Domestic Installs Metal CU's also = Metal PV Isolators

[matthunt]

Re: Domestic Installs Meta CU's also = Metal PV Isolators

Hi folks, had it in writing from the IET themselves that Rotary isolators will need to be housed in metal enclosure!!

 

[Darkwood]

Re: Domestic Installs Meta CU's also = Metal PV Isolators

Hi folks, had it in writing from the IET themselves that Rotary isolators will need to be housed in metal enclosure!!

Can you forward a copy of your correspondence if possible and post it up, wording and interpretation can be key to such an important point.

 

[TedM]

And how many rotary isolators also comply with BS EN 61439-3?

 

[matthunt]

E-Mail as follows:

Dear Matt,

Thakyou for your query. Richard Townsend, Senior Engineer with the Technical Regulations team has provided the below response

From me: "Would this mean that Rotary Isolators for a PV System,both on the AC and the DC side need to be metal or completely enclosed in a metal Enclosure?"

Richards response: "Yes a rotary isolator is classed as switchgear and therefore would need a metal enclosure, or an alternative isolator would need to used"

 

[Gavin A]

Hi Matt, could you please pm me the email address as I'd really like to nail them down on that for the DC side at least, as I don't think they've thought that through at all and it contradicts regulation 712.412

 

[BruceB]

Interestingly, Napit technical on their forum have taken a different view a few days ago. At least they give a reason for their view. I hope they will not mind if I quote it:

"Regulation 421.1.201 Non-combustible Consumer Units and Similar Assemblies
Q. Would solar PV dedicated consumer units need to be metal?
A. Yes, if fitted in a domestic (household) premises. Regulation 421.1.201 applies to both consumer units and similar switchgear.
Q. Do solar PV rotary isolators have to meet Regulation 421.1.201?
A. Regulation 421.1.201 refers to similar switchgear assemblies complying with BS EN 61439-3, this standard is for low voltage switchgear and control assemblies. Distribution boards intended to be operated by ordinary persons.
The standard isolators used in PV systems fall under a different standard: BS EN 60947-3 Switches, disconnectors and switch-disconnectors. Therefore these isolators are exempt from this regulation."

 

[Gavin A]

That looks to me like Napit technical understand the new regulations better than the IET, and as I'm with NAPIT I think I'll go with their answer.

 

[TedM]

The standard isolators used in PV systems fall under a different standard: BS EN 60947-3 Switches, disconnectors and switch-disconnectors. Therefore these isolators are exempt from this regulation."

Exactly the point I was making.

 

[BruceB]

In my view there is some ambiguity in the answers from both the IET and Napit. Here’s my 2p’s worth.

Let us start with definitions:

Accessory. A device, other than current-using equipment, associated with such equipment or with the wiring of an installation.

Switchgear. An assembly of main and auxiliary switching equipment for operation, regulation, protection or other control of an electrical installation.

And the regulation:
421.1.201. Within domestic (household) premises, consumer units and similar switchgear assemblies shall comply with BS 61439-3 and shall etc………..

The IET asserts ‘a rotary isolator is classed as switchgear’. Why? It meets the definition of accessory above to my mind. To be switchgear it has to have ‘main and auxiliary switching equipment’. A single isolator is not switchgear by definition. Therefore in my view it falls outside ‘similar switchgear assemblies’ phrase in 421.1.201.


Napit I think comes to the right answer, although there is a slight misquote. It is wrong to say, ‘Regulation 421.1.201 refers to similar switchgear assemblies complying with BS EN 61439-3’; it actually says ‘……… shall comply with BS EN 61439-3’. So if it is a ‘similar switchgear assembly’ then it must comply with that BS. Isolators comply with BS EN 60947-3, but if in a consumer unit or forming part of a switchgear assembly then their enclosure must meet BS EN 61439-3, but a single isolator appears to fall outside the 421.1.201 requirement to meet that enclosure BS.

Personally I think I am happy to keep single isolators in plastic enclosures, as well as a REC2s or upfront rcd.

 

[SibertSolar]

What if you have multiple switch disconnectors housed within the same enclosure?...

 

[matthunt]

That looks to me like Napit technical understand the new regulations better than the IET, and as I'm with NAPIT I think I'll go with their answer.

You pay your money you take your choice I suppose mate, no doubt they will all agree to disagree

 

[TedM]

I thought we had already gone through all this sometime earlier.

Whether an item is simply "switchgear" or not seems beside the point to me.

It is a question of does the switchgear perform a function similar to that of a consumer unit - e.g. a garage or shower unit.

For any metal enclosure to conform to Amd 3 then it must comply with BS EN 61439-3 and therefore Amd 3 must apply only to assemblies that are capable of falling under the ambit of that standard.

An assembly that complies with any standard other than BS EN 61439-3 automatically does not fall under the Amd 3 reg and therefore does not need to be metal.

 

[BruceB]

I had thought of that but there did not seem an 100% clear answer. There is no 7671 definition of main or auxilliary switching but would they meet the definition of an accessory or switchgear. I incline to the former if not 'main and auxilliary switching'.

 

[Worcester]

The wording of

421.1.201 Within domestic (household) premises, consumer units and similar switchgear assemblies shall comply with BS EN 61439-3 and shall:

(i) have their enclosure manufactured from non-combustible material, or

(ii) be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Regulation 132.12.

NOTE 1: Ferrous metal, e.g. steel, is deemed to be an example of a non-combustible material.

NOTE 2: The implementation date for this regulation is the 1st January 2016, but does not preclude compliance with the regulation prior to that date.

The British Standard; BS EN 61439-3, mentioned in the regulation, is entitled "Low-voltage switchgear and controlgear assemblies; Part 3: Distribution boards intended to be operated by ordinary persons (DBO)"


The key thing is the regulation says that the type of switchgear they are referring to SHALL comply with the above BS, so IF the isolators are covered by the interpretation of: "consumer units and similar switchgear assemblies" then they'll need to be built to comply with the BS, and not the other way round, (if they don't comply with the BS / built to a different BS, then they're not considered "consumer units and similar switchgear assemblies")

So I disagree with WHY napit says it doesn't apply to rotary isolatorsm though do agree with the outcome


From Part 2 definitions of Amd3:

Consumer Units: (See below)

Switchgear: An assembly of main and auxilliary swithcing eqipment for operation, regulation, protectionor other control of electrical installations


According to the IET: Consumer units - IET Electrical

Similar switchgear assemblies

The phrase ‘similar switchgear assemblies’ in Regulation 421.1.201 means those assemblies used for the same fundamental application as a consumer unit. A consumer unit is defined in Part 2 of BS 7671:
‘Consumer unit (may also be known as a consumer control unit or electricity control unit). A particular type of distribution board comprising a type-tested co-ordinated assembly for the control and distribution of electrical energy, principally in domestic premises, incorporating manual means of double-pole isolation on the incoming circuit(s) and an assembly of one or more fuses, circuit-breakers, residual current operated devices or signalling and other devices proven during the type-test of the assembly as suitable for such use.’

An example of a similar switchgear assembly is a three phase distribution board that is intended to be operated by ordinary persons. This would have to have isolation that interrupts the three incoming line conductors and the neutral, rather than just double-pole isolation as mentioned in the above definition

.

The key thing hear is that we are dealing with Part 3 of the BS, which specifically deals with CU's / DB's

Reading the above, I reckon NICEIC have it wrong, and Napit have it right, though for the wrong reason

Qn: Anyone got or seen a copy of BS EN 61439-3:2012 ?

 

[BruceB]

My last comment above was in response to a post that has been deleted, so is looking a bit lonely now, but with no way to edit/delete.

For Ted: Rarely do I disagree with you, but to my mind the function question comes after being switchgear in the first place. I do not see how a single isolator (or even multiple isolators) falls within the definition of switchgear or has the characteristics of a consumer unit. I think isolators if not combined with for example rcds or mcbs etc are just 'accessories'.

In response to Worcester's Qn:
The BSI store says currently not available for some reason.
Here is part of it - go past the Danish front cover.
https://webshop.ds.dk/Files/Files/Products/M249414_attachPV.pdf

 

[TedM]

I don't think we are disagreeing (that might be a first!). What I was trying to say was:

If something isn't a consumer unit/switchgear assembly then it is out of scope. But if an assembly is switchgear then it is not automatically in scope - it must also perform the function of a consumer unit.

Can anything not be switchgear, not be a consumer unit and still perform the function of a consumer unit? I don't think so.

 

[BruceB]

I agree with that! Perhaps I had been reading things out of order - I have posted sometimes without refreshing so others have got in first which messes up the flow.

I see I am not reading closely enough. My response #33 was in response to Sibert's which has not been deleted but is on a different page in my browser.

 

[Gavin A]

so we're all agreed on this other than the IET technical rep, who unfortunately would be among the authors of the stuff being discussed.

tbh he's posted on the IET forums before, I wonder if he'd come and defend his position / discuss it on here.

 

[TedM]

Examining the contraindicative position for a moment - i.e. assume that isolators do fall within the requirement of 421.1.201 - then what unit would you actually use?

I see that Wylex make a dual DC/AC isolator in a metal case and their (old, 2013) technical documentation says:

"Factory Built Assemblies BSEN60439-3 when fully assembled" but it is not clear from the context if this applies to all assemblies listed in the leaflet or only to consumer units.

http://storage.electrika.com/manu/man-0150/pdftech/0150-wylex-13-tech.pdf

So unless Wylex produce updated documentation to say that this unit complies with BS EN 61439-3 then you wouldn't be able to use it to comply with Amd 3 anyway.

Does anyone else know of any metal enclosure isolators that may or may not be approved to BS EN 61439-3?

 

[SibertSolar]

Not for domestic/1ph applications Ted, no