Discuss Top-feed or bottom-feed RCDs? in the Electrical Forum area at ElectriciansForums.net

pc1966

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Another disparaging Hager-related question: does anyone know if it matters which set of terminals are feed power, and which are load for RCDs?

Typically incomer RCDs are fed from the bottom, but the supplied instructions/datasheet (for what they are worth) for the likes of the CDA425U 4-pole RCCB do not indicate any preferred direction for power (i.e. power supplied from below on even-numbered terminals, or from above on odd-numbered terminals). One side obviously must power the electronics, but it may or may not matter is that remains live upon a trip event.

I asked Hager technical support and they sent me the data sheet, so obviously did not read my question as I had already referred to it :(

So I asked again and no reply for 2 weeks now.

Any thoughts?
Post automatically merged:

Amazing, just on posting this I got a reply:

"Our Main switches & RCD are neither pole dependant and makes no difference if you feed the supply from the top nor bottom."

So now this post is just for general interest.
 

ipf

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I know it doesn’t matter regarding in and out but reply from Hagar? ‘HAGAR IS WATCHING’ ??? and on the ball, too. (today)
 
Sorry probably a bit dense of me RCD in ccu would be fed from the top yours is some kind of FCU RCD ?

Side not I've sent Wylex message requesting info on a RCBO trip curves etc that I can't find anywhere what are the chances Ill get a reply like you got from hager
 

pc1966

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Sorry probably a bit dense of me RCD in ccu would be fed from the top yours is some kind of FCU RCD ?
In a "type B" TPN board the power comes up to the central bus-bar arrangement from below.

But in our case we have some separate RCDs in a DIN rail box as you can't so easily (or cheaply) get RCBOs for 3-phase, or double-pole RCBOs for single phase, for most UK TPN boards. Also we have a few other oddities to connect so the DIN box is handy.

Side not I've sent Wylex message requesting info on a RCBO trip curves etc that I can't find anywhere what are the chances Ill get a reply like you got from hager
Don't hold your breath!

I'm still waiting for clarification of the Wylex industrial MCB current limits, but gave up and moved to Hager (for other reasons, not simply the lack of an answer).
 
I always wondered how you add a RCD to a TPN board with bus-bar down the middle going to the MCBs , assumed it must go where the isolation switch is or you HAD to use RCBOs
 

pc1966

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I always wondered how you add a RCD to a TPN board with bus-bar down the middle going to the MCBs , assumed it must go where the isolation switch is or you HAD to use RCBOs
Some of the manufacturers offer RCD add-ons that basically flip the MCB leaver to do implement an RCBO arrangement but, AFIK, only Schneider offers a neutral bar option for this sort of thing to be neat/simple and even then it is still not so neat as a proper RCBO the RCD is taking at least another 3-way slot out of the TPN board.

It is fairly common to have an RCD incomer on TPN boards, but usually for TT supplies (or for fire risk reduction) as a 100mA / 300mA delay type.
 

Mike Johnson

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pc1966

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Getting DP RCBOs is not too hard, making them fit their TPN board is the real challenge...

You see a lot of DP RCBO in use for the likes of caravan feeds, etc.
 

Mike Johnson

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Don't want to sound a SA, but using a two pole bus bar I don't find it difficult, is there another problem I am missing?
 

pc1966

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Don't want to sound a SA, but using a two pole bus bar I don't find it difficult, is there another problem I am missing?
Most TPN boards only have buses for L1/L2/L3

Schneider has something that looks like it pops up for a neutral bar, but I don't think it is standard.
 

pc1966

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But as an Engineer we should be able to get over any adversity. :innocent:
I just wish that the engineers that designed board had grasped this long ago and provided a neutral for every phase point. Then you could have DP single phase RCBO, or a 3-phase RCBO without loss of space or needing flying neutral wires.

And also that the likes of Wylex that do DP-switching RCBOs would have them listed as compatible with their TPN boards.

But they don't. So I use what I can buy, and thus end up with a side-mounted DIN rail box for the extra RCD gubbins as not enough height for either a top-mounting DIN rail box or going from 12 to 18 or so way board if you allow for the space used for add-on RCD trips, etc.
 

davesparks

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Most TPN boards only have buses for L1/L2/L3

Schneider has something that looks like it pops up for a neutral bar, but I don't think it is standard.
Schneider Acti9 PoN boards have a neutral and earth bus incorporated in the pan assembly that SP RCBO's plug in to removing the need for any flyleads.
They also have a distributed neutral kit allowing you to convert any outgoing way to a neutral pole for DP or 4P devices to be fitted.
 
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