Bit of a Problem!

[Multitech]

I am new to this chat room so please be easy with me. I am in the middle of rewiring my house but have come across a problem that I hope you lot can help me with.

I have miscounted how many circuits I have, and the new consumer unit is not bigenough. I have doubled up my lights and put them on a 16A trip switch to be safe, I have doubled up two of my socket rings and put that on a 40A trip. But as I have a lot of other circuits I find I need to have two 45A trips for the cooker and the shower, is it OK to double these up as they will never be used together, and the even if they are the wife only uses the oven and one hotplate.

Also this thing about connecting all pipes together with cable, is it really necessary, my main switch is an RCD trip so we are safe. It looks really horrible with decorated walls and green and yellow cable attached to every radiator and bit of pipe in the kitchen and bathroom. Do I really need to do it with an RCD trip?

thanks for your help.

 

[AdamW]

Welcome to the forum! It really is a great source of information, usually very quickly too.

But as I have a lot of other circuits I find I need to have two 45A trips for the cooker and the shower, is it OK to double these up as they will never be used together

With this question there are a variety of possible answers:

1) No
2) No
3) No

Seriously though, I assume that you are talking about an electric shower, and by doubling up you mean connecting two circuits into one device on the CU? Those are the two circuits you least want to do this with.

Whilst you know you won't be using the two simultaneously, the next people who get the house will not know (would you mention it to them showing them round? I doubt it!). So they will end up with the electric shower tripping every time someone uses the oven simultaneously. It isn't unfeasible "you have a shower and I will cook you a nice breakfast" for example.

I know it will be a lot of hassle for you, but from what you have said it would appear that your new CU is not up to the job of powering your whole house.

 

[securespark]

Yes, Adam is right.

You must never "double up" circuits, even if you upgrade the mcb. Bite the bullet, and replace the consumer unit.

How come you installed it b4 realising it was too small? Obviously, you could have returned it unused but not now.

 

[Inspector]

Multi

Why don't you add another consumer unit thus eleviating your dangerous actions of doubling final circuits. (16A for your lighting circuit and 40A for your socket circuit will not afford correct protection in both cases)

 

[Multitech]

Thank you for your help. I have taken your advice and will be changing the consumer unit to a 16way. I will have enough space for all my circuits and still have some spare.

I was rushing to get the job finished and did not think about it. What about all these green and yellow cables, do I really have to put them on every pipe?

 

[Inspector]

Yes

You must bond all incoming supply pipework (water mains etc) to your main incoming earth. The csa of these main bonding conductors is determined by the csa of your incoming supply phase conductors and the type of supply provided by your supply authority ...

TN-S = you have a collar around the authority's supply cable which has an earth conductor coming off it,
TN-C-S = the neutral and earth are combined and you'll see the main earth termination on the supply authorities fuse connection
TT = you have an earth spike.

You should also cross bond metal pipework in your bathroom, kitchen, utility, etc but maybe that already exists if your doing a rewire. This extends to include bonding ...
(1)between metal pipes,
(2)metal pipes and fixed electrical components (light fittings etc) and
(3)between electrical components,
... which you can touch at the same time (simultaneously accessible)

 

[Multitech]

Thanks, In knew I needed them, just wondered if there may be a reaon not too. You know woman, SHMBO does like them, to quote her "They are an ugly eyesore"

Woman!!

There are real problems getting electricians and materials here, everything like this costs a fortune.

 

[kendor]

I am new to this chat room so please be easy with me. I am in the middle of rewiring my house but have come across a problem that I hope you lot can help me with.

I have miscounted how many circuits I have, and the new consumer unit is not bigenough. I have doubled up my lights and put them on a 16A trip switch to be safe, I have doubled up two of my socket rings and put that on a 40A trip. But as I have a lot of other circuits I find I need to have two 45A trips for the cooker and the shower, is it OK to double these up as they will never be used together, and the even if they are the wife only uses the oven and one hotplate.

Also this thing about connecting all pipes together with cable, is it really necessary, my main switch is an RCD trip so we are safe. It looks really horrible with decorated walls and green and yellow cable attached to every radiator and bit of pipe in the kitchen and bathroom. Do I really need to do it with an RCD trip?

thanks for your help.

Alarm Bells Ringing!!!!
You say you have doubled up the lighting circuits and doubled the breaker protecting them aswell as doubling up your ring circuits and protecting them with a 40A breaker?!?!?!
Have you doubled up the cable rating? I assume not! you must also take into consideration the protection of the wiring and doubling up the Fuse/Breaker rating so it copes with the extra load is the wrong way of thinking!
The breaker rating is not the only consideration when you are designing a circuit ,cable rating also plays a part amongst other things.
I feel you are leaving yourself open to fire risk here.

 

[Multitech]

Thanks for the warning Kendor, I have corrected that problem after the advice above. A friend back in the UK has also emailed me a scanned copy of the On Site Guide from the IEE..I have learnt a lot today and will be making some changes to my work.