Mech. Protection of Emerg. System

[dpenbert]

I am a little unclear by what the code states in the exceptions under article 517.30(3). I have an emergency system that serves patient care areas. The main components of the system comprises of a branch circuit panel, an emergency circuit distribution panel, an automatic transfer switch and a generator. I am foggy on the run between the transfer switch and the generator because it can be put in the slab which brings me to exception 4. That particular run doesn't serve patient care, but the system does. So my question is, can I use PVC Sched. 40 for this run per exception 4?

Thanks.

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David

 

[rick hart]

Re: Mech. Protection of Emerg. System

The way I read it is that the BRANCH CIRCUITS can have the exception applied. The runs from the generator to ATS to distribution to branch circuit panel must be in metallic conduit or MI, if part of the emergency system.
By definition the emergency system is made up of the critical (patient care) branch and life safety branch.

I can see why you are a little fuzzy and I would wait for a few more opinions on this section.

 

[George Stolz]

Re: Mech. Protection of Emerg. System

517.30(3)

 

[caj1962]

Re: Mech. Protection of Emerg. System

517.30(c)(3) exceptions is where I believe he was refering. I agree with the other poster that the intent is that the emergency sytem be protected by a non flexible meatlic raceway. There are some that would disagree and read more words into the exceptions that would say if the down stream brach circuits did not feed patient care areas then the feeders from the gen set to the ATS could be in PVC. But if you look at the emergency part of the required system both life safety and critical life end up serving patient care areas. If the system is large enough and the facility wants to add the bussiness portion of a health care facility to the generator it could be fed from a seperate transfer switch and called a non-essential load. Then you could if all other codes are met use PVC. This is just my humble opionion

 

[dpenbert]

Re: Mech. Protection of Emerg. System

517.30(c)(3) is correct. I thought about it some more and it makes sense that the emergency system should be "Mechanically" protected (protecting the conduit itself from damage) unless it serves patient care areas. Which brings me to a grounding/bonding question. Does the critical branch system serving the patient care areas require metallic raceway for an extra grounding path, and how exactly is this extra grounding path connected? Does it have to connect all the way back to the service? Roger, can you explain this?

Thanks.

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David

 

[caj1962]

Re: Mech. Protection of Emerg. System

I am not Roger but I will give it a shot. In answer to your question, yes it must be bonded throughout the system. All of the non current carrying metal parts have to be bonded back. I don't have the correct code in front of me but also in 517 it says all of the panels serving the patient care areas must be bonded together. Both normal and emergency

 

[dpenbert]

Re: Mech. Protection of Emerg. System

Jeff, I read 517.14 PanelBoard Bonding and I believe that is the section you were referring to. Thanks for pointing that out. Why does the code require this? Is it so there is no potential between panels?

Thanks

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David

 

[roger]

Re: Mech. Protection of Emerg. System

David, I agree with Jeff. Looking at the "Emergency System" i.e. Critical and Life Safety branches in the FPN, figure 517.30, No 1, notice the brackets enclosing all the componets back to the "Alternate power source". As Jeff says, if there are any "Patient Care Areas" downsteam, that entire portion of the branch would have to be metalic back to the source.

Add another panel from the same transfer switch to serve a "Non Patient Care Area" and you could use the exception.

The bonding in 517.14 is as you said, for "Equipotential" between the systems that could be common to a patient, and must be less than .1 ohm.

Roger

[ January 19, 2005, 04:25 PM: Message edited by: roger ]

 

[dpenbert]

Re: Mech. Protection of Emerg. System

Thanks for replying Roger, I agree now as well.

Could you reference me to anything that requires the resistance between systems to be less than .1 ohm?

(Comment by Mike Holt in EC&M): Equipotential bonding isn't intended to provide a low-impedance ground-fault current path to help assist in clearing a ground fault.
...Equipotential bonding is intended to reduce or eliminate voltage gradients from stray voltage

I found this while researching the subject.

Thanks

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David

[ January 19, 2005, 05:24 PM: Message edited by: dpenbert ]

 

[roger]

Re: Mech. Protection of Emerg. System

David, the test criteria is in (using 2002) NFPA 99 (Health Care Facilities) 4.3.3, before 2002 it would be found in chapter 3 of NFPA 99.

The test equipment is also spelled out (specialized) in 4.3.3 and must be tested and calibrated yearly. Ours is made by Bio Tek which is now owned by Fluke. We will have to update next year since Fluke is discontinuing support for the older units.

Roger

[ January 19, 2005, 06:04 PM: Message edited by: roger ]

 

[dpenbert]

Re: Mech. Protection of Emerg. System

Speaking of Fluke I just read a newsletter that reported CPSC and Fluke announced the recall of the 1000 VAC multimeters.

Thanks for the references.

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David

 

[roger]

Re: Mech. Protection of Emerg. System

David, I also read a news letter from MH on this today.

Roger