storage heaters and lack of MET

[marcjano]

Hi,

I'm replacing a consumer unit on an installation which has economy seven storage heaters.
Before heaters were on their own feed from the time clock(located next to meter). I think that I shouldn’t put two supplies in to one CU so do i need to replace with two CUs or can I just use one?

I have never wired up economy 7 before.

Also I am not sure about type of installation as there is no MET and only 3x 16mm2 protective conductors joined to main cut out. No RCDs installed. I am not sure as well How I should connect separate CU when there is no MET. Can I connect PC between CUs?



Any advice would be greatly appreciated.....

 

[Guest123]

Hi, welcome to the forums.

First of all you have a TN-C-S system there as is indicated by the sticker on ther front of the DNO cut -out (PME).

What you have there currently is a dual tariff board, on 1 half is the 24hr power & lighting, and on the other half is the economy 7 storage heaters.

There is no problem with fitting a new dual tariff board and running the supplies into it. Or 2 c.u's are fine also, this may be an easier option for you as you will need to fit 30mA RCD/RCBO protection to the circuits now depending on installation methods.

You could quite easily install a single pole service block (henley) for the earthing conductors, take one out from the DNO cut-out to your henley block and then one to each of your new c.u's.

You also need to make sure that all bonding conductors are in place, water, gas etc, also as you will be putting 30mA protection in then an insulation resistance test on existing circuits may be an
idea, just to see if there are any existing faults on any of the circuits that may cause you grief later on.

Having looked at your pictures a bit more it doesn't look like the storage heaters are used anymore as there are no cables at the MCB's for them, Maybe you wont need to reconnect them?? or have you removed them already??

Hope this helps.

Cheers.

 

[Spudnik]

Can i ask why the CU is being changed?

Looks fairly tidy to me, albeit with a lack of RCD protection.

Why not just use RCBO's?

Mind you, being a Merlin CU, would probably be more expensive than swapping out for a new one.

Also, an MET is not a requirement, providing that the testing of Ze can be easily achieved without taking apart the installation.

 

[marcjano]

Thanks for prompt answer,

Cables for storage heaters have been removed already that why they are not connected.

Reason why I want to change CU is that beside CU doesn't look so bad all the rest of cabling need to be changed as more circuits are needed and location of board was in my opinion inappropriate(too high - next to the ceiling).

As that will be tanning salon I wonder how I should arrange earthing for sun beds. I've pulled separate earth wire which is going to all beds but I am not sure if that needs to be connected straight to bed or can I use some kind of arthing bar or something.

 

[Spudnik]

Do the sun beds not have their own connections?

If they do then im sure they would be earthed via the supply cable.

Never done them before, so i could be on the wrong track.

 

[Guest123]

Maybe worth looking at any manufacturers instructions....
Agreed, cant see why they would need a seperate earth unless foreign and have 2core flex or something??

 

[marcjano]

Do the sun beds not have their own connections?

If they do then im sure they would be earthed via the supply cable.

Never done them before, so i could be on the wrong track.

They will have their own connections but for now I'm just using information provided by seller of those beds. There is a line "The sunbed must be earthed" and now I am not sure is that means separate earth or I can use cpc.

 

[Guest123]

Hey.

I think they mean that the beds must have a CPC to them as they are class 1 appliance, and not the extra earthing you have installed.

Cheers.

 

[Spudnik]

What he said^^^

 

[marcjano]

Hey.

I think they mean that the beds must have a CPC to them as they are class 1 appliance, and not the extra earthing you have installed.

Cheers.

That what I thought at the beggining but client suggesting to pull those wires just in case. I'll try to convince him to drop that idea.


Cheers