Board change on 16mm tails

[Dartlec]

Hello all

Just some input needed

I have 16mm meter tails & earth looks undersized coming unto the board also. I want the consumer unit changed, I understand that the tails need to be 25mm & earth 10mm I spoke with my electricity supplier who is going to get the technical department to call next Friday about changing these. Seems like it's going to take a while.

Can I get the board changed with the existing set up first, new rcbo board installed on the 16mm tails & current earth, then after upgrade the meter tails?

Yes, it's fine to get the board changed now. The best option would be to get a Henley block installed with the existing 16mm tails from the meter going in, then 25mm tails to the new board. That way, if you get the fuse upgraded the DNO/meter supplier can easily change their tails with no inconvenience to the existing installation...

Note you may need to get the meter tails changed separately by your electrical supplier - they own the meter, and the DNO look after the main head (in some areas they will liaise, but in others you may need to get both involved...)

Whoever you get to install the board should be able to give guidance on earth sizing and whether any upgrade to existing bonding will be needed.

 

[HappyHippyDad]

I would class 16mm tails as acceptable with a 100A fuse if max demand is not going to exceed the current carrying capacity of a 16mm conductor, also it would have to meet regulation 434.5.2. I.e Any fault occurring shall be interrupted before the permitted limiting temperature of the conductor is reached. You calculate this by using the given equation within the regulation.

The above advice can be seen in Best practise Guide 6, point 6.1 note 4.

 

[dodger421]

The above advice can be seen in Best practise Guide 6, point 6.1 note 4.

Just to note this is now Best Practice Guide 1 (Issue 4) Point 5.1, Note 4.

BPG 1 Replacing a consumer unit in domestic premises.

BPG 6 is now portable and stationary appliance testing in private rented accommodation.

Up to date BPG’s here.

 

[pc1966]

I would class 16mm tails as acceptable with a 100A fuse if max demand is not going to exceed the current carrying capacity of a 16mm conductor

Certainly for tails in open air. While they stop at 25mm for that case, a look at Table 4D1A columns 11 & 12 shows 25mm rated at 130-146A and scaling that by the sort of ratios seen for, say, clipped direct (column 6) gives ratings of at least 100A for 16mm.

But often DNOs complain if it is not 25mm so if installing new than it is easier to go with that. If you use the Doncaster easy-fit 19-standed version they are not too difficult to wrangle.

 

[hasel5]

Will also depend on your supply from the DNO if they will let you upgrade. Your supply may be looped

 

[DPG]

Heating the outdoors - it's a crazy world.

 

[Dave OCD]

I thought that's what the sun was for ? ?

 

[pc1966]

I thought that's what the sun was for ? ?

Not in Scotland...

A blinding flash of light was reported over Glasgow, turned out to be summer!

 

[DNO1981]

Yes, it's fine to get the board changed now. The best option would be to get a Henley block installed with the existing 16mm tails from the meter going in, then 25mm tails to the new board. That way, if you get the fuse upgraded the DNO/meter supplier can easily change their tails with no inconvenience to the existing installation...

Note you may need to get the meter tails changed separately by your electrical supplier - they own the meter, and the DNO look after the main head (in some areas they will liaise, but in others you may need to get both involved...)

Whoever you get to install the board should be able to give guidance on earth sizing and whether any upgrade to existing bonding will be needed.

Just had the electrician in and the incoming earth is 6mm so he wont change the board until the earth is upgraded. the bonding is also 6mm

 

[MJPD29]

Just had the electrician in and the incoming earth is 6mm so he wont change the board until the earth is upgraded. the bonding is also 6mm

If tncs then that's fair enough. 16mm live and neutral tails will be fine thoufh