TN-S or TN-C-S

Stringbags · Feb 19, 2010

Have I got this correct

[FONT=&quot]"It is not permissible to install TN-C-S (PME) systems in petrol stations or large arenas and stadiums, for this reason and for standardisation, all new installations will be TN-S."
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[FONT=&quot]It flies in the face of logic that a PME system is less safe than TN-S, can anyone enlighten me if and why this is true?[/FONT]

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[FONT=&quot]Stringbags
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Notsosmart · Feb 19, 2010

In TN-C-S systems, any connection between the combined neutral-and-earth core and the body of the earth could end up carrying significant current under normal conditions, and could carry even more under a broken neutral situation therefore with this in mind; use of TN-C-S is inadvisable in situations such as petrol stations, where there is a combination of lots of buried metalwork and explosive gases.

Guest123 · Feb 19, 2010

Hi

The HSE banned the use of TN-C-S systems in petrol stations due to the risk of open circuit neutral currents travelling through all the bonded steelwork and the presence of underground storage tanks and flammable gases......little bit iffy!!!!

Although theres no petrol present at stadiums and arena's and the like, it's due to the presence of all that exposed metalwork coupled with questionable equipotential bonding and corrosion of the joints of the structure, possibly becoming live under an open circuit fault again, bit iffy!!!!

Another area that suppliers dont like you using their PME is agricultural buildings, again lots of exposed steelwork and questionable bonding.