Does a new boiler need electrical work?

A boiler is a gas appliance that does not work without electricity. That catches people out when the quotes come back, because there are two separate electrical questions on a boiler job and only one of them is normally inside the price.

The first is the supply to the boiler itself. The second is the earth bonding at your gas meter, and that one is the single line on the job a Gas Safe registered engineer is not allowed to put right, however willing they are. It is worth knowing about before you book, because it is one of the honest reasons an install stops short of commissioning.

The supply to the boiler, which is the easy half

A modern condensing boiler needs a permanent mains supply, fed through its own switched fused connection so the appliance can be isolated without pulling a plug out of a socket. On a straight swap, where the new boiler goes back in the same place, that supply already exists. The engineer reuses it and tests it, and that is why most quotes do not itemise it at all.

It stops being the easy half in three situations. The boiler moves, so a cable has to be run to the new position and sometimes a new circuit taken from the consumer unit. The controls change, which is routine on a combi swap because the installation has to add a control measure beyond the basic thermostat. Or the drainage needs a condensate pump, because a pump needs power of its own.

None of that is exotic work. It is just work that was not in the original sum if nobody looked.

The one line the gas engineer cannot include

Metal gas pipework in a house has to be electrically bonded back to the main earthing terminal. It is a safety measure, it has nothing to do with how well the boiler runs, and it is the first thing an engineer looks for at the meter.

Here is the part no comparison site prints. The Gas Safety (Installation and Use) Regulations 1998 say that anyone who connects installation pipework to a primary meter shall, in any case where electrical equipotential bonding may be necessary, inform the responsible person that such bonding should be carried out by a competent person.

Read that again. The duty is to inform. It is not a duty to do it, and it is not a job the gas qualification covers. So if the bonding at your meter is missing or wrong, what you get from the boiler installer is a conversation and a note on the paperwork, not a fix. Somebody else has to put it right, and on a tight install day that is the difference between a boiler that gets commissioned and one that does not.

Source: Gas Safety (Installation and Use) Regulations 1998, regulation 18(2)

What you can look at before anyone quotes

Look, do not touch. Nothing here is an instruction to work on gas pipework or on your electrics, and both are jobs for the right registered trade. But the bonding connection is visible, its position is set by a standard, and five minutes with a torch tells you whether this is likely to come up.

Gas Safe's technical bulletin on the subject sets out where the connection belongs, quoting the wiring and gas installation standards:

• Within 600mm of the meter outlet union, or within 600mm of the point of entry to the building if the meter is outside.
• Before any branch or tee in the pipework, so that every leg downstream is covered by it.
• Not clamped directly to pliable corrugated stainless steel tube, the flexible silver pipe used at some meters.

Source: Gas Safe Register Technical Bulletin 102, location of protective equipotential bonding on gas pipework in domestic premises, quoting BS 7671 clause 544.1.2 and BS 6891 clause 8.4.3.2

The external meter box is the one worth a second look locally. A great deal of the post-war housing around Northampton and Milton Keynes has the meter outside in a box on the wall, which means the 600mm is not measured at the box at all. It is measured from where the pipe comes into the house, which might be in a cupboard, under a floor or behind a kitchen unit. That is exactly the connection an installer quoting from photographs has never seen.

When the electrical work has to be notified

Some electrical work on a house has to be notified to building control, and some does not. The Building Regulations guidance for England names three things: the installation of a new circuit, the replacement of a consumer unit, and any addition or alteration to existing circuits in a special location. A special location means the zone around a bath or a shower head, or a room containing a swimming pool or a sauna heater. Everything else, including additions and alterations to existing circuits outside those places, is not notifiable.

Put a boiler job through that and it sorts itself out quickly. A fused connection spurred off an existing circuit in a kitchen or an airing cupboard is not notifiable. A new dedicated circuit run from the consumer unit is. And a boiler sitting in a room with a bath or a shower in it means any alteration in there is, which is a point worth raising if yours lives in the bathroom.

Source: Approved Document P, electrical safety, dwellings, 2013 edition, paragraphs 2.5 and 2.7

Three questions that sort the quotes out

You do not need to know any of the above to ask about it. Three questions do the work.

Does the quote assume the existing supply is reused and tested, or is new cabling and a new circuit allowed for? Did you look at the bonding at the meter, and what did you find? And if a new circuit or a bathroom is involved, who notifies the work and who issues the certificate?

An installer who surveyed the house has answers to all three and will give them without hesitating. One who priced off photographs will not have looked at the meter, and that is a concrete reason two quotes for the same boiler can be built on different assumptions without either installer being dishonest. It is also why the cheaper number sometimes grows on the day, which is not the same thing as being misled.

Get it looked at properly, on your meter

General rules only take you so far, and the thing that settles this is somebody standing at your meter with a torch. Tell us about the job and we will put you in touch with three vetted local installers who will survey it before they promise anything.