Does the NEC mandate the use of ATSs?

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don_resqcapt19

don_resqcapt19

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m sleem said:
Aside from that, ATS has a maintenance bypass switch which is very important for emergency power
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I don't see a requirement in the NEC or in UL 1008 that an emergency ATS have a maintenance bypass switch. I believe that is a design issue and not a code issue.
 
don_resqcapt19

don_resqcapt19

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mbrooke said:
At one point it was even 4-5 branches, lol. Research my friend, that is key (y)
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Not sure when that would have been. I have code books back to 1975 and they are all 3. As far as research, I only do that for things I have an interest in. I have no interest in the rules in Article 517.
 
mbrooke

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don_resqcapt19 said:
Not sure when that would have been. I have code books back to 1975 and they are all 3. As far as research, I only do that for things I have an interest in. I have no interest in the rules in Article 517.
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I thought you were interested in the code as a whole. I mean its all interrelated.
 
m sleem

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Also, there are listed ATSs have motorized breakers only...isn't it?
 
steve66

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mbrooke said:
Looking at article 517 and article 700, the NEC keep referring to stand alone automatic transfer switches but make no mention of automatic circuit breakers as part of auto-throw over. Does that mean switch-gear with motorized breakers and PLCs is not allowed for these applications? This seems to go against the NEC's intent of not being a design manual. But then again I'm wondering if the code making panels know something?
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I thought NFPA 110 required mechanical switching, but it only requires mechanical holding.

( Now that I think about it, any type of automatic transfer operation is going to require an electric or magnetic signal to start the operation, even if it results in some type of mechanical mechanism to do the actual transfer. So I guess we can't really have a purely mechanically operated ATS.)

Anyhow, it does seem to allow circuit breakers since they are mechanically held:

NFPA 110:
6.2  ATS Features.
6.2.1*General. Automatic transfer switches shall be capable of all of the following:
(1)
Electrical operation and mechanical holding

Electrically held contactors (like a lighting contactor) would be prohibited.
 
m sleem

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steve66 said:
I thought NFPA 110 required mechanical switching, but it only requires mechanical holding.

( Now that I think about it, any type of automatic transfer operation is going to require an electric or magnetic signal to start the operation, even if it results in some type of mechanical mechanism to do the actual transfer. So I guess we can't really have a purely mechanically operated ATS.)

Anyhow, it does seem to allow circuit breakers since they are mechanically held:

NFPA 110:
6.2  ATS Features.
6.2.1*General. Automatic transfer switches shall be capable of all of the following:
(1)
Electrical operation and mechanical holding

Electrically held contactors (like a lighting contactor) would be prohibited.
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So, motorized breakers are applicable
 
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