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Topic Title: Correction Factors
Topic Summary: Points of concern with regard to grouping and single circuits
Created On: 29 June 2012 06:23 PM
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 29 June 2012 06:23 PM
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Avatar for Legh.
Legh

Posts: 3488
Joined: 17 December 2004

Just updating my notes and find that App.4 no longer has grouping for similar circuits enclosed in trunking ( F=1/(rt(N)). I assume that this one has been dropped? (It would make sense)

and

5.1.1 and 5.1.2
It>= In/(Cg.Ca.Cs.Cd.Ci.Cf.Cc)
Leaving out Cs, Cd, Cf, there appears to be no mention of non-concurrency.

I don't fancy installing a 9kW shower with 35mm2 conductors.

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 29 June 2012 06:36 PM
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OMS

Posts: 19674
Joined: 23 March 2004

Originally posted by: Legh

Just updating my notes and find that App.4 no longer has grouping for similar circuits enclosed in trunking ( F=1/(rt(N)). I assume that this one has been dropped? (It would make sense)

2.3.3.1 legh ?


and



5.1.1 and 5.1.2

It>= In/(Cg.Ca.Cs.Cd.Ci.Cf.Cc)

Leaving out Cs, Cd, Cf, there appears to be no mention of non-concurrency.

There never was Legh, if it's grouped in a hot environment and surrounded by insulation and protected by a BS 3036 fuse then all the factors apply - not just the "worst" one

If different parts of the run have different conditions you can evaluate on the "worst condition" for each factor but you can't ignore lesser factors if they apply - they weren't derived collectively - only in isolation



I don't fancy installing a 9kW shower with 35mm2 conductors.

Don't use a 3036 fuse, with lots of other grouped circuits run through a heating chamber then


Legh


OMS

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Failure is always an option
 29 June 2012 07:00 PM
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Avatar for Legh.
Legh

Posts: 3488
Joined: 17 December 2004

Thank you OMS,

2.3.3.1 How did I miss tha t- I'm going to resist the temptation and say that the pages were stuck together.....

Its amazing how these little regulations disappear when you look for them and then like magic reappear again.

As far as non-currency goes. and as a design consideration, I would have thought a note to say where there is no concurrency of correction factors it would be acceptable to use the worst factor rather than all of them.

9kW instantaneous water heaters covered by BS3036 rewireable fuse links - old habits die hard !

While I'm on a roll, hopefully not downward

533.1.1.2 contains no vertical line next to it, there are others as well

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
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