "Contact a qualified electrician or your electricty provider." The misspelling of "electricty" is Ideal's, not ours. The installer chart gives the same answer with no diagnostic steps in between. If your neighbours are affected too, or the whole house is, ring 105 first. It is free, it is answered day or night including weekends, and it reaches the electricity network operator for your area.

You only need a Gas Safe registered engineer for F7 in one situation: an electrician has tested the supply at the boiler, proved it is a healthy and stable 230V, and F7 is still showing. At that point the suspicion moves to the boiler's PCB misreading the supply, which sits inside the boiler casing. If the boiler is still under warranty, contact Ideal, because warranty work is handled by Ideal, and check your own warranty paperwork for who is allowed to work on the boiler. You can check any engineer's registration on the Gas Safe Register before they start work.

Tell whoever you ring three things: the code exactly as it appears on your screen, whether the lights in the house dim or flicker, and whether F7 arrives at the moment the boiler starts up or at random. Those three answers separate a street-side supply problem from a loose connection from a boiler fault, and they save the first half of the visit.

We will not quote a price for this repair. The cause could sit in the last stretch of cable before the boiler, or out on the network where the work is not yours to arrange, and Ideal publishes no figure. It could equally be cable or circuit work running into several hundred pounds. Ask for the cause to be confirmed and the job quoted in writing before any work goes ahead.

One thing a boiler cover plan will not do is rewire your house. F7 is usually a fault in your electrical supply rather than in the boiler, so the supply work itself is an electrician's job and not a boiler repair. A new plan also covers future faults, not a fault your boiler already has, so it is not the answer to the F7 on your display tonight. What cover is for is the next fault that genuinely is the boiler. A Smart Plan boiler and central heating module covers parts and labour up to £500 per 12-month period if your boiler is under 7 years old, or up to £200 if it is over 7. Smart Plan is a service plan, not insurance: it arranges and funds covered repairs up to your limit rather than paying you a sum of money. Cover is modular, so you build your own plan and pick only what you want.

The parts worth reading before you sign up: a £95 call-out fee, paid in advance, applies in your first 30 days, for faults the plan does not cover, if the engineer cannot get access, and for early annual-service requests. Cover-plan call-outs run Monday to Friday, 08:00 to 18:00. Outside those hours you are only seen sooner for a genuine emergency breakdown, so a Saturday fault may wait until Monday. Within those hours we aim to get an engineer out to you within two working days, which is a target rather than a promise. Using a module starts a 12-month agreement period the first time you use a service. There is a 14-day cooling-off period, but it ends the moment a service is carried out, and leaving early after that costs the remaining months or 75% of the outstanding balance.

Repairs are carried out by a national network of thousands of Gas Safe registered engineers, and Smart Plan comes from UK Boiler Company Ltd, which has traded since 2014. If you would rather deal with the boiler as a standalone job once the electrician has been, book a one-off repair. One-off repair visits run Monday to Friday, 09:00 to 17:00, carry a £95 call-out fee paid in advance, and are not covered by a workmanship guarantee, and the engineer tells you what is needed before any work goes ahead. Our phone line is open Monday to Friday, 08:00 to 18:00 on 0333 772 6247.

Ideal F7 fault code FAQs

F7 back after one reset? Start with an electrician, and let us handle the boiler.

If F7 has returned, follow Ideal's own advice and contact a qualified electrician or your electricity provider first, because the supply is where this fault normally lives. If the whole street is affected, ring 105, the free national power cut number. If the supply checks out and the boiler is still faulty, book a one-off repair and a Gas Safe registered engineer will diagnose it and tell you the cost before any work goes ahead. One-off repair visits run Monday to Friday, 09:00 to 17:00, carry a £95 call-out fee paid in advance, and are not covered by a workmanship guarantee. Or set up a Smart Plan boiler and central heating module so the next boiler breakdown is already covered: parts and labour up to £500 per 12-month period if your boiler is under 7 years old, or up to £200 if it is over 7. A new plan covers future faults, not one your boiler already has. It is a service plan, not insurance. A £95 call-out fee, paid in advance, applies in your first 30 days, for faults the plan does not cover, no-access visits and early annual-service requests. Cover-plan call-outs run Monday to Friday, 08:00 to 18:00, and outside those hours you are only seen sooner for a genuine emergency breakdown. Within those hours we aim to get an engineer out to you within two working days, which is a target rather than a promise. Using a module starts a 12-month agreement period once you first use a service, there is a 14-day cooling-off period which ends the moment a service is carried out, and leaving early after that costs the remaining months or 75% of the outstanding balance. The wizard shows your price before you commit to anything. Call 0333 772 6247, Monday to Friday, 08:00 to 18:00.

Helpful links

• Build your boiler cover and see your price
• All Ideal boiler fault codes
• Ideal F9 fault code (unconfigured or faulty PCB)
• Ideal F1 fault code (the real low water pressure code)
• Ideal F2 fault code (flame loss)
• Ideal L5 fault code (too many resets in 15 minutes)
• Ideal L2 fault code
• Ideal Heating help hub
• Boiler not working? Book a one-off repair
• Boiler & central heating cover
• Ideal Heating official boiler fault code FAQ
• Check an engineer on the Gas Safe Register
• Power cut? Call 105 (Energy Networks Association)