Why loads in the downstream panelboard should be SMALL.
Why loads in the downstream panelboard should be SMALL.
(OP)
I have a client who is trying to "cut fat" from a project, and one item they are proposing is moving some of the larger loads on their system from the main distribution switchboard (where breaker "real estate" is much higher) to a downstream distribution panel. We're talking a couple of 400A loads more suited to a robust 3000A 277/480V switchboard than what's basically a wall-mounted 1200A I-Line panel that we were ear-marking for more localized loads. The distance from the load to either of the two boards is about the same, so they're pressing to feed them from the I-Line panel.
Can it be done? Yeah. Is it good engineering practice? No. As a rule of thumb, big loads go on big switchboards and smaller loads go on smaller boards/panels. But I can't really figure out a way to explain why other than the standard "that's just the way it's always been done around here" response. Any suggestions as to how to make my point?
Can it be done? Yeah. Is it good engineering practice? No. As a rule of thumb, big loads go on big switchboards and smaller loads go on smaller boards/panels. But I can't really figure out a way to explain why other than the standard "that's just the way it's always been done around here" response. Any suggestions as to how to make my point?






RE: Why loads in the downstream panelboard should be SMALL.
You may take the approach that your client’s requests will limit growth and make additions/modifications to the electrical system potentially much more expensive.
It may be that the subject feeders will initially have higher losses and reduced spare capacity.
RE: Why loads in the downstream panelboard should be SMALL.
RE: Why loads in the downstream panelboard should be SMALL.
Reliability: The breaker located in the main board will be more robust and inherently more reliable
Maintenance: It is easier to isolate a particular circuit in a main board to do maintenance than in a sub-board
Cabling: There may not be enough room to terminate a large number of large cables in a sub-board.
Single Point of Failure: Putting a lot of important circuits on a sub-board creates a single point of failure
RE: Why loads in the downstream panelboard should be SMALL.
The best argument is probably that if the breakers were installed in the I-Line panel, servicing them would require the entire panel to be shut down, whereas this would not be the case with the drawout gear. That is in fact the main selling point of drawout gear. And since downtime would be a fairly serious issue here, I can probably play up that angle to them pretty convincingly.
RE: Why loads in the downstream panelboard should be SMALL.
I think the draw are easly to service. But in todays thinking 1st cost carries a lot of weight. Question-If you had to pay for the installation yourself would you pick the draw-outs.