Multi-Section Panelboard 1

[Bin510]

Having more then 42 poles, i need to use Multi-Section Panelboards interconnected via Gutter Taps, Sub-Feed Lugs or Through-Feed Lugs.
1) How many panels (max) can be connected to be a Multi-Section Panel.

2) Do the panels need to be mounted each next to the other or are there gaps between allowed?

PS:I am from Switzerland and not so familiar with all US-regulations. Anyway the installation the question is asked for is in the US.

 

[alehman]

1. Limit is determined by the load. Many inspectors won't let you get too crazy. They may ask questions or may refuse to allow a lot of breakers with unspecified (designated "spare" or similar) or poorly-defined loads.

2. It doesn't matter as long as all conductors and busses are adequately protected by the feeder overcurrent device.

 

[mc5w]

You might find that using 2 or more standard panelboards each on its own feeder will be cheaper.

Joining 2 or more panelboards together with gutter taps of power takeoff lugs is can be expensive and putting each section on its own feeder overcurrent device may have equal or lower cost. If each section has its own feeder then doing deenergized maintenance and branch circuit additions is a lot easier because you can use power from the still energized section to supply lights and tools.

Mike Cole, mc5w@earthlink.net

 

[Bin510]

I forgot to mentione that the panel(s) would be fed by a tranformer. Thats why i want to use a multi-section panel to avoid the need of more then 1 transformer.

 

[alehman]

I'm not sure I understand why the fact that they are fed from a transformer makes a difference. You could certainly feed multiple panels from one transformer, either with one breaker protecting them all or with individual breakers.

What Mike said applies in either case.

 

[Bin510]

That was refering to use 2 or more standard panelboards each on its own feeder (answer from mc5w).
Coming byck to my original request: is there a limitation in the amount of panels? (i may have the case where i need to use up to 4 panels as a multi section panel) Is that OK with the code?

 

[alehman]

It is acceptable per the NEC if the continuous load doesn't exceed 80% of the feeder and panel bus ampacity and the feeder overcurrent protection doesn't exceed the feeder and bus ampacity.

 

[mc5w]

A transformer is allowed to have 6 circuit breakers or 6 fusible switches on the secondary provided that the sum of the fuses or circuit breakers does exceed what National Electrical Code allows for a single overcurrent device.

Quite often we will attach a pair of 200-amp 120Y208 volt main circuit breaker panelboards to the secondary of a 150 KVA transformer.

You can also get transformers with 2 or 4 phase displaced secondaries that will cancel out ( neutralize ) harmonics from nonlinear loads provided that the nonlinear load is reasonably balanced across the seondaries. These are also legal in the U.S.

 

[Bin510]

mc5w: that confuses me now. In which section of the NEC can i read the passus you mention? (maybe it helps to understand, that i use the transformer to step US-voltage down to european voltage of 400VAC to feed european bulit machinery)

 

[mc5w]

Article 450. The text permitting the 6 disconnect method was moved to the table that governs overcurrent protection for transformers with 600 volt or less secondaries.

 

[rbulsara]

Review articles 408.15 and 408.16 in NEC 2002.

It is OK to have four (or more) panelboards on one feeder, as long as one of the following is met:

1. The overcurrent protection of the feeder does not exceed the rating of any of the panelboards (section) bussing. You will need through feed bus conncetions or loop feed. (For expample you can have (4)225A MLO panles on one 225A feeder)

OR

2. If one of the susequent panel is rated less than the first one, it has to have a MCB or protected by a breaker in the preceding section.

I think the limitation is not to have more than 42 breakers in a single section of a 'lighiting and appliace' paneboards. But for that matter each section is a separate enclosure. For that you need to read up the 'panelboard' article in NEC.