Isolators

[Earthstore]

But then the system would not be complient would it?
Lockable AC isolator (with a padlock), that needs to be fitted where you can access it, and then a DC isolator that is specifically for DC load, which is fast switching.

 

[cryo]

I find the in general that owners and a number of installers do not as a rule follow correct procedures when isolating systems so I would suggest a seperate easily obtained and cheap isolator is the way to go. I would estimate that the isolation procedure instructions are read, if at all? in the first week of installation and then quickly ignored or missplaced.

 

[duggy1979]

I have been working for a company using the garage board they install as the main point of isolation and not installing a seperate lockable rotary isolator, i think this is bad practice and im trying to get a straight answer on this from the NICEIC as there assessors have been letting this go. It goes against what ive been taught as ive been installing pv for nearly 4 years.

 

[moggy1968]

it's not just bad practice, it's a breach of the regs which require a lockable isolator (by padlock)

 

[moggy1968]

Does the Electronic Solar Switch on a SMA inverter act as a DC isolator? Also, Do you need an AC isolator at the garage unit, when it can just be isolated from the garage unit?

Not according to 7671 712.537.2.2.5 which requires a switch diconnector

 

[Gavin A]

it's not just bad practice, it's a breach of the regs which require a lockable isolator (by padlock)

hmm... if it's got a dual pole cut off eg an RCD unit within the garage unit, then I can see that there can be an argument made for it being a lockable dual pole isolator, as given the correct equipment they can be locked off.

Personally we usually install both - RCD unit in a garage unit by the main consumer unit / tails block, and lockable rotary isolator next to the inverter. I'm pretty sure we've never installed one without the rotary isolator either, but I can see that an argument could be made about it.

 

[moggy1968]

no, not at all I'm afraid. we have discussed this before. it must be securable in the off position by a padlock. A MCB lock is a specialised piece of equipment and doesn't meet the requirement. There is no argument about it, that is the requirement. It's not a point of interpretation.
I'm pretty sure you need one at both ends as well but would have to check on that.

 

[Gavin A]

yeah well, we'll not be installing one at both ends regardless, as IMO the RCD / MCB is just as lockable as any other circuit off the consumer unit, and if someone needs to lock it off to a greater degree without having the specialist MCB lock to prevent generation from the inverter they can do so at the isolator next to the inverter.

eta... reading through the DIT guide, you're right that it is clear that relying on an MCB lock is not acceptable for the main isolator, however it's less clear about any secondary isolation.

I'll have to double check, but I believe the garage units themselves that we use are lockable with a padlock. If this is the case, then this should class as being a lockable isolator anyway.

 

[moggy1968]

Hmmn, interesting, do you take that view with other parts of the regs as well?

 

[Gavin A]

Hmmn, interesting, do you take that view with other parts of the regs as well?

1 - these are not regs, they are guidance.
2 - where they are unclear we will use our professional judgement to determine reasonable safe practicable methods of carrying out our installations within the overall spirit of the guidance.
3 - using an RCD as a secondary isolator may not comply precisely with the guidance for the main system isolators, but then we fit a rotary isolator that does, and the RCD does offer additional protection for the circuit as a whole. I'd argue that the systems we install are actually safer overall than a system relying purely on an MCB and lockable rotary isolator.

 

[Gavin A]

I thought I'd check the guidance in the 3rd edition of the guide to see if they were planning to clarify this situation. It seems the guide authors agree with my position on this

An a.c. switch or combination of switches must be provided for isolation and maintenance in the installation.


A switch for mechanical maintenance shall be provided in close proximity to the Inverter and shall fulfil the following conditions:
 switch all live and neutral conductors
 be securable in the OFF position only
 clearly show the ON and OFF positions and be labelled as ‘PV system – main a.c. isolator’


An accessible means of isolation shall be provided to isolate the a.c. circuit. MCB’s, RCD’s and main switches installed in accordance with BS7671 and in an accessible location can be used to fulfil the requirements for an accessible mea ns of isolation.

This is precisely the method we've been using, and while this new guidance is still only in draft form, I'll take it as sufficient evidence that our interpretation and application of the guidance is valid and safe.

 

[The Solar King]

Draft of DTI Guide third edition no longer mentions need for padlock.

[FONT=Helvetica, sans-serif]A.C. Switching Device[/FONT]


[FONT=Helvetica, sans-serif]Switching of the a.c. side of the installation shall comply with the requirements of BS7671,[/FONT]


[FONT=Helvetica, sans-serif]An a.c. switch or combination of switches must be provided for isolation and maintenance in the installation.[/FONT]


[FONT=Helvetica, sans-serif]A switch for mechanical maintenance shall be provided in close proximity to the Inverter and shall fulfil the following conditions: [/FONT]


[FONT=Helvetica, sans-serif]Switch all live and neutral conductors [/FONT]
[FONT=Helvetica, sans-serif]Be securable in the OFF position only[/FONT]
[FONT=Helvetica, sans-serif]Clearly show the ON and OFF positions and be labelled as 'PV system - main a.c. isolator'[/FONT]


[FONT=Helvetica, sans-serif]An accessible means of isolation shall be provided to isolate the a.c. circuit . MCBs, RCDs and main switches installed in accordance with BS7671 and in an accessible location can be used to fulfil the requirements for an accessible means of isolation. [/FONT]


[FONT=Helvetica, sans-serif]Note: At the point of installation of any a.c. switch-‐disconnector, the public supply should be considered the source and the PV installation the load.[/FONT]

 

[moggy1968]

you have to install to current regs (guidence if you like) not what is projected or in draft for the future. wether you think it makes sense or not thats the way it is.
I don't agree with paying tax, but I still have to!
I did say I wasn't absolutely sure of the situation with 2 isolators. It doesn't crop up with us as we would fit 2 rotary isolators if the inverter is away from the DB but I am more than happy to be wrong about this.

 

[Gavin A]

you have to install to current regs (guidence if you like)

do you actually appreciate that the 2 are different things?

not what is projected or in draft for the future.

As far as I'm concerned we have been complying anyway, it's just that our interpretation of the existing regulations and guidance obviously differs from yours.

In terms of working out who's interpretation is correct however, it's perfectly valid to point to the latest revised guidance even if it's in draft form to support the interpretation that matches the new guidance, as it clearly shows that the experts employed by the government to write the new guidance have taken the same view as us.

Bottom line on this stuff would be if a reasonable person would consider this to be safe and compliant with the regulations. I'm confident they would.

 

[moggy1968]

I do appreciate the difference thanks (did that on my business degree).
regrettably too much in this work is open to interpretation. Is it reasonable to ommit a £20 device in a £8000 installation, well, that depends I guess!!
I would certainly agree with the sentiments of your last post, especially the last paragraph. Most of this ultimately comes down to can you stand up in court and justify what you have done in the face of evidence from an 'expert' witness who will use the CURRENT regulations and guidence notes in their evidence. If you can, then happy days.