Full rcbo boards????

[D00DY_T00DY]

Hi all,

Probably going to seem like a novice question just wondering what techniques you lot have for full rcbo boards to keep it neat.

Put 5 in today for a temporary supply for ground workers on a genny; earth rod with a Zs of 2.13ohms (fairly good?)

Anyway it was a complete nightmare trying to keep it neat with the earth and neutral flexes out of them.

I've only installed less than 10 just wondering all your techniques for rcbos?

I kept all the length on these and tried to coil them nicely behind the cpc and neutral terminals.

 

[davesparks]

Wonder if it actually makes a difference or it's just them putting their tin hats on.

Duely noted though.

Yes it does make a difference, cables bundled tightly together get hot. I've replaced a couple of rcbos with overheated neutral tails over the years, some from bundling up and some from a lack of ferrules. It's always been on the larger sizes of rcbo where the neutral tail is seeing it's full rated current.

 

[Ian1981]

Does your boss not include you in the testing process? Did you see him set up temporary electrodes and test the earth rod at any point in time?

Your Zs measurement almost certainly did not include the earth rod. You will have been testing via the cpc straight back to the star point via the N-E link at the generator

With a generator fed installation the earth electrode is the earth reference of your TNS system. In comparison to a normal installation the generator is equivalent to the substation transformer.

Yeah the rod doesn't form part of the earth fault loop impedance path so an earth electrode tester is the only way to test the electrode.

I was given a value of below 200 ohms which is also mentioned in the on suite guide for installing generators over 10kva.
I know the supply electrode at the transformer end in a substation set up is normally quoted at 21 ohms max.

Ze Seams high tho if the generator is a TNS which they normally are.

 

[D00DY_T00DY]

Does your boss not include you in the testing process? Did you see him set up temporary electrodes and test the earth rod at any point in time?

Your Zs measurement almost certainly did not include the earth rod. You will have been testing via the cpc straight back to the star point via the N-E link at the generator

With a generator fed installation the earth electrode is the earth reference of your TNS system. In comparison to a normal installation the generator is equivalent to the substation transformer.

Hardly if ever. Going to ask soon since I'm going into my forth year in July.

I didn't see him do that. Haha looks like he's been caught out.

Main supply is coming in soon, the company wants it connecting upto that once it gets put in.

 

[tomspark93]

I always shorten and ferrule the Neutral and Functions Earths. That's if i'm not installing the SBS compacts as Lee mentioned. They are a joy to work with!

 

[D00DY_T00DY]

I always shorten and ferrule the Neutral and Functions Earths. That's if i'm not installing the SBS compacts as Lee mentioned. They are a joy to work with!

View attachment 36668

Just seems so wrong with nothing in the neutral bar
Top job by the way

 

[westward10]

What is the unterminated cpc to the left for.

 

[tomspark93]

What is the unterminated cpc to the left for.

The lids have a bolt in with the lug is connected too.

 

[davesparks]

Hardly if ever. Going to ask soon since I'm going into my forth year in July.

I didn't see him do that. Haha looks like he's been caught out.

Main supply is coming in soon, the company wants it connecting upto that once it gets put in.

There are a scary number of electricians who don't seem to understand the subject. A lot of electricians don't go near independent generator supplies and so never have the need to think about it.

 

[Deleted member 26818]

What is the unterminated cpc to the left for.

Think your eyes are playing tricks on you.

 

[westward10]

Think your eyes are playing tricks on you.

It is bolted to the left side panel with one end unterminated.

 

[The Ghost]

It is bolted to the left side panel with one end unterminated.

He did say for the lid.

 

[westward10]

He did say for the lid.

Ah yes didn't read that

 

[Midwest]

The only thing I don't like about RCBO's, is there's no obvious sign as to whether it's the rcd or mcb element that has tripped. I understand most user instructions suggest trying to reset 'once', and sparks flying out of the thing might give the game away, but you'd think the manufactures might of developed some form of visual indicator (someone's gonna tell me there is). Seem to recall the early MK RCBO's tripped to the half way point, if it was the rcd?

 

[Andy C]

Cut and ferrule for me every time.

Like to leave a little bit length still so the RCBO isn't completely useless if it does need to be moved a little in the future.

View attachment 36659

That looks good with the tails all ferruled, i think I will be doing that myself

 

[davesparks]

That looks good with the tails all ferruled, i think I will be doing that myself

Hopefully you always fit ferrules to flex in crew terminals, as otherwise you are not complying with the regulations!

 

[Deleted member 26818]

Regs don't require ferrules be fitted.
They require the fine stranded wire be protected against damage from the screw terminals which can be satisfied by twisting and then doubling over the strands.

 

[Ian1981]

Think the regulation is every connection shall have adequate mechanical strength and be suitable for the terminal or something along those lines

 

[davesparks]

Regs don't require ferrules be fitted.
They require the fine stranded wire be protected against damage from the screw terminals which can be satisfied by twisting and then doubling over the strands.

The requirement is that the conductor ends be suitably treated, which as usual is as clear as mud.
But, twisting and doubling over does not provent the strands from being broken when the screw is tightened, if you undo the screw and take the conductor out you will find a number of broken strands.
Ultrasonic welding and ferrules are the two commonly used methods which actually work.

 

[davesparks]

Think the regulation is every connection shall have adequate mechanical strength and be suitable for the terminal or something along those lines

That is not the regulation i was referring to, see 526.9

 

[davesparks]

Think the regulation is every connection shall have adequate mechanical strength and be suitable for the terminal or something along those lines

That is not the regulation i was referring to, see 526.9

 

[Dave OCD]

So there must be hundreds of thousands of 13 amp plugs which don't comply then ?!

 

[davesparks]

So there must be hundreds of thousands of 13 amp plugs which don't comply then ?!

how many 13A plugs are there which form part of the fixed wiring and therefore come under the remit of bs7671?

 

[Dave OCD]

Regardless of which rules and regulations they fall under I'm talking about fine stranded flexible copper cable tightened with a screw terminal and without further 'treatment' , and with absolutely no ill effects.

 

[Ian1981]

I believe that regulation regards fine wire only.
It's upto the installer to be satisfied that the connection made is electrically sound and is suitable terminated.
If worried about crushing then use a torque screwdriver to manufacturers instructions

 

[davesparks]

Regardless of which rules and regulations they fall under I'm talking about fine stranded flexible copper cable tightened with a screw terminal and without further 'treatment' , and with absolutely no ill effects.

Yes there are a lot of fine stranded cables terminated in screw terminals with no ill effects, but there are also a lot which have failed as a result of it.
I find it hard to believe that you have never encountered a flexible conductor which has been damaged by the tightening of a screw terminal.

any plug fitted by a manufacturer or supplier of appliances will have ferrules used on the flex, all of the equipment which we get new with a fitted flex has ferrules on the end ready for connection.
The standards which apply to equipment building, panel building etc all require ferrules.

Should we all just stick our heads in the sand and resist simple changes which make things just a little bit better?

 

[Dave OCD]

In my opinion and experience fine stranded conductors when twisted tightly and even doubled can become much more rigid and tightening under a flat or rounded bottom terminal screw doesn't cause any significant damage.

 

[davesparks]

I believe that regulation regards fine wire only.
It's upto the installer to be satisfied that the connection made is electrically sound and is suitable terminated.
If worried about crushing then use a torque screwdriver to manufacturers instructions

And flex is a fine wire conductor.

Applying the correct torque won't prevent the fine strands of flex from being damaged, that's why the regulations require that ends be suitably treated

 

[westward10]

Direct on screw terminal will damage any conductor regardless of construction.

 

[Dave OCD]

Yes there are a lot of fine stranded cables terminated in screw terminals with no ill effects, but there are also a lot which have failed as a result of it.
I find it hard to believe that you have never encountered a flexible conductor which has been damaged by the tightening of a screw terminal.

any plug fitted by a manufacturer or supplier of appliances will have ferrules used on the flex, all of the equipment which we get new with a fitted flex has ferrules on the end ready for connection.
The standards which apply to equipment building, panel building etc all require ferrules.

Should we all just stick our heads in the sand and resist simple changes which make things just a little bit better?

No I'm all for changes which make things better Dave and actively try new products and methods but ferrules aren't always necessary and could be seen as another attempt to make something 'idiot proof'.

 

[Ian1981]

Take 1mm I double it up when terminating especially in db terminals mcb etc but take it out and it looks damaged regardless yet I'd say this is a fine wire that requires no specific treatment to it.
Most cases a doubled over flex is a better connection in my opinion.
I'm not convinced by that regulation perhaps connecting flex to copper say in a connection block then it may apply more id say.