Greetings,
Wiring a new home and was going to run 14ga to the 2nd flr branch as theer are only 14 fixtures with a 75watt max capacity. Soon realized 4 of these fixtures are fan lights combos. What do I figure as for wattage per fan motor or is there a wattage I should use for the fixture as a whole?

Wattage is not important it's the amount of AMPS the upstairs is requiring

You cannot convert watts to amps, since watts are power and amps are coulombs per second (like converting gallons to miles). HOWEVER, if you have at least least two of the following three: amps, volts and watts then the missing one can be calculated. Since watts are amps multiplied by volts, there is a simple relationship between them.

However, In some engineering disciplines the volts are more or less fixed, for example in house wiring, automotive wiring, or telephone wiring. In these limited fields technicians often have charts that relate amps to watts and this has caused some confusion. What these charts should be titled is "conversion of amps to watts at a fixed voltage of 110 volts" or "conversion of watts to amps at 13.8 volts," etc.
This text is from http://www.powerstream.com/Amps-Watts.htm

This site can give you an ide of the size cable ( if you know how many amps you need ) http://jaw.iinet.net.au/stuff/cablecalc.html

If you are wiring a new home, you should run more than 1 circuit to the 2nd level. If you run 1 and trip a breaker, all the power, outlets and lighting go out. I'd run a couple of outlet circuits at 20 Amp and then a couple of light circuits at 15 Amp. Bathrooms will need to be GFCI and bedrooms arc faulted, easy with an arc fault breaker, another reason to use separate circuits. If you really want to make wiring smooth, put a sub panel on the second floor and run everything off that. 1 wire up from the main panel and the rest lateral. Uses less wire and you have room to expand from that level and not try to pull wires up walls from the first floor or basement.

Lets see if the third answer actually answers your question.

While a ceiling fan motor does not draw much power, it does need to be calculated into the circuits load, so good question.


Here is a datasheet for a typical fan:

http://www.nutone.com/PDF/Specifications/PFCH42spec.pdf

You can see it draws .5 amps. At 120 volts, that is 60 watts.

You will need to confirm the electrical specs of your fans by locating the manufacturers specification sheet for your fan. I suspect most would not be much different. Perhaps a bit less, most likely a bit more.

Next you need to know how many 75 watt lamps each fan and light fixture will have.

Assume each fan and light fixture will have two 75 watt lamps. Calculating total load must be based on the MAXIMUM wattage each fixture is rated at.

14 fixtures/fan lights x 2 lamps x 75 watts each lampholder = 2100 watts.

4 fans at 60 watts each = 240 watts plus the 2100 watts of lighting totals 2340 watts.

P=EI or Power equals volts times amps, or amps equals power divided by volts.

P= Power, or wattage
E= Electromotive Force, or voltage
I= Intensity, or amperage.

I did not make these letters up to represent electrical values, you can blame Georg Ohm, see Ohm's Law.

So,

2340 watts / 120 volts = 19.5 total amps.

This total load will exceed what a 15 amp circuit can handle.

Here is where it can be tricky. If these lights are in various rooms of a dwelling, it may be considered as a general purpose lighting circuit, and one 15 amp circuit may be sufficient. This will assume that all the load would not be on at the same time.

If there is the chance that all lamps and fans would be all on at the same time, it is now to be considered as a lighting circuit, and two 15 amp circuits would be needed.

Because a home would have many receptacle and lighting outlets, but never be all used at the same time, the minimum quantity of circuits are calculated by allowing 3 watts per square foot. Note I stated MINIMUM amount.

Personally, I would install at least two 15 amp circuits for these fixtures and fans.