Consumer unit full - what are my options?

Isolgrac · 7 Nov 2019

We've just bought a plug-in car and are looking to get a charging point fitted. This will need a new connection to the consumer unit, but ours is already full.

One installer we spoke to said that we would need to get a whole new consumer unit fitted with more space before they could do the work. Another said that they could install a "one way board" as part of their installation. I assume this is just some sort of add-on consumer unit that allows for an additional single connection?

The existing consumer unit was installed in 2012 as part of an extension, so I would hope that other than space issues there are no reasons to want to replace the whole thing.

So - are these one-way boards a good idea or are they a bit of a fudge? If adding one of these, is there a mutli-way type so that I then have spare space for more new connections that I may need in future? What other things should I be considering?

JohnD · 7 Nov 2019

Show us some photos of your existing CU, meter, and the wires around and between them. There may be other reasons why your old installation is unsatisfactory.

You can probably have an additional new CU fitted. I wouldn't get a single circuit one though. For almost the same cost you can have a larger one, with capacity for additional circuits in future such as outdoor lighting or garden sockets, with the additional ways blanked off until needed.

As the car socket will be used outdoors, consider an RCBO which, in the event of an earth fault, will trip off that one circuit only.

reds42 · 7 Nov 2019

I believe the addition of an extra separate CU dedicated to a car charger is quite common, and some charger providers do it that way as a matter of course.

alan333 · 7 Nov 2019

The spark who fitted ours split the incoming feed into two, and fed an additional small consumer unit for the car charger with the split-off.

I'm not a spark but I believe there's a maximum load consumer units can handle. For example in my particular house I believe we're not supposed to fit an extra electric shower as it might overload the CU if they were both in use along with the cooker etc - so I reckon a car charging point could easily overload it too. Installing the small CU was the spark's solution when I asked about this. BTW other identical houses in our estate have the car charger straight into the CU.

Isolgrac · 7 Nov 2019

Pic of CU attached. Don't have a pic of meter etc but can add later if that's useful

BTW Quote for the one-way board was £65 ontop of standard installation. I assume a new CU would be significantly more than that?

reds42 · 7 Nov 2019

Isolgrac said:
BTW Quote for the one-way board was £65 ontop of standard installation. I assume a new CU would be significantly more than that?

Most likely.

JohnD · 7 Nov 2019

Isolgrac said:
Don't have a pic of meter etc but can add later if that's useful

And the wires and cables around and between them.

JohnD · 7 Nov 2019

Not "significantly"

The price of a small metal box with one switch, one breaker in it is surprisingly similar to the cost of a slightly larger box with the same contents.

Examples
https://www.tlc-direct.co.uk/Main_Index/Consumer_Units_Index/CP_Range_Main_Switch/index.html

Look at the price of a 2-way

And of a 10-way

Which is cheaper?

reds42 · 7 Nov 2019

JohnD said:
Not "significantly"

The price of a small metal box with one switch, one breaker in it is surprisingly similar to the cost of a slightly larger box with the same contents.

The cost of the time spent testing and rectifying any issues in the rest of the installation during a CU change would have to be factored in as well.

Isolgrac · 7 Nov 2019

JohnD said:
The price of a small metal box with one switch, one breaker in it is surprisingly similar to the cost of a slightly larger box with the same contents.

Yes, I was thinking more of the labour costs. For the single circuit box I can get it installed at the same time as the charging point and so I assumed the £65 extra was mostly for the cost of parts as there would only be a small extra amount of labour. Whereas if I wanted a larger additional CU then that would require a separate job for a different sparky and would result in more cost. I know this is a DIY forum, but I know enough to know that this isn't something I'm going to be doing myself. I would assume that adding a second CU (no matter the size) would still be less work than replacing the existing CU with a larger one?

JohnD · 7 Nov 2019

Yes, very much less work.

Perhaps the people installing the charger point bought a thousand small boxes and need to get rid of them. No other reason not to install a larger one.

Note that I said "an additional new CU"

I have not advocated removing the existing one.

Isolgrac · 7 Nov 2019

Ok, so it seems my options are:

#1 Book the charging point installation and have them install the one-way board.
Pros: Single job, Cheapest option (£65)
Cons: No space for future expansion, Two boxes on wall

#2 Have a sparky fit a 2nd CU and then get the charging point installed once done
Pros: Allows space for future expansion
Cons: Requires two jobs. Costs more, Two boxes on wall

#3 Have a sparky replace existing CU with a larger one and then get the charging point installed once done
Pros: Allows space for future expansion, One box on wall
Cons: Requires two jobs. Costs even more

Other than the not having a second box on the wall, is there any reason why it would be better to replace the existing CU with a larger one? (Assuming that there are no issues with the current one and all wiring is up to spec etc - I'll get more photos tonight) Any other pros/cons that I should be aware of?

What would be the approximate cost getting a sparky in to do #2 or #3?

AndyPRK · 7 Nov 2019

yes its normal to have a seperate unit to supply the car charger. and the sensbile way for you to go

Isolgrac · 7 Nov 2019

Couple more photos
Inside the meter cabinet:

Inside the CU:

There are no cables around the CU, all the cables come out of the wall already inside the CU

sparkwright · 7 Nov 2019

Isolgrac said:
Ok, so it seems my options are:

#1 Book the charging point installation and have them install the one-way board.
Pros: Single job, Cheapest option (£65)
Cons: No space for future expansion, Two boxes on wall

#2 Have a sparky fit a 2nd CU and then get the charging point installed once done
Pros: Allows space for future expansion
Cons: Requires two jobs. Costs more, Two boxes on wall

#3 Have a sparky replace existing CU with a larger one and then get the charging point installed once done
Pros: Allows space for future expansion, One box on wall
Cons: Requires two jobs. Costs even more

Other than the not having a second box on the wall, is there any reason why it would be better to replace the existing CU with a larger one? (Assuming that there are no issues with the current one and all wiring is up to spec etc - I'll get more photos tonight) Any other pros/cons that I should be aware of?

What would be the approximate cost getting a sparky in to do #2 or #3?

Another advantage of replacing the consumer unit for a whole new one is that you could have all RCBOs instead of MCBs and two RCDs.

This means you would have circuit breakers with their own individual RCD built in.

This therefore means if there is an earth leakage fault, only the one 'RCBO' will trip, whereas before one RCD would trip taking out several circuits rather than just one.

If you can afford it, I'd go for a new, metal consumer unit with RCBOs.

The biggest problem is finding someone who will do a decent job for you...

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Consumer unit full - what are my options?

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