Art. 645, Info Tech Equip Rooms

[Jeff Greef]

Just getting my feet wet with Article 645 on requirements for Information Technology Equipment Rooms. Let's see if I have this right....

IF you meet the requirements for the IT room in 645.4 (disconnect, separate HVAC, occupancy separations with fire rated walls, etc.) THEN you can use the provisions of 645.

With respect to transformers, I take it that this means you don't have to follow the standard rules for grounding and bonding when the transformer is part of listed IT equipment.

SO- if they instal listed IT equipment with internal transformers that would ordinarily require the standard rules of grounding/bonding for transformers, BUT they don't meet 645.4 requirements, they is in violationland, right?

Point is, we don't know what kind of IT boxes/machines they are going to roll into the place after we final the TI permit, or at plan check, so how do we know to require the rules of 645.4?

Thnx :thumbsup: :thumbsdown: hmy:

 

[ron]

Your eval of 645 is correct.

You need to talk to the owner to see which way they want to go. Almost never worth following 645.

Just because you don't follow 645, doesn't mean that IT listed equipment can't be installed.

BTW, most IT equipment will follow SDS bonding rules if you follow the instructions.

 

[steve66]

I believe article 645 generally modifies or omits the rules in Chapter 3 (which are generally wiring methods).

So in a 645 room, you can run a 15' power cord under the floor. You can also use a multitude of wiring methods under the raised floor, and run data cables under the floor.

But I don't think 645 would have anything to do with internal transformers in IT equipment. That would be covered by the equipments listing, and its installation instructions.

So I don't think 645 would have anything to do with a transformer being bonded or not.

But I agree on not knowing if 645.4 needs to apply or not. No one ever knows what the IT people will roll in there and connect next week, or even next year. But I think you can only inspect what is present when you do the inspection.

Edit: Ron posted while I was typing.

 

[Jeff Greef]

Thanks you guys

Looks to me like installing a raised floor will probably trigger the requirements of 645.4. You can't run cord and plugs through holes otherwise, as well as all the other relaxed wiring method rules which you will have to use if you have a raised floor and any quantity of wiring. Still, I suppose it's possible to instal a raised floor and follow all the standard rules, so a raised floor cannot necessarily trigger 645.4. I can see a contractor or owner that just doesn't want to do it, and argues the point, such that all we can do is inspect after the fact, after it's too late to do anything about it without creating a huge fuss.

But, it seems that any larger scale IT equipment is necessarily going to require the relaxed wiring methods involved. I don't know anything about the equipment, but I'm sure it's fairly standardized using industry accepted cabling and power cords. I doubt they have one set of equipment and cabling that is for non-645 compliant rooms, and one set that is. So then a dividing line needs to be established between having one small server bank in the closet down the hall and a huge room powered by 5 PDUs with rows of servers over a raised floor. I guess in plan check the question needs to be asked to determine if the planned installation 'crosses the line' into equipment that, by it's design, will necessarily require wiring methods than can only be installed if 645.4 is used.

Since all equipment must be listed, I wonder why 645.15 contains the sentence which relieves SDSs from grounding rules in 250.30. If it's listed equipment, the engineers can configure an internal transformer any way they want, anyway, right? I wonder if there could be a circumstance where the issue would concern a piece of equipment that is not already approved by it's listing, or the listing doesn't cover the grounding of the transformer.

Thoughts?

 

[ron]

Raised floor does not invoke 645. I've designed a DC with thousands of sq-ft of raised floor without 645 and I've done DC's with a slab only using 645. It just depends on whether you need the leniencies. Most leniencies are not worth it, especially if on slab.

 

[iwire]

Most leniencies are not worth it, especially if on slab.

Yeah, what would you gain?

 

[Jeff Greef]

I see- so it really just depends on what the designers/owners want to instal- if they have their reasons for wanting to install with more lenient rules, they'll bother with 645, so I take it. Sounds like it's always possible to install without 645, it's just a matter of how problematic it may be to instal everything using standard wiring methods and rules. Right?

I called a friend who does plan check and inspection of elec systems here in Silicon Valley, he said in his area they frequently choose to use 645 cause it gives a lot of liberty with wiring methods under a raised floor. Problem, he said, is that they then take too much liberty under the floor, and before you know it they've got large J boxes with multiple flex lines (power circuits) coming out of them that are not secured to anything and are just floating around down there (his words).

 

[Jeff Greef]

So Ron- when do the leniencies sway you to want to use 645? What triggers it for you? Sizes of equipment, proximity of equipment, need for future expansion, etc?

 

[suemarkp]

I think half of it is just changing your mindset. When I first worked in computer rooms, that all had liquidtight flex under the floor unsecured and holes in the raised floor to run cords through. That was normal. Then suddenly we couldn't do that anymore unless you want all the 645 hassles.

To me, it is much easier to just install floor boxes in the raised floor tiles, or just run all the power overhead and run the plugs up. Reconfiguring is more of a pain though, and you can't just move a holey floor tile and be done.

A 645 decision would be based on how much of the required infrastructure you already have. If you're going to pay to add most of it, you can add a lot of extra circuits during the initial install instead of all the 645 goodies.

 

[ron]

So Ron- when do the leniencies sway you to want to use 645? What triggers it for you? Sizes of equipment, proximity of equipment, need for future expansion, etc?

I would say it is almost never worth it. The EPO (disconnecting means) and the cease of airflow under a raised floor if smoke is detected, are huge reliability nightmares to avoid.

We used to use the non plenum rated comm cable under the floor all the time, but then the AHJ's smartened up and said that it might be okay with the NEC, but NFPA 13 would then require suppression because of the combustible nature of non-plenum rated cable. Some liked that they didn't have to secure listed boxes and that they could run cords through the floor to receptacle mounted in the below floor space, but it is not offset by the reliability nightmares mentioned above.

Yikes I just gave away a lot of IP!

 

[Jeff Greef]

Thanks all of you