Tail sizes - max demand suggests too small

[LlandrilloSpark]

Fellas

Im just writing up the 5 flats I inspected last week, all the service heads/fuses are new to within 3 years, the cut out fuses are all 100A and tails all 16mm, I know discretion is sometimes needed in this area, on some flats the Max demand reaches 90-100A whilst in others 65-75A, would anybody agree that this is basic circuit design and those with the high max demand need the tails changing?

cheers

 

[Tris Zanker]

I always think 100A cut outs 25mm tails, 60A cut outs 16mm tails.

 

[telectrix]

it all depends on whether the actual max. demand is close to the calculated value. technically, you should fit 25mm tails with 100A DNO fuses, but recently i had a site where 16mm was carrying 95-100A for over an hour . highest temperature of the cable was recorded at 40geg.C. well short of it's rated max. of 70.

 

[LlandrilloSpark]

If I stick to the book I should replace all the tails, but the example you have given proves there is no real danger, Im eering on the side of letting this one go

 

[Moses]

I always think 100A cut outs 25mm tails, 60A cut outs 16mm tails.

I agree.

 

[telectrix]

i'll bet if you switch on everything you can and clamp a tail you won't get more than 60 - 70 A .

 

[Tris Zanker]

another way of looking at it, if you've just done a EICR you'll be wanting to do any work that needs doing so replacing 16mm tails is yet another job you can earn money for doing.

 

[Top Cat]

Fellas

Im just writing up the 5 flats I inspected last week, all the service heads/fuses are new to within 3 years, the cut out fuses are all 100A and tails all 16mm, I know discretion is sometimes needed in this area, on some flats the Max demand reaches 90-100A whilst in others 65-75A, would anybody agree that this is basic circuit design and those with the high max demand need the tails changing?

cheers

I would be very surprised if the total load for 5 flats at any given time was more than 150Amps unless they had NSH's.

 

[telectrix]

Nsh?????

nice to see you again , TC, thought you had drifted off into a CATATONIC state.

 

[KevinS]

I agree - 25mm 100A 16mm 60A
BUT the NICEIC assessed a job that i had done, (c/u change in an average sized 2 bed house) and she claimed max demand for that house would be 10A!!!!!!!
Her opinion was "ignore lighting (that uses no power) ignore the shower (its not on long enough) take 40% of he cooker & socket circuit & thats our maximum demand"
As i said this was the opinion of the NICEIC assessor - not mine. So if this is the case do we ever neeed 25mm in a normal house. and before you ask - no - i didnt argue with her!

 

[Top Cat]

Nsh?????

nice to see you again , TC, thought you had drifted off into a CATATONIC state.

Night Storage Heaters, by the way it came up what you deleted! I am not in a CATATONIC state!

 

[telectrix]

LOL> :snore:

 

[Moses]

For max demand for blocks of flats or blocks of houses, refer to Curve "a" on Figure 3.1, page 24 of the "Commentary on IEE Wiring Regulations 16th Edition", by Paul Cook.

 

[Air Conditioner]

What does it say Moses?

 

[Top Cat]

LOL> :snore:

Always nice to get one over on Tel!:50: