Size of mcbs for ring of sockets and radial

[hazey7]

Hello,
Have searched the site to no avail so must post...

My house has two ring mains of sockets plus two radial circuits of sockets.
If I replace the CU with a split load, should the radial circuit MCBs be 16A or 32A as per the rings?

Cheers

 

[sterose]

Hello,
Have searched the site to no avail so must post...

My house has two ring mains of sockets plus two radial circuits of sockets.
If I replace the CU with a split load, should the radial circuit MCBs be 16A or 32A as per the rings?

Cheers

You don't indicate the purpose of the radial circuits, nor the current amperage of the MCB/fuse, nor the reason for replacing the CU, and nor the reason you ask this of us (i.e. I'll help you, but you don't sound particurlarly competent if you ask these questions, so watch you dont bug*er it up).

 

[hazey7]

Well basically at the moment the radial circuits are off 30A fuses and the two rings are off 30A fuses.

Why should the purpose of the sockets have anything to do with it? It depends on what gets plugged into the sockets doesn't it?

Presently one ring main has a fridge, a socket currently used for a toaster and two room sockets which may get used for hoovers, etc. The other ring main is for TV, stereo, table lamps, etc.

One radial is a feed for the garage, 2 sockets and a two flouros.
The other radial is for a circuit of 3 sockets, one tumble dryer, one washing machine and a freezer.

Now you know the contents of the back section of my house, can you tell me the answer?

In my mind, 32A MCBs should protect a ring main (basically 2 ffeds/2 cables) and a 16A MCB should protect a radial as ots one cable out.

See my point?

I'm replacing the fuse board because:
a) Its 30 years old
b) Is too small, am expanding to put an oven on it.
c) To comply with latest regs and pass my elec survey I need a split load.

 

[sterose]

Well basically at the moment the radial circuits are off 30A fuses and the two rings are off 30A fuses.

Why should the purpose of the sockets have anything to do with it? It depends on what gets plugged into the sockets doesn't it?

Presently one ring main has a fridge, a socket currently used for a toaster and two room sockets which may get used for hoovers, etc. The other ring main is for TV, stereo, table lamps, etc.

One radial is a feed for the garage, 2 sockets and a two flouros.
The other radial is for a circuit of 3 sockets, one tumble dryer, one washing machine and a freezer.

Now you know the contents of the back section of my house, can you tell me the answer?

In my mind, 32A MCBs should protect a ring main (basically 2 ffeds/2 cables) and a 16A MCB should protect a radial as ots one cable out.

See my point?

I'm replacing the fuse board because:
a) Its 30 years old
b) Is too small, am expanding to put an oven on it.
c) To comply with latest regs and pass my elec survey I need a split load.

"Why should the purpose of the sockets have anything to do with it? It depends on what gets plugged into the sockets doesn't it?"

Yes... Funny...
The reason the purpose of the sockets matters, is beacuse 16amp may not be sufficient to run a couple of kettles and a cooker off.... alright, i'm exagerating, but you have to consider whether 16amp is sufficient to run what is going to be plugged into the circuit. And the reason I ask what is the present rating of the fuse, is because that might give an idea of what you should replace it with.

But to answer your question, yes, 16amp will do fine for the radials.

 

[securespark]

sterose


see my answer for the other posting in this listing.

When you consider what loading is on the three "radial" sockets, 16A is insufficient. The mcb should be 20A, but personally I would consider making these three outlets part of the ring.

See the "on-site guide" for data about radial circuits.

 

[phil28]

I always work on a radial to be 20 amp a fixed applance on a seperate fuse to be 16 amp and a ring to be 32 amp shower and ovens to be done on a calculation on the size of the oven or shower however if you are putting in a split load CU I now run a seperate fuse 16 amp for the frigde/ freezer on the main switch side and not the rcd side this I was taught when I was in australia the reason being that if a fault interrupted the rcd side the fridge/freezer would still work (meaning you do not lose the contents of your fridge because the rcd had worked)