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Hey guys I am hooking up my bathroom fan and wanted to get clarity on the electrical requirements.

The fans requirements state:

“Run 120V AC house wiring to the location of the fan” On the box is says 120V/60Hz

My current 20a/12-2 will be to much power for this fan correct?

Does the 120V mean it is expecting 15a/14-2?

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    You seem to have a fundamental misunderstanding about how electricity works. Bathrooms typically require dedicated 20A circuits, but that has no bearing on how much power your fan consumes. – isherwood May 22 '20 at 16:42
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    As long as the voltage is correct the fan will only draw what it needs assuming the wiring to it has sufficient capacity, which both 12/2 and 14/2 do. If you think through your question a bit more, any device connected to a circuit that wasn't using it's full capacity would be blown to smithereens. Think of electricity like water, you can turn the tap on at the sink "just a bit" to fill a cup or you can run a bath faucet at full, both are supplied by the same piping. Both are just using what they need. Hope this helps. – George Anderson May 22 '20 at 16:54
  • Thanks I think my question was asked incorrectly - what I was more attempting to ask was: “based on the electrical requirements from my fan is it not rated for the power from my dedicated 20a breaker” – Andrew May 22 '20 at 16:59
  • A fan will typically use about 30-60 watts, which is about 1/4 - 1/2 of an amp. So given your logic even a 15 amp circuit would be 30-60 TIMES the amount of power the fan uses. Bottom line, you'll be fine putting it on a 20 amp circuit. I just did this on my son's house, no issues. – George Anderson May 22 '20 at 17:08
  • Thanks George - this was very helpful. Feel free to post answer for credit – Andrew May 22 '20 at 17:09
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A fan will typically use about 30-60 watts, which is about 1/4 - 1/2 of an amp. So given your logic even a 15 amp circuit would be 30-60 TIMES the amount of power the fan uses. Bottom line, you'll be fine putting it on a 20 amp circuit. I just did this on my son's house, no issues

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Your fan really only draws a few watts. You need the wire size to match the circuit breaker if it is a 20 amp circuit breaker you must use 12 gauge wire. 14 gauge is too small and can start a fire. If it is a 15 amp circuit breaker it needs to be 14 gauge or larger (you can use a larger wire gauge than required). The circuit breaker is protecting the circuit wiring. The UL listing says it’s OK to use in the US. On a 15 or 20 amp circuit.

  • Thank you for addressing minimum wire size for breaker rating, none of the comments made that clear. – Jimmy Fix-it May 22 '20 at 17:26
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For simple understanding, it's often helpful to think of electricity flowing through a wire as analogous to water flowing through a pipe. Voltage is like pressure and amperage is like flow. To accommodate more flow, you need a larger pipe but both a narrow pipe and a wide pipe can have the same pressure.

Regardless of whether you have a 14-gauge wire or a 12, the pressure (voltage) is the same. The difference is the amount of flow (amperage) it can handle. This is where the analogy breaks down a bit: when you don't have a big enough wire to handle the flow (amperage), it gets hot, possibly really hot.

To prevent this from happening, we have circuit breakers. They are designed to kill the power almost instantly in the event the flow exceeds the breaker rating. A 14-gauge wire (in typical circumstances) can handle up to 15 amps so if there are any 14-gauge wires connected to a circuit, you need a 15A breaker (or amller). For a 20A circuit, you need all 12-gauge wires (or bigger.)

You are completely fine to connect this to your 20A circuit just don't add any wires to the circuit that are smaller than 12-gauge. That is, don't connect any 14-gauge wires to the circuit.

  • FYI Wire size is based on circular mill area, in the US we use gauge where 12 is larger than 14 when the wire is larger than 4/0 Or 0000 Said four ought . We use Kcmil or Mcm depending on your age what you were taught. This becomes important when the conductors are not round. – Ed Beal May 22 '20 at 17:44
  • @EdBeal Thanks. I would say to anyone who is getting their information here that if they are dealing with something other than the normal 12 or 14 wire on the shelf of their local big-box store, they should consult a professional. – JimmyJames May 22 '20 at 17:53
  • @EdBeal kcmil, k being kilo and must be lowercase because it's an SI unit. Big K is something else. The M in MCM is Roman for thousand. Regardless, I prefer to think in terms of circular inches, because that works quite well for thinking about conduit fill (no need to divide by pi). Square the wire diameter for its cross section in circular inches, square the conduit ID , and that's it. – Harper - Reinstate Monica May 22 '20 at 18:16
  • As I said it depends when you were taught , I have a degree in electronics and know SI units and that is the reason I specified because some here get triggered on things like 220v , and romex . – Ed Beal May 22 '20 at 19:14

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