Adapting CU for dual tariff, am i missing anything

[MickSmith5824]

Hi all

I've been ask to change another dual tarriff consumer unit (17 useable ways) I've changed a few of these in past but choice does seem limited and always seem to pay over the odds for what it is. I am considering adapting a dual rcd FuseBox consumer unit. I'm just checking am I missing anything in plan for this? The FuseBox consumer units come with 3 neutral bars from what I remember so no problem there. So my theory is all I need to do is purchase another main switch and consumer unit cable kit BG Consumer Unit Cable Kit - https://electrical-showroom.co.uk/catalog/product/view/id/5501/s/bg-consumer-unit-cable-kit?gclid=Cj0KCQiAmL-ABhDFARIsAKywVadon4FzxhouM62TtMtRkwj9jG-WerEUWITZY3D1xmTN1iJ3U53trHMaAsjTEALw_wcB

And I'm good to go? Or am I missing anything? Been a long day : )

 

[SparkyChick]

Given it's a Fusebox board you're proposing I would use Fusebox gear only to avoid the possibility of it coming back to bite you if something did go wrong.

You should also consider adding a 4th neutral bar... you're going to have 1 for each RCD and 1 for the off-peak side which means you won't have one to use for splitting the switched neutral on the dual RCD side. You could probably get away with using the main switch terminal but again, to ensure your backside is covered I would use the cables how they are intended by adding another neutral bar.

 

[westward10]

Your link is to a BG product not FuseBox.

 

[MickSmith5824]

Given it's a Fusebox board you're proposing I would use Fusebox gear only to avoid the possibility of it coming back to bite you if something did go wrong.

You should also consider adding a 4th neutral bar... you're going to have 1 for each RCD and 1 for the off-peak side which means you won't have one to use for splitting the switched neutral on the dual RCD side. You could probably get away with using the main switch terminal but again, to ensure your backside is covered I would use the cables how they are intended by adding another neutral bar.

Thanks SparkyChick I've actually just had to take cover off my own CU to check how would all be linked together. Does look like 3 bars would do job but your right 4th would be better. Call me a numbnut but how do you actually go about fitting a 4th bar? Cheers

 

[MickSmith5824]

Your link is to a BG product not FuseBox.

Westward I've not actually been able to find any Fusebox cable kits

 

[SparkyChick]

Thanks SparkyChick I've actually just had to take cover off my own CU to check how would all be linked together. Does look like 3 bars would do job but your right 4th would be better. Call me a numbnut but how do you actually go about fitting a 4th bar? Cheers

That largely depends on the manufacturer.

Hager for example will sell you neutral bars and the clips required to mount them on the bar at the top. I've just looked on the Fusebox site and they don't appear to have anything in the way of that kind of accessory so it may be better to use another manufacturer.

My primary area of concern in suggesting this is that if you attempt to use the cables that would ordinarily be present in a split load board, one end is typically terminated in a crimp lug and the other is welded. Without the crimp lug you may struggle to properly terminate two cables in the main switch. With the lug you may find it difficult to get a good sound connection as the lugs are quite solid and cage clamps rely (to an extent) on deforming the conductors to get a solid connection. But also modifying them may also invalidate the type testing used to ensure it conforms to the required standards.

It's a tricky one and to be honest I would perhaps be inclined to use two separate boards to avoid any of this kind of nonsense.

 

[MickSmith5824]

That largely depends on the manufacturer.

Hager for example will sell you neutral bars and the clips required to mount them on the bar at the top. I've just looked on the Fusebox site and they don't appear to have anything in the way of that kind of accessory so it may be better to use another manufacturer.

My primary area of concern in suggesting this is that if you attempt to use the cables that would ordinarily be present in a split load board, one end is typically terminated in a crimp lug and the other is welded. Without the crimp lug you may struggle to properly terminate two cables in the main switch. With the lug you may find it difficult to get a good sound connection as the lugs are quite solid and cage clamps rely (to an extent) on deforming the conductors to get a solid connection. But also modifying them may also invalidate the type testing used to ensure it conforms to the required standards.

It's a tricky one and to be honest I would perhaps be inclined to use two separate boards to avoid any of this kind of nonsense.

Thanks SparkyChick really helpful. Going with the two boards might actually be a better bet the FuseBox ones are cheap enough. I'll have to check out the dimensions

 

[kropaske]

Can you use Rcbo's instead of rcd? You would only need 2 neutral bars and 2 main switches?
Also correct information on CU about isolation...

 

[MickSmith5824]

Can you use Rcbo's instead of rcd? You would only need 2 neutral bars and 2 main switches?
Also correct information on CU about isolation...

Thanks Kropaske. I'm trying to keep costs down though. The board requires 15 MCB's and 2 ways for a contactor

 

[kropaske]

Type ac rcbo is around 10 quid and type a around 14. Two rcd boards maybe more expensive than 1x rcbo board and you can do it quicker and neater

 

[MickSmith5824]

C

Type ac rcbo is around 10 quid and type a around 14. Two rcd boards maybe more expensive than 1x rcbo board and you can do it quicker and neater

Cheers I'll do the calculations tomorrow

 

[richy3333]

I'd be asking Hager or similar to make a board up for you. You're direction makes you the designer and you'll have to deal with any faults that occur out of your own pocket.

Hagers own dual tariff board only gives you 12 usable ways split over peak, off peak and water - with RCBO's. I cant say I've ever needed anything larger. Whats the story behind needing so many ways?

 

[MickSmith5824]

I'd be asking Hager or similar to make a board up for you. You're direction makes you the designer and you'll have to deal with any faults that occur out of your own pocket.

Hagers own dual tariff board only gives you 12 usable ways split over peak, off peak and water - with RCBO's. I cant say I've ever needed anything larger. Whats the story behind needing so many ways?

Thanks Rich I've been down that route before with Hager with getting one made up, pretty pricey plus waiting times. I personally don't think there is a great danger in modifying a Board if all components are made to spec. In effect all we are doing is rearranging them I hear you with arse covering but may go ahead with it, not decided yet. One query I've got a pretty simple one really is if in situation tails are to short and move one of the main switches furthest left, other than the L and N markings being revered there is no actual operating differences with the DP is the there? It is just a DP switch after all. Have installed wylex boards with the L and N markings reversed pre manufactured so can't be an issue but just checking

 

[SparkyChick]

There can be differences. If the switch has line/neutral labelled I would be inclined to stick with it. I looked into this myself because I did exactly what you're hinting at with an MK board. If I recall correctly, the main switch is designed to break line first, then neutral and connection is the opposite.

 

[richy3333]

@MickSmith5824 Yeah, I'd agree with sparky chick. If you are using Fusebox give them a call to see if on side breaks quicker than other. They're replay helpful - I'd even ask them about adding a heating board to their range. They do a massive 20 odd way one or a duplex board so one of those should see you ok. You can buy the main switches separately and the tail glands are cheap. Their RCBO's are cheap too. Put up a pic of the board, be interested to see it.