... So now my curiosity is peaked, does the manufacturer have to supply 18" of clearance to cover this scenario or could they say that they provided say 10" which could be done with the 4 - 250's.
If he provides lugs that are only capable of 250kCMIL and documentation saying that is what it's designed for, then yes, that's permissible (I didn't check the values here, just the concept). If the lugs are capable of 600kCMIL, then the spacing has to be based on the maximum conductor allowed. Nothing says he has to accommodate whatever the installer wants to use.
But, if the equipment was SPECIFIED to be capable of accepting 600s, and he sent a box design that did not allow for that to happen, HE is responsible for the change order, in my opinion. Unfortunately, that doesn't happen often enough. Users buy equipment on price, then expect the electrician to "figure it out".
And this covers from the terminals to the cabinet walls, if the attachment lugs are on the bottom of the breaker, that would give me a height but what determines the width.
Physical constraints in that there must be a minimum of 1" of air space from a live part to a conductive element like a metal wall if it is 600V, slightly less if below 300V. The only other issue is air volume inside of the box, based on the expected temperature rise of the equipment at full rated load (usually 80% of rating on a CB) and stated ambient conditions. So basically if the heat rise issue is fine, his box can technically be 2" wider than the breaker itself, unless of course the lugs stick out wider, which at 1000A might be the case.
Do the manufacturers have a handy chart which tells them what size cabinet is required.
Nope. It's engineered, but often based on available standard box sizes.
I would like to call the provider and tell him because of "insert code or calculation" that the cabinet is too small (which it really is tight). Probably won't get anywhere with it on this job. I do know how to make it work but would really like to know the what's and why's of it all.
I agree, not going to happen on this job, just learn the lesson. When bidding, get all of the info up front, i.e. you can't use 3 - 600s, you have to use 4 - 250s and the box is too small for your conduits**. If that info isn't available, add $$ to cover yourself for contingencies like that and if it means losing the project, take solace in knowing that it went to the guy who just made a mistake like this one!
We all do it once, maybe more than once. But eventually we learn...
** By the way, take note that this is REALLY common with equipment that comes from Europe because for the most part, they wouldn't use conduit, they would use something like multi-core unarmored cable.
for us we have 3 - 4" with 600 AL. which would need 18". So now my curiosity is peaked, does the manufacturer have to supply 18" of clearance to cover this scenario or could they say that they provided say 10" which could be done with the 4 - 250's. And this covers from the terminals to the cabinet walls, if the attachment lugs are on the bottom of the breaker, that would give me a height but what determines the width. Do the manufacturers have a handy chart which tells them what size cabinet is required. I would like to call the provider and tell him because of "insert code or calculation" that the cabinet is too small (which it really is tight). Probably won't get anywhere with it on this job. I do know how to make it work but would really like to know the what's and why's of it all.
