Replacing an old CU with a new one

[333rocky333]

Earth connections ? It is a TT circuit, so no earth from the supplier.

Voelcb would only work with the Earth connected to it.
Ban suggests it can still be used as an isolater.
However a new install would not use that Voelcb as a Rcd and that purpose wopuld be replaced by relevant Rcd combinations within the new Cu.
I cannot see how you got the relevant parts as per your long list in your original post for around 100 pound

 

[Naz1977]

There is deffo no earth going into the breaker:

As for the parts, I said about,

CU was £80
RCDs and MCBs, £40

total £120
I have a electricfix account at Screwfix and also trade at CEF. So get them cheaper than retail.

 

[Naz1977]

On another note then, on new installs, how is the mains fed into the CU from meter?

Does it go to a breaker first before coming across into the CU? I assume you have to be able to somehow isolate incoming mains somehow if you for instance need to change the CU without the need to break the seal from fuse and remove supplier fuse?

 

[333rocky333]

Are you sure thats Voltage operated, afaik voltage ones wont work without 1 connection to the Earth MET and 1 connection to the Earth rod.

If you intended keeping that as your upfront RCD then it is wrong regardless if its Voltage or Current operated

Noweadays even with TT Usually cabling direct from meter to the Cu, some pay extra to have an isolater between, but to be honest would you ever need to use it.

Breaking the seal has been an issue since day 1 as it even restricts electricians working, but there is a recognised isolating procedure to get the supply temporary isolated to do said works.

Your TT set up is more involved than a normal set up, and to me your costs dont add up, do you have a breakdown of what Rcds you have brought

 

[securespark]

It's no good as an isolator if your main fuse is bigger than 60A.

 

[Naz1977]

Thanks for the info.

don't forget this is a 1930s house with old wiring.

The main fuse is 80A, the voltage operated breaker is 60A.

The plan is I am gonna have a dual RCD unit fitted. So will probably keep that ( the voltage breaker) as an isolator for if/when the main needs to be cut off from the CU to do any possible work. Obviously normally you just turn off the power to the rest of the CU from inside the CU.

I have the following:

4 x 6A MCBs
3 x 32A MCBs
2x 40A MCBs
1x 16A MCB
1 x 20A MCB
1 x80A RCD
1 x63A RCD

Not all the MCBs will be used to begin with as there is future expansion in mind and have bought them so that they are all matching just incase they decide to discontinue one after 12 months or bring in a new model.

There is provision for outside lighting, feed to the garage, upstairs ring, upstairs lighting and Smoke detector which don't exist on the current CU at the moment. The new unit is a 19W unit.


I forgot to include the RCDs in my calculations as they were bought separately to the MCBs. THe RCDs came to £40 on its own. So about £160 all in.

 

[phatboy]

You have just 1 RCD?

 

[securespark]

The main fuse is 80A, the voltage operated breaker is 60A.

It has to go.

 

[Naz1977]

You have just 1 RCD?

2: 63A and 80A

 

[Naz1977]

It has to go.

so that means either the board have to come and take it off as the fuse will need to be removed, or we will remove and then let the board know so they can come back and seal it?

 

[ban-all-sheds]

Why doesn't your electrician know what to do?

 

[securespark]

Some DNO's fit iso switches, some don't.

Best bet is to ring them and tell them you are planning a board change.

Ask if they can come out and isolate the supply while you fit an iso switch then return (or wait while you do it) and re-energise the supply.

Make sure the tails leaving the iso switch will be long enough to reach the main switch of the new board in its new position.

 

[333rocky333]

I think you also need to allow provision for the TT incoming tails where they enter the METAL casing of the new board.

 

[John D v2.0]

We called the dno ukpn and they said they don't fit isolators, it's the supplier's job. The supplier eventually agreed to do it for a small fee. It was actually the meter reading company that did the work.

 

[Iggifer]

Yea usually seems to be the supplier on existing installs.

The DNO will do it on a head move if you ask them nicely but as it's after the meter they like the meter guys to do it.