Suitable RCBO for EESS install

[spynage]

Hi

Doing my first Inverter and Battery install on a domestic property having just completed my EESS course with LCL.

Question is how do I install a bi directional RCD/RCBO at the distribution board to supply and feed back power from the the inverter? I think I need an RCBO to the standard 61009 -2-1. Can't find anything easily online though. The best I could find was a video from Artesian Electrics where they supplied a separate RCD that was bidirectional via an RCBO. It would mean a fuse board change for my client.

Any answers?

Thanks

Spynage

 

[mainline]

Hi

Doing my first Inverter and Battery install on a domestic property having just completed my EESS course with LCL.

Question is how do I install a bi directional RCD/RCBO at the distribution board to supply and feed back power from the the inverter? I think I need an RCBO to the standard 61009 -2-1. Can't find anything easily online though. The best I could find was a video from Artesian Electrics where they supplied a separate RCD that was bidirectional via an RCBO. It would mean a fuse board change for my client.

Any answers?

Thanks

Spynage

 

[timhoward]

It looks like a decent video, but I'd be quite interested if these questions could be answered with respect to the regs and section 712 too.
My limited understanding is that the main principles are:
-never supply the inverter from a shared RCD (if the RCD trips the inverter cannot be allowed to backfeed final circuits even momentarily)
-if an RCD is required to protect the supply to the inverter due to cable type installation methods it should be a type B.
-comply with any additional manufacturers instructions.

I don't think I've ever seen the term bi-directional in the regs regarding RCD technology.
Maybe a good starting point would be for someone to answer "What is a di-directional RCD". Is it simply an RCD that will still detect imbalance if current is flowing through it backwards too? If so, I've never known an MFT test or the test button fail to trip an RCBO feeding an inverter that was generating current. So maybe almost all of them are?!

I have a cynical suspicion that one or two manufacturers are adding the word "bi-directional" to their marketing seeking to imply that other's out there that don't have this label are not.

 

[spynage]

Just to add some detail. Here is a paragraph from the IET code of practice on EESS. Page 98. You can see just under the box it mentions suitability with regard to bi directional use of RCD's. It was mentioned in the class a few times as well so I thought it was significant? Then this video came up on my searches >>

 

[timhoward]

@spynage thanks for sharing those things.
So far what I can discover online about this topic is that the issue/point of distinction may be the Test button , which if held in while back-fed could possibly lead to over-heating the test load resistor. (dependant upon design)
That said, the inverter should shut down if there is no supply, so this condition could only exist for a finite time.

I'm curious/concerned as I've used type B Fusebox Lewdon RCBO's on a couple of occasions when I've done a CU change on an install that had PV. Hence me wanting to understand more about this.

 

[pc1966]

I would be most surprised if the Fusebox RCBOs where Type B for the RCD side, B-curve on the MCB yes, but probably Tpe A RCD aspect.

If the inverter is capable of DC leakage then you do need Type B RCDs and they are expensive, but check inverters' instructions as many don't. I have dealt with one (ABB brand now) that said it was happy with Type AC which surprised me!

The bi-directional aspect is something to be aware of but many RCD these days don't care - I had to check with Hager about thiers and eventually they confirmed that the lack of feed direction info in the data-sheet really was due to the device not caring.

 

[timhoward]

I would be most surprised if the Fusebox RCBOs where Type B for the RCD side, B-curve on the MCB yes, but probably Tpe A RCD aspect.

You are right - just checked my records and they were Lewden, probably because I couldn't get Fusebox! It was a good while ago.

 

[Danny H]

I work for a renewable energy company that install PV systems and battery storage and one of the lads mentioned that the tutor on the PV and battery course said that RCBOs are not suitable as they are not Bi directional. Since then i've been trying to get confirmation or any info from manufacturers on this and getting no joy, as a rule we install a new DB but on some retro fits an RCBO would be ideal as installing a separate board would cause to much disruption. Very Frustrating.

 

[DPG]

I work for a renewable energy company that install PV systems and battery storage and one of the lads mentioned that the tutor on the PV and battery course said that RCBOs are not suitable as they are not Bi directional. Since then i've been trying to get confirmation or any info from manufacturers on this and getting no joy, as a rule we install a new DB but on some retro fits an RCBO would be ideal as installing a separate board would cause to much disruption. Very Frustrating.

What does your manager/supervisor say?

Oh and welcome to the forum by the way!

 

[Danny H]

I'm the QS and my manager doesn't have a sparking back ground, I've stopped using them for the time being until I can get definite answers, we only ever used 2 pole RCBOs but most don't state if they are Bidirectional and like I say very little info out there. I can see a reason why myself. Hopefully will get some Statements/replys of manufacturers soon. Would appreciate any info anyone comes across, and I'll keep the thread updated if/when I find out.

 

[Danny H]

I mistyped 'I can see' meant to type Can't.

 

[DPG]

I mistyped 'I can see' meant to type Can't.

We've had worse don't worry.

 

[mainline]

I work for a renewable energy company that install PV systems and battery storage and one of the lads mentioned that the tutor on the PV and battery course said that RCBOs are not suitable as they are not Bi directional. Since then i've been trying to get confirmation or any info from manufacturers on this and getting no joy, as a rule we install a new DB but on some retro fits an RCBO would be ideal as installing a separate board would cause to much disruption. Very Frustrating.

16 A 1 Mod DP Compact RCBO 6kA B Curve 30mA Type A - M2 Electrical

Available in 6 A to 40 A 30mA, Type A tripping sensitivity800 mm long Neutral CableSwitched Neutral as standardReduces time for insulation resistance testingBi-directional

m2electrical.co.uk

 

[pc1966]

@mainline has pointed to the M2 RCBO that explicitly say they are bidirectional, I also know the Wylex/Crebtree compact RCBO will be OK as they are also neutral-switching and fully isolated on the output when tripped - they allow you to IR test on the load side without any issue.

Sadly so many companies now have as "data sheet" that has damn-all information of any technical nature.

 

[Danny H]

Thanks mate, I neglected to say we only used DP RCBOs,or SP an N but some manufacturers dont specifically state its Bidirectional. like you say though mate some companies are better than others,

 

[GalaxyTS]

Hi all....just catching up on the subject of bi-directional devices, having recently undertaken the EESS course. I usually fit Elucian boards but don't have an answer on whether their RCBOs are bi-directional at the moment, however I have just downloaded a Proteus datasheet which clearly states that their Type A devices ARE bi-directional

 

[GalaxyTS]

Hi all....just catching up on the subject of bi-directional devices, having recently undertaken the EESS course. I usually fit Elucian boards but don't have an answer on whether their RCBOs are bi-directional at the moment, however I have just downloaded a Proteus datasheet which clearly states that their Type A devices ARE bi-directional

Update....have also just had confirmation from WCED that their full range of RCBO, RCD and MCB are bi-directional and suited to solar/EESS installs

 

[pc1966]

Relating to this discussion I saw this today:

BEAMA Technical Bulletin - Connection of Unidirectional and Bidirectional Protective Devices

www.beama.org.uk

Basically it says if they are marked line/load or have direction arrows they are not suitable, which seems to rule out the Wylex compact RCBO as they have direction arrows on them.