Radial off a rings mcb

C

ColinJacobson

A normal 32A ring with both live wires into the 32A mcb. A 2.5mm T&E cable is screwed into the the 32A ring mcb's terminal. This goes to the garage. This mean the radial now has a 32A mcb, while the ring is properly rated.

Should the garage socket be take off the ring mcb and have its own 16A mcb?

Thanks.
 
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Give up asking sensible questions? This ban-all-sheds fellow sent me an offensive email. He is a clear nutter. I assume the Mods received an email from him and did what he wanted in deleting a perfectly good thread. Amazing. Are the rules not to offend the opinions of the regulars?

Back to the thread topic:

A normal 32A ring with both live wires into the 32A mcb. A 2.5mm T&E cable is screwed into the the 32A ring mcb's terminal. This goes to the garage. This mean the radial now has a 32A mcb, while the ring is properly rated.

Should the garage socket be take off the ring mcb and have its own 16A mcb?


If you can't answer then do not clutter the thread.
 
This ban-all-sheds fellow sent me an offensive email.
Don't come here telling your pathetic lies, then you won't need to hear things about you which you don't like.


He is a clear nutter.
I'm not the one posting c**p to get a reaction in a futile attempt to raise my self-esteem.


I assume the Mods received an email from him and did what he wanted in deleting a perfectly good thread.
Actually I didn't flag any of your topics to the Mods.

I know you don't want to believe it, but a lot of people, including the Mods, came to the same conclusion about you.

Moderator 8 said:
It became apparent to the moderators that this user was nothing more than a wind up merchant.

The desicion was made to remove all his time wasting posts.
 
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< snip incoherent babble from ban-all-sheds >

< to the Mod nothing was a wind up >
< I was given opinions, not any reg >
< sensible opinions are fine but only the regs matter >
< Do not be influence by a gang >

Back on topic...

A normal 32A ring with both live wires into the 32A mcb. A 2.5mm T&E cable is screwed into the the 32A ring mcb's terminal. This goes to the garage. This mean the radial now has a 32A mcb, while the ring is properly rated.

Should the garage socket be take off the ring mcb and have its own 16A mcb?


If you can't answer then do not clutter the thread.
 
A normal 32A ring with both live wires into the 32A mcb. A 2.5mm T&E cable is screwed into the the 32A ring mcb's terminal. This goes to the garage. This mean the radial now has a 32A mcb, while the ring is properly rated.

Should the garage socket be take off the ring mcb and have its own 16A mcb?

Thanks.

Just because I like some thanks....... (so hit the button) :D

It's fine to spur direct of a 32 amp mcb with a 2.5mm cable feeding 1 x double socket.

A TE 2.5mm copes with approx 27 amps, defacto a double socket can only be loaded to 26 amp (2 x 13 amp devices).

However cable distance does come in to play, and if the distance to the garage is more than a nominal 10m or so then there a chance that the cable is underrated.

You don't mention if the garage is detached or attached or the distance of the run.
You don't mention if the circuit is rcd protected.
You don't mention if the cable breaks to an external type which it should be if at any point it 'goes' external.

You also don't mention what the cable serves, but I would suspect a double socket with a tap in for lighting.

It would be best to derate and this could be done by moving the cable to a 20 amp MCB (if rcd controlled) or a 20 amp B type RCBO.

Another method would be to terminate the cable on to a 13 amp rcd fuse spur and the load side of that on to the socket and whatever else you have in the garage.

Could I suggest you use the search facility, all the questions you ask have been asked already by previous posters, You might like to buy an OSG which also details the answers to the majority of your questions.
 
A normal 32A ring with both live wires into the 32A mcb. A 2.5mm T&E cable is screwed into the the 32A ring mcb's terminal. This goes to the garage. This mean the radial now has a 32A mcb, while the ring is properly rated.

Should the garage socket be take off the ring mcb and have its own 16A mcb?

Thanks.

That would be a spur from the point of origin, not a separate circuit. How long is the spur? What is on the other end?

You can't just go around changing protective devices.

Colin C
 
Just because I like some thanks....... (so hit the button) :D

It's fine to spur direct of a 32 amp mcb with a 2.5mm cable feeding 1 x double socket.

thanks.

A TE 2.5mm copes with approx 27 amps, defacto a double socket can only be loaded to 26 amp (2 x 13 amp devices).

Thanks. 27 amps? Wow! So if the washing machine and freezer draw 5 kW that is 20 AMPS. So well within scope.

However cable distance does come in to play, and if the distance to the garage is more than a nominal 10m or so then there a chance that the cable is underrated.

You don't mention if the garage is detached or attached or the distance of the run.
You don't mention if the circuit is rcd protected.
You don't mention if the cable breaks to an external type which it should be if at any point it 'goes' external.

You also don't mention what the cable serves, but I would suspect a double socket with a tap in for lighting.

Thanks good Qs.

1. The garage is attached
2. The dble socket is about 4 metres away.
3. RCD protected.
4. Socket supply's a washing machine and "may" do a small freezer.

It would be best to derate and this could be done by moving the cable to a 20 amp MCB (if rcd controlled) or a 20 amp B type RCBO.

I was thinking of a 16A mcb just for the garage.

Another method would be to terminate the cable on to a 13 amp rcd fuse spur and the load side of that on to the socket and whatever else you have in the garage.

The CU backs onto the garage wall, so no problem. I see your point though, which would solve problems in many situations.

Could I suggest you use the search facility, all the questions you ask have been asked already by previous posters, You might like to buy an OSG which also details the answers to the majority of your questions.

What is an OSG?

Thanks.
 
A normal 32A ring with both live wires into the 32A mcb. A 2.5mm T&E cable is screwed into the the 32A ring mcb's terminal. This goes to the garage
A 2.5mm cable taken from a rings MCB counts as a spur off the ring as far as regs are concerned. That means it should only feed one single or double socket or one fused connection unit (FCU). If that is all it feeds then there is no problem otherwise some correction is required.

The best soloution would be to put the garage on it's own breaker. Assuming no thermal insulation is involved in the run you should be able to use a breaker up to 20A.

Another option is to insert a FCU before the first item in the garage so that everything is protected by the fuse in the FCU. This is less preferable though as it limits the total load in the garage to 13A.

All the above assumes an attatched garage and hence relatively short cable runs, with detatched garages volt drop also needs to be taken into account as does the use of a suitable cable type for underground running.
 
A normal 32A ring with both live wires into the 32A mcb. A 2.5mm T&E cable is screwed into the the 32A ring mcb's terminal. This goes to the garage. This mean the radial now has a 32A mcb, while the ring is properly rated.

Should the garage socket be take off the ring mcb and have its own 16A mcb?

Thanks.

That would be a spur from the point of origin, not a separate circuit. How long is the spur? What is on the other end?

You can't just go around changing protective devices.

Colin C

thanks.

5 meters away
wahing machine and small freezer.
One double socket.

To me now it would be obvious to put the garage radial on a separate 16A mcb. Divide and rule.

Say the garage spur is loaded to 20 amps, the ring then is restricted in capacity as there is only 12A remainig until the mcb trips.
 
A normal 32A ring with both live wires into the 32A mcb. A 2.5mm T&E cable is screwed into the the 32A ring mcb's terminal. This goes to the garage
A 2.5mm cable taken from a rings MCB counts as a spur off the ring as far as regs are concerned. That means it should only feed one single or double socket or one fused connection unit (FCU). If that is all it feeds then there is no problem otherwise some correction is required.

The best soloution would be to put the garage on it's own breaker. Assuming no thermal insulation is involved in the run you should be able to use a breaker up to 20A.

Another option is to insert a FCU before the first item in the garage so that everything is protected by the fuse in the FCU. This is less preferable though as it limits the total load in the garage to 13A.

All the above assumes an attatched garage and hence relatively short cable runs, with detatched garages volt drop also needs to be taken into account as does the use of a suitable cable type for underground running.

Thanks. I agree with your point of giving the garage its own mcb.

If lighting is taken off this garage spur, would it be best to have the lighting on a FCU with a 3A fuse? Or the light switch the FCU? (odd I know, but may be practical).
 
Nothing wrong with using a FCU to switch a light on and off and provide it with overcurrent protection.

Remember that you can't add anything to the garage spur while it is still an unfused spur so you either need to move it to it's own MCB (making it a radial) or insert a FCU covering everything in the garage (making it a fused spur from the output of the FCU) before you can add anything to it.

Note that moving it to it's own MCB is notifiable under part P. (I don't really care whether you follow the law on part P or not, just pointing it out)
 
Nothing wrong with using a FCU to switch a light on and off and provide it with overcurrent protection.

Remember that you can't add anything to the garage spur while it is still an unfused spur so you either need to move it to it's own MCB (making it a radial) or insert a FCU covering everything in the garage (making it a fused spur from the output of the FCU) before you can add anything to it.

Note that moving it to it's own MCB is notifiable under part P. (I don't really care whether you follow the law on part P or not, just pointing it out)

Thanks. All coming clear.
 

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