Redundant 6mm Cooker circuit to 4mm radial?

[Noob2013]

Hi there.

Just a discussion with a colleague.

Is it acceptable to use a redundant 30A cooker circuit wired in 6mm, and downsize to 4mm via JB for a kitchen radial?

For example, if there is one ring supplying a house and you would like to reduce the risk of overloading with all the kicthen appliances.

Obviously new circuit is the best option but would this be acceptable?

Cheers

 

[Andy78]

30A existing circuit you say ? Is it a BS3036 OCPD ?

 

[Pete999]

Hi there.

Just a discussion with a colleague.

Is it acceptable to use a redundant 30A cooker circuit wired in 6mm, and downsize to 4mm via JB for a kitchen radial?

For example, if there is one ring supplying a house and you would like to reduce the risk of overloading with all the kicthen appliances.

Obviously new circuit is the best option but would this be acceptable?

Cheers

What sort of JB do you intend to use, and will it be accessible?

 

[Noob2013]

Standard 30A JB amd yes assessing under floorboards.

 

[Pete999]

Standard 30A JB amd yes assessing under floorboards.

Have to check but I don't think under the floor constitutes as accessible.

 

[Noob2013]

30A existing circuit you say ? Is it a BS3036 OCPD ?

Yes correct

 

[Andy78]

Standard 30A JB amd yes assessing under floorboards.

A standard screw terminal JB will not be suitable if under floorboards as this will not be accessible.

 

[Andy78]

Yes correct

Then I suggest you carry out a cable calc for your proposed alterations, assess the current piece of cable for suitability for continued use, and consider the RCD requirements needed for the proposed alteration too.

 

[telectrix]

but if a trapdoor is fitted, with the carpet cut and gripper strip applied around the access point? when will the iet define what is accessible? will this be a new edition, another £75.?

 

[Noob2013]

The 6mm cable tests out fine. Will be used to supply 4 double sockets and a fcu on a kitchen so not a big load.

It's just an alternative to pulling in a new circuit and also prevents the risk of overloading with the house on one ring.

Needs RCD protection.

Can you get a maintenence free JB for 6mm ?

 

[telectrix]

wago do a 6mm 40A connector. it's how you interpret M/F includeing the enclosure.

 

[Noob2013]

wago do a 6mm 40A connector. it's how you interpret M/F includeing the enclosure.

Ideal, just found the wagos.

Wago do the maintenance free JB's but I'm guessing a 6mm and 4mm won't fit easily.

Would you say that this wiring method (with MF JB) is an acceptable alteration?

The only other way other than new circuit or massive alteration is to keep the kitchen on the ring. I'm just concerned about overloading.

 

[hightower]

By my reckoning, with a rewirable fuse the 6mm isn't gonna cut it on a 30A OCPD, let alone a 4mm. You might get away with it on a 20A OCPD depending on your calcs.

 

[Andy78]

Ideal, just found the wagos.

Wago do the maintenance free JB's but I'm guessing a 6mm and 4mm won't fit easily.

Would you say that this wiring method (with MF JB) is an acceptable alteration?

The only other way other than new circuit or massive alteration is to keep the kitchen on the ring. I'm just concerned about overloading.

I would be concerned about the apparent going ahead with this without cable calcs for this alteration. My initial suspicion is that the alteration as you have described will not be suitable or compliant.

 

[7029 dave]

By my reckoning, with a rewirable fuse the 6mm isn't gonna cut it on a 30A OCPD, let alone a 4mm. You might get away with it on a 20A OCPD depending on your calcs.

Take a look at table h2.1 appendix h.

 

[hightower]

Take a look at table h2.1 appendix h.

Sorry, only got red OSG in digital... will check later at home unless you can enlighten me?

 

[hightower]

Ah, is it table 8A in the red OSG, you referring to A1, A2, & A3 circuits?

 

[7029 dave]

Ah, is it table 8A in the red OSG, you referring to A1, A2, & A3 circuits?

Yes indeed.

 

[hightower]

Yes indeed.

Okay, OSG table 7.1 says a 30A circuit in 4mm is not permitted on a BS 3036.

 

[7029 dave]

Okay, OSG table 7.1 says a 30A circuit in 4mm is not permitted on a BS 3036.

I have the green book and it states you can on bs 3036, so I stand corrected.

 

[Pete999]

Crikey how did we get to this stage it only started off as a discussion topic, now it looks like the OP is actually doing the job.

 

[Noob2013]

I have the green book and it states you can on bs 3036, so I stand corrected.

So the new regs state that a 4mm radial can be used with bs 3036 OCPD?

So what I proposed to do is perfectly acceptable?

 

[Noob2013]

Crikey how did we get to this stage it only started off as a discussion topic, now it looks like the OP is actually doing the job.

It was a discussion about a job I will be doing. Colleague wasn't too sure so we were debating

 

[Pete999]

It was a discussion about a job I will be doing. Colleague wasn't too sure so we were debating

Oh, right

 

[7029 dave]

So the new regs state that a 4mm radial can be used with bs 3036 OCPD?

So what I proposed to do is perfectly acceptable?

Unless the yellow book is amended, but if it's same as green osg, then yes IMO.

 

[Andy78]

So the new regs state that a 4mm radial can be used with bs 3036 OCPD?

So what I proposed to do is perfectly acceptable?

The regs say that cable size is to be determined by calculation. If you do one you will find out whether it complies or not.
Hint: You will find that it won't.

 

[Andy78]

Unless the yellow book is amended, but if it's same as green osg, then yes IMO.

I have the green book and it states you can on bs 3036, so I stand corrected.

Not in table 7.1 which is referenced under table H2.1. Contradictory information as always. Table 7.1 states that the minimum size is 6mm for BS3036 at 30A and only if installed in method C.

Cf will always change cable calcs dramatically so quite how the onsite guide thinks an all encompassing table for all OCPDs and all installation methods will work is beyond me

 

[hightower]

Yellow osg, not permitted

 

[telectrix]

it's the dumbing down syndrome. just bung in a cable big enough for the worst case scenario, no need to do calcs. a bit like fitting 25mm tails after a 60A DNO fuse,

 

[Noob2013]

Ok so by replacing the BS3036 with a Wylex plug in 60891, it would then comply?

 

[7029 dave]

Yellow osg, not permitted

10mm jokes, would love to see somebody wrestling them into a socket.

 

[Andy78]

Ok so by replacing the BS3036 with a Wylex plug in 60891, it would then comply?

There are many possible variables that would allow the arrangement to comply. It's up to the designer to choose the most appropriate method of doing so for the use, situation, installation method, and practical application of installation for the circuit.

I notice you are an apprentice. You should get your head into some calculations to find out what will and won't comply for your own education.

 

[ruston]

Especially in a surface mounted pattress or a fast fix. That would be fun tightening those down

 

[Noob2013]

I've read the tables in the yellow OSG and 6mm complies with bs3036 but 4mm doesn't.

60898 does comply.

The current carrying capacity is acceptable for 4mm.

The length of circuit is approx 30 metres and will be supplying 5 double sockets. It's clipped direct.

The only issue I can see is the protective device.

 

[7029 dave]

I've read the tables in the yellow OSG and 6mm complies with bs3036 but 4mm doesn't.

60898 does comply.

The current carrying capacity is acceptable for 4mm.

The length of circuit is approx 30 metres and will be supplying 5 double sockets. It's clipped direct.

The only issue I can see is the protective device.

Method c only.

 

[Flanders]

You will still need RCD protection fro the sockets

 

[Noob2013]

Method c only.

The cable run is through partition from c.u, under the floorboards with no insulation and then in oval conduit buried in plaster.

So reference method c?

 

[telectrix]

ref. method C appears to be appropriate.

 

[Flanders]

The cable run is through partition from c.u, under the floorboards with no insulation and then in oval conduit buried in plaster.

So reference method c?

Yes I would agree with that

 

[7029 dave]

Ref c is clipped direct ie surface.

 

[Andy78]

Ref c is clipped direct ie surface.

Method C is also applicable to multicore cables buried direct in non thermally insulated walls and also under capping buried in non thermally insulated walls. You could technically class oval conduit as method B I suppose though.

 

[7029 dave]

Method C is also applicable to multicore cables buried direct in non thermally insulated walls and also under capping buried in non thermally insulated walls. You could technically class oval conduit as method B I suppose though.

Don't know about method b conduit or trunking on wall not in wall. lol

 

[Andy78]

Don't know about method b conduit or trunking on wall not in wall. lol

Methods 59 and 60 in table 4A2 BS7671 give an example of conduit buried in a masonry wall as method B too.

 

[rich.250]

Am I the only one thinking why not just extend in 6mm?
Then you have a 2.5mm cpc and a clipped direct CCC of 47amps....


Sent from my iPhone using Tapatalk

 

[Pete999]

Am I the only one thinking why not just extend in 6mm?
Then you have a 2.5mm cpc and a clipped direct CCC of 47amps....


Sent from my iPhone using Tapatalk

Could be difficult to get 2x6mm into 13Amp socket?

 

[jimjimjim]

What about a lollipop circuit?! 2x2.5 from the 6mil. (forgive me if i've missed something, i only skimmed the thread)

Jim