commercial receptacle limits

[roger]

How many receptacles can be installed on a 20 amp 115 v circuit in a commercial office building?

A 10
B 12
C 13
D as many as you can fit in the building.

This is a true exam question so please explain your answer. (I being asked to have others agree on the answer, has some thing to do with the hand book which I don't own.)

Thanks

Roger

 

[dereckbc]

Re: commercial receptacle limits

A.10

What is a handbook?

180 VA per outlet limitation.

Roger you know the answer. What are you after?

 

[roger]

Re: commercial receptacle limits

Hello Dereck, I'm shoping your talent around, I hope you want to move to the Smokies.

The reason for the thread is a friendly discussion that needs more than my sole answer.

Roger

 

[iwire]

Re: commercial receptacle limits

Hi Roger and Dereck I will confess that Roger and I have a disagreement on whether or not there is a limit of receptacles on a circuit.

I feel the answer would be "D".

I am not saying "D" is good design, just NEC compliant.

Bob

 

[iwire]

Re: commercial receptacle limits

I too will say friendly discussion and I will try not to be stubborn

 

[bennie]

Re: commercial receptacle limits

C-13

 

[dereckbc]

Re: commercial receptacle limits

Roger and Bob, sorry if I came accross as being rude, that was not my intention.

As I go back and read 220.3(B)(11) and exhibit 220.4, it appears the correct answer is 13 on a 20-amp breaker.

That will tech me to shoot from the hip.

 

[don_resqcapt19]

Re: commercial receptacle limits

I think you need to combine the load obtained by the application of 220.3(B)(11), the branch circuit conductor size rule in 210.19(A)(1) and the branch circuit rating in 210.3 to get the 13 receptacle limit.
Don

 

[bennie]

Re: commercial receptacle limits

I did it this way...20 X 120= 2400 watts, divided by 180= 13.3333 receptacles. The 13 are easy, good luck on the .3333.

 

[joe tedesco]

Re: commercial receptacle limits

The correct answer is 12 because of the voltage.

20 x 115 = 2300 divided by 180 = 12

See 220.2

220.2 Computations.

(A) Voltages. Unless other voltages are specified,......

This is one of those trick questions!!

 

[roger]

Re: commercial receptacle limits

Joe, you are correct. This is a point that everyone preparing for an exam must remmember.

Answer the question as asked, so in this case I wouldn't consider this a trick question.

Dereck, I certainly didn't see any rudeness in your post.

Roger

 

[ryan_618]

Re: commercial receptacle limits

Joe, doesn't 220.2 state 120 volts?

Oh!!! OOPS! got it now

[ July 30, 2003, 10:18 AM: Message edited by: ryan_618 ]

 

[bennie]

Re: commercial receptacle limits

Refer to ANSI C84.1-1995, Voltage ratings for Electric Power Systems and Equipment.(60 Hz)

For purposes of calculating load, the nominal line voltage is 120/240 for power supply. The nominal voltage for equipment is 115/230.

Put in 13, who's counting?

 

[roger]

Re: commercial receptacle limits

Bennie,

Put in 13, who's counting?

unfortunatly whoever grades the exam.

Roger

 

[joe tedesco]

Re: commercial receptacle limits

Bennie:

When questions of this type are asked on an examination they are developed so that the testing agency or city, etc., can determine if that person understands the code rules.

The answer 13 is WRONG!

I agree, who's watching, and to tell you the truth, I would not put any more than 10 on the circuit anyway.

The code rule in 220.2 is very clear, and the reference you supply is of value, but the bottom line is that the dude will get another 2 or more points that may be the reason that the dude passed the test.



[ July 31, 2003, 06:55 PM: Message edited by: joe tedesco ]

 

[ron]

Re: commercial receptacle limits

Joe,
My 220.2 indicates to use 120V. What am I missing that you used 115V in your calc.

 

[roger]

Re: commercial receptacle limits

Ron, look at the first sentence in 220.2(A)

Roger

 

[bennie]

Re: commercial receptacle limits

The number 13 is correct, the question is wrong.

ANSI/NEMA developed the voltage standards, for the purpose of making calculations. 115 volts does not compute.

Make a calculation using 120 volts and the line drops to 115, do you remove one receptacle?

This standard was developed to end such foolishness.

A new person should learn the correct intent of the code. This question is a trick question. It defies logic.

Check the intent of the test author.

 

[bennie]

Re: commercial receptacle limits

Prior to 1975 the nominal voltage was 115/230. If this question is that old, 12 was correct before 1975.

In 1975 120/240 volts was the agreed nominal voltage for calculation purposes. After 1975 the answer is 13.

The test apparently has not been upgraded.

The other test question.

Ten gauge THW is 75?C insulation. Ampacity is 35 amps. Derating for ten conductors is 50%. This is 17.5 amps. A branch circuit breaker not to exceed 30 amps after any correction factors have been applied. The connected load can not exceed 17.5 amps. The equipment grounding conductor is #10 AWG.

[ July 30, 2003, 12:47 PM: Message edited by: bennie ]

 

[ron]

Re: commercial receptacle limits

What am I missing. The article seams to indicate 120V for calcs.

220.2 Computations.

(A) Voltages. Unless other voltages are specified, for purposes of computing branch-circuit and feeder loads, nominal system voltages of 120, 120/240, 208Y/120, 240, 347, 480Y/277, 480, 600Y/347, and 600 volts shall be used.