Joining different size cables

[les.gandee]

I am in he process of insulating a bedroom.
The existing 2.5mm ring main needs to be upgraded to 4mm in the new insulated wall.
So my question is can I terminate 2.5mm and 4mm in the same screw connection in a socket outlet. Or do I need to provide a dedicated connector to join the two different size wires. (Wago)
Thanks for any advice

Les

 

[Murdoch]

If the ring is just the upstairs sockets then reducing the OCPD from 32A to 20A is probably more appropriate

 

[Chewbacca]

What matters is the cables are secure in the terminals. That doesn't always work well with different size cables, but most sockets use screw terminals in which it normally works fine. Try it, and give the wires a good tug to see if they are secure. If there's any doubt use the 3way wagos and take a single wire into the terminals

 

[les.gandee]

Thank you for your quick responses
I am reluctant to lower the opcd rating in case someone in the future reverts the opcd back to 32amps. Much rather have cables that can take standard ring main loads

 

[SPECIAL LOCATION]

Thank you for your quick responses
I am reluctant to lower the opcd rating in case someone in the future reverts the opcd back to 32amps. Much rather have cables that can take standard ring main loads

Is this just upstairs sockets? Or the whole property?

Unless this is a ring final suppling the whole property then I cannot see any any sensible reason for expecting anything to be drawing 4.6kW or more..?
(if it is the whole property it could probably do with splitting off anyway by now?)

I haven't installed a 32A ring for upstairs sockets for donkeys years?

Possibly even better solution to split it onto 2x 20A radials than a single 32A ring?

There is a common failure is logic assuming all sockets should be on a 32A ring..
when in reality other than Kitchens / utilities very few other rooms come anywhere near the capacity of 32A OCPD's

 

[mort2376]

Totally agree. Ring final circuits should be stopped being installed. I now put 4mm radials in if a 32a socket circuit is needed. And 20/25a radials elsewhere.

Lots of people still in the sockets must be on a ring mindset.

 

[Murdoch]

Ring final circuits should be stopped being installed.

Not sure I agree with that

BUT dual RCD boards need outlawing ..........

 

[bhamoggy]

We’re so far behind Europe in the way they wire it’s untrue.
Take France for example, never do ring circuits. Always and only radials. The cooker, washing machine, dishwasher all have their own dedicated circuit

 

[BorisJ]

The existing 2.5mm ring main needs to be upgraded to 4mm in the new insulated wall.

Are you sure about that?

 

[MikeJhn]

We’re so far behind Europe in the way they wire it’s untrue.
Take France for example, never do ring circuits. Always and only radials. The cooker, washing machine, dishwasher all have their own dedicated circuit

Although I agree, France needs to catch up with the use of RCBO's.

And the UK need to bring in legislation on where a CU can be located.

 

[Murdoch]

And the UK need to bring in legislation on where a CU can be located.

Really ?

Why ?

 

[Pops]

Is this just upstairs sockets? Or the whole property?

Unless this is a ring final suppling the whole property then I cannot see any any sensible reason for expecting anything to be drawing 4.6kW or more..?
(if it is the whole property it could probably do with splitting off anyway by now?)

I haven't installed a 32A ring for upstairs sockets for donkeys years?

Possibly even better solution to split it onto 2x 20A radials than a single 32A ring?

There is a common failure is logic assuming all sockets should be on a 32A ring..
when in reality other than Kitchens / utilities very few other rooms come anywhere near the capacity of 32A OCPD's

I suspect it is more to do with the thermal effect on the cable in the extra insulation rather than the expected draw.

 

[MikeJhn]

Really ?

Why ?

How many times have you needed a ladder to reach the CU, and how many times have you been laying on the floor under a staircase to get too the CU, or inside a cupboard without any access on all sides, can't believe you questioned that.

 

[Murdoch]

How many times have you needed a ladder to reach the CU, and how many times have you been laying on the floor under a staircase to get too the CU, or inside a cupboard without any access on all sides, can't believe you questioned that.

not familiar with Part M then?

you can’t change the rules for what’s already installed

 

[SPECIAL LOCATION]

I suspect it is more to do with the thermal effect on the cable in the extra insulation rather than the expected draw.

That's not what the OP suggests?
It sounded like they realistically think this ring could need to supply 32A??

and has the common misguided assumption that sockets must be on a 32A ring??
e.g. from their earlier post...

Thank you for your quick responses
I am reluctant to lower the opcd rating in case someone in the future reverts the opcd back to 32amps. Much rather have cables that can take standard ring main loads

Which, unless its a whole-house ring, and/or ring that includes a kitchen sockets..
then 20A is more than adequate for 90%+ of typical domestic bedroom circuits...
and with a bit of suitable installation methods even where insulation is needed 2.5mm is good for 20A.

 

[MikeJhn]

not familiar with Part M then?

you can’t change the rules for what’s already installed

But you can for a new CU install.

Very familiar with Part M Regulations as someone who was involved with their introduction through the CIC, they where in the first instance to ensure that buildings where accessible, not only to disabled people, those with limited mobility and wheelchair users, but also to people who regularly use prams and other wheeled devices, don't know many electricians who that would apply to or how the Part M Regulations has any bearing on access to a CU.

 

[Fleeting]

What on earth does any of this drivel mean to the original question.

 

[MikeJhn]

Further to my drivel above, if you are an electrician and responsible for the design of an installation then the positioning of the CU falls under the CDM Regulations and ease of access to the CU for installation and maintenance has to be considered.

 

[Murdoch]

Further to my drivel above, if you are an electrician and responsible for the design of an installation then the positioning of the CU falls under the CDM Regulations and ease of access to the CU for installation and maintenance has to be considered.

Which in an existing installation is irrelevant

 

[Andy™]

I suspect it is more to do with the thermal effect on the cable in the extra insulation rather than the expected draw.

my guess too. the 2.5 needs to be able to take 20a after derating, which i suspect in this case it may not which nis why they want 4mm