Fuse board replacement: what happens on the day?

What happens before the day itself?

A survey, and it is the part that decides whether the day goes smoothly.

We look at where the board sits and whether it can stay there, how many circuits there are and what each one feeds, the earthing arrangement, and whether the main protective bonding to the gas and water pipes is present and the right size. We also ask what in the house cannot simply be switched off for a day: a freezer, a home office, an alarm, a stairlift, anything medical.

Tell us about all of it. A freezer full of food keeps well with the door shut, a home office can move to a café, and medical equipment changes the plan entirely. None of those should be a surprise at nine in the morning.

What happens in the morning, before the old board comes off?

Testing, and it happens while everything still works, so the electrician knows what was working before anybody touched it.

The checks are practical ones. Lights are switched to see they work, sockets are checked for correct polarity, and outside lights and sockets are looked at because they are where water gets in. With the supply isolated, the earth coming in from the network is measured and the main bonding is checked for continuity. NICEIC technical guidance sets out exactly this sequence, and it says any break or problem found should be raised with you straight away, because the remedial work involved could be significant.

Isolation itself is normally the main switch. The sealed cut-out before your meter belongs to the network operator, not to you or to us. If there is no isolator between the meter and the board, the tails cannot be made dead without the network operator, which is worth knowing at survey rather than on the day. Our three phase article explains who owns what at the incoming supply.

What does fitting the new board actually involve?

Taking the old board off, putting the new one up, and connecting every circuit to its own protection. It is careful rather than dramatic work.

The new consumer unit has to be made of non-combustible material or sit inside a non-combustible cabinet, which in a home means a metal enclosure. Each circuit is terminated and labelled, RCD protection is provided, usually as RCBOs or dual RCD splits, and a decision is made about surge protection, which NICEIC lists as one of the recommended safety features a modern board should have.

What you will not find here is a how-to. Replacing a consumer unit is notifiable work and it is not a job to learn from an article. Our fuse board replacement page sets out what a modern board gives you.

What if the old wiring fails the tests?

Then the board has done its job before it is even switched on, and you get a decision rather than a surprise.

Old rewireable fuses tolerate a lot. A shared neutral between two circuits, damp in an outside light, an ageing immersion heater element or a nail through a cable can all sit quietly behind a fuse for years. Put the same circuit behind a 30mA RCD and it trips. People ring us afterwards thinking the new board is faulty, and almost every time it is the board telling them the truth.

Here is the part a quote-and-go firm leaves out. We test the circuits at survey, before we quote the board, so if an old circuit is going to fail, you hear about it with the lights on and time to think. Sometimes the honest answer is that you need fault finding and a repair rather than a new board at all, and our repair or replace article covers that decision. Sometimes the tests show the wiring itself is the problem, which is a rewire conversation.

How long will the power be off?

For most of the working day on a typical house, and the whole house rather than one room at a time.

NICEIC is candid that the time depends on a range of factors and is hard to estimate in advance. What moves it is the number of circuits, how untidy the old board is, whether the earthing or bonding needs putting right, and above all what the tests find. Circuits come back one at a time as each one is tested, so the fridge and the lights are usually first.

What paperwork should I have at the end?

Two pieces, and it is worth asking for both by name.

An Electrical Installation Certificate, with a schedule of test results showing every circuit. It records what was done and that it was tested. Keep it with the house deeds, because a buyer’s solicitor or your insurer may ask for it.

A Building Regulations compliance certificate. Replacing a consumer unit is notifiable under Part P in England and Wales. Because we are registered with NICEIC, a government authorised competent person scheme, we notify building control ourselves and the certificate is sent to you afterwards. You do not need to apply for anything.

What changes the price of a board change?

We price it after the survey rather than from a photo, because the things that move the number are the things a photo does not show.

• The number of circuits, and whether any need splitting or adding while the board is open.
• Whether the main bonding to gas and water is present and the right size.
• Whether the board can stay where it is or has to move, for example out of a cupboard that is about to become a kitchen.
• Whether there is an isolator ahead of the board or the network operator has to be involved.
• What the pre-work tests find on the existing circuits.
• Surge protection and the style of RCD protection you choose.

Book a survey through our quote page, or WhatsApp a photo of the board and the meter so we can see what we are walking into.

Questions we get asked about this