Ring vs Radial - Sockets

[ldoodle]

In which case you go for 20A radials and use 2.5mm², and install 2 radials if 20A is not sufficient.

Or to make use of the existing 32A breakers, 2.5mm rings?

I'm sure I've seen the table of calculations on this site before - can any one point me to it.

 

[davelx]

In which case you go for 20A radials and use 2.5mm², and install 2 radials if 20A is not sufficient.

Or to make use of the existing 32A breakers, 2.5mm rings?

I'm sure I've seen the table of calculations on this site before - can any one point me to it.

Yes - I wasn't thinking rings. 2x 20A radials is more flexible, especially if they are on different RCDs - a fault won't take out the whole kitchen.

 

[ldoodle]

In an ideal world I'd have a dedicated circuit for every room, with the kitchen having 3 - one for cooker, one for sockets and one for hard wired appliances.

That would mean a CU with 12 ways for socket circuits!

 

[Aragorn84]

Such CU's are available if you so desire...

Any why stop there, give each appliance in the kitchen its own circuit

 

[ldoodle]

Any why stop there, give each appliance in the kitchen its own circuit

You say that, but I had a chat with a sparky recently as we were discussing appliance isolation in the kitchen. We both agreed FCUs above worktop are fugly uckers so I 'joked' about having something like a 20a breaker with a 20 amp wall switch for each appliance.

Seen this at TLC. Just over £130 + VAT fully loaded. Not that bad really.

http://www.tlc-direct.co.uk/Products/MK5681ED17.html

 

[ldoodle]

Yes - I wasn't thinking rings. 2x 20A radials is more flexible

Just like they used to join 2 radial circuits to make a ring, I guess you can split them up as well (cable permitting)

So take a 2 room setup, 2 doubles in each room. CU > socket 1 > socket 2 > socket 3 > socket 4 > CU.

Wired in 2.5mm on a 32A breaker.

Socket 1 and 2 in room 1, 3 and 4 in room 2. Break the connection between the 2 rooms and wire into 2 20A breakers.

 

[davelx]

Any why stop there, give each appliance in the kitchen its own circuit

You say that, but I had a chat with a sparky recently as we were discussing appliance isolation in the kitchen. We both agreed FCUs above worktop are fugly uckers so I 'joked' about having something like a 20a breaker with a 20 amp wall switch for each appliance.

Seen this at TLC. Just over £130 + VAT fully loaded. Not that bad really.

http://www.tlc-direct.co.uk/Products/MK5681ED17.html[/QUOTE]

You can get engraved grid switches and grid fuseholders:

http://www.tlc-direct.co.uk/Main_In...nu_Index/Grid_System/Grid_System_3/index.html

 

[ldoodle]

You can get engraved grid switches and grid fuseholders:

Yeah seen those. My problem with them though is really you need a grid switch/fuse pair to make it sensible (which then looks uglier than FCUs) - no point in having a grid switch accessible and socket inaccessible behind an appliance that the appliance is plug topped into (if the fuse goes you have to pull the appliance out).

I'm trying to find an egraver who will custom engrave my FCUs (suggestions please!) - as Dymo labels look even worse! Sometimes wish I didn't care - life would be so much easier.

 

[ldoodle]

VD for 2.5mm² T&E is 0.018V/A/m 0.018*20*25 = 9
9/230=0.039, i.e. 3.9%

similarly for 4mm² at 0.011V/A/m

What is the acceptable percentage, and do you adjust for rings? If I change for a 30m run, I get

0.075, or 7.5%

0.018*32*30 = 17.28
17.28/230 = 0.075

 

[seasickstevie]

... running in the joist bays going down > up > down > up.

You don't normally need to go up & down much in a kitchen, as the runs tend to run behind the units, or even just go horizontal from socket to socket.

 

[ldoodle]

You don't normally need to go up & down much in a kitchen, as the runs tend to run behind the units, or even just go horizontal from socket to socket.

I'm not normal . What I do in one room has to be the same elsewhere.

 

[EFLImpudence]

In explaining everything this has all become overcomplicated for a 'normal' house.

 

[ericmark]

The ring is very limited, designed to save copper directly after the second world war in conjunction with the 13A plug it worked well but alterations in building practice and electrical regulations which control how wires have to run and how much wire is allowed have reduced the advantages to such an extent that really it is often better to have radials.

To follow the rules with ring finals in real terms you have to have a 32A MCB but with radials you can have anywhere between 16A and 32A depending on cable used but using 4 mm² may not allow a 32A MCB often reduced to 25A and using 2.5mm² allows a 20A MCB so really needs 6mm² for 32A radial which means in turn no spurs as no room in the terminals.

So really it's 2.5mm² and 20A MCB radial or 2.5mm² and 32A MCB ring. Using 20A RCBO's does mean less trips when there is a fault but using just 2 RCD's really does away with the advantage of the 20A radial. Because the RCBO route is more expensive than the twin RCB route it still works out more expensive to run radials so I would say today radials are in the main better but ring is cheaper.

 

[davelx]

VD for 2.5mm² T&E is 0.018V/A/m 0.018*20*25 = 9
9/230=0.039, i.e. 3.9%

similarly for 4mm² at 0.011V/A/m

What is the acceptable percentage, and do you adjust for rings? If I change for a 30m run, I get

0.075, or 7.5%

0.018*32*30 = 17.28
17.28/230 = 0.075

VD for socket circuits is 5% (I think I mentioned that earlier).

With a Ring Final Circuit (RFC- which your example must be to use 32A MCB with 2.5mm² cable) for VD purposes the best you can really do is calculate the VD to the mid-point of the ring and that point has two runs of 2.5mm in parallel, so it's not 0.018 it's 0.009. The trouble is that the RFC is a kluged design and doesn't really fit neatly with the rest of the regs.

 

[ban-all-sheds]

Yeah seen those. My problem with them though is really you need a grid switch/fuse pair to make it sensible (which then looks uglier than FCUs)

Does a 2-aperture single-gang faceplate with a grid switch and a grid fuse module look uglier than a single-gang faceplate with a switch and a little drawer with a fuse in it?

Still - in the eye of the beholder, of course.

I'm trying to find an egraver who will custom engrave my FCUs (suggestions please!)

Here's one:

http://www.engraved-labels.co.uk/electrical_accessories.htm

I'm sure that if there are others then Google will find them.

Also, some makers might produce engraved FCUs - I know that Crabtree used to.