This calculator requires the use of Javascript enabled and capable browsers. The purpose of the calculator is to determine the size of the conductor wire in a circuit of a given distance with a given amperage load. Select the type conductor wire material, the circuit voltage and the phase of the circuit. Enter the total amperage on the circuit; also enter one half of the total length of the circuit. A sample of 120 volts, single phase, copper wire, 144 feet (one half of a 288 foot circuit) with 10 amps load on it yields a number 10 awg wire size. Our calculator yields results that are within code in most locations however we advise you to check your local electrical code. Since we have tried to consider safety as our primary factor, any marginal decision factors are toward the safe side. We allow a maximum voltage drop of about 3% before the wire specification increases. If you need to calculate actual voltage drop, you might want to consider using our voltage drop calculator for both wire circuits and circuit boards, AC and DC.

One Half The Total Circuit Length Required Minimum Wire SizeThree Phase Electrical Motors Full load amps, wire and conduit sizes for three phase electrical motors Typical full load current, minimum wire size and conduit size for 230V and 460V three phase electrical motors: HorsepowerFull Load (amps)Minimum Wire Size (AWG - Rubber)Conduit Size (inches) 230V460V230V460V230V460V 1 3.3 1.7 14 14 1/2 1/2 1.5 4.7 2.4 14 14 1/2 1/2 2 6 3 14 14 1/2 1/2 3 9 4.5 14 14 1/2 1/2 5 15 7.5 12 14 1/2 1/2 7.5 22 11 8 14 3/4 1/2 10 27 14 8 12 3/4 1/2 15 38 19 6 10 1-1/4 3/4 20 52 26 4 8 1-1/4 3/4 25 64 32 3 6 1-1/4 1-1/4 30 77 39 1 6 1-1/2 1-1/4 40 101 51 00 4 2 1-1/4 50 125 63 000 3 2 1-1/4 60 149 75 200M 1 2-1/2 1-1/2 75 180 90 0000 0 2-1/2 2 100 245 123 500M 000 3 2 125 310 155 750M 0000 3-1/2 2-1/2 150 360 180 1000M 300M 4 2-1/2The circuit breaker’s job is to protect wiring in the walls of your house, not the air conditioner and not the air compressor. As long as cross sectional area of the conductor is properly matched to the circuit breaker or fuse, it’s ok.

That said, if you want to protect your air compressor, you should install a motor starter protection device calibrated to the nominal current, or at most 105% of the nominal current. This device may be installed either instead of the circuit breaker, or downstream from it. A three phase motor protection device, such as Eaton’s PKZM-0 series device may be wired in a special manner for use in a single phase circuit.To meet code you should run the wire to the compressor that can handle 30 amps. Off the top of my head, I think this would be 10 gauge copper. Depending on the length of the wire run, it might be cheaper to just change out the breaker with a 20 amp. If it is a short run and the wire is just going to be in the air from the box to the compressor, I would feel safe running #12 wire without changing the breaker since the compressor is never going to be pulling anywhere near 15 amps except when starting. There is a very slight chance the compressor could fail in a way that put 29 amps on the wiring constantly.

This would overheat the wire and maybe cause a fire, but this is so unlikely a situation that it would truly be a freak accident like in one of the Final Destination movies.The other possibility of using 12 gauge wire with a 30 amp breaker would be if someone in the future removed the compressor and put in something that did draw near 30 amps continuously like a welder. cost to service hvac unitThey could see the breaker was 30 amps and assume the wiring could handle this. air conditioner and heater filtersA good electrician would catch this because he would check the wire size when he installed a new load.ac unit fan motorI’m assuming you are planning on hard wiring the compressor, not use something like an oven or dryer receptacle rated for 30 amps.

In that case I would always run the proper wire size. I just looked the proper wire size up and my memory was correct.Written The answers below are somewhat valid. Assuming the wiring from the panel to the point the compressor receives its supply, is #10 it is could be OK. Codes permit Electric motor loads to have a much higher breaker or fuse rating than the nameplate running current amps. Overload protection is provided by the motor running over current protection that is either inside the motor or in a motor control associated with it.The NEC permits inverse time breakers, that you likely have, to be sized as much as 250% over the motor’s nameplate full load current. So if your Compressor Motor has a nameplate full load current of no less than 12 amps, it is ok. That current would mean a minimum compressor motor rating of 2HP. However if not, you will need a smaller breaker, or a breaker located at the point the 30 amp circuit ends and connects to the compressor. It is easier to replace the 30 amp breaker with a 15 or 20 amp rated breaker that is made for the panel, same brand or otherwise listed on the breaker’s package as fitting in that particular panel.

Code wise, you cannot put anything less than a 30 amp rated receptacle on the 30 amp branch circuit, or even put a 30 amp plug on the factory provided compressor’s cord. The cords rated ampacity would have to be evaluated for use on a 30 amp breaker., or upgraded in a code agreeable manner. Remember you need a motor disconnecting means where the motor is located unless the breaker is in the same room and in sight, if you hard wire it.Incentives for installing it in accordance with the codes? Do you have employees or the general public, relatives, children or friends that will be in the building where this is going to be installed?I am a licensed electrician with electric motor repair and installation experience, large and small.Written If the breaker is 30 type B maybe not, you need at least 15 type C for motor.The compressor motor could easily put 5 times rated current on start unless the head unit start without compression (head pressure relief valve)Instrumentation, Electrical, Control and Sensing Devices

Product and Services Companies AWG Copper Wire Table Size and Data Chart @ 100 Degrees F The American Wire Gauge (AWG) measurement system was designed with a purpose: for every three steps in the gauge scale, wire area (and weight per unit length) approximately doubles. This is a handy rule to remember when making rough wire size estimations! For very large wire sizes (fatter than 4/0), the wire gauge system is typically abandoned for cross-sectional area measurement in thousands of circular mils (MCM), borrowing the old Roman numeral "M" to denote a multiple of "thousand" in front of "CM" for "circular mils." The following table of wire sizes does not show any sizes bigger than 4/0 gauge, because solid copper wire becomes impractical to handle at those sizes. Stranded wire construction is favored, instead. kcmil = circular mils x 1000 For some high-current applications, conductor sizes beyond the practical size limit of round wire are required. In these instances, thick bars of solid metal called busbars are used as conductors.

Busbars are usually made of copper or aluminum, and are most often uninsulated. Although a square or rectangular cross-section is very common for busbar shape, other shapes are used as well. Cross-sectional area for busbars is typically rated in terms of circular mils (even for square and rectangular bars!), most likely for the convenience of being able to directly equate busbar size with round wire. Reference: Handbook of Scientific and Engineering Data Staff of Research and Education Association American Wire Gauge (AWG 1. These resistance values are valid only for the parameters as given. Using conductors having coated strands, different stranding type, and, especially, other temperatures changes the resistance. 2. Formula for temperature change: 3. Conductors with compact and compressed stranding have about 9 percent and 3 percent, respectively, smaller bare conductor diameters than those shown. American Wire Gauge (AWG) Wire Size Chart