Understanding the 2011 revisions to Art. 645
The main goal of Art. 645 is to reduce the spread of fire and smoke (for any room that conforms to NFPA 75, Standard for the Protection of Information Technology Equipment). The raised floors common in information technology (IT) rooms pose additional challenges to achieving this goal; therefore, much of Art. 645 covers raised floor requirements. It also addresses fire-resistant walls, separate HVAC systems, and other measures to achieve this goal.
Terms to Know
It’s been confusing to try to differentiate between “information technology (IT) equipment” and “communications equipment.” This matters, because when IT equipment is installed in an IT equipment room, it must comply with Art. 645, but communications equipment must comply with Art. 800.
The 2011 NEC makes it clear that IT equipment doesn’t process communications circuits, thus distinguishing between the two different systems and equipment. Article 645 now defines an IT room; it’s a room that contains IT equipment [645.2]. If the room also contains communications equipment, it’s still an IT room. If it also contains other systems, you need to re-evaluate the room from an engineering and reliability standpoint. Section 645.4(6) limits the equipment allowed in an IT room to only electrical equipment and wiring associated with the operation of the IT room.
Article 645 now defines “remote disconnect control” [645.2] to help distinguish between the disconnecting means and the controls that operate it. It’s a term used in 645.10, so a definition here should help you understand the requirements.
Applying the Rules
In the 2011 NEC, it’s clear that Art. 645 provides alternate practices from those found in other Codearticles [654.4]. Often, a room contains IT equipment, but the owner (or other decision-maker) wishes not to consider it an IT room in order to avoid being compelled to use the requirements of Art. 645 for IT rooms. The Informational Note about the scope of this article [645.1] should help clarify the rules regarding IT rooms. The change to this Note makes it clear that Art. 645 applies only if the room is constructed per NFPA 75, Standard for the Protection of Information Technology Equipment. So when must you comply with NFPA 75? Only when you want to reap the benefits allowed by Art. 645.
The 2011 NEC mandates that only electrical equipment and wiring associated with the IT room may be located in that room [645.4(6)]. A new Informational Note clarifies the types of equipment covered by this rule. Additionally, it’s now clear that all IT and communications equipment must be listed [645.4(3)], and the ITE room can be accessible only to the personnel needed for the maintenance and functional operation of the IT equipment [645.4(4)].
Supply Circuits and Interconnecting Cables
The undefined term “data processing system” is now replaced with the defined term “information technology equipment” [645.5]. It’s now clear that the 15-ft limitation of 645.5(B)(1) applies only to cord- and plug-connected interconnecting cables — not all interconnecting cables.
The 2011 NEC improves upon the listing requirements for power-supply cords and cord connectors, and a new Informational Note helps you understand what types of cords are permitted [645.5(B)(1)], as shown in Fig. 1.
The provisions for protection against physical damage have been addressed in 645.5(D).
Under the Floor
What about raised floors in IT rooms? That’s the subject of 645(E). Before reading this section, look at Table 645.5. You’ll need to refer to this table when deciding which cables are allowed under raised floors. Something you may notice is you can use any listed signal or communications cable included on Table 645.5 within the raised floor area of an IT room, as shown in Fig. 2.
Previously, the NEC didn’t specifically address the use of boxes under raised floors of IT rooms. The 2011 NEC addresses this in 645.5(E), which now specifically allows you to use metallic and nonmetallic boxes or enclosures under raised floors. You can use nonmetallic raceways within the raised floor area, because this space:
- Isn’t subject to physical damage.
- Need not comply with the environmental airspace requirements of 300.22(C) [300.22(D)].
- The 2011 revision clarifies the formerly baffling requirements for “DP” rated cables [645.5 (E)(6)]. Cables must be Type DP having adequate fire-resistant characteristics suitable for use under raised floors of an IT room, except for:
- Power-supply cords of listed IT equipment [645.5(E)(3)].
- Cables enclosed in a raceway [645.5(E)(6)(a)].
- Cables identified in Table 645.5 [645.5(E)(6)(b)].
One of the requirements of Art. 645 that makes people hesitant to use this article is the requirement that a disconnecting means must be provided to shut down all power to electronic IT equipment. A disconnecting means is also required for air-handling equipment servicing the IT room or designated zone and must cause all required fire/smoke dampers to close [645.10]. These disconnecting means are not required to disconnect other non-electronic equipment, such as lighting, in the IT room or zone.
That’s the odd thing about Art. 645. It requires a shutoff switch installed at approved locations that are readily accessible to authorized personnel and emergency responders [645.10], which allows someone to shut down IT equipment and HVAC power from a single location. So despite having a UPS and taking every precaution against a power outage, the IT system is still vulnerable to a shutdown from a kill switch. A person using the disconnecting means accidentally can cause a catastrophic and expensive interruption in operations with resultant data loss or data corruption.
What was the Code-Making Panel thinking of when they added this requirement? They were thinking that fire and rescue teams needed a means to shut down power to the IT room so that the rescue team can use fire hoses and other equipment without risking contact with energized equipment.
In some cases, the UPS isn’t in the IT room, and it will still supply the load with the mains shut off. This is what makes entering an IT room so dangerous for first responders. To make it safe for them, you must provide a means for them to disconnect the room from its electrical supply. With a disconnect often located immediately outside the room, first responders can quickly perform a pre-entry shutdown. Yes, the shutdown means you lose the IT function. But if the room needs fire and rescue teams, that room is about to lose that function anyhow.
That brings us back to the disconnecting means itself. A common method is to install a remote disconnecting means in an approved, readily accessible location at the principal exit doors. For many years, installers have used a breakaway lock to protect the IT room from inadvertent shutdown via this switch. Good signage also helps, and the Code specifically requires that the remote disconnect controls for electronic equipment power and HVAC systems must be grouped and identified [645.10(A)(2)].
A new allowance in the 2011 Code permits the use of “additional means to prevent unintentional operations of remote disconnect controls” [645.10(A)(4)]. Other changes to this section are mainly editorial, other than the new allowances in (B), which apply only to Art. 708 installations for critical operations data systems.
Correlating changes have been made to 645.10(B)(5) to point you to particular sections in Arts. 770, 800, and 820.
A single means to control both the electronic equipment and HVAC systems is permitted [645.10(A)(2)]. The disconnecting means must comply with 645.10(A), unless used for critical operations data systems. This often is accomplished by using a normally open (NO) momentary-contact push button at each principal exit door. When any one of these emergency buttons is pressed, it operates a contactor or opens one or more shunt trip circuit breakers, thereby turning off power to the room.
- Remote disconnect controls must be at an approved, readily accessible location.
- The remote disconnect controls for electronic equipment power and HVAC systems must be grouped and identified (a single means to control both is permitted).
- Additional means to prevent unintentional operations of remote disconnect controls are permitted.
When the decision must be made as to whether the benefits of the alternate requirements allowed by Art. 645 outweigh the costs, the answer is generally yes. The deal breaker is nearly always a desire to avoid installing the disconnecting means for the IT and HVAC equipment. By applying commonly used engineering and administrative measures, you can reduce the IT room “kill switch” risk to a much lower level. With this switch in place, you will reap the considerable benefit that first responders can more safely enter that room so that they may, in turn, save lives and reduce property damage.
Holt is the owner of Mike Holt Enterprises, Inc., Leesburg, Fla. He can be reached at www.mikeholt.com.