Recently purchased a cheap box fan to go in my window and cool my room at night so I wouldn’t have to run the AC. The plug of the box fan plugged into the back by the electric motor. I couldn’t put the fan up directly against the window screen to get the cooler air from outside in my room the most efficient way possible so I rewired the fan and routed the plug to the side of the casing. When I was taking apart the fan to re-wiring I forgot to take a picture of which wire plugs into the positive and which wire plugs into the return… I think I have it right, the fan is running in the correct rotation direction though I don’t know if wiring it backwards would reverse the rotation direction. The fan does not seem to be running as fast as it did before I rewired it though that could be my imagination. I also used thinner gauge wire the wire does not seem to be heating up at all. Don’t wanna blow up the fan don’t want to do anything dangerous so if anybody could give me some direction I would greatly appreciate any help.enter image description here

  • 1
    AC motors usually don't care that much. DC motors will run backwards. Thinner/smaller gauge wire is most times a big no-no, even if not heating up.
    – crip659
    Jul 24 at 20:54
  • Thanks for the reply I appreciate it. Can I assume that a box fan motor is probably an AC motor? Also the wire I used is 18awg and only has 67 watts (according to The wattage meter I plugged it into) going through it at most… you say not to use thinner gauge wire however if it’s not heating up then what harm could I do? I’m not arguing with you I’m just trying to understand.
    – Teddysurf
    Jul 24 at 21:11
  • It is what electrical code says. If the fan or whatever comes with smaller gauge wire from factory/store it is okay. If you change to smaller gauge, then that against code and your insurance can and probably will denied any claim you make, even if it has nothing to do with the claim(flood instead of fire). Any thing made to plug directly into a wall outlet(without a wall wart/battery) is AC(most of the world).
    – crip659
    Jul 24 at 21:29
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    Note that box fans usually work better when blowing outward than blowing inwards. The fan does not pull air from just behind it, but from all around, including front side corners. So when it is placed on the inside side of the window blowing inwards, a large part of the air is just the same indoor air being recirculated.
    – jpa
    Jul 25 at 8:06

The fan doesn't care... but you might

The fan runs on AC power, so it really doesn't care if you swap leads.

However, the system is designed so that one of those leads has an electrical potential near safety ground. The other one is 120V from safety ground. The one near ground is called "neutral". The other one is called "hot".

This is designed so that, under normal conditions, if you came in contact with neutral you will probably be OK. However you don't want to meet the 120V one in a dark alley. This polarity is enforced by the extra-wide blade on the plug. The wide one is neutral, as is the ribbed wire on the cord.

The way most appliances are built, you are far more likely to come in contact with one rather than the other. UL requires that one be attached to neutral. Some appliances have a very low probability of contacting either one, and if those are then "double insulated", the polarization is not required.

So anyway... your appliance WAS wired so that the one you're far more likely to come in contact with was the neutral. 50/50 chance you broke that. You should fix that.

  • Both hot and neutral must be isolated from anything that could touch a person. The distinction has to do with fusing and switching. If a plug is wired correctly, turning off the switch will disconnect the hot wire. In addition, if the fan contains any sort of fuse or other such protection device, it will disconnect the hot wire when it opens.
    – supercat
    Jul 25 at 18:18
  • @supercat Yes, but hot has to be more isolated. On a polarized appliance, UL will tolerate less insulation on neutral. Jul 25 at 20:13

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