Mcb rcd rcbo

[solgen]

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]

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]

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]

why not call Hager!

 

[electricians]

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

 

[solgen]

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]

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]

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]

Thats another optiton , good luck

 

[saint]

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

 

[Martin Dawes]

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]

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]

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.

 

[kentop2]

Ask about the MCBs at your local electrical wholesaler (take an existing one along to show them) or some of the bigger B&Qs might do them.

 

[solgen]

Hi Mark C,

According to the 17th Edition 712.411.3.2.1.2 a type B RCD is required, the same applies for RCBO's.

 

[Markc]

Hi Mark C,

According to the 17th Edition 712.411.3.2.1.2 a type B RCD is required, the same applies for RCBO's.

Bugger better get the book out from under the desk again!

 

[Markc]

Hi Mark C,

According to the 17th Edition 712.411.3.2.1.2 a type B RCD is required, the same applies for RCBO's.

Hang on Type B or Class B?

 

[solgen]

MCB's Type A, B, C, etc
RCD's Class A, AC, B (also referrred to as type)
RCBO's are both so usually Type {x}, class {x}

 

[miah205]

sorry to be a pain in the back. Just wanted to ask can u reply with anything regarding electrics as im not sure if my messages are being posted as this is the first time ive joined a forum. not very good with websites!!!!

 

[solgen]

miah205,

This part of the electrical forum is specific to solar PV. Depending upon the nature of your question this might not be the most appropriate of the forum for your question. Please have a look at the categories available to post to. There is a general category.

 

[Markc]

I think a big thank you to Solgen is in order here!

Not one to sit back I have done some research. There are specific Class B RCD's out there and RS do one by ABB. See links.

The BRB states: 712.411.3.2.1.2:

Where an electrical installation includes a PV power supply system without at least simple separation between the A.C side and the D.C side, an RCD installed to provide fault protection by automatic disconnection of supply shall be Type B according to IEC60755 Amend 2.

Where the PV converter is, by construction, not able to fed D.C fault current into the electrical installation, an RCD of Type B according to IEC60755 Amed 2 is not required.

So inverters without separating transformers WILL require a Type B RCD.

I've put a couple of links below all from ABB and a RS link. Cost of PV RCD as they call it is £80 and is rated at 300mA.

Again good work Solgen for bringing this up.

ABB | Electrical Installation | Consumer Units | RCCBs | Protection Devices |2CSF202121R3400
http://www05.abb.com/global/scot/scot209.nsf/veritydisplay/40abe76927e9e01dc12576ba003c22bf/$file/solar%20cat%20lr%20v.06.pdf

 

[Energetic]

So another case for an isolating transformer inverter. No hassles with earthing the array frame and no need for exotic rcd's. I'm sold...

 

[solgen]

I've not used TL inverters for most of the above reasons, however, if used the dti guide talks about earth-rod spiking when system is a PME. Any tips with this or has someone come up with a clever way around this?

 

[Martin Dawes]

As the regs are, I can't see any alternative to earth-rod spiking when using PME unless an Isolating Transformer inverter is used.

Maybe the regs could be relaxed for roof mounted PV systems?