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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] 3 points 6 months ago* (last edited 6 months ago) (2 children)

As a 25 year construction worker, many of which have dealt with electricity. Two full years as an electrician.

Running one 240 circuit might sound intimidating. But it's an efficient way to run a lot of juice to one location. All of your large appliances are ran on a 240, if they're electric.

I can't exactly explain to you why, but most efficient electric motors are 240. I agree with his initial recommendation. Without being on site, or having exact measurements, I cannot say that the cfm is uncalled for. I was going off of your 1300sqft est on the attic.

Just know that the things you are looking for are appropriate air exchange. Not too much, not too little.

Edit

With 240, it's more about the amperage. Basically he's talking about still running two 20A circuts, but in one wire. Level two car charges are like 48A 240, and level three is like 100A 240.

If you have an electric stove, that's 50A 240

[–] [email protected] 2 points 6 months ago (1 children)

So the product he is installing, on Amazon, says it runs off 120 volts. Here is the link to the amazon listing.

https://www.amazon.com/Master-Erv6smww-Power-Mount-Ventilators/dp/B01AA6Y2YS

I appreciate your comment, and I agree and understand that some appliances function better off of 240 volts, but with this extra context, wouldn't this particular fan not benefit from a 240 volt line because the unit is only rate to operate at 120 volts? I believe this would damage the fan, or outright destroy it.

[–] [email protected] 2 points 6 months ago

So with the whole 240/120 thing you're talking about phases. These are basically electrical currents that function like wavelengths, operating at specific frequencies. The amperage basically says how much punch that phase/frequency can have.

If you put two twenty Amp circuits on the same neutral. The electricity will pass through both motors, and come back to the panel. The panel will read that those breakers are putting out more than 20A and trip the breakers.

BUT

If you put those breakers on different phases, the wavelengths alternate. Instead of really high peaks and valleys, there are more frequently occurring similar ones. So the breakers will read with in limits, and function. This is called sharing a neutral

What your guy is trying to do, is save a lot of work, and some money on material. Instead of running two wires, he's trying to share neutrals.

[–] [email protected] 0 points 6 months ago

Is it possible the 1500 cfm fans are intended to be run at lower capacity, and are just sized for a factor of safety?