NEC Article 645

[curtis_insite]

My question is in reference to the interpertation of 645.10 (Disconnecting Means) of information technology equipment.

Can an EPO system be installed that is separated between "A" system and "B" system in a facility that has two utility services, and is separated throughout the facility and designated "A" & "B"?

The "A" EPO push button would disconnect power to: Half of the HVAC equipment, and half of the power distribution units in the technology equipment room.

The "B" EPO push button would disconnect power to: The other half of the HVAC equipment, and the other half of the power distribution units in the technology equipment room.

Note: The IT equipment is dual corded, meaning that is has an "A" feed and a "B" feed.

 

[ron]

Re: NEC Article 645

My first suggestion is to avoid Article 645 like the plague, if you do not need the wiring leniencies provided by that article. Remember that 645 is optional.
If you must, then unfortunately 645.10 requires a disconnect for all electronic equipment and all dedicated HVAC's and to close FSD's. There is no separation into areas. The dual corded equipment sits in one IT Equip. Room and power must be disconnected to it, no matter the source.

This happens to be my kinda work, and finding loopholes for data centers requires some real creativity. Keep trying though, it is a good start.

 

[iwire]

Re: NEC Article 645

Ron my first reaction and I even started typing was that he has to have one button for all power and one button for all HVAC, or One button for both.

But the language in in 645.10 does not support that, it speaks of grouping the disconnects and one button shall be permitted.

I think he may be able to do what he is asking about even if that was not the intent of the CMP.

645.10 Disconnecting Means.
A means shall be provided to disconnect power to all electronic equipment in the information technology equipment room. There shall also be a similar means to disconnect the power to all dedicated HVAC systems serving the room and cause all required fire/smoke dampers to close. The control for these disconnecting means shall be grouped and identified and shall be readily accessible at the principal exit doors. A single means to control both the electronic equipment and HVAC systems shall be permitted. Where a pushbutton is used as a means to disconnect power, pushing the button in shall disconnect the power.

I am surprised or missing something.

 

[ron]

Re: NEC Article 645

"A means shall be provided to disconnect power to all electronic equipment in the information technology equipment room."
"The control for these disconnecting means shall be grouped and identified..."
All AHJ's that I have run into, consider the wording above regarding grouping, applying to one power and one HVAC, not two powers and two HVAC's. Although anything is possible. IMHO, the wording above doesn't support two separate buttons to shutdown power to a piece of electronic equipment, but it's worth asking the local AHJ.
Two power EPO's still provides the "means", and if you group them and identify them, it is a possibility.
Good suggestion.

 

[steve66]

Re: NEC Article 645

Ron:

I agree, 645 is optional. If the room meets the requirements of 645.2, then the less stringent rules of 645 can be used.

However, I think two disconnects can be used. The handbook states "two separate disconnecting means are required, but a single control, such as one pushbutton, is permitted." By two disconnects being required, they mean one for the HVAC systems, and one for the power system. But the definition of a disconnecting means may be a group of devices. Like Iwire said, the pushbuttons would have to be grouped, and put at each door.

Steve

 

[iwire]

Re: NEC Article 645

I typed to soon

[ April 14, 2004, 05:29 PM: Message edited by: iwire ]

 

[ron]

Re: NEC Article 645

The phrase is "A means.....". The word "A" does not always mean one. Does the word "means" mean one?
For example, a group of mean children have taken over my home.

[ April 14, 2004, 07:39 PM: Message edited by: ron ]

 

[charlie b]

Re: NEC Article 645

I interpret the phrase ?A means? as requiring that disconnection be possible, that a solution must exist, that a method must be available. It is not the same as saying ?a single means.? Later in the paragraph, it permits a single means to disconnect electronics and HVAC. But if you do not choose that option, then nowhere does it require a single means for the electronics and a second single means for the HVAC. In other words, it does not constrain you to a single disconnect device. If you have a control station conveniently located, and if it has ten switches, and if you need to throw all ten in order to kill power to the room, then the set of ten switches fulfills the requirement for ?a means.?

 

[benaround]

Re: NEC Article 645

Which EM. is going to activate "all" of the fire/smoke dampers,I think this could be a problem to concider.

 

[steve66]

Re: NEC Article 645

The phrase "A means" can still mean 2 or more switches. And the definition states that a "disconnecting means" can be more than one device.

Benaround: Activating both disconnecting means would close all the fire dampers. Nothing says "one switch only".

I think two switches would be allowed. Can anyone make a good argument that two switches wouldn't be as safe as a single switch would?

 

[benaround]

Re: NEC Article 645

steve66, I don't know how the smoke/fire dampers are wired at this location,I have always seen them wired all together as a unit,all shut down at the same time or open at the same time.One of the EM's will activate all the dampers.So here we are at test day and press in EM#1,all the dampers close,half the HVAC stops,half the power shuts down.Now before EM#2 can be pressed in the Inspector wants to see what shut down,in the mean time the other HVAC units are still running and they are trying to blow the ductwork apart because the dampers are all closed.That's what concernd me about the set-up. Frank