ECN Forum Forums Code Related Discussion NEC & other Code issues Voltages used for branch circuit calculations

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

B. 10

C. 12

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!!!
<joke>

Scott35

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.

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

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.

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

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).]

Don,
allbeit 'code' spec's are 'nominal', would one say they rely on the manufacturer's listings?