Respective Branches for Legally Required and Optional Standby Loads

[Sam@CEgeeks]

Hello All, I am new to this so be nice!!

Here's my question, I understand that legally required and optional standby systems can have the same transfer switch, and even be fed from the same cabinet or switchboard section.. But since they are defined as different systems, do the respective branches eventually have to be separated at all?

Example, A single ATS feeds a distribution panel, that panel has main breakers for legally required and optional standby systems, once the panel branches are the legally required and optional standby systems required to remain separate? Can you mix in the branch circuit loads with one another after the separation occurs? The reason I ask is I am running into an issue in the field with this, and the engineer is telling me its perfectly fine.. Why separate the systems at all?

I cannot find anything to dispute this, but it seems like an uncommon practice, and do not think its a good one!

I hope to learn a lot from this forum, and some of your Great Minds!!!:happyno:

 

[roger]

The engineer is fudging or at least stretching the wording. Read 700.10(B) taking special note of (5) and then 701.10 taking note of "general wiring" it does not mention "emergency wiring".

Look at page 49 of this link for examples.

Roger

 

[dkidd]

Unless the facility falls under 517.

 

[roger]

Unless the facility falls under 517.

Even then you can pretty much look at the Life Safety Branch in alignment with 700 (see 517.26), the Critical Branch as 701 (except you can not install in raceways or enclosures with "general wiring"), and the Equipment Branch as 702.

Roger

 

[steve66]

I understand that legally required and optional standby systems can have the same transfer switch, and even be fed from the same cabinet or switchboard section..

Only in a health care facility with a total demand on the essential system is less than 150KVA.

Otherwise, you need separate transfer switches.

 

[Sam@CEgeeks]

Only in a health care facility with a total demand on the essential system is less than 150KVA.

Otherwise, you need separate transfer switches.

Thank you for the response, could you give me some more information regarding this? So if it’s not a health care facility with a total demand on the essential, separate transfer switches are needed? This is an Assembly Occupancy, considered a high rise under the Florida Building Code.. any input is greatly appreciated

 

[steve66]

700.6 D - Transfer equipment shall only supply emergency loads.

That is assuming you have a true emergency system, and you don't have battery powered exit lights and emergency lights.

Also, if its a high rise, you should also read through article 700. It has some additional requirements for a high rises and/or assembly occupancies.

 

[Strathead]

700.6 D - Transfer equipment shall only supply emergency loads.

That is assuming you have a true emergency system, and you don't have battery powered exit lights and emergency lights.

Also, if its a high rise, you should also read through article 700. It has some additional requirements for a high rises and/or assembly occupancies.

his wording implies that he is referring to article 701 systems not 700 systems

 

[Strathead]

Hello All, I am new to this so be nice!!

Here's my question, I understand that legally required and optional standby systems can have the same transfer switch, and even be fed from the same cabinet or switchboard section.. But since they are defined as different systems, do the respective branches eventually have to be separated at all?

Example, A single ATS feeds a distribution panel, that panel has main breakers for legally required and optional standby systems, once the panel branches are the legally required and optional standby systems required to remain separate? Can you mix in the branch circuit loads with one another after the separation occurs? The reason I ask is I am running into an issue in the field with this, and the engineer is telling me its perfectly fine.. Why separate the systems at all?

I cannot find anything to dispute this, but it seems like an uncommon practice, and do not think its a good one!

I hope to learn a lot from this forum, and some of your Great Minds!!!:happyno:

I am not familiar with a code that allows (or prohibits) a single ATS and panel to act as both NEC 701 and 702 systems. If it exists I assume it would be in NFPA 110. That said, 701.10 clearly allows both system to share the same everything. No ambivalence.

 

[steve66]

I am not familiar with a code that allows (or prohibits) a single ATS and panel to act as both NEC 701 and 702 systems. If it exists I assume it would be in NFPA 110. That said, 701.10 clearly allows both system to share the same everything. No ambivalence.

Yes, your are right - he did say legally required. And if that is the case, then I agree with your answer.

But it really makes me scratch my head because to the best of my knowledge, I have never ran across a "legally required system".

So now I'm wondering if I have been mis-classifying systems. I know I have asked the difference between what systems are emergency and what are legally required, but I'm not sure I ever got an answer that was definitive.

Almost all buildings require egress lighting and exit lighting with a second source of power. I have always assumed those lights and exit signs are "Emergency Systems". The IBC even uses the phrase "emergency power".

So are exit lights and dual head egress lights emergency, or legally required?

 

[packersparky]

Yes, your are right - he did say legally required. And if that is the case, then I agree with your answer.

But it really makes me scratch my head because to the best of my knowledge, I have never ran across a "legally required system".

So now I'm wondering if I have been mis-classifying systems. I know I have asked the difference between what systems are emergency and what are legally required, but I'm not sure I ever got an answer that was definitive.

Almost all buildings require egress lighting and exit lighting with a second source of power. I have always assumed those lights and exit signs are "Emergency Systems". The IBC even uses the phrase "emergency power".

So are exit lights and dual head egress lights emergency, or legally required?

The IBC requires that many elevators be supplied by a legally required standby system.

 

[Strathead]

Yes, your are right - he did say legally required. And if that is the case, then I agree with your answer.

But it really makes me scratch my head because to the best of my knowledge, I have never ran across a "legally required system".

So now I'm wondering if I have been mis-classifying systems. I know I have asked the difference between what systems are emergency and what are legally required, but I'm not sure I ever got an answer that was definitive.

Almost all buildings require egress lighting and exit lighting with a second source of power. I have always assumed those lights and exit signs are "Emergency Systems". The IBC even uses the phrase "emergency power".

So are exit lights and dual head egress lights emergency, or legally required?

Unless I misunderstand your question, the code at least touches it. Some people here have the ability to cut and paste I don't, but article 700 is only for legally required power ESSENTIAL for safety to human life. For article 701 there is an informational note that gives examples. This, like many things is an AHJ decision. The University I do a fair amount of work at, for example has been incorrectly mixing there loads for a long time. They have a lot of refrigeration in one part where loss of it could result in release of bio hazards. That is supposed to be 701 power.

 

[Sam@CEgeeks]

Thank you for the reply's greatly appreciated!

As far as my research has gone the IBC and IFC both identify Emergency and standby systems- Emergency being 700 defined as backup power within 10 seconds, and Standby power being Legally Required defined as back up power within 60 seconds. Optional standby of course is not defined.

There is a catch all, both IBC and IFC state emergency systems are an acceptable substitute for standby systems.. So theoretically you could place all required loads on Emergency and have an optional standby for customer requested loads.

Also the NFPA 99 does segregate the transfer switches and systems, but that only applies to hospitals unfortunately.

My issue is I have an existing high rise Building, Existing 3 separate systems, and the engineer wants to mix the legally required and optional standby loads at the point where the final circuits branch from the panels, even though originally a separation was made in the systems.. It just seems wrong, why would the NEC even define the two systems if you could always just mix the legally required and optional standby in the same panels? He is stating its a cheaper option and a practice they do all over.

Head scratcher for sure
:ashamed1:

 

[Sam@CEgeeks]

Just to clarify as well.. When I say "So theoretically you could place all required loads on Emergency and have an optional standby for customer requested loads" I mean the required emergency and standby loads required by the IBC and IFC

 

[Strathead]

Just to clarify as well.. When I say "So theoretically you could place all required loads on Emergency and have an optional standby for customer requested loads" I mean the required emergency and standby loads required by the IBC and IFC

I don't see that in regards to the NEC. In my opinion the AHJ could classify all the loads you are referring to as Emergency loads and feed them from the emergency panel, but you couldn't have legally required standby loads fed from the same panel as article 700 loads. The end result is the same as that you describe but the semantics are technically different.