Mcb rcd rcbo

solgen · Oct 31, 2010

Hi,

Does anyone have an opinion on the usage of RCBO's for PV systems.

As I understand it - Type B , Class B are the only ones to use. The reason I ask is that I have a 3 phase Hager distribution board (commercial property) which is ideal for RCBO but Hager don't produce only produce Type B, Class A.

Thanks.

electricians · Oct 31, 2010

I think you may find another RCBO manufacturer that fits into the same board , I'm not positive but I think the electrium range ( eg wylex ) may fit . See if you can rob a spare from the original board and take it to the wholesaler

solgen · Oct 31, 2010

I've googled RCBO's and the only type I can find is Type B ClassA or Class AC. I cannot seem to find any class B. I would be grateful for links to ANY that are Type B, Class B but preferably compatible.

Thanks

poheZ · Oct 31, 2010

why not call Hager!

electricians · Oct 31, 2010

Can I ask , who told you you required a Class B and what part of the PV system is it feeding ?

solgen · Oct 31, 2010

It was tech advise from Hager - they said they are looking at producing this type of device for the PV market. The RCBO is the means by which AC from the inverter is fed to the property or to the grid.

electricians · Oct 31, 2010

Ok , I understand , well therefore it would not go directly into the existing distribution unit , I use Solar Panels - Photovoltaic Solar Panels & Solar Water Heating Panels for my panels and they have a range of feed in options , they provide good advise over the phone also

solgen · Oct 31, 2010

OK, I give them a call. Thanks.

The only other option I was thinking of was to take a supply from the existing distribution board to a new separate consumer unit where I would use a Type B MCB and type B RCD.

electricians · Oct 31, 2010

Thats another optiton , good luck

saint · Oct 31, 2010

What's the need for RCD protection? Isn't just an mcb ok? have i missed something?

Martin Dawes · Nov 1, 2010

17th edition? I think most installations, unless the inverter is sited close to the fuseboard, will need RCD protection.

Regarding the original post, why not install a seperate enclosure next to the board with the RCD in that?

Oops, just read the thread closer - you've already considered that.

solgen · Nov 1, 2010

RCD protection is not always needed, but for example if you use an inverter which doesn't have a transformer (i.e. no electrical separation ) then you should use an RCD. If AC cables are buried in walls then again use an RCD. Trouble is that type B RCD's which take care of the dc component are exceptional in this country rather than the norm. Most RCB's we have are type A which protects partly against dc.

Markc · Nov 1, 2010

Now don't shoot the messenger guys.....but......from my understanding a Class A or AC is acceptable for use on PV systems.

There are currently four basic types of RCD. Class AC devices are used where the residual current is sinusoidal (Sine wave)- this is the normal type which is in the most wide use. Class A types are used where the residual current is sinusoidal and/or includes pulsating direct currents (Some DC breaks for rotating machines as an example)- this type is applied in special situations where electronic equipment is used. Class B is for specialist operation on pure direct current or on impulse direct or alternating current. Class S RCDs have a built-in time delay to provide discrimination

So a Class B would be used on a DC circuit like on board some ships for example as well as AC or pulsing DC. As a PV system is requiring protection on the AC side class A or AC is acceptable. DC protection is offered from within the inverter.

Now I may be wrong here but this is my understanding. I am open to comments to confirm the correctness of this.