The Electrical Code

220.61 Feeder or Service Neutral Load.

Let’s dissect this one shall we. To begin with the first part of this “A”. Ok here what we are going to do is we are going to say that a circuit is going to be 20 amps then we are going to run the 12 AWG load wire wire a 12 AWG neutral wire (which is white 120/240 volts or grey 277/480 volts. That is that don’t get it confused 20 AWG with another 20 AWG nice and safe that is it.

Let’s go to “B”. Part 1 of B deals with is household appliances and normally the manufacturer has electrical engineers there to figure things out internally but when giving the information to install the appliance they also give you that information nation and do the calculation for you. But what they do not to get things heated up and fail prematurely is what ever the load is they calculate 70% demand factor so not to expose the installation materials to extra loads that might cause it to fail prematurely. Remember the code is here to help not to hurt yourself. Ok part 2 of “B” shall not be covered because it is giving us engineering situation that will require an electrical engineer to sign of on the design so I will not indulge you in this one.

Let’s go to “C”. The code will begin to tell you where it is able to use the neutral for two wires so it refers you to part 1 and 2 of this part of the article and telling you that with a 4 wire, 3-phase, WYE connected system. If you don’t understand this part please don’t touch it. You will get hurt.

“220.61 Feeder or Service Neutral Load.
(A) Basic Calculation. The feeder or service neutral load shall be the maximum unbalance of the load determined by this arti‐ cle. The maximum unbalanced load shall be the maximum net calculated load between the neutral conductor and any one ungrounded conductor.
Exception: For 3-wire, 2-phase or 5-wire, 2-phase systems, the maximum unbalanced load shall be the maximum net calculated load between the neutral conductor and any one ungrounded conductor multiplied by 140 percent.

(B) Permitted Reductions. A service or feeder supplying the following loads shall be permitted to have an additional demand factor of 70 percent applied to the amount in 220.61(B)(1) or portion of the amount in 220.61(B)(2) deter‐
mined by the following basic calculations:
(1) A feeder or service supplying household electric ranges, wall-mounted ovens, counter-mounted cooking units, and electric dryers, where the maximum unbalanced load has been determined in accordance with Table 220.55 for ranges and Table 220.54 for dryers
(2) That portion of the unbalanced load in excess of 200 amperes where the feeder or service is supplied from a 3-wire dc or single-phase ac system; or a 4-wire, 3-phase system; or a 3-wire, 2-phase system; or a 5-wire, 2-phase system
Informational Note: See Examples D1(a), D1(b), D2(b), D4(a), and D5(a) in Informative Annex D.
(C) Prohibited Reductions. There shall be no reduction of the neutral or grounded conductor capacity applied to the amount in 220.61(C)(1), or portion of the amount in (C)(2), from that determined by the basic calculation:
(1) Any portion of a 3-wire circuit consisting of 2 ungroun‐ ded conductors and the neutral conductor of a 4-wire, 3-phase, wye-connected system
(2) That portion consisting of nonlinear loads supplied from a 4-wire, wye-connected, 3-phase system
Informational Note: A 3-phase, 4-wire, wye-connected power system used to supply power to nonlinear loads may necessitate that the power system design allow for the possibility of high harmonic neutral conductor currents.”