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submitted 6 months ago by [email protected] to c/[email protected]

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General info: Looking to get current attic ventilator fan replaced. The attic is about 1400 sq. ft. Current attic ventilation fan is a foot from the ridge of the roof. Live in USA.

Handyman wants: To install two 1500 CFM fans. Two 120 volt 20amp dedicated circuits, one for each fan. He wants to install the second fan 4 feet away from the current fan. He stated that the attic ventilator fan would need to be replaced within 6 years.

My questions: Would two fans be better than one fan? Would I need two 120 volt circuits to run two fans? Is there an attic ventilator that has a user replaceable fan?

Thank you in advance for any help.

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[–] [email protected] 1 points 6 months ago (9 children)

Depends on the cfm (cubic feet per minute) of the fan. This will tell you how much it's working to replace the air in your house.

Also depends on your current circuit, and your circuit current, lol. I'm willing to bet that the current circuit is 20amp, so I don't know why he's trying to replace that. I'm willing to bet the fan is also using almost all of the available circuit. You need to find out what the draw is on the fan for that. A 20amp circuit can handle 2400 watts. But due to code limiting draw at 70%, you can only put 1680w on there legally. That's for saftey(fire) reasons.

[–] [email protected] 4 points 6 months ago (2 children)

Each fan would be 1500 cfm. I'm guessing the attic is about 3500 cubic feet.

I forgot to say this, but the current circuit, as far as I can tell, doesn't connect to the breaker box. The lines are dead and the attic ventilation fan hasn't worked since we bought the house. The fan doesn't spin smooth when manually rotated, so we assumed it needed replacing.

The handyman originally insisted on installing a 240 volt wiring and circuit breaker. I don't know much about electricity but that set off red flags. I have no problem going with higher gauge wiring if the cost is cents more, but there is no reason to run that many amps unless we're plan on charging an electric car in the attic.

Thank you for your comment.

[–] [email protected] 7 points 6 months ago* (last edited 6 months ago) (1 children)

Yeah, that 240v line run suggestion puts a gigantic question mark on anything they've suggested at all. I'd recommend a second opinion.

[–] [email protected] 3 points 6 months ago

240v for an attic fan? Wtf?

Yea, fire this "handyman". 240 in the US is for high load devices, like AC, electric stove (electric heat is a direct short), electric water heater.

A fan draws a very small amount of current - less than 5 amps at 120v.

I have a small portable blower (this uses a compressor wheel, so draws more current than a fan), and it's rated for 5 amps.

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