Consumer Unit Change

[Nickj]

Hi All,

I am tomorrow going to be changing a consumer unit ahead of my Elecsa assessment next week.

Just wanted to check that I'm not missing anything with regards to amendment 3.

I'm going to be using a BG consumer unit supplied with RCBOs.

It has a cut out at back for cable entry and so I am going to pass all cables through that using a grommet strip around the metal edges. Do I need to seal the entry hole? I believe not however I have heard arguments that it needs to be sealed. Passing all cables through the rear entry may require de-rating cables due to grouping however the cables enter the current board (3036's) through the rear. Can i therefore assume ratings are fine?

I am going to attach the consumer unit to the wall using dewalt wall dogs which require no anchor in wall meaning I don't have to worry about plastic wall plugs falling out in the event of a fire.


If the cables are too short (I sincerely hope they won't be) I'll use an adaptable box above the board to mount a din rail to extend wiring. Does this adaptable box need to be non-combustible too? (associated switch gear covers this possibly?)

Thanks in advance

Nick

 

[sparksburnout]

Not on the ****, just like the odd glass, nothing serious, it's just people's take on my posts, aint really been on the razz for many a year or two, had my fill of that during my world tour, red wine is my tipple, now I'm retired, but er in doors has got me on a shed building course for OAPs, of course I will be asking advice on how to run a supply to the sheds I build. LOL

Now i'd like to expand on this. I too like the odd tipple, of an evening, well most evenings to be honest. Beer mostly but also appreciate a decent red. Seems to be a bit of an undercurrent of frowning upon this sort of thing, can't even turn on my favourite planet rock radio station now without somebody harping on about cutting down: "Do you really need that glass of wine while cooking the dinner". I enjoy a little livener around the 5 O'clock mark myself, bit like yourself by the sounds of it. Do you think it is becoming frowned upon?

 

[westward10]

Who cares, white Pino or Gavi for me.

 

[Wilko]

Speaking to Mr Quack recently, he was extolling the virtues of moderation. Then he stopped and said - you know the medical definition of an alcoholic? That's the patient who drinks more than the Doc. Looks like I'm ok then .

 

[Midwest]

Pierre or you on the **ss every evening?

Not wishing to defend anybody here, but that's none of your business. People make like hearted remarks on this forum, to scoff themselves. You shouldn't be judgemental.

 

[Nickj]

I'm fairly certain it's 1.5mm cpc. I can check tomorrow but pretty sure.

Its going to be quite a timely thing to solve where the roughly 0.2Ohm increase is coming from.

Would you guys invest the time to find the cause or would you say 1 ohm is close enough to calculated value and with all other results being good change board?

In your opinion, based on previous assessments, is this something that could fail an assessment?

 

[westward10]

Depends how on the ball the assessor is, clear the problem and it is one less worry. It wouldn't be something you would outright fail on

 

[NDG Elecs]

I'm fairly certain it's 1.5mm cpc. I can check tomorrow but pretty sure.

Its going to be quite a timely thing to solve where the roughly 0.2Ohm increase is coming from.

Would you guys invest the time to find the cause or would you say 1 ohm is close enough to calculated value and with all other results being good change board?

In your opinion, based on previous assessments, is this something that could fail an assessment?

What is 0.20 ohms between friends on a conductor that is usually only called upon when something goes wrong. Zs's are good and you have additional RCD protection. Personally I would not worry too much. And yes I would be tempted to record the L and N end to end's as being a little higher and the CPC as a little lower! The assessors are generally pen pushers that like to look at paperwork and not the nitty gritty side of things I have found. That's not having a go at them, it's just the way they are. So, if the paperwork looks about right they are generally happy, and as long as the install is safe. Which I think this one is by the sound of it.

Don't shout at me though if he ain't happy!!
Well done for finding it though mate. I am a little surprised that no one on here asked whether there was a possible long forgotten socket, as it is something a lot of members will have come across, especially on EICRs.

 

[NDG Elecs]

Good luck Nick with your assessment, and you've have been given some good advice by members, especially fault finding!

As regards the fixings for the CU, I take NDG's point, but I do not think that relates to the fixing of CU's more to that of cable supports in escape routes. reg 421.1.201 was all to do with (so I'm told), remove a source of fuel (plastic CU) from the source of a fire. So sealing holes (intumescent), fixings etc don't relate.

As regards using a plastic enclosure above a CU to extend cables, I was advised by Elecsa Tech support a while back (wrongly IMO) that such an enclosure would not comply with the reg, and could not be used in such circumstance. Now that we've had some time, to allow for the dust to settle as it were, I have asked Elecsa for some clarification on the subject. Thought you should perhaps know this before your assessment, just in case. Having said that, when I had my recent assessment, the Elecsa Inspector raised his eyebrows when I told him of the advise given.

Personally, I would use MF joint boxes, in ceiling void above CU, if the cables weren't long enough to terminate in new CU or Ideal in-line splice connectors inside the CU. I would only do that for one or two circuits. Anymore, and I would consider part rewire.

Hi Mid,

My link was a bit off as you say. I have not looked at the full download for a little while but I thought it did a test of standard red/brown wall plugs to hold some of the cable supports up whereby they failed after the fire test. Might be wrong though!

I would think that a CU would hold quite steady in a fire largely due to the various copper conductors stopping it from dropping significantly. But fair play to the OP using a belts and braces approach to keeping it on the wall.

 

[Andy78]

What is 0.20 ohms between friends on a conductor that is usually only called upon when something goes wrong. Zs's are good and you have additional RCD protection. Personally I would not worry too much. And yes I would be tempted to record the L and N end to end's as being a little higher and the CPC as a little lower! The assessors are generally pen pushers that like to look at paperwork and not the nitty gritty side of things I have found. That's not having a go at them, it's just the way they are. So, if the paperwork looks about right they are generally happy, and as long as the install is safe. Which I think this one is by the sound of it.

Don't shout at me though if he ain't happy!!
Well done for finding it though mate. I am a little surprised that no one on here asked whether there was a possible long forgotten socket, as it is something a lot of members will have come across, especially on EICRs.

I'd be tempted to record the values as they are seeing as repeating tests and comparing them to recorded values is a usual part of the assessment procedure. I'd rather be explaining an identified anomaly, the action already taken, and the reasons behind not being overly concerned about it, than why values don't match those of the schedule of test results.

 

[NDG Elecs]

I know what you are saying Andy, and yeah OK it's a tiny bit naughty. But cheating L-L up by 0.02 ohms and the CPC down by the same is hardly likely to be picked up on. You will know how values can dance around a bit when testing low impedances.
This install sounds safe to me. It's not like doing a drive by EICR is it.

 

[Andy78]

I know what you are saying Andy, and yeah OK it's a tiny bit naughty. But cheating L-L up by 0.02 ohms and the CPC down by the same is hardly likely to be picked up on. You will know how values can dance around a bit when testing low impedances.
This install sounds safe to me. It's not like doing a drive by EICR is it.

Totally agree in this specific instance, maybe not in another though.

I know my Elecsa assessor would have picked up on different values as an opportunity for a bonus question such as "Why do you think the values are not as expected ?" or "What could be causing the change in values between measurements ?" But then, most aren't as thorough/bothered as him.

 

[NDG Elecs]

I just had a look at that BRE report and it does use yellow and red plugs to fix some of the supports up. And scan reading it some of these failed. I was responding to Westward originally in relation to the post saying that the plugs would likely hold firm. It was my belief also that they would hold firm, but maybe they won't. So perhaps concrete screws are the way forward.

 

[Pete999]

Make sure you TT it. Wooden shed, so got to be a wooden earth spike. No, hold on a minute - that wooden work. OK, I'll get me coat. Daz

Why wooden it work

 

[Midwest]

I just had a look at that BRE report and it does use yellow and red plugs to fix some of the supports up. And scan reading it some of these failed. I was responding to Westward originally in relation to the post saying that the plugs would likely hold firm. It was my belief also that they would hold firm, but maybe they won't. So perhaps concrete screws are the way forward.

But that report relates to the installation of electrical cables supports & fixings, and the IET references the report as fire performance of cable supports. Regulation 421.1.201, which specifically makes recommendations about the non combustibility of consumer units and similar switchgear, does not make any specific recommendations on how to fix them to the wall.

Perhaps the 18th edition may have a new note, or 421.1.202 which will tell us to use non combustible fixings. But until then, I don't think we should make that strategic decision IMO.

Thanks for finding & posting the report though.

 

[westward10]

Why wooden it work

It wood if it was wet.