Life Support Branch

[mbrooke]

What is a life support branch and what does it normally feed? I can't find any specific definition.

 

[Bluegrass Boy]

517.2 Definitions 2020 NEC

 

[Bluegrass Boy]

Then refers to 517.29 and .30

 

[Bluegrass Boy]

It refers to NFPA 99-2018 a lot in Art. 517. It also sends you searching Art. 700. I saw mention of Type 1,2, or 3 circuits. It is a bit of a run around.

 

[don_resqcapt19]

It refers to NFPA 99-2018 a lot in Art. 517. It also sends you searching Art. 700. I saw mention of Type 1,2, or 3 circuits. It is a bit of a run around.

Yes, it refers to NFPA 99, because that is the controlling document for all of the electrical in a health care facility.
The rules in 700 only apply to the life safety branch of an essential electrical system, and even there, not all of the Article 700 rules apply. See 517.26

 

[Bluegrass Boy]

It appears, from what I am seeing, it would fall under EES, Type 1, Cat. 1. And says Cat 1 shall not be served by a Type 2 EES
Start with 517.25

 

[mbrooke]

I'm still not seeing anything that specifically describes the system this branch feeds, or its purpose/intent.

 

[mbrooke]

Then refers to 517.29 and .30

Interesting. Thanks Code mentions it, but 517 makes no mention of the power supply that is supposed to feed it.

 

[Bluegrass Boy]

I couldn’t find it worded in that specific way in the NEC. But appears to fall under Essential Electrical Systems

 

[Bluegrass Boy]

See also Articles 700 Emergency Systems, and 701 Legally Required Standby Systems, for additional “ shall, or shall not”. Lol

 

[d0nut]

The note on the plans states that the Life Support branch may be combined with the Life Safety branch. In my opinion, I would treat it as a second critical branch. The life safety branch saves lives by getting people out of the building. The critical branch saves lives by giving the providers power and lighting to keep patients who aren't leaving the building alive during a power outage. Either of those branches must be available within 10 seconds, and cannot be shed.

 

[mbrooke]

The note on the plans states that the Life Support branch may be combined with the Life Safety branch. In my opinion, I would treat it as a second critical branch. The life safety branch saves lives by getting people out of the building. The critical branch saves lives by giving the providers power and lighting to keep patients who aren't leaving the building alive during a power outage. Either of those branches must be available within 10 seconds, and cannot be shed.

Same.

But it begs the question- what is the difference between a life support branch and a critical branch. Is a critical branch not a life support branch?

 

[d0nut]

I would say there is no difference between that life support branch and a critical branch. It may be some terminology that the hospital or engineers used internally to differentiate between certain loads, or it may be a holdover from older NEC requirements that don't exist anymore. If I was doing anything with that distribution system, I would treat it as a second critical branch.

 

[Bluegrass Boy]

I don’t have an NFPA book to refer to, but wonder if that’s where the wording comes from?
And I suppose NEC is not allowed to quote NFPA.

 

[mbrooke]

I would say there is no difference between that life support branch and a critical branch. It may be some terminology that the hospital or engineers used internally to differentiate between certain loads, or it may be a holdover from older NEC requirements that don't exist anymore. If I was doing anything with that distribution system, I would treat it as a second critical branch.

The wording is in the 1971 NEC, but I still find the definition rather vague. Or something that I'm not familiar with in old hospitals.

 

[mbrooke]

I don’t have an NFPA book to refer to, but wonder if that’s where the wording comes from?
And I suppose NEC is not allowed to quote NFPA.

It comes from the NECs in the 70s, but have no idea what its actually referencing in the real world.

 

[mbrooke]

Yes, it refers to NFPA 99, because that is the controlling document for all of the electrical in a health care facility.
The rules in 700 only apply to the life safety branch of an essential electrical system, and even there, not all of the Article 700 rules apply. See 517.26

I can't find copies of NFPA99 from the 70s

Why does 700 only apply to the life safety branch when hospitals work on compartmentalization? Makes no sense.

 

[don_resqcapt19]

I can't find copies of NFPA99 from the 70s

Why does 700 only apply to the life safety branch when hospitals work on compartmentalization? Makes no sense.

Because NFPA 99 wants it that way...all of the electrical rules for heath care facilities are under the purview of NFPA 99, not NFPA 70. The NEC only provides installation requirements to meet the performance objectives set by NFPA 99.

 

[don_resqcapt19]

I don’t have an NFPA book to refer to, but wonder if that’s where the wording comes from?
And I suppose NEC is not allowed to quote NFPA.

The NEC is NFPA 70.

There are lots of places where the NEC uses text that has been extracted from other NFPA documents.
When that is done, a reference to the other document is shown in [...] after the extracted text. There are a number of cases of this in Article 517. Here is one example.

Life Safety Branch.
A system of feeders and branch circuits supplying power for lighting, receptacles, and equipment essential for life safety that is automatically connected to alternate power sources by one or more transfer switches during interruption of the normal power source. [99:3.3.93]

The first number in the brackets is the NFPA document that the text has been extracted from. In this case it is NFPA 99, Heath Care Facilities Code. The remaining numbers shown in the brackets, is the section where the text is located at in the original document. Note that most of the other NFPA document use a different numbering system for sections as compared to the NEC.

Where extracted text is used from another document in the NEC, the NEC technical committee is not permitted to make any technical changes in the text and the purview of the text remains with the original technical committee for the other document. A proposal to change extracted text shown in the NEC cannot be made to the NEC technical committee and must be made to the technical committee that has purview. So if someone wanted to change the definition of Life Safety Branch in the NEC, they would not submit a PI to NFPA 70, the NEC, they would have to submit the PI to NFPA 99, the Health Care Facilities Code.
There are times where the extracted text in one document is out of sync with that in the original document as a result of differing code cycles.

 

[mbrooke]

Because NFPA 99 wants it that way...all of the electrical rules for heath care facilities are under the purview of NFPA 99, not NFPA 70. The NEC only provides installation requirements to meet the performance objectives set by NFPA 99.

If they under preview of NFPA 99, then why do early versions of 99 quote the NEC word for word going on for pages?


Every want has an inference. NFPA 99 must have some reasoning, even if it goes against physics, their design manual or intent. I know you don't know their substantiation which is fair considering I can't find it on the NFPA website. The 1971 has an ROP PDF, but not much is said beyond that.