Hi Edgar,

I presume, due to you references to NEC, that you are in the USA, or another place that wires using the USA codes ?

Here in the UK, and indeed 230V/400V land generally,  load diversity factors are calculated a bit differently, and although the physics is the same, the language used and the final circuit layouts in use end up being rather different.

There are a few folk who pop up on here from time to time who are familiar with US practice, and the rest of us can discuss the ideas in principle, but you may get a faster and better defined  answer by asking on a US-centric forum as well - and if you do, please come back and tell us the answer..

And I'm sorry,  have no idea why American hospital lights are special cases - here they would not be except in terms of perhaps needing unusual levels of emergency and task specific lighting, but the cable sizing maths etc would be as per standard.

Mike.

Thank you very much, Mike.

I was hoping this site would be it, but you're right, I indeed work I the US and need a forum where most of the users are also not only working here, but familiar with the NEC.

Thank you so much for clarifying. Going to look for a US-based EE forum now

Cheers,

Edgar

Do let us know how you get on. It is always informative to know what other places do and why they do it.

Mike.

"Mike holts forum"  is USA based and might be helpful.

Thanks, broadgage.

I created an account there and already re-posted this question there last week, soon after doing that here. We'll see if they reply any time soon.

Thanks

The demand factor for common lighting loads seems to be misunderstood in some way. The demand factor for "all other" loads, which are general lighting loads rather than specialised hospital or hotel loads, is 100% according to NEC table 220.42; any special remarks provided are not immediately relevant.

Each firm may apply its own internal rules or preferences when determining these values; the NEC may not mandate that businesses utilise 125% as their demand factor when it comes to general lighting loads. It's important to keep in mind that the NEC rules specify that a demand factor of 100% is permissible for "all other" loads.

Thank you, revida marcos . Just as I thought - the NEC does not require this 125% factor demand, but only 100% as a minimum (for the "all others" class) - so, engineers are welcomed to increase that factor if they so choose.

Cheers