Fridays rumination

Johno12345:


Anyway, I want to have some distribution equipment replaced due to the age and condition of it.


I always specify Schneider Acti 9 boards or Powerpact 4 boards


These boards wont require anything bigger than 63a 3ph, so ill be ok with an Acti 9 board, but the total load is likely to be around 200 amps over an 18 way board. I was thinking that sounds a lot to put through a DB as a continuous load, but the website implies that its going to be fine. Is this right? I'm visualising a heating effect etc, so what point do you stop with a DB and go to a panelboard? Usually, if I need to supply something larger than 63a, I know ill need to have a panel board and can budget accordingly


 

Hi johno, as these are existing dbs when you say the total load is ‘likely’ to be 200amps continuous can you not confirm the loads on site? 

weirdbeard:

Johno12345:


Anyway, I want to have some distribution equipment replaced due to the age and condition of it.


I always specify Schneider Acti 9 boards or Powerpact 4 boards


These boards wont require anything bigger than 63a 3ph, so ill be ok with an Acti 9 board, but the total load is likely to be around 200 amps over an 18 way board. I was thinking that sounds a lot to put through a DB as a continuous load, but the website implies that its going to be fine. Is this right? I'm visualising a heating effect etc, so what point do you stop with a DB and go to a panelboard? Usually, if I need to supply something larger than 63a, I know ill need to have a panel board and can budget accordingly


 

Hi johno, as these are existing dbs when you say the total load is ‘likely’ to be 200amps continuous can you not confirm the loads on site? 

And when you say, "These boards won't require anything bigger than 63a 3ph," - do you mean that the DBs that you are replacing will not need a supply into the DBs main switch of 63 Amp three phase-  and the 200 Amps referred to above is the sum of the MCBs in the the DB?


or do you mean (I suspect you do) that each DB will not need to supply further down stream SUB DBs (from the MCBs inside your DBs) at loads greater than 63 Amp three phase? Total likely load in such an 18 way DB unlikely to exceed 200 Amps; even though this DB has a number of 63 Amp 3 phase ways going out of it, plus I assume other circuits?


So - are we talking about a normal 18 way 3 phase DB which happens to have a circuit or 2 in it @ 63Amp 3 phase,supplying further DBs.


Or are we talking about a DB that Only has 63 Amp, Three phase sub distribution circuits in it? perhaps 18 of these? Total likely load 200 Amps?


I kind of suspect the OMS has already answered the question though.......... a 250 Amp DB will be well suited to supplying loads of 200 Amps and you'd not need to install MCCBs for example. 


I do like MCCB "panel" boards though. Big fan of them.


Kind Regards


Tatty

Johno12345:

if we all think they will run fine all day at the incomer rating, then all should be ok, and I'm just over thinking things a bit 

I think you said maximum load sustained was 200A through a 250A rated DB - that should be fine


250A sustained through a 250A rated board is a different proposition  - it will get hot, and then it depends on the quality of manufacture - sadly, many DB's won't survive full load for extended periods


Regards


OMS

Johno12345:

Hi,


been sunning it up for a week here.



if we all think they will run fine all day at the incomer rating, then all should be ok, and I'm just over thinking things a bit 

Hi hope you had a great 10 day holiday between posts, do you have any pics of the existing arrangement? Is it showing signs of overheating?

OMS:

Well, in old skool terms, I would run a minimum of a 300A supply (and ideally a 400A supply) to a short busbar chamber and fit the 250A boards close coupled to it - and then design to limit the demand on each board to say 125A (eg 4Way Type B with 2 x 63A TP MCB's)


That's still probably cheaper than a 400A rated MCCB panel with a lot of 63A outgoing ways - depends a bit on the capability of the "house" sparks though to assemble it properly


Regards


OMS

that sounds pretty much like what I'm thinking, and would look pretty neat in the process. I have some decent contractors that are more suited to slightly more complex things like this. Also have some that don't like to stray beyond anything even slightly unconventional!