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#85730 - 08/02/03 03:34 AM Voltages used for branch circuit calculations
Joe Tedesco Offline
Member

Registered: 10/07/00
Posts: 3325
Loc: Boston, Massachusetts USA
Based upon the National Electrical Code:

Question:

How many 125 volt, 15 ampere duplex receptacles are allowed to be installed on a 20 ampere, 115 volt branch circuit in a commercial building?

A. 11
B. 10
C. 12
D. 13
_________________________
Joe Tedesco, NEC Consultant

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2014 / 2011 NEC & Related Books and Study Guides
#85731 - 08/02/03 04:46 AM Re: Voltages used for branch circuit calculations
zapped208 Offline
Member

Registered: 02/18/03
Posts: 201
Loc: Somewhere in USA
B. 10
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Shoot first, apologize later.....maybe

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#85732 - 08/02/03 06:53 AM Re: Voltages used for branch circuit calculations
Fred Offline
Member

Registered: 04/30/01
Posts: 461
Loc: Straughn, IN 47387
C. 12

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#85733 - 08/02/03 08:03 AM Re: Voltages used for branch circuit calculations
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
10 Receptacles.

115 VAC × 20 AMPS = 2300 VA

80% of 20 AMP Ckt (Gen. Purpose Recept. Ckt. NEC art. 210-21 and 210-23):

2300 VA × 0.8 = 1840 VA.

180 VA per Duplex Receptacle:

1840 VA ÷ 180 VA = 10.2222

10.222 Receptacles per circuit

That would be 10 complete Duplex Receptacles, and parts of a Duplex Receptacle - to make it 0.222 of a Duplex Receptacle


Easier to just round off to 10 Receptacles! 0.222 of a Receptacle is not useful!!!


Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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#85734 - 08/02/03 08:25 AM Re: Voltages used for branch circuit calculations
Ron Offline
Member

Registered: 03/13/02
Posts: 577
Loc: White Plains, NY
Wow, this question has made it rounds to 2 or 3 forums already.
Section 220.2(a) 2002 NEC®, or 220-2(a) 1999 NEC® and the first words, "Unless other voltages are specified ...".
Read the original question again. I missed it the first time.
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#85735 - 08/02/03 09:05 AM Re: Voltages used for branch circuit calculations
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
Who is permitted by the code to specify a voltage. Why couldn't someone specify 126 volts and install 14 duplex receptacles?

Scott,
The 80% does not apply so the answer based on the 115 volts is 12, but I don't think that anyone has the right under the code to specify a voltage for this circuit. It is my opinon that the calculation should be based on 120 volts.
Don
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#85736 - 08/02/03 02:09 PM Re: Voltages used for branch circuit calculations
George Offline
Member

Registered: 02/23/02
Posts: 380
I will say 10, 11, 12, or 13.

The max is 13. 120*20/180

You can only specify the voltage if you control the voltage.

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#85737 - 08/02/03 07:25 PM Re: Voltages used for branch circuit calculations
Roger Offline
Member

Registered: 05/18/02
Posts: 1779
Loc: N.C.
George, controling the voltage wouldn't be a problem, and if an aspiring young Jman exam taker answered anything but 12, he or she missed the question.

Roger

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#85738 - 08/03/03 08:50 AM Re: Voltages used for branch circuit calculations
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
Roger,
So if I specified a voltage of 126 and installed 14 duplex receptacles, the inspector would have to pass my installation?
I'll say what I have posted on other forums. The question is bogus. The installer does not have the right to specify the voltage.
Don

[This message has been edited by resqcapt19 (edited 08-03-2003).]
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Don(resqcapt19)

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#85739 - 08/03/03 09:29 AM Re: Voltages used for branch circuit calculations
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
Don,
allbeit 'code' spec's are 'nominal', would one say they rely on the manufacturer's listings?

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