NEC 2008
210.21 Outlet Devices. Outlet devices shall have an ampere rating that is not less than the load to be served and shall comply with
210.21(A) and (B).
(B) Receptacles
(1) Single Receptacle on an Individual Branch Circuit. A single receptacle installed on an individual branch circuit shall have an
ampere rating not less than that of the branch circuit.
Exception No. 1: A receptacle installed in accordance with
430.81(B).
Exception No. 2: A receptacle installed exclusively for the use of a cord-and-plug-connected arc welder shall be permitted to have an
ampere rating not less than the minimum branch-circuit conductor
ampacity determined by 630.11(A) for arc welders.
(2) Total Cord-and-Plug-Connected Load. Where connected to a branch circuit supplying two or more receptacles or outlets, a
receptacle shall not supply a total cord and-plug-connected load in
excess of the maximum specified in Table 210.21(B)(2).
(3) Receptacle Ratings. Where connected to a branch circuit supplying two or more receptacles or outlets, receptacle ratings shall
conform to the values listed in Table 210.21(B)(3), or where larger
than 50 amperes, the receptacle rating shall not be less than the
branch-circuit rating.
Exception No. 1: Receptacles for one or more cord-andplug-connected arc welders shall be permitted to have ampere ratings not less than
the minimum branch-circuit conductor ampacity permitted by 630.11(A)
or (B) as applicable for arc welders.
Exception No. 2: The ampere rating of a receptacle installed for electric discharge lighting shall be permitted to be based on
410.62(C)
(4) Range Receptacle Rating. The ampere rating of a range receptacle shall be permitted to be based on a single range demand
load as specified in Table 220.55.
If it is a single receptacle on a 20 Amp circuit, it must be a 20 Amp receptacle (aside from the 2 exceptions). If there are multiple receptacles on a 20 Amp circuit, the receptacles can be either 15 or 20 Amp (aside from the exceptions).
This is to allow You to have multiple devices plugged in drawing less than 15 Amps each, but the total draw on the circuit may be greater than 15 Amps.
NOTE:
Keep in mind that NEC defines a receptacle as follows.
Receptacle. A receptacle is a contact device installed at the outlet for the connection of an attachment plug. A single receptacle
is a single contact device with no other contact device on the same
yoke. A multiple receptacle is two or more contact devices on the same
yoke.
So a duplex receptacle would be considered two receptacles, according to this definition. Which means you can install a single 15 Amp duplex receptacle on a 20 ampere circuit, without violating this code.
The reference to a switch loop in the related question describes a pair of wires that are both hot or live. The white wire is serving as a black and should have a black marking or tape on it. The switch is serving as a break in the hot line.
Every operating device (like a fan or lamp) in standard wiring needs a hot line and a neutral line, and usually a ground, although that is not strictly necessary in all circumstances. In the wiring described in the other question, there was no neutral running through the switch box, but there had to be a neutral connected to the device itself, in the box that the fixture was attached to. The neutral wire is never switched, so only the hot lead was routed to the switch loop. Modern code requires that new switch circuits also have a neutral present, since some newer switch devices need a neutral to function.
Your situation may be different. On your circuit, one of the three boxes is closest (electrically) to the main panel. There is a live circuit line running either to one of the outlets or to the switch box. In either case the outlets you describe must have a neutral wire present as well as a hot wire.
If you want the fan to be switched on and off by the same switch as the outlets, you can simply add a wire from either outlet box to the fan location and connect all wires in parallel (black/white/ground).
If you want a separate switch for the fan, you need to tap into the power where the live circuit comes in to the room. It may be either of the outlets or it may be the switch box (if there is a neutral in that box). You need to tap into the unswitched hot, run that hot to a new switch and connect the neutral and ground in parallel. Then run the full cable from the new switch to the fan.
If you want to use separate hard wired switches for fan and light, run 14/3 from a switch box fed by the always hot line, using the two hots separately for the two features.
An alternative if you want separate switching is to run a full cable (14/2 or 12/2) directly to the fan from the box that has an unswitched hot. Use a fan that has a hand-held or wall mounted remote and wire the fan as always hot (no line switch). Then the remote controls whether power is going to the fan. This also simplifies installing a fan/light combination.
As to your other outlets, white wires are generally not hot unless used to connect to switches and should be so marked. Most white wires are neutral. You can test your outlets for correct wiring with a plug-in tester like this one.
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If the tester reveals miswiring, you should consider calling in a pro. It also sounds as if you are not too familiar with wiring in general, so you may want to enlist the help of someone with a bit more experience until you become more confident. In any event be sure to turn of the circuit breakers before opening any box and confirm wire are not live with a non-contact tester like this one
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Best Answer
You do not need a permit to replace fixtures or devices (outlets) with new ones.