bigger than a cu

[i=p/u]

was woking with panel today that these circuit breakers
http://www.mebamfg.com/pdf/NF250-CS-Moulded-Case-Circuit-Breaker.pdf

can you use one side as a live feed to another circuit breaker

what is bs numbers for these circuit breakers is it bs 4752

you can set the I (amps) with a dial and there is a red button to test the thermal magnetic disconnection

big board than normal for me

 

[Snapester]

I believe that the BS is indeed BS4752. I have worked with these a fair bit on larger industrial installations and they are usually used to supply sub-main boards around the installation. Is this what you were thinking of?

 

[Knobhead]

You have to keep in mind discrimination, so long as the upstream breaker holds longer or at a higher current than the downstream then it’s OK.

Just like you wouldn’t install a 30mA RCD in a garage fed by a board in the house protected by a 30mA RCD. You would cascade the discrimination by either using an unprotected way or with time and sensitivity. I know RCD’s are different to MCCB’s but the principal of cascading is the same.

Cascaded discrimination in a distribution system is a minefield. A subject normally the realm of a specialist.

Have a close look at the Ith and In of the two breakers there will be a difference. (Hopefully)

 

[plugsandsparks]

As mentioned these types of breakers are used as mid distribution meaning they are seldom used as final cct breakers. Normally there would be a TP board with a proper isolater on the end of this and then the usual final cct breakers. Not sure why you would connect it direct to another cct breaker but remember you need to protect the cable betweem the two with this breaker. Some of them do have a very good adjustability but you need good eyes. Only yesterday i had to turn one down from 800A to 400A, i needed a torch and my reading glasses.

 

[i=p/u]

i seen the dial you could select the rating.... so this what i have on this job...

feed coming in, which has its own section of the panel, which is sealed and bolted plastic covers on, do i need to remove this to get my primary supply over-current protective device rating?

then goes into a chamber which i didn't open cover too, then too a 175-225A cb, which is main isolator for panel. this in turn then feeds my 100A 3p cb which feeds a new doorman smith panel 3phase and neutral with a 250A main isolator . now this panel came pre built which i know nothing about and has four like consumer units on it running vertical down the panel some with single phase going to them and some with 2 phases, all new to me.

would i record a new schedule of test results for each section of the panel, i,e 1 is for heating, 2is for lighting, 3 is for power etc??? they do have there own 50A main switch.. so

 

[i=p/u]

ps on a 3p 100A breaker does this mean each pole can take 100A???/ scary enough

 

[RISElectrical]

Treat each section of the panel as you would a new db, if I am imagining this correctly as you described it. Each MCCB would usually supply a sub distribution circuit as has already been said. The only times I have seen otherwise are where the fire alarm panel comes from main board and will be from a 20a MCCB or similar.

 

[i=p/u]

the thing is here they have all these circuits up and running and no labels .. means il have to dismantle light fitting etc.. ----ers



is the older 3871 type 2 mcbs the same as type b in max zs

 

[i=p/u]

ok i see from my book aswell that m9 = 9KA :nonod:

 

[i=p/u]

another thing i know i shouldnt be doing this testing alone but i am taking my time weather boss likes it or not as this is kinda out of my league... but its great expierience

 

[plugsandsparks]

When i am doing commecial / industrial, i go one step upstream to check the supply i am being given is suitable. A few times i have found that the supply given to me has fuses or breakers too large for the cable supplied to me. Once i have sorted that out and am happy with the supply to me and cable, then i start as if that was the "distributors" supply. So my board would have a main switch and cct breakers, if any of those ccts is a supply to another DB, like a SP board then i would treat that as a sub board and repeat the exercise.

 

[brucelee]

edited incorrect info sorry

 

[i=p/u]

the cable is massive that's feeding the panel, huuuuuuuuuuuuu mungus not you average 25mm..

yeah he has give me eic, soi, sotr, plus circuit charts and extra schedule of test results. so that means each lookalike board will be done separately thanks fellow americans.

i did ask for old test results and he hadn't a scooby, the guy running the build .

ads or ebbad

 

[Knobhead]

ps on a 3p 100A breaker does this mean each pole can take 100A???/ scary enough

You got it, 100A per phase.

Look at it another way, it’s a house with a 300A single phase service head. Same ****e different location. Bigger bang!

Don’t worry about it, it’s the worse thing you can do. You’ve tested live before, you know to keep your pinkies out of harms way. Use your common sense.

BUT do not go in to the main incoming cubical without supervision, two heads are better than one. If you feel uncomfortable with something, say so and stop.

 

[i=p/u]

what page in gn3 is this... cant be in gn3, cant cant cant, isit in the new wiring regs under different class

Hi mate what size type 2 do you want to know max ZS and by that do you want the maximum measured value or the maximum tabulated value
GN3 has the 80% max measured values
5A is 5.3
6A is 4.42
10A is 3.71
15A is 1.77
16A is 1.66
20A is 1.32
25A is 1.06
30A is 0.88
32A is 0.83
40A is 0.66
45A is 0.82
50A is 0.74
63A is 0.59
100A is 0.37
125A is 0.30

think there is a pdf somewhere on the forum i have downloaded it so if i find the link or pdf will post it up