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dannydore
Hi all. Been reading a lot of topics in regards to grouping factors, none of which seem to have the exact answer I'm looking for.
I'm currently in the process of doing a project for my 2396 Design & Verification course which is a 2 storey college block. I'm using metal trunking (method B) and pvc 70ºc singles (Table 4D1). There are 3 runs of trunking which encompass the whole building, 2 for the ground floor, and 1 which rises to the 1st floor. My grouping factors are 0.47 (11 circuits) for both of the ground floor runs, and 0.43 (14 circuits) for the 1st floor run.
After doing all of my Lighting circuits, I came to the Power calculations. Obviously, these grouping factors applied to a 20a Ib (or In) produces ridiculously high Iz (or It) figures (10mm to be precise).
"Use Note 9", I hear you say... Well, even after changing all of my lighting circuits to 2.5mm, only 6 circuits were lightly loaded (2 on each run) Thanks to the Guilds for making the majority of the lighting fluorescent/discharge with a 1.8 factor.
As the drawings merely show twin s/o's, I have no idea what the actual uses are for each circuit, and I would actually prefer to use the correct figures found in the Regs.
The only solution I can see is changing all of my containment to either add another trunking, or a completely different installation method. But seeing as I've had these all printed out on A1 scaled drawings, I'm a bit reluctant to do so. Also having worked on site for 4 years or so, I (and no doubt every other commercial/industrial spark) have seen trunking runs stuffed to the brim. Something just doesn't add up!
Am I missing something here, or can anybody suggest an alternative?
Thanks
Danny
I'm currently in the process of doing a project for my 2396 Design & Verification course which is a 2 storey college block. I'm using metal trunking (method B) and pvc 70ºc singles (Table 4D1). There are 3 runs of trunking which encompass the whole building, 2 for the ground floor, and 1 which rises to the 1st floor. My grouping factors are 0.47 (11 circuits) for both of the ground floor runs, and 0.43 (14 circuits) for the 1st floor run.
After doing all of my Lighting circuits, I came to the Power calculations. Obviously, these grouping factors applied to a 20a Ib (or In) produces ridiculously high Iz (or It) figures (10mm to be precise).
"Use Note 9", I hear you say... Well, even after changing all of my lighting circuits to 2.5mm, only 6 circuits were lightly loaded (2 on each run) Thanks to the Guilds for making the majority of the lighting fluorescent/discharge with a 1.8 factor.
As the drawings merely show twin s/o's, I have no idea what the actual uses are for each circuit, and I would actually prefer to use the correct figures found in the Regs.
The only solution I can see is changing all of my containment to either add another trunking, or a completely different installation method. But seeing as I've had these all printed out on A1 scaled drawings, I'm a bit reluctant to do so. Also having worked on site for 4 years or so, I (and no doubt every other commercial/industrial spark) have seen trunking runs stuffed to the brim. Something just doesn't add up!
Am I missing something here, or can anybody suggest an alternative?
Thanks
Danny
