Circuit breakers are rated for 120V, but yet electric items are 110?

What is the difference. Also 220V vs 240V.

When I try compute voltage drop, which would I use.

Thank you for your time.

 

Generally, a residence is nominally 240/120V. Calculate based on the nominal (typical) unless you know the installation site has a different voltage.

 

Voltage drop depends exclusively on current, not on voltage. Of course, all other things being equal, current depends on voltage.

If you have a 60-watt 120-volt light bulb, it will pull 0.5 amps if supplied with 120 volts. If supplied, however, with only 110 volts, it will only pull 0.46 amps (and is really only a 50-watt light bulb).

So measure your voltage at the receptacle. Then figure what kinds of things you will be putting on this wire, and how many watts they use at their nominal voltage (which might be different than your actual voltage). This combined with the basic set of electrical forumlas will allow you to compute amps. The amps combined with the gauge and type and length of wire will allow you to compute voltage drop.

If your loads include motors, then the above calculations based on Ohm's law won't be exactly right, but they'll probably still be close.

You made the assertion that "electric items are 110." I don't know where you came up with that, but if I look at most light bulbs, they say "120V" on them. What are you looking at that says "110V"?

 

Im in CANADA but in general all residential voltage on North America is 120/240 at the pole. Depending on the code in your area you are allowed a certain amount of voltage drop from the pole to point of consumption (plugs lights ...etc)Where I am for instance we can have a total of 5%.This is where NAMEPLATE RATINGS come into it.Nameplate supply voltage ratings are nominal and supply voltage may deviate + or - 10% without reducing equipment life expectancy. I'm working in a plant where the the supply should be 600 volts instead of 643v.motors run a little hotter but not enough for the PO CO to justify a new xformer.

 

Concerning electrical calculations the apparent {nominal} voltage is normally used being 110 or 220 volts. Whether it is Apparent, RMS, or Real applied voltages really should not make much of a difference in real life calculations but using the proper apparent or listed in the question voltage concerning a test questoin may mean a difference of passing or flunking a test for a license.

Hope this helps

Wg

 

I would argue that nominal is 120 or 240V.

 

HandyRon, apparent voltage or aka nominal voltage is like an implied voltage which is accepted calculation values used concerning voltage in your calcualtion formats. This nominal voltage has nothing to do with the actual voltage serving a home that is often allowed to range from 100 volt to 130 volts and be considered as acceptable voltage supplied in the utility industry varying throughout the nation depending on distance, grid position connections and transformer locations. There is a wide variety of actual voltage experienced at each individual structure.

What is being sought in the original post is what voltage value to use while using an electrical calculation format such as a format concerning voltage drop calculations. This is the nonminal or apparent voltage value that is used in those calculations only. Does not apply to actual voltages found in a structure in real life.

Does this help

Wg

 

I just finished writing my exams and we have to take the Manufacturer Nameplate Data over even code calculations This in fact was the "SPIN" on a compressor motor question .We have to refer to our CEC for direction on nominal voltage if the question does not state Nameplate Data .

 

442a, I have seen many similarities between the NEC and the CEC. However I have also seen just as many suttle differences that makes a big difference in design between these two Codes.

In the NEC 430.6.A.1 requires us to size our equipment per our tables unless specialty designs of a certain motor is involved. Then I reverses requiring the name plate rating be used if stated on the motor to size overloads to protect that motor and conductor. Makes sense to me but then I am a bit looney at times too! Ha Ha.

Wg

 

You will find the following reference in NEC 1999 Appendix D "Examples"
Voltages. for uniform application of articles 210, 215 and 220, a nominal voltage of 120, 120/240 ...... is used in computing the ampere load on the conductor.
No where else, does the NEC define the nominal voltage. I would go by the code's own reference and use 120 or 240V (in leiu of 110 or 220).
There is also a IEEE and ANSI reference that I cannot find at this time.

 

ANSI/IEEE C84.1 establishes nominal voltages and acceptable excursions (+ or - 5%).