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Topic Title: Atex rated chemical stores. Metal construction bonding questions.
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Created On: 05 October 2017 06:21 PM
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 05 October 2017 06:21 PM
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Posts: 15
Joined: 24 November 2013

Hi guys

Another metal container bonding question unfortunately.

We have two pre fab ATEX rated stores being delivered to site. One light fitting in each and an extract controlled via a control panel on the external face. ATEX installation / inspections will be completed when on site.

Supply to the cabin is TN-S. Cablin is located outside on a large inductrial site. Cabins can be simutanuesly touched. The stores are will be installed permanently however I am mindfull of section 717 mobile or transportable units. And also the fact the installation has been designed to Zone 2 incase a chemical spill occurs.

My intention is to protect the supply to each via seperate 30mA rcds as per section 717.

The question for me lies with bonding of the units. The units are in essence bonded through the steel work via the control panel which is bolted to the structure. There is also a 6 or 10mm bond coming from the panels onto the unit.

I am proposing to supplementary bond between the containers to lower any potential difference. However I am questioning if I should be asking our electrical contractor to install an additional 25mm main bonding conductor (Regulation 544.1.1) to the units given they could be seen as extraneous-conductive-parts. Or if supplementary bonds from the power supplys would be adequate.

I have been digging around on the forums but there appears to be no difinative answer on this. Any thoughts would be much appreaciated

 05 October 2017 08:26 PM
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Posts: 15
Joined: 24 November 2013

Just to add I have seen a similar installations carried out in two different ways. Both on a TN-S supply and similar conditions.

One was installed with the 25mm bond and the other installed with an RCD with no bond to add to my confusion.


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