Bonding Control panel

[edexlab]

Currently building a system for a PITA customer
Did stage 1 last year
( I only did onsite install)
They snagged and changed totally nonsensical things at a whim and my company let them
Resulted in job being completed 4 mths late

This year stage 2 only had 4 electrical snags versus 176 last time ,which is good as I've been in charge of electrical build this time

So it looks like they've been told not to delay the job and it's been done better this time

2 snags bother me
First is we have earth studs on back plate of panel with wiring to an earth block, the door , and to din rail earth terminal

They don't like the stud having more than 1 wire connected by ring crimp
I can't think of anything preventing this as long as there isn't so many as to cause a bad connection



2nd is
We are using an existing machine integrated into the system has it's own Drawing from manufacturer (German)
We've been asked to copy these drawings and allocate our own core numbers , So 2 numbering styles in one panel

Any thoughts?

 

[cliffed]

Nothing wrong with several earth conductors on stud,especially if connections are sound & good.
Don’t seem right to alter the numbering,what if the company needs to do some remods to the panel,it will get confusing.
Leave it as original numbering.

 

[ipf]

With the numbers, if you re-number or keep it as, just have details of both systems at hand when required. As regards the stud......what’s better than earth cables being jointed at the same point if it’s a designated one . Strange snagging.

 

[The Ghost]

Maybe they think it is safer as if the stud fails then all the earths will go but if they are separate then only one earth will fail?

 

[edexlab]

Yes I think it's just them being pedantic, got to find something wrong!
I asked for a reg number, still waiting

last year the people wiring it made a mess of it , short cables joined out under a platform and lots of untidy workmanship plus the unnecessary things the client insisted on
Which I spent 4 mths tidying and sorting to get it done properly onsite

Both issues have already been agreed by the project manager who is not electrically minded

The machine numbering I really don't agree with as it's wired to a German drawing ie numbered cores throughout , we've had to number half of each panel only
Stupid thing is there's nothing wrong with the existing indents or drawing
But now I think it'll be confusing

 

[spark 68]

I have seen it specced that no more than two connections to a stud before, usually in cases like that we have either/and/or added another stud and/or a separate Earth bar/block.
Then we have had "discussions" regards high integrity Earthing as far as the panel itself went, which was valid up to a point.

Difficulties nearly always arise where interfacing takes place, system overlap so to speak, there is almost never a clear cut black and white solution here I am afraid.
Another point is where some office dweller is concerned is that a little knowledge is dangerous and leads to all sorts of problems further down the line, particularly where two systems meet.
Some consensus is usually a better idea if some compromise is met.

Edit: The Germans are seriously into EMC regs too, their panels also usually have a functional Earth (aka a clean or system Earth) separate from the protective Earth which is also sometimes but not always segregated, this though depend on the panel itself.

 

[edexlab]

The studs on these Rittal panels do sometimes fall off with a little torque as they're stud welded.

The studs in question are drilled tapped and locknutted to the backplate.

 

[spark 68]

I have used a lot of Rittal panels, the back plates we normally drill and tap for 8mm brass bolts from the back and then lock-nutted from the front before the back plate is fitted, but to be fair it depends on the spec.
Some are specced completely overkill, so I feel your pain

 

[edexlab]

I have seen it specced that no more than two connections to a stud before, usually in cases like that we have either/and/or added another stud and/or a separate Earth bar/block.
Then we have had "discussions" regards high integrity Earthing as far as the panel itself went, which was valid up to a point.

Difficulties nearly always arise where interfacing takes place, system overlap so to speak, there is almost never a clear cut black and white solution here I am afraid.
Another point is where some office dweller is concerned is that a little knowledge is dangerous and leads to all sorts of problems further down the line, particularly where two systems meet.
Some consensus is usually a better idea if some compromise is met.

Edit: The Germans are seriously into EMC regs too, their panels also usually have a functional Earth (aka a clean or system Earth) separate from the protective Earth which is also sometimes but not always segregated, this though depend on the panel itself.

Was this a spec from Pharmaceutical job?
Most of the clients Project Engineers are from Pharmaceutical companies

The interfacing between our equipment and bought in stuff we do is ok

Its clear and easy to follow which is all that's needed.


Ha don't mention Clean earths!
They decided they wanted it

We modify panels and drawings to accomodate

I go onsite and speak to Electrical contractor ( they wired the whole place originally) they know nothing about it
No one will admit they asked for it so it's wired separately but connected to earth locally at panels " Just in case they change their mind later"

 

[spark 68]

I have done some panels for hospital/operating theatres in the past where they specced the panels as hi-integrity with no more than two connections to a stud and more than one stud plus an Earth reference bar, also built panels for the off shore and data centre industry which was fairly highly specced as well, I have also built panels for use in the nuclear industry which far exceeds anything else in this department lol, you have no idea lol, as I said it depends on the spec.

 

[spark 68]

Most of the data centre distribution panels had double size Neutral bars compared to the phase bars to account for triplen third harmonics (a lot of big switch-mode supplies apparently) and these always had a totally separate and insulated clean Earth bar as well as the usual 'protective' Earth bar, some had to have the Earth bar made into a ring, either by connecting in to another suite of panels, or if standalone made into a ring within the panel.
The hospital stuff had to have at least two studs per door and covers and as I said no more than two connections to each, this was I suppose to ensure Hi-integrity Earthing for the panel itself.

 

[netblindpaul]

If this is machinery covered by the machinery directive, and thus EN 60204-1, then the customer is totally correct. EN 60204-1 limits 1 protective conductor to 1 connecting point. Multiple crimped connections to the same stud are NOT acceptable. Multiple (2) protective conductors in a 2 way bootlace ferrule is NOT acceptable. More than 1 protective conductor in a screwed connection such as a DIN rail terminal is NOT acceptable.
This should be known by the designer and builder. It's not new and has been in the last couple of versions of EN 60204.

 

[edexlab]

Thanks netblindpaul , as ever very informative

I'm not knowledgeable to design requirements under the machinery directive and I know that there are several things which are a bit iffy with some of the design of our panels and also safety systems , these were historic and never changed before

However We do have some Engineers moving up through the company that have and are continuing to bring things up to date.

I've no problem with changing things when required if necessary and justified,

This company has wasted a lot of our time changing things backwards and forwards for no genuine reason so maybe I've become a little sceptical here !

 

[netblindpaul]

Thanks netblindpaul , as ever very informative

I'm not knowledgeable to design requirements under the machinery directive and I know that there are several things which are a bit iffy with some of the design of our panels and also safety systems , these were historic and never changed before

However We do have some Engineers moving up through the company that have and are continuing to bring things up to date.

I've no problem with changing things when required if necessary and justified,

This company has wasted a lot of our time changing things backwards and forwards for no genuine reason so maybe I've become a little sceptical here !

Well I am more than willing to come in and deliver some bespoke training on 60204, 13849, 13850, 13855 & 13857, 14119, pretty much any of the other B-type standards, the A-type, and most of the c-type if there are any c-type standards that apply to your equipment.
I spend most of my time these days assessing machinery against the standards, and helping OEM's & end users comply.

 

[edexlab]

I will mention it to one of the more influential Engineers as the company are slowly trying to improve things and if they do show interest I'll Pm for your details