Automatic Transfer Swith

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Jim W in Tampa said:
If the transfer switch is also the main disconnect do we have a problem ?Seems to me that there is no way to turn power off fast.Am i missing something ?
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Jim, the Main is not for turning power off fast, this seems to be a common misconception. E Stops and E Offs are for this purpose.

Roger
 
OK but then why do we limit services to 6 disconnects ?Situation i have is pad mounted transformer underground to meter,meter underground to inside of electric room to transfer swith then 2 42 circuit ML panels.In emergency how will they cut power off without generator starting and turning power back on ?
 
wilsa said:
I am missing some there are some transferswits that have main built in
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This one is a Cutler Hammer that uses 2 400 amp main breakers.One for utilty and one for gen.Neat looking mechanical arm operates both breakers and one is turned upside down.Small motor does this automaticly or you can do manuel.
 
Jim, if the Fire Department is involved, believe me, they will take axes or what ever it takes to kill the power from all available sources.

Think about buildings with secured Electrical rooms where the main is located within this room, they have to find the room, then get into the room, then get to the main, then turn it off, there is nothing fast about this in relation to the task at hand.

As far as the 6 disconnect rule, I think it's a hold over from the days when better technology or codes were not available

Roger
 
Jim,
I think most T.S.'s have a switch that disables the "automatic" part for servicing and for disconnects. I have seen them on the outside of the cabinet and or on the inside. Also, the power for the "automatic" part is usually supplied by a single phase breaker in a near-by panel that can be snapped off in a hurry.
 
Jim W in Tampa said:
If the transfer switch is also the main disconnect do we have a problem ?Seems to me that there is no way to turn power off fast.Am i missing something ?
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What are you asking?
The auto transfer switch should not be the main disconnect.
If the main disconnect is turned off the Auto transfer switch will automatically start the generator & power up the selected panels or circuits.

Who is looking to turn off power fast?
Why?
 
There are transfer switches that are service rated. The poco and the generator are both on the line side of the disconnect so if the disconnect is turned off it does not matter which source is on the power will go off.

Andrew
 
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