[BC] Electrical Code

[Jerry Mathis]

How about this method?

Put up a sign (embossed tape or similar) on the front of the transmitter, 
specifying how many circuit breakers supply power, and their location. 
Problem solved, with no code violations.

'Course, this doesn't help you if it's not YOUR transmitter, and you're 
walking in on it for the first time.



Jerry Mathis
Clear Channel Radio, Tupelo & Meridian MS





>From: Dave Karr <dave at vyex.com>
>Reply-To: Broadcast Radio Mailing List <broadcast at radiolists.net>
>To: broadcast at radiolists.net
>Subject: Re: [BC] Electrical Code
>Date: Tue, 25 Oct 2005 01:05:38 -0500
>
>At 10:14 PM 10/23/2005, you wrote:
>
>> > The three phase Wye connected power is actually 208 volts leg to leg 
>>and 120
>> > volts to neutral.  So it is perfectly legitimate to use any leg to 
>>neutral
>> > for a single phase load.  The code problem gets to be one of fusing, 
>>the
>> > three phase is most likely fused (or circuit breaker) at a high value 
>>and
>> > the wiring on the single phase load is not capeable of that kind of 
>>current.
>> > If you fuse the single phase load at a proper value there should not be 
>>a
>> > problem.  If the three phase is Delta connected (Not common anymore) 
>>then
>> > the voltage is 240 volts leg to leg and one of the leg to leg 
>>connections is
>> > normally center tapped to form the neutral and 120-0-120 for single 
>>phase
>> > load.  Either end of the center tapped transformer winding to neutral 
>>is 120
>> > volts and is usable. The third leg (often reffered as the "wild leg") 
>>can not
>> > be used to neutral as it varys wildly depending on the load and current
>> > unbalance.
>>
>>While all of the above is quite true, there is a simple solution. Install 
>>a
>>single three phase disconnect and wire a smaller single phase disconnect 
>>as
>>a branch of its load. Then, when the three phase switch is pulled, all is
>>dead. I would go so far as to add a shrieking "howler" on the three phase
>>switch so that if the low power single phase is pulled, a relay falls and
>>the big box starts screaming like a banshee until it is also pulled. Thus
>>the small box is there for meeting the intent of the code that each wire
>>be fused with a fuse correct for its ampacity, and the large three phase
>>box provides single switch safety for personnel.
>
>While logical, assuming the above would be located external to the served 
>equipment...that wouldn't pass an inspection here...
>
>The feeder branch created by the first three-phase fusible disconnect and 
>the subsequent 'feeder tap' by the single phase fusible disconnect cannot 
>simultaneously supply the three phase load directly without the addition of 
>a second fusible disconnect for the three-phase load.
>
>In other words, a "branch feeder" (conductors that supply power to 
>equipment) cannot simultaneously be used as a "feeder tap" (conductors that 
>supply power to other fusible disconnects).
>
>Tap conductors are allowed to be sized smaller according to the downstream 
>fusible disconnect's rating as long as the distance between the tap and 
>disconnect fall inside guidelines.
>
>
>This code issue could be circumvented if the fusible disconnect for the low 
>current single phase load were made part of the equipment itself.  Perhaps 
>a small Eaton-Heinemann/Airpax/ABB/etc. panel or DIN rail mount breaker 
>could do the trick.
>
>
>--Dave
>
>
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