sundance-communications.com/forum Forums General General Telephone & Systems Information Equipment Rack Clearance

I get to install a new Call Center, I'm working on the layout of equipment racks and cabinets. I know that out in the open office there is a 36" aisle requirement. Is there any requirement for the clearance between the backside of my rack mounted equipment and the walls? 30" would be enough for me to work comfortably and would give me a four foot wide aisle up the middle between the frontsides of the equipment racks and cabinets.

Mike -

A long time back (25 years) I installed a CO at a hospital here in NYC. I had my crew chalk out the floor before starting to install the bays. Good thing. It turned out the hospital sent the wrong scale on the floor plan to GTE's engineering dept.

Anyway, I had to really shrink the aisles to make everything fit. At the time I went to OSHA and got their minimum requirements for pathways and walkways.

I THINK (and my memory could be wrong, and/or the requiremnents could have changed) that the minimum was 30" then for equipment room walkways. The interbay spacing might have been as little as 27".

My advice is, (lacking guidance from the customer) get the minimums from OSHA and then build up from there.

Sam

I only suggest getting as much as you can somebody will always come in behind you and mount something in your way after you are done and gone, you will find out when you go back for a service call of some kind.

This is a very good question. Because you are not in a "public access" area and you may be in a room with power panels, one standard may offer no guidance while another does. As a rule, I always start my rack placement at 3ft. When double-sided shelves are installed clearance can get down to less than 2ft. Know the product you're installing and how much real estate it will take.

I've always made the assumption that you should have at least a 3' clearance between the front of the rack and the back wall. I believe the NEC requires a 36" clearance be maintained for anyone working on an electrical connection, even if it is low voltage. But, I could be wrong...

Electrical panels you are supposed to have three feet clear around. Most of our rooms have yellow tape in front of the breaker panels, and signs that say 'Do Not Block Panel', yet that seems to be the place they stack everything.

I would like to think that this type of installation does technically fall under the general guidelines of the NEC, meaning that a full 36" of front-facing work space must be provided from either side. It's a bit of a gray area though since many AHJ's (Authorities Having Jurisdiction), or inspectors are wishy-washy in how they apply the code requirements.

The NEC also has stipulations regarding pipes, structures, etc. that are mounted above panels, disconnects, transformers or other fixed equipment. It's up to the AHJ to decide if low-voltage equipment in cabinets falls into this category. My guess would be "no" since racks are considered to be portable equipment, as in not a permanent part of the building's electrical system. This would be especially true if all electrical components within the rack are cord and plug connected.

With that being said, a quick call to the electrical inspector's office sounds to be in order. I think that you'll get more of a suggestion from them rather than any level of enforcement. I can't imagine having anything less than 36" of working space anyway, especially if the cabinets involve sliding shelves.

Welcome to the gray area of the NEC. For every requirement, there are usually at least two exceptions elsewhere within the book. I wish I could offer a more definitive answer, but there really isn't one with regard to the NEC. A cabinet or rack is about the equivalent to a refrigerator in the view of the code.

Just remember, nearly every jurisdiction maintains quite a few requirements above and beyond NEC requirements. Local codes always supersede the NEC, so that's why you need to ask this question of the AHJ or code compliance department in your local city, town or county.

My experience was that Telecom Equipment did NOT fall under the NEC. When I worked for GTE, as a utility they did not have to abide by the NEC. Bell was notorious for that - including 120/240 electrical work which they claimed exemption from (GTE claimed exemption under the DC portion, not the AC, but as a rule their regulations were MUCH stricter than the NECs, so it didn't matter.)

Sam

I agree as well that it's best to consult directly with the property's local inspectors, just to be on the safe side. :thumb:

Just wanted to add that this is a great topic, Mike. I saw your post this morning, and have been digging thru the NEC, FCC Part 68, and others just to see what I could find as well. The only true reference that I could locate in writing (other than in many College and University locally enforced codes) was in ANSI/TIA/EIA-942 [Telecommunications Infrastructure Standard for Data Centers]

Here's the copy and pasted reference:

Hot and Cold Aisles

Cabinets and racks shall be arranged in an alternating pattern, with fronts
of cabinets/racks facing each other in a row to create “hot” and “cold” aisles.
Cold aisles are in front of racks and cabinets. If there is an access floor, power
distribution cables should be installed here under the access floor on the slab.
Hot aisles are behind racks and cabinets. If there is an access floor, cable trays
for telecommunications cabling should be located under the access floor in the
hot aisles. A minimum of 1 m (3 ft) of front clearance shall be provided for installation
of equipment. A front clearance of 1.2 m (4 ft) is preferable to accommodate
deeper equipment. A minimum of 0.6 m (2 ft) of rear clearance shall
be provided for service access at the rear of racks and cabinets.
A rear clearance of 1 m (3 ft) is preferable. Some equipment
may require service clearances of greater than 1 m (3 ft).

Unfortunately, I'm unable to post the link here, due to it containing parentheses; so I've sent the link to your email.

It's always best to check and confirm with the local inspectors.

Big Congrats on the install! :thumb:

Congrats on the install.

One note of caution is some of the newer IBM & Sun equipment is coming in at 39"+ of depth. Some equipment cabinets are 42" deep and have the ability to have another 6" or 9" extender to that to allow for the deeper equipment to reside.

Check with the AHJ for their specific requirements - most are very accommodating and would rather work with you ahead of an install versus the aftermath.

KCDD