Marquee... temporary installation

[drazza]

Temporary power distribution for events is covered by BS7909.
generators would normally be TNS not TT

 

[ukpablo]

this depends if it a public paying event or private function like weddings!
private events can be run via a generator with earth electrode. (TT system)

 

[geofff]

I have to agree with Drazza, it would be a TNS system.

 

[ukpablo]

im not saying u are wrong, but if u are using an earth electrode as supplied with a mobile generator, u may be hard pushed to get lower than 0.8 ohms as per TNS in BS7671. I have not read requirements as per BS7909?? im not saying im right either so i will stand corrected???
May give Woodlands generators a call tomorrow for some of their input.

 

[mattmoo1974]

would the circuits jusst need to be rcd protcted and frame if metal eartthed...????

I used to put up said frames. 2ft 6 of iron rod(think yourself lucky tehy dont use these in the spark trade) 15 mins on a sledgehammer was the norm Even the wooden 1s use these

 

[geofff]

ukpablo, i'll try to explain my thinking on it being a TNS system to clarify my comment, I will also be more than happy to be corrected if wrong.
Here goes, lets take your output cable from the generator to your socket outlet, assume a bs4343 16A (blue) plug on genny end, socket on other end utilising 3 core cable. you have effectively run a seperate CPC from source to outlet by using 3 core cable, making the system TNS.
Looking at it the other way, if it were a TT system you could use 2 core from genny to socket but if you were to connect an industrial hotplate for example you would need to connect that equipment to its own earth spike with a max impedance of less than 200 ohms and your generator earth spike would need to be less than 21ohms to become a TT system.
Hope that makes sense

 

[ukpablo]

perfect sense geoff. i see ur way of thinking now.
seems a bit confusing on what reading to look for when driving earth rod?
thanks all the same.
every genny i have used in the past (some yrs ago now) is supplied with an earth rod which in turn suppllies a distribution board also with an earth rod???
see the confusion!! lol

 

[drazza]

The earth rod is so that you can bond the generator with mass of the earth. this is required if you are in close proximity to another supply ie a fixed supply or unlinked generator supplying another system, & a possability of a cross connection exists.
you are also required to test temporary systems even plug together ones. especially if you are a hire co & responsable for the event power.

 

[ukpablo]

thanks drazza, useful post this