Normal and Critical or 2 Critical

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mbrooke

mbrooke

Batteries Included
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Technician
When dealing with patient care areas, what conditions must be met in order for 2 critical branch circuits to be permitted? And when they say normal circuit, this means bypassing the entire emergency system?
 
mbrooke said:
When dealing with patient care areas, what conditions must be met in order for 2 critical branch circuits to be permitted? And when they say normal circuit, this means bypassing the entire emergency system?
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feed from two separate critical branches including the transfer switch
 
david said:
feed from two separate critical branches including the transfer switch
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So the branch is considered separate when it originates out a independent transfer switch? If the load is under 150kva, this then becomes a separate breaker?
 
mbrooke said:
So the branch is considered separate when it originates out a independent transfer switch? If the load is under 150kva, this then becomes a separate breaker?
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On a small hospital with one transfer switch the rule allowing two critical circuits in lieu of a critical and a normal circuit is not applicable, read exception #3 to 517.18(A) and exception #2 to 517.19(A). The circuits would have to be from different transfer switches.

Roger
 
roger said:
On a small hospital with one transfer switch the rule allowing two critical circuits in lieu of a critical and a normal circuit is not applicable, read exception #3 to 517.18(A) and exception #2 to 517.19(A). The circuits would have to be from different transfer switches.

Roger
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So a small hospital must have 1 critical and one normal unless a second transfer switch is present?
 
mbrooke said:
One more question, does anything prohibit me from subdividing the life safety branch? Ie, having 2 life safety transfer switches?
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Each essential system branch can have multiple transfer switches, see 517.30(B)(2)

Roger
 
roger said:
Each essential system branch can have multiple transfer switches, see 517.30(B)(2)

Roger
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Ok its doable then. And nothing restricts how I divide the life safety loads on each panel?


Basically I have a design scenario at hand with 2 1000kw generators. Each feeds its own switch-gear and both gears are linked via a normally open tie breaker. One life safety ATS coming from one side and another life safety ATS coming from the other side. Half the LS in the building takes one ATS half takes the other. Similar for critical and equipment, except that critical has 3 from bus section one and 3 from bus section two.
 
roger said:
Each essential system branch can have multiple transfer switches, see 517.30(B)(2)

Roger
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mbrooke said:
Ok its doable then. And nothing restricts how I divide the life safety loads on each panel?


Basically I have a design scenario at hand with 2 1000kw generators. Each feeds its own switch-gear and both gears are linked via a normally open tie breaker. One life safety ATS coming from one side and another life safety ATS coming from the other side. Half the LS in the building takes one ATS half takes the other. Similar for critical and equipment, except that critical has 3 from bus section one and 3 from bus section two.
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And its being debated if the life safety and 2 ultra critical branches can be fed through 2 ATS or a 3 source ATS, such that if either gen set fails to start, the ATS can then close into the other buss thats still live. I can draw this out if need be.
 
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