tray bonding

[opm electrical]

what do most do with tray to ensure its bonded, earth tags at each joint like on galv trunking or are the joins substantial enough, only ask as a dont generally use it but its specced on a job to install for data cabling and can i run power cables in the same tray if i keep them segregated?

 

[Essexboy7]

on tray you need to use earth braids at each joint.Dont use earth tags.I cant see why you couldnt run power and data on the same tray as long as they are segregated but i would check the spec to see if there is anything against it

 

[Knobhead]

Have a look at THIS

 

[ian.settle1]

Have a look at THIS

Tony is this a US site?

 

[benji]

generally use wire basket for data lot easier to install, bond at one end if correct joints are used

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generally use wire basket for data lot easier to install, bond at one end if correct joints are used

 

[benji]

bit more info , if your using the basket as part of the earthing system it should be bonded at each end and every 15 mtr of the run
CABLOFIL Couplers
The standard IEC 61537 states that coupler resistance must not exceed 50mΩ. The test involves running an electric current trough the system (cable trays + couplers and measuring coupler resistance.

 

[Spoon]

Nothing wrong with putting power and data cables in the same trunking as long as it has multi-compartments.
We get ours from TOTAL CABLE MANAGEMENT SOLUTIONS - specialists in trunking, cable tray and ladder: Unitrunk

 

[Spoon]

Is it cable tray or trunking you intend to use?
These are the earth links for some cable tray or trunking Earth Link | Unitrunk

 

[Knobhead]

Tony is this a US site?

Read it. Some of the best information you will get. It doesn't go in to reg's it goes in to theory and good practice.

 

[Engineer54]

We always earth our cable trays, which are pretty extensive too. We use two copper earth connections at each joint diagonally opposed. Generally our tray/basket work runs are dedicated to either comm's, LV, MV, but if the need arises i have no problem if space allows, to run LV and Comms on the same tray for shorter distances. All our comms cabling is screened and rated 600V anyway...

 

[johnboy6083]

Personally, I don't see any point whatsoever using copper links on trunking or tray, when solid joiners are used, and fastened correctly.
The lugs are connected to the same steel as the joiners, and have a smaller CSA, and smaller area of contact.
i would like to see a comparison on a long length of tray/trunking, straps vs no straps.
if for any reason fresh air bends are used, then I always use a strap, or use a min of 6mm2 6491x

 

[Engineer54]

Yep!! The manufacturers supply those copper earth joint straps for no reason what-so-ever!!! lol!!!

 

[johnboy6083]

Well, they are driven by other factors other than safety, profit being one of them.
as I've said, less contact area and less CSA the the joiners.
As long as the joiners are at least 8x the CSA of the min size copper link that a said manufacturer would supply then they would be fine. 8x is the difference in conductivity between copper and steel, which would be the worst case scenario.

of course we could then discuss whether the tray would need earthing at all?

its something that I have always done by the way, and will continue to do.

 

[Tesla1980]

I had the lovely job of earthing miles of cable tray in Avonmouth I got some earth cable wound it round a screwdriver for 8 turns or so then round earth crimped both ends and joined the tray up, cheap and cheerfull looked very neat.

They then had me pilot drilling loads of RSJ'S for earthing with sparky going round after me with bigger drill with which was not so great you know when your through you hang on to that 110 drill for dear life.

 

[Knobhead]

It's a wonder they didn't make you take the pigtails out. Bad practice.

Can't see the point of earth links on a bolted joint.

 

[High Tower]

This thread had me concerned as we do not bond bolted joints the only thing we do do is bond between multiple level trays

 

[Tesla1980]

It's a wonder they didn't make you take the pigtails out. Bad practice.

Can't see the point of earth links on a bolted joint.

It's what they wanted and what I was was told to do it was not between bolted joint there would be no point in doing it then would there it was between mulitple levels of tray ? but thanks for your input

 

[High Tower]

It's what they wanted and what I was was told to do it was not between bolted joint there would be no point in doing it then would there it was between mulitple levels of tray ? but thanks for your input

In fairness I thought the same as tony!

 

[Spoon]

Just been sent a couple of electrical test reports from our trunking/cable tray supplier. Here are the conclusions:

Trunking Conclusion:
All samples tested passed the electrical tests.
A representative sample of trunking was tested to demonstrate that earth straps in copper, tinned copper or none do not make a measurable difference to the impedance of conventional bolted links and snail (punched thread form) fasteners.

Cable Tray Conclusion:
All samples tested passed the electrical tests.
A representative sample of tray sizes and gauges was tested to demonstrate that earth straps in copper do not make a measurable difference to the impedance of both spring clips and conventional bolted links.

 

[johnboy6083]

I feel vindicated!
to be honest, we couldn't of expected any different, it's very basic electrical theory!

 

[Guest112]

I never see the point in fitting the earth links either, but in my experience most jobs ask for it,

waste of time and money by the looks of it

 

[benji]

I think earth links on trunking goes back to when most trunking was supplied painted

 

[johnboy6083]

I think it comes down to common sense. Unfortunately an awful lot of sparks I've seen on site seem to lack it.

 

[grantr37]

Nothing wrong with putting power and data cables in the same trunking as long as it has multi-compartments.
We get ours from TOTAL CABLE MANAGEMENT SOLUTIONS - specialists in trunking, cable tray and ladder: Unitrunk

thanks for that I never heard of this company before...might be better than the various wholesalers ....

 

[Knobhead]

I think earth links on trunking goes back to when most trunking was supplied painted

They never provided links when I was using miles of GE Power Centre trunking.

 

[Spoon]

thanks for that I never heard of this company before...might be better than the various wholesalers ....

We used to use Legrand, but they are too expensive and Unitrunk are very good and same quality as Legrand. Been using them for a few years now.

 

[Engineer54]

Why wouldn't you use earth straps when they are supplied with the tray and trunking?? Before they started supplying earth straps, all our metallic containment systems (apart from conduit) in the factories I did my training in had to have a strap between joints etc. Every project i've ever worked on, call for them!! I'll stick to what i know and have done for over 40+ years, ....the straps go in!! lol!!

I can't ever remember using painted Tray Or trunking, it was always Galvanised stuff i've ever used. I take it your referring to the grey trunking, (can't remember try being painted) often used in office buildings etc??...

 

[Spoon]

I know where you are coming from Eng54. I have always listed earth lugs with the galvanised trunking and cable tray, but these reports say that it doesn't make a difference if they are fitted or not, and in this day and age where we have to save as much money as possible, then I cant see the need to list them any more. Saving on purchasing cost and also installation costs (time used up fitting them)

 

[High Tower]

I really fail to see how any earth link would make a difference to a properly bolted joint.

I just had to install 120m of 125mm tray 2 level with numerous changes of direction and intersections.

25m of 4" trunking again with various changes of direction.

Supply and install with a budget of £2250 I'd love to see anyone fit in bonding joints into that budget.

 

[Knobhead]

Why wouldn't you use earth straps when they are supplied with the tray and trunking?? Before they started supplying earth straps, all our metallic containment systems (apart from conduit) in the factories I did my training in had to have a strap between joints etc. Every project i've ever worked on, call for them!! I'll stick to what i know and have done for over 40+ years, ....the straps go in!! lol!!

I can't ever remember using painted Tray Or trunking, it was always Galvanised stuff i've ever used. I take it your referring to the grey trunking, (can't remember try being painted) often used in office buildings etc??...

I never used anything but powder coated GE Power Centre trunking. It was the standard for our company. One contracting company was told to take out some galvanised that they put in as it looked an eyesore when run between panels that were all our "standard" colour.

 

[johnboy6083]

If they are supplied with the gear, then I'll fit em, however none of the gear I'm supplied with comes with earth straps. In fact, as far as I'm aware, only ladder rack joiners come with earth straps as standard.

all of the tray and trunking we use comes with steel joiners, and I fit them, and always ensure they are tight.

regarding specifications, a lot of company specs are over engineered. Our spec calls for all electrical equipment to have voltage labels, which is above and beyond BS7671 (unless over 230v to earth, which 99% of LV installations are not).
we also have to link from the banjo of the load end of a cable to the nearest metalwork.
this is also above and beyond BS7671.

just because you see it in specs, it doesn't mean they we have to follow the same rules, when you can prove that the alternative is just as safe, and more economical.

 

[Engineer54]

just because you see it in specs, it doesn't mean they we have to follow the same rules, when you can prove that the alternative is just as safe, and more economical.

You can do whatever you wish to do, and i'm sure you will, but if a specification calls for them, (or working on a project of mine) they Will go in... lol!!

 

[johnboy6083]

That's fair enough, and if working on your jobs, I would do as I'm told.

 

[cobrauk]

I agree its a waste of time using straps unless you make a bad job of connecting, and powder coated was the only time i have seen links supplied with trunking you have to buy them as a extra nowadays, also if you look the 90 and T bends only have one or two holes to connect between the trunking and the bend most don't have couplers between a bend and the trunking and its self so that means you would have to drill a second hole to install & connect a link yes ?

 

[Knobhead]

You can do whatever you wish to do, and i'm sure you will, but if a specification calls for them, (or working on a project of mine) they Will go in... lol!!

And here was me thinking you weren't one to follow dogma.
Sorry E54 but we’ll have to agree not to agree on that one.

I will add it would be a rare occasion where I would be mounting trunking or tray against a brick wall. When we did our normal practice would be construct a welded frame in the workshop with everything drilled to suit before hand.

 

[Engineer54]

And here was me thinking you weren't one to follow dogma.
Sorry E54 but we’ll have to agree not to agree on that one.

I will add it would be a rare occasion where I would be mounting trunking or tray against a brick wall. When we did our normal practice would be construct a welded frame in the workshop with everything drilled to suit before hand.

Depends on the dogma!! lol!!

As i have always worked primarily on highly spec'd projects, it's almost second nature to me to use copper straps across tray and trunking installations. Same goes with flexible earthing straps across isolating flexible joints on A/C ducting.

 

[Knobhead]

Depends on the dogma!! lol!!

As i have always worked primarily on highly spec'd projects, it's almost second nature to me to use copper straps across tray and trunking installations. Same goes with flexible earthing straps across isolating flexible joints on A/C ducting.

I'll not disagree with bonding flexible joints. Ducting depends on its construction.

The companies I've worked for were all blue chip so money hasn't really been an issue, just what's required.