Commercial grade 20amp branch ckts

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VZENG

Member
Is there anything in the NEC that says a commercial branch ckt must be rated for at least 20 amps ? I am installing a relay rack of telecom equipment that includes a pre wired rectifier that comes with a 15 amp twist lock plug on it. I have been requesting that my customers install a 15 amp twist lock outlet for me to plug my equipment into. Recently I have been challenged by one of my contractors who is insisting that because this is a commercial application it must be plugged into a 20 amp outlet. The equipment only draws about 5 amps under a full load. I cannot find anything in the NEC saying that it must be 20 amps. Am I missing something? If not what section can I use to back myself up?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Re: Commercial grade 20amp branch ckts

I would suggest running 12 gauge wire, but use a 15-amp breaker. That should satisfy everyone.
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
Re: Commercial grade 20amp branch ckts

Originally posted by VZENG: Am I missing something?
No. But unfortunately you are in a difficult argument to win. That is because it is never clear who has the burden of proof. Your best position would be to assert that "it taint so," and call upon that contractor to prove otherwise. I predict that their response will be along the lines of, "it just is," or "hey I'm the expert in this area," or "it's always been that way," or "that is what I was taught," or something equally lame.

There is always a possibility that a local code exists, and that it is more restrictive than the NEC. But you do have a very reasonable option of standing your ground: tell them it goes in your way unless they can produce a code requirement that says it must be done their way.
 

pierre

Senior Member
Re: Commercial grade 20amp branch ckts

Two things may actually be in your favor here.

1. The attachment plug is rated at 15 amperes.

2. The installation instructions may require a 15 ampere rated branch circuit.

110.3(B) requires the EC to follow the installation instructions.
 

RUWired

Senior Member
Location
Pa.
Re: Commercial grade 20amp branch ckts

VZENG,You might have a leg to stand on if you can show that manufacturers request a 15 amp circuit because;
Article 210.21(b)(2002) states that if this single 15a twistlock is the only recpt. on this circuit,it has to be the same rated circuit (15 amps).
This contractor might be thinking you need a 20 a circuit because most new commercial jobs have specs.and in these specs it usally states that there shall be minimum 20a circuits, and no less than 12awg wiring.
Rick
 

gndrod

Senior Member
Location
Ca and Wa
Re: Commercial grade 20amp branch ckts

vzeng,
The interface you are using can mate with a straight twistlok connector-adapter cord rated for 20 amps. The transition into a 20 amp circuit is generally of no consequence unless your hookup is for keying purposely done this way for circuit isolation in a commercial application. In the case of having an isolated circuit requirement, then that is a special order application that needs to be reconsidered in the contract with your client.

Power line inputs affecting rectification are most unlikely with the modern rack interface for telecom and other line-compensating sensitive electronics that exist today. I can see the interface as a mechanical inconvenience that is frustrating to say the least, especially if all your OEM are supplied that way. Approaching the manufacturer may get positive results for an interface adaption. Let us know what is the outcome.
rbj, Seattle
grammer

[ February 11, 2006, 01:09 AM: Message edited by: gndrod ]
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: Commercial grade 20amp branch ckts

Originally posted by gndrod:
vzeng,
The interface you are using can mate with a straight twistlok connector-adapter cord rated for 20 amps.
There is no way I would install an adapter on a cord.

The equipment came with a twist lock for a reason.

I am a professional, if they want mickey mouse work they can do it themselves. :p
 

LawnGuyLandSparky

Senior Member
Re: Commercial grade 20amp branch ckts

This kind of conflict is common when "The Geek Squad" (modern technology) and the real world mingle. When new ideas meet existing and often archaic codes, or even common practice, engineering specifications or just bad habits some design/install firms, engineers, or contractors can't seem to break.

Today's modern servers, switches and electronic equipment found in computer rooms and even desktop PCs and laptops have no need for an "isolated ground" either. Only the 70's era IBM-mainframes actually spec'd out that requirement. But the mere mention of the exaggerated, unlikely, if not impossible consequences of data & hardware losses are used by the unscrupulious beneficiaries every day, if not designed in from the getgo by sheer force of habit.

A similar situation arises in the residential arena- when a dedicated 15a circuit and receptacle is installed for a window shaker. (Or, heaven forbid, one 20a circuit is installed for TWO!) Be prepared for a fight when the inspector demands a single 20a circuit for a 4.5 - 6.5 amp portable room air conditioner. After all, window units are still 30" x 24" by 42" deep, are made of cast iron, and weigh as much as a refrigerator, right?!

Am I missing something? If not what section can I use to back myself up?
RUWired offered a sensible solution. If this receptacle was being installed for some unknown or future use, the EC might be more in the right to press for minimum 20a rated devices and circuits only. However; when the use and load is known, the ball is completely in your court and it's your call.

Don't be too suprised to find this "fight" all boils down to the fact that the E.C. simply doesn't stock, or doesn't wish to have to stock or aquire 15a rated twistlock receptacles.

BTW, as an FYI most of MCI's telco switch rooms call for 15a twistlock, UNLESS OTHERWISE stated. (#12 awg conductors were however, a NYC code requirement.) Same for MFN, MFS, Lightspeed, Lightpath, RCN, Time Warner, the former Global Crossings, Telergy... you've got plenty of backup. :D
 

gndrod

Senior Member
Location
Ca and Wa
Re: Commercial grade 20amp branch ckts

LawnGuy,

Please read 'isolated circuit' as 'dedicated' not isolated ground. You can still lose your particular equipment function if another load is parallel and trips the line.

iwire,

I agree. Scratch adapter, i am referring to 15 amp to 20 amp twistlok 20amp rated cord interface from the manufacturer. As an EC or electrical sub, the 20amp commercial stands. The 'geek squad' has the interface problem. :)

rbj, Seattle
 

james wuebker

Senior Member
Location
Iowa
Re: Commercial grade 20amp branch ckts

VZENG, I can't say that I can find anywhere in the NEC book that you have to have this on a 20 circuit. Unless it's a town,cities or state must. I've put these in several of times for customer's. Yes sometimes I ask them if they want a 20 amp circuit instead of a 15 amp circuit. But again the customer is paying the bill to the contractor. As long it's within the code I agree with the customer.
Jim
 

VZENG

Member
Re: Commercial grade 20amp branch ckts

Thank You everyone for the feed back. I did speak with the equipment manufacturer and they assure me that their equipment and plug are rated properly and after seeing all the equipment specs I would have to agree. My problem boils down to a single person (who is not even an electrician) who has been forcing others to do what he thinks is the right thing for years. I will be pushing back to this individual! Thank You all again!
 
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