Mixing new and old model RCBOs

[fex10]

Guys, my electrician says that the new model domestic Wylex RCBOs are a direct replacement for the older NSB model RCBOs. But Wylex have said that the old type NSB cannot be mixed with the current model, but the old type can be fitted to a current NH consumer unit.

I've asked my electrician and he's not giving a direct opinion.

I've got a handful of the older model NSB RCBOs, but not enough. Either replace them all or can try to buy more older model ones from fleabay? Or just mix them?

 

[Adam_151]

Generally you should go with the information obtained from the manufacturers technical dept.

But I cannot get my head round why the devices are suitable for the board but that you shouldn't use a mixture. Either the devices are compatable or not.

Unless he is saying that the new range RCBOs are not backward compatable [with older boards], but the new range boards are [backward compatable with older rcbos].... which seems absurd as it would be the reverse of what is sensible

but the old type can be fitted to a current NH consumer unit.

My understanding is that the NHX range is suitable but looks a little out of place. But if wylex are saying differently and there has not been a breakdown in communication...

 

[AndyPRK]

I think it depends which type of bus bar you have.

Do you have a picture of the internals ?

 

[JohnW2]

Guys, my electrician says that the new model domestic Wylex RCBOs are a direct replacement for the older NSB model RCBOs. But Wylex have said that the old type NSB cannot be mixed with the current model, but the old type can be fitted to a current NH consumer unit.

Provided they are physically compatible (particularly in relation to terminal type/positions) IMO that really makes no electrical sense. An RCBO does not 'know' what RCBOs may be protecting other circuits - so it makes no sense to say that either type is suitable, provided they are not mixed.

Kind Regards, John

 

[333rocky333]

I may be wrong but the old NSB had "U" shaped prongs and the new ones are a single prong
The old NSB breakers fitted U type and single prong therefore would fit the newer board.
Whereas the new breakers possibly dont have the cutout bit so will fit a newer board and not the older board With the U prong

 

[JohnW2]

The old NSB breakers fitted U type and single prong therefore would fit the newer board. Whereas the new breakers possibly dont have the cutout bit so will fit a newer board and not the older board With the U prong.

Fair enough. Maybe the OP has misunderstood Wylex, but he implies that they have told him that he can put all new-style breakers, or or all old-style breakers, into his board (which I assume is 'old', but could be 'newer), but not a mix of the two - which, as I said, really makes little sense.

Kind Regards, John

 

[kai]

I have noticed that Wylex and MK change their breaker designs every few years in order to keep up with fashion trends!

 

[stillp]

Maybe the OP has misunderstood Wylex,

I read that as being what the electrician had been told. Chinese whispers?

 

[JohnW2]

Maybe the OP has misunderstood Wylex,

I read that as being what the electrician had been told. Chinese whispers?

Yes, possibly. It would make more sense if what they had said, or had meant to say, was what rocky said - namely that one can put 'old' breakers into new boards but not new breakers in old boards (the latter, I think, being essentially what the OP wants to do - 'to make up the numbers'.

Kind Regards, John

 

[fex10]

To be clear on what Wylex said:

I have a bunch of older NSB RCBOs. Wylex said these these can be fitted into a new NH1404 consumer unit. But the consumer unit cannot contain a mix of older NSB and newer NHXS RCBOs.

Electrician appears happy to use my older NSB RCBOs and top up with new NHXS RCBOs. Ie the consumer unit would then contain some old, some new.

I personally rather go with what Wylex said, so I have a choice of either ditch the old RCBOs and buy all new ones, or buy some extra old type on fleabay. I've asked Wylex to clarify the technical reason for not mixing to be sure I haven't misunderstood, but also, because I am very curious why they can't be mixed! Isn't ultimately the consumer unit just distributing current, how is one RCBO even know there's a different model RCBO connected to another circuit? And if it does know then why aren't my RCBOs affected by other brand RCBOs connected to the neighbours consumer unit, seeing as they're all on one circuit from the local tranformer (well every third house is right? one from each "phase").

 

[stillp]

I would guess it's just that Wylex haven't type-tested their CUs with a mixture of old and new RCBOs.
There can be some influence on the RCD part of RCBOs from adjacent circuits carrying high currents though.

 

[JohnW2]

I would guess it's just that Wylex haven't type-tested their CUs with a mixture of old and new RCBOs.

Yes, that's possible - but will they have tested the old RCBOs in a new CU - since they appear to have told the OP that would, per se, be OK.

Kind Regards, John

 

[stillp]

You'd have to ask them, not me! Personally if I was in Wylex technical support I would be careful about making any claim that I couldn't back up with test results.

 

[JohnW2]

You'd have to ask them, not me!

I know - it was essentially a rhetorical question. I could certainly understand them testing new devices in an old CU, particularly if they had discontinued (or were going to discontinue) manufacturing the 'old' ones - but it's not quite so obvious that they would necessarily test 'old' (maybe no longer manufactured) devices in a new CU (which is the situation that they apparently told the OP would be OK).

Kind Regards, John

 

[333rocky333]

(well every third house is right? one from each "phase").

Not always