main breakers

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keela1005

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main breakers, when dose a panelboard need them or not. I am coming from a 480v busduct to a 480-120-208 transformer then to a 120/208 panel. Do I need a main breaker in my panel or can it be main lug. What if my 480v tap switch is in line of sight. Is this considered my panel disconect?
 
There needs to be a main disconnect between the transformer and the panelboard, either in its own cabinet before power reaches the panelboard or in the panelboard itself.
 
All lighting and branch circuit appliance panelboards must have a main device. The main can be remote from the panel, but it must be on the 208V side of the transformer.
 
Also the transformer secondary conductors need protection per 240.21(C).
In many cases a single OCPD can protect both the transformer secondary conductors and the panel.
Don
 
Your disconnect must be within line of sight of the device.
Say you are dealing with a transformer that is feeding a panel in a separate room, you need a disconnect within line of sight of the transformer. The panel in the separate room also needs a disconnecting means either by disconnect switch or main circuit breaker for the panel. That is how I usually set it up.
 
rzuffi,
Your disconnect must be within line of sight of the device.
Say you are dealing with a transformer that is feeding a panel in a separate room, you need a disconnect within line of sight of the transformer.
Click to expand...
Please cite the code section that supports your statement. Thanks.
Don
 
code ?

code ?

jim dungar said:
All lighting and branch circuit appliance panelboards must have a main device. The main can be remote from the panel, but it must be on the 208V side of the transformer.
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where is this in the code?
 
NEC 408.36 Is the code reference for the requirement for over-current protection of a lighting and appliance panel board.
 
Bea said:
NEC 408.36 Is the code reference for the requirement for over-current protection of a lighting and appliance panel board.
Click to expand...
Not in MY book ('02), it ain't! :confused:
 
408.36 of the 2005 NEC states that a branch circuit panelboard will have OCPD on the supply side of the panelboard and on the secondary side of the transformer. But it says nothing about being within sight of anything. HVAC equipment and water heaters require a disconnect within sight, but those are not panelboards.
 
The load side conductors from the bus duct must be protected within their ampacity. If your bus duct switch is fused, size your fuses per 310.16 (assuming cabling is used).

If bus duct switch is unfused, you may view its load side conductors as a tap, in which case tap rules apply (240.21.....). Another factor in sizing your TX Primary side OCPD (Transformer Over Current Protective Device) is whether you will choose to install a transformer secondary OCPD (fuse or breaker) OR just the primary (450.3(B)). A transformer secondary OCPD can serve as both a TX secondary OCPD and a Line side panel OCPD (see 450, 408, 240 etc)

Additionally as other folks mentioned above, you must provide for a line side disconnecting means for the panel (which may be fused and serve as a TX secondary OCPD as per above) if any of the following apply:
The panel is in another room
The panel is out of line of sight from the TX primary OCPD
The panel is to be used as a lighting and appliance panelboard (408.16); Farther than 50 feet (Article 100)

Mike Holt sells some great books that detail this (lots of pictures).
 
ABB said:
Additionally as other folks mentioned above, you must provide for a line side disconnecting means for the panel (which may be fused and serve as a TX secondary OCPD as per above) if any of the following apply:
The panel is in another room
The panel is out of line of sight from the TX primary OCPD
The panel is to be used as a lighting and appliance panelboard (408.16); Farther than 50 feet (Article 100)
Click to expand...

WRONG

Line of sight and distance have absolutely nothing to do with the selection and location of a disconnect or overcurrent protection for panelboards.

Services must be protected per 230, which has a vague distance limit
Conductors must be protected per 240 which has specific distance limits
Transformers must be protected per 450 which has no distance limits mentioned.
Panelboards must be protected per 408 which has no distance limits mentioned.

Do not infer that distance limits for motors (430) and appliances (422) as apply to any other articles.
 
Some codes do require a disconnect at a transformer, as I found out in a former life in the NW. Unfortunately it was too many years ago to remember which. WA, OR or possibly the Seattle City Code. Charles?
 
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