645 info Tech disco

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Was reading the article in 645 about power off disconnect. theres a installation i see where they have a UPS on the load side of the supply branch circuits, so even if you hit the shunt trip to turn off the power to the room the info tech would still be on via the ups . i dont think this is in compliance with the code. Please correct me if im wrong.
 
ron said:
What size UPS is it? If it is small (750kVA or less), check 645.11
Click to expand...

Ok, didnt see that one at first. the ups may be under 750 kva, . then i wonder would there be any NEED at all for the 'e shut off'. ?? Its wired to the thermostat so if the room reach a certain temp then it shuts down, but if its on a ups , that defeats the purpose. Oh well, more reasearch needs to be done.
 
Help me with a little more clarity on this article 645.10,11 2005 NEC. If the UPS falls under the 645.11(2) part, does this mean that the HVAC system in 645.10 wheather its dedicated or NOT, have to have a means of disconnecting when you push the "button"(e stop type) in this room still when the ups is under 750 va?? It looks like this section is ONLY talking about the UPS and not the HVAC so 645.10 would still apply. I know it has to be close to the exit (push button that is).

Also can anyone give me a little history on this 645.10,11 and tell me why they needed a disconnecting means at a 'single' push button located at the principal exit in this electronic/infotech room when most of this equipment is USUALLY on a UPS and needs to 'run at all times no matter what'?? I can see the HVAC having it to some degree (fire alarm etc..dampers) but i just cant see the reasoning on the electronic/info tech equipment.

Also is there a periodic testing required for this shunt/trip disconnecting means push button to be sure it works??
 
You should read Ron's paper on this subject. :)

Maybe he can put up a link.

In a nutshell the use of Article 645 is a choice, not a requirement.

If you want to use the less restrictive rules allowed by 645 for running cords under the floor then you must provide the disconnecting switch.

I believe the idea is that if a fire under the floor the hitting the button kills the power to those cords.

I personally have never see one set up that did not also kill the UPS power.
 
As Bob mentions, there are certain more relaxed rules found in Article 645, such as not having to secure certain raceway, etc.
In order to use these leniencies, you have to install some pre-requisites such as a disconnecting means (EPO) 645.4. The EPO must shut down power and HVAC with an oddball un-achievable exception.
So decide if you need the leniencies then if so, install the pre-requisites.

http://www.csemag.com/article/CA6290839.html

http://www.csemag.com/article/CA6407670.html
 
iwire said:
You should read Ron's paper on this subject. :)

Maybe he can put up a link.

In a nutshell the use of Article 645 is a choice, not a requirement.

If you want to use the less restrictive rules allowed by 645 for running cords under the floor then you must provide the disconnecting switch.

I believe the idea is that if a fire under the floor the hitting the button kills the power to those cords.

I personally have never see one set up that did not also kill the UPS power.
Click to expand...

I would love to see the link, hope he sees this post. I will say this is FIRST time i have ever heard that 645 2005 NEC was a CHOICE and not a REQUIRMENT. can you tell me where i can find this at??

As for the cords under the floor if there was a fire, can one just install a type of heat/fire sensor or detector that would shut off the power to this area (ie HVAC)??

This is not a job im doing, its just a job ive seen and they have a small ups thats under 750kva, So they get the exception of not turning off the power to the info tech equipment. it just doesnt make sense to have a 'power off button' and still have everything on with a ups. I dont think they have it completely right because the HVAC system is not closing the dampers or shutting off when the 'power off button is pushed.'.

Thanks for the info.
 
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