got 1 socket ring main. The MCB is rated at 32 amps which gives around 7.3KW. Now got a couple of extra heaters now and i fear we will be quite close to tripping it out. Could i uprate it to a 40amp as the ring will be wired with 2.5mm sq cable which can take up to about 23amps. So thats like 46amps in total. So the 40amp should still protect.

CLiff

Speaking from a physics, "I-don't-know-the-regs" view, then how long is your cable run?

If it's relatively short, you should be fine.

There may be regs which prevent this anyhow.

It it were me, I'd add another ring and try to limit the load you put on each.

the regs limit the length of any 1 ring anyway. Cant remember what the figure is but its something like 20m.

Also no point adding another ring its a 1 bed flat so where do you split it. Also another ring is an overkill.

I was just thinking that if a 3 electric heaters were on, the microwave, dryer, washing, machine and TV/Hifi etc then it would probably be over the limit

Cliff

I certainly wouldnt..

Depends how cables are routed as well..

have a look at http://www.tlc-direct.co.uk/Book/4.3.9.htm

David

also...

seee http://www.tlc-direct.co.uk/Book/6.2.1.htm

also 6.3.2 The final ring circuit...

1. - The floor area served by each ring must not exceed 100 m² for domestic situations, Where ring circuits are used elsewhere (such as in commerce or industry) the diversity must be assessed to ensure that maximum demand will not exceed the rating of the protective device.

2. - Consideration should be given to the provision of a separate ring (or radial) circuit in a kitchen.

3. - Where there is more than one ring circuit in the same building, the installed sockets should be shared approximately evenly between them.

4. - Cable sizes for standard circuits are as follows:

a) p.v.c. insulated cable are 2.5 mm² for live (phase and neutral) conductors and
--- 1.5mm² for the CPC.

b) mineral insulated: 1.5mm²for all conductors.

These sizes assume that sheathed cables are clipped direct, are embedded in plaster, or have one side in contact with thermally insulating material. Single core cables are assumed to be enclosed in conduit or trunking. No allowance has been made for circuits which are bunched, and the ambient temperature is assumed not to exceed 30°C.

5. - The number of unfused spurs fed from the ring circuit must not exceed the number of sockets or fixed appliances connected directly in the ring.

6. - Each non-fused spur may feed no more than one single or one twin socket, or no more than one fixed appliance.

7. - Fixed loads fed by the ring must be locally protected by a fuse of rating no greater than 13 A or by a circuit breaker of maximum rating 16 A.

8. - Fixed equipment such as space heaters, water heaters of capacity greater than 15 litres, and immersion heaters, should not be fed by a ring, but provided with their own circuits.

This sounds a bit dodgy to me. If there are any junction boxes in the ring they are probably rated at 32 amps, so you could be pushing more through them than they are designed for. Not a good thing.

BTW, as far as I have read up the length of the circuit is a two-stage calc. There is the permitted floor area covered of 100 sqm for a 32A domestic ring, based off the number of electric heaters reasonably required to heat that much space, plus there's a maximum distance that the furthest point of the circuit must be within from the MCB. This is to make sure that the MCB activitates within a specified safe time after a fault condition occurs. If the distance is too far, response is too slow.

Go to the Screwfix site, sign up for the forums and post on the Electricians board. Then you'll get a definitive answer.

I will stick with 32 as it was obviusly put in for a reason

cheers

CLiff