Check out some similar questions!

NoSparksPlease · Apr 8, 2009, 01:42 PM

I am working in a manufacturing facility and am trying to figure where to get power from for some new equipment that will be replacing some existing production lines.

The configuration of the power distribution will be very different, i.e. centralized control panels as opposed to individual branch circuits. I am trying to determine which load center panels to tap for the feeders needed. But since most panels will almost always look overloaded if you just add up the circuit breaker ratings, I am trying to figure out what rules to use (with the help of the NEC Handbook) to determine what capacity I have left in any given panel, once I remove loads that are going away. Even using 80% of capacity one panel looks overloaded all ready. This does not really surprise me in a 10 year old facililty, but I do not know what other criteria I should be using. Most loads on the new equipment are motor loads.

Can anyone point me in the right directions, please?

I will consult an outside expert if I do not get a good feeling on my own. But I am trying to get re-acquainted with, and get a deeper understanding of, the NEC.

Thank you for all suggestions and pointers.

KISS · Apr 8, 2009, 02:03 PM

Forget adding up the circuit breaker sizes. It's a meaningless exercise.

You need to look at the loads and if they are expected to be on for more than 3 hrs at a time multiply by 1.25 for a continuous load.

So you really have to know what's attached.

A recorder for current could tell you a lot.

Putting a clamp on meter at various times can also tell you a lot.

The right way, is to know the continuous and non-continuous loads and what the NEC says are continuous loads.

Space heating is continuous if residential or commercial.

An electric oven in a commercial setting is continuous, but in a residential setting it is not.

It would also be helpful to know your power factor.

NoSparksPlease · Apr 9, 2009, 12:16 PM

Dear KeepItSimple...

NoSparksPlease · Apr 9, 2009, 12:20 PM

Dear KeepItSimple...

Thank you very much for this information. It gives more direction than I had before.

This could get interesting; this is a production environment so I believe most loads are continuous.

KISS · Apr 9, 2009, 12:32 PM

Yep.

Your wellcome.

To put it another way: Each breaker should have no more than 80% of it's rating if the loads are continuous. Breakers are rated for wire size, primarily. Actual loads determine minimum wire size.

sathe1963 · Apr 18, 2009, 08:51 AM

Dear Sir,

1. You have to categorise the load first,
2. As per categorisation; distribute the load evenly on any of the proposed panels,
3. For above 2, one has to make first single line diagram SLD of the system enabling to distribute the loads,
4. Essentials and non essentials are to be categorised (Enabling to feed them through DG set or without DG set)
5. Broadly, 1st receiving panel would be PCC i.e. Power Control Centre where in incomer for this panel will be added and others would be out going feeders to MCC's.
6. MCC's means motor control centres... in which one incomer is added and others would be out going to individual motors. (These feeders will be starters for motors)
7. Another one would be PDB power distribution board, which will feed power to Lighting distribution boards and power receptacles.

Hope, you may get some idea from this. (Prepare SLD first)

NoSparksPlease · Apr 20, 2009, 05:58 AM

Dear sathe1963:

Thank you for the response. The information is helpful, and it answered some other questions about the names given to different panel boards.