Getting info from DNO

[pcboffinuk]

Hi all,

[crawl]
I've already seen some excellent advice on this forum, and there are clearly some experienced sparkies out there[/crawl] so though I might see what the view is on getting the necessary info from DNOs when doing domestic electrical work.

I will be looking to get competent person registration soon and letting myself loose on the general public, but I am already detecting a difference between the 'correct theoretical' way of doing things, and the way that people have to do things in order to get the job done...

We all know that the DNOs *should* provide written information on a domestic property with Ze, PFC and incoming Cut off Fuse rating, necessary to fill out the required paperwork - however, I have my doubts as to how easy this will be, based on a single attempt to get said info on my Mother's house.

Obviously the Ze and PFC can be measured, which at first glance would seem more accurate, but I also see some benefit in allowing for future cases by using the maximum figures quoted by the DNO - after all changes in the future (new meter installed by DNO) could render the measured Ze inaccurate?

Have others managed to get this information easily? or do you use the 'standard' figures given in the books (0.35, 0.8 etc from memory).

The rating of the house cut off fuse is also required to calculate loads, etc. when adding new circuits - not much point allowing for 100A on a nice shiny new DB if the house fuse blows at 60! The only way of finding that out other than getting the info from the DNO is of course to break the seal, which I'm sure no sparky ever does!

Would be interested to hear what others find and do in practise.

Many Thanks


Gavin

 

[plugwash]

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Obviously the Ze and PFC can be measured, which at first glance would seem more accurate, but I also see some benefit in allowing for future cases by using the maximum figures quoted by the DNO - after all changes in the future (new meter installed by DNO) could render the measured Ze inaccurate?

it could although in reality it probablly won't get much worse unless something really drastic happens to the country as a whole (war major energy shortage etc) leccy use is going up not down.

afaict if you ask them they'll most likely quote the worst allowed case (0.35 for TN-C-S 0.8 for TN-S) or possiblly measure it for you, i think its highly unlikely that they will give any gauranteed variation range beyond whats required of them.

The rating of the house cut off fuse is also required to calculate loads, etc. when adding new circuits - not much point allowing for 100A on a nice shiny new DB if the house fuse blows at 60!

afaict they tend to swap it up to 100A if and when it blows anyway so i wouldn't worry too much about it.