Consumer unit

[wreck-it-steve]

Hi,

Can anyone recomend a good quality consumer unit that is good for a sub board use in a commercial building? it can be either dual RCD or one for RCBOs. Metal would be good.

Thanks

 

[Bill Stickers]

You don't use dual RCD boards on commercial jobs.

What makes you think all circuits will require RCD protection anyway?

Schneider is the only make of board to use on commercial installations.

Are you sure you're really competent to be undertaking this job?

 

[timbim]

Schneider is the only make of board to use on commercial installations.

That's not even close to true.

 

[streetlighter]

Crabtree loadstar, Wylex, Hager, Eaton MEM. I've seen dual RCD boards used on small single phase commercial units and that one was a cheap nasty Chint.

 

[wreck-it-steve]

I wont be doing the work my self , im just getting an idea of the best boards to use as I dont want a crap one put in. I think the electrician I spoke to said to go for one that will allow all RCBOs.

 

[scottyboyiow]

We tend to stick with either Hager or Wylex stuff. Not quite sure, and never heard that you are not allowed to use dual RCD on commercial jobs as Bill has mention, only the installer will know what board is best for the application.

 

[plugwash]

The only reason dual RCD boards are common is because someone seems to have decided that having all the circuits in the house go down when a rcd trips is unacceptable but having half th circuits in a house go down when the rcd trips isn't. Personally I think this is nonsense but it seems to be what the powers that be have decided.

 

[JohnW2]

The only reason dual RCD boards are common is because someone seems to have decided that having all the circuits in the house go down when a rcd trips is unacceptable but having half th circuits in a house go down when the rcd trips isn't. Personally I think this is nonsense but it seems to be what the powers that be have decided.

I would have thought that "nonsense" is putting it a bit strong - since it is obviously a step in the direction of enhancing convenience - particularly when one realises how rare an RCD trip of any sort is (or should be) in a well-designed and well-maintained installation. You don't really make it clear which direction you feel the 'nonsense' is in - are you a 'one RCD' or an 'all RCBO' man at heart?

Kind Regards, John.

 

[scousespark]

I agree with plugwash that this idea of dual RCDS is a bit nonsensical.
John is correct in that it is a step towards a safer environment and RCD failures are rare (but they do happen).

For as long as I've been in the trade (and a lot lnger) the regs have required a single CPD for a single circuit. Therefore a fault in the lighting circuit, takes out that circuit alone.

I take the view that the safest, RCD option, is to RCBO all circuits. The pity is that this is still an expensive option, so a lot of customers will go for a dual RCD CU. This is better than a single RCD, but I doubt your customer would be happy when a fault on a downstairs circuit takes out your upstairs lights as your old granny is halfway down the stairs.

 

[JohnW2]

I agree with plugwash that this idea of dual RCDS is a bit nonsensical. John is correct in that it is a step towards a safer environment and RCD failures are rare (but they do happen).

I didn't actually mention RCD failures - I was talking about (appropriate) operation of RCDs - which is also rare (but does happen). RCD failure is, of course, also another issue - but they usually fail in the sense of not tripping when they should, not by interrupting the supply.

I take the view that the safest, RCD option, is to RCBO all circuits. The pity is that this is still an expensive option, so a lot of customers will go for a dual RCD CU. This is better than a single RCD ....

It's difficult to argue against that as the 'ideal'. There are obviously some potential issues with TT installations, unless literally all the final circuits have RCBOs (i.e. no 'unprotected circuits) and there is no perceived need to have up-front Type S RCD protection for tails, sub-mains etc. Otherwise, one would be stuck with having to try to find, accommodate and pay for DP RCBOs.

Kind Regards, John.

 

[plugwash]

You don't really make it clear which direction you feel the 'nonsense' is in - are you a 'one RCD' or an 'all RCBO' man at heart?

If you fit one RCD for the whole install you are basically saying "I think RCD trips are rare enough that I won't worry about the inconvenience they cause".

If you fit a dual RCD board then you are basically saying "I'm going to pretend to worry about the inconvenience RCD trips cause but not really do much about it" and/or "i'm doing this on the cheap but the powers that be don't like single RCD boards anymore"

If you fit a board full of RCBOs but keep one ring for each floor you are basically saying "I've done the best I can to minimize inconvenience without resorting to installing new circuits".

If you fit a board full of RCBOs AND fit dedicated circuits for stuff where loss of power would be particularly inconvenient you are saying "i've taken as many steps as reasonablly possible to reduce the inconviniance of RCD trips"

If you fit MICC and SRCDs and don't have RCDs/RCBOs at the CU at all you are saying "i'm going to have the best and damn the cost"

 

[scousespark]

I agree with plugwash that this idea of dual RCDS is a bit nonsensical. John is correct in that it is a step towards a safer environment and RCD failures are rare (but they do happen).

I didn't actually mention RCD failures - I was talking about (appropriate) operation of RCDs - which is also rare (but does happen). RCD failure is, of course, also another issue - but they usually fail in the sense of not tripping when they should, not by interrupting the supply.

I take the view that the safest, RCD option, is to RCBO all circuits. The pity is that this is still an expensive option, so a lot of customers will go for a dual RCD CU. This is better than a single RCD ....

It's difficult to argue against that as the 'ideal'. There are obviously some potential issues with TT installations, unless literally all the final circuits have RCBOs (i.e. no 'unprotected circuits) and there is no perceived need to have up-front Type S RCD protection for tails, sub-mains etc. Otherwise, one would be stuck with having to try to find, accommodate and pay for DP RCBOs.

Kind Regards, John.

I didn't mean RCDs not working, as I'm sure you were aware I was agreeing with your assertion that 'trips' were rare.

My post did mention that the expense is a major consideration. In the scenario you describe, the use of RCBOS is a big issue.

It still doesn't alter the fact that it is not ideal to lose a number of circuits when a fault happesn on one.

 

[JohnW2]

If you fit a dual RCD board then you are basically saying "I'm going to pretend to worry about the inconvenience RCD trips cause but not really do much about it" and/or "i'm doing this on the cheap but the powers that be don't like single RCD boards anymore"

Again, I think you're being a bit harsh - 'reasonable compromise' comes to mind.

If you fit MICC and SRCDs and don't have RCDs/RCBOs at the CU at all you are saying "i'm going to have the best and damn the cost"

If we're going to extremes, you'd probably have to do a bit better than that! Even if you had single-socket RCDs (and, presumably, local RCDs for lighting fittings/circuits and fixed loads etc., as appropriate), with no 'central' RCDs/RCBOs in the CU, there would still be the possibility that an overload or L-N fault could take out a whole circuit's MCB - so, for the 'best (convenience) money can buy' option you're contemplating, you would have to wire a separate circuit for each socket or fixed load - in which case you might as well use RCBOs for each of them!

Kind Regards, John.

 

[JohnW2]

It still doesn't alter the fact that it is not ideal to lose a number of circuits when a fault happesn on one.

As I said in my last post, it's difficult to disagree with the fact that such a situation is 'not ideal' (in a perfect world) - and, give or take the TT issues, if cost (and space in CUs!) were not an issue, then 'all RCBOs' would be the obvious way to go.

However, I do think that the concept of 'reasonable compromises' is very valid here. RCD trips are usually very rare (and, if they're not, the installation probably requires attention) and with a little bit of sensible installation design, the impact of operation of one (of two) RCDs can be minimised. In the parts of my house which have dual RCD CUs (or twin RCD CUs), operation of one of them would not result in any room being without access to light (there would always be light 'outside of the door') and nor would it result in loss of sockets in any two adjacent rooms.

Kind Regards, John.

 

[RF Lighting]

Schneider is the only make of board to use on commercial installations.

That's not even close to true.

I wouldn't use anything else.