cables in parallel, anyone?
4Mm Radial Off Ring Cct
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OK.
A couple of points stand out here - and a thought (half formed after quite a bit of real ale yesterday :x )
Six core - I see no reason why not - personally I`d prefer that to a 4mm radial from the ring.
Two other options - one is okay, depending on what the existing ring serves - would be to split the ring into 2 radials, and take your summer house line from the now-radialised circuit.
The other option I haven`t thought through yet - but would involve fitting a small enclosure, with a 16A MCB, to feed your sub-main. It isn`t ideal - but it isn`t a fixed load, you`re protecting the cable.... But if they`re your only options - my preference is to extend the ring, tbh
KME
A couple of points stand out here - and a thought (half formed after quite a bit of real ale yesterday :x )
Six core - I see no reason why not - personally I`d prefer that to a 4mm radial from the ring.
Two other options - one is okay, depending on what the existing ring serves - would be to split the ring into 2 radials, and take your summer house line from the now-radialised circuit.
The other option I haven`t thought through yet - but would involve fitting a small enclosure, with a 16A MCB, to feed your sub-main. It isn`t ideal - but it isn`t a fixed load, you`re protecting the cable.... But if they`re your only options - my preference is to extend the ring, tbh
KME
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YES.... Dependant upon certain design criteria...
and
NO... based on certain design criteria...
BUT........................
as we have been told very little fact about the proposed design...
its damn near impossible to give an accurate answer....
Possibility this is due to the subtle difference between learning regulations and installtion..
without understanding design...
few hints...
i) proposed max demand or load of the new bit you want to add onto the installtiuon...
ii) suitable cable big enough to carry this load...
iii) suitable protective device for this cable...
iv) any relevant correction factors that will alter the above values...
and then we go into....
what is the load on the existing circuit that you want to extend...
how physically big is the existing circuit?
what floor area does it cover?
how many other radials are there branching off it?
where about around the ring are you looking at extending from, halfway..quater..third..fifth??
how long is your new radial?
what are your existing Zs vales.. what is your calculated prospective Zs..
what will you amended R1+R2 be
what will the new volt drop be?
etc..
etc..
I can think of numerous arguments to make if both acceptable AND unaccepatble..
but..
I cannot write out all the feasibilities or I will be on here all afternoon!
:C
I've done this a number of times and cannot see the problem
As stated one spur can be run from a ringmain circuit but this refers to one single run of 2.5mm the diagram in osg even shows this and hopefully we all understand why.
But 4mm can handle 32a, I can't see a reg or reason why it could not be done
As already said a lollipop in reverse
And two 4mm's can be connected into a double socket comfortably however a single box for a fused spur can be a struggle!
As stated one spur can be run from a ringmain circuit but this refers to one single run of 2.5mm the diagram in osg even shows this and hopefully we all understand why.
But 4mm can handle 32a, I can't see a reg or reason why it could not be done
As already said a lollipop in reverse
And two 4mm's can be connected into a double socket comfortably however a single box for a fused spur can be a struggle!
Hi all,
It looks all plain enough to me.....
Unfused spur; one socket outlet, twin or single
Fused spur; Anthing you like, BUT the fuse CANNOT be larger than 13A
How difficult can that be to understand... Have a radial if you want, but it can either supply the one socket, or be fed via an FCU with a 13A fuse
It states in the book that; This appendix sets out options for the design of ring and radial circuits for household and similar premises in accordance with regulation 433.1 using socket outlets and fused connection units.
So, if these are the options, i presume anything else is not an option????
It goes on to say that "the load current in any part of the circuit should be unlikely to exceed for long periods the current carrying capacity of the cable"
As the current carrying capacity of the 2.5 is only about 20A this is the reason they stipulate only ONE twin socket or anything you like, but it MUST be via an FCU [ to limit load current presumably]
john...
It looks all plain enough to me.....
Unfused spur; one socket outlet, twin or single
Fused spur; Anthing you like, BUT the fuse CANNOT be larger than 13A
How difficult can that be to understand... Have a radial if you want, but it can either supply the one socket, or be fed via an FCU with a 13A fuse
It states in the book that; This appendix sets out options for the design of ring and radial circuits for household and similar premises in accordance with regulation 433.1 using socket outlets and fused connection units.
So, if these are the options, i presume anything else is not an option????
It goes on to say that "the load current in any part of the circuit should be unlikely to exceed for long periods the current carrying capacity of the cable"
As the current carrying capacity of the 2.5 is only about 20A this is the reason they stipulate only ONE twin socket or anything you like, but it MUST be via an FCU [ to limit load current presumably]
john...
is there anything in the regs state that you cannot use a ring final to supply a sub-main?
Hi Steps,
Be a small submain though fed by a FCU !!!
[bike going great by the way, averages about 115MPG!!]
john...
Be a small submain though fed by a FCU !!!
[bike going great by the way, averages about 115MPG!!]
john...
I find it hard to believe that the load for a Summer House will be over 13A (3KW)
Most conservatories I've fed on a 13A fused supply . From 2-4 twin sockets , couple of wall lights , punkka wallla fan and a couple of brick lights.
Never had a problem .
Most conservatories I've fed on a 13A fused supply . From 2-4 twin sockets , couple of wall lights , punkka wallla fan and a couple of brick lights.
Never had a problem .
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bit like the C70 days, John, my thinking is, a FCU is for a spur, can a proper 16A submain be run,?
I dont think there is a reg specifically prohibits a CU with 16A MCB being added to a RF..... :C
I dont know, trying to think laterally I suppose after someone suggested that option, 2.5 can safely carry over 20A BTW, and the regs only cater for common scenarios,
nothing wrong with being a deviant. ]
Well, you'd know about that !!!! :innocent
yeah yeah,
did Sandra tell you to say that?
did Sandra tell you to say that?
stuartmcclean
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what is a lollipop in reverse
its like getting your girlfriend to be nice to you.
the more you suck the bigger it gets.
the more you suck the bigger it gets.
lol, that's why she blows
unbalanced ring I think is the reasons behind the wondering if its allowed.
Do you know , I've never had any worries about unbalanced legs of rings , I've never come across a problem with it , specially with alternate looping as in conduit . Just wire the ring , no control over what may or may not be plugged into one side or the other and get on with life .
In my humble opinion another case of electricians creating problems for themselves . As long as the correct overload device is fitted and with the addition of RCDs these days , there 'aint a lot more you can do .
I did a job where you couldn't get back to the board without massive disruption to flooring and decoration so removed the one plug in a utility, feed a 2 way CU with RCD main switch with the 2 legs of the ring and install 2 X 16A radials for washing m/c, drier and freezer. You won't find it in the OSG I don't think.
In my humble opinion another case of electricians creating problems for themselves . As long as the correct overload device is fitted and with the addition of RCDs these days , there 'aint a lot more you can do .
I did a job where you couldn't get back to the board without massive disruption to flooring and decoration so removed the one plug in a utility, feed a 2 way CU with RCD main switch with the 2 legs of the ring and install 2 X 16A radials for washing m/c, drier and freezer. You won't find it in the OSG I don't think.
unbalanced rings - that brings back memories! I remember some of the older sparks, wiring sockets alternately on the same ring and other nonsense to even up load on circuit. Since then i think every spark I have seen has completely ignored this old practice, and I can't say I have ever seen a problem caused by it. Have fitted spur with in line 20A MCB before to supply washing machine and tumble drier where there was no real way of constructing proper ring extension, but 13A would just not do.
Had argument with a couple of old (but not bright) sparks whilst re-wiring flat in very large old house. Circuit exceeds recommended 90m2 they harped, Zs about half allowed I replied....if you do the connections nicely you get low resistances :^O
If you plugged 2 electric fires into first socket of ring, how un-balanced would that be, and would circuit go terminal and melt????
Had argument with a couple of old (but not bright) sparks whilst re-wiring flat in very large old house. Circuit exceeds recommended 90m2 they harped, Zs about half allowed I replied....if you do the connections nicely you get low resistances :^O
If you plugged 2 electric fires into first socket of ring, how un-balanced would that be, and would circuit go terminal and melt????
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ah, but did you allow for PD over such a large area?
its not simply about Zs or VD , its about potential change,
and I'll bet you never measured that.
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