attic fan project

packdaddy
packdaddy Solar Expert Posts: 27 ✭
in Solar Beginners Corner #1
I have
- 405 watts of PV 12/24,
- 420 AH of batteries
- 30 amp controller
- 750 watt inverter.
I use for my travel trailer when camping and I want to put them to work when I'm not camping.

I live in South Texas so my attic is very hot and humid (much like Florida). I want to install some attic exhaust fans but can only find 12-36 volt kits with 15watt PV included. I know the PV is driving up the cost. Where can I find a kit without the PV?

Or do I have enough hardware to power a couple of 120v fans.

Fan Example:
Gable Mount Ventilator, Voltage @ 60 Hz 120 Volts, Current Rating 3.4 Amps, Speed 950 RPM, Maximum Attic Area 1630 Square Feet, Blade Diameter 14 Inches

Thanks in advance.
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Comments

  • wtwoods_az
    wtwoods_az Registered Users Posts: 18 ✭
    #2
    Re: attic fan project

    Hello. I bought the 16-inch "German Attic Fan" from Horizon Energy Systems here in Phoenix because I was tired of replacing the "home depot" mushroom fan every summer. And, I didn't want to cut anymore holes in the roof, so I opted for the expensive single one. They have others if you think that is too much. The 12" is probably a bit small for you, the 14" a little big but I can attest that these things are overbuilt and reliable. This is my 3rd year and in PHX my fan runs A LOT.

    The fan runs off my inverter, but I have 4.5KW available. You might do better with a smaller one so the turn on surge doesn't kick out your inverter.

    I just noticed that they also sell a solar fan, but with a panel and it's kinda pricey. They might sell you just the fan if you ask.

    http://www.savenrg.com/solaratticfan.htm

    Good Luck!
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  • drees
    drees Solar Expert Posts: 482 ✭✭✭
    #3
    Re: attic fan project

    Not all attic fans are the same - some are efficient - some use more energy than they can save.

    Make sure you get one that is Energy Star rated - they are rated to at least move a certain amount of air per watt.
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  • LucMan
    LucMan Solar Expert Posts: 223 ✭✭✭
    #4
    Re: attic fan project

    Why not take a look at the whirylbird roof ventilators.
    No power required and a light breeze makes them operate.
    http://www.ehelpfultips.com/do_whirlybird_vents_work.htm
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: attic fan project

    At the risk of starting a few arguments ...

    You shouldn't need attic ventilation fans. If the house is properly constructed, the air flow will naturally occur. Even in Texas. Trouble is, many houses aren't properly vented. Check with a reputable contractor regarding yours. Sometimes it's an inexpensive fix. Sometimes it's an awful lot of money and the fan is cheaper.

    Your fan pick of 120 Volts @ 3.4 Amps = 408 Watts. At best your batteries could run this for 6 hours. In all likelihood it would be less. The start-up current on that fan motor will be higher, and most likely would overwhelm a 750 Watt inverter. If you already have the fan you can try it and see.

    "Whirligig" roof vents are worse than useless. You can't create power from thin air. :p Air movement over a roof vent will provide a drop in pressure which will draw air through the vent. The turbines can not increase this, and often do the opposite: create a turbulent spot that prevents airflow through the vent. I have two on this house here and they are coming off. All they do is make noise.

    Everyone is free to disagree with me on any point. I won't argue; you won't be spending my nickle.
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  • GreenPowerManiac
    GreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    #6
    Re: attic fan project

    Coots right here.

    What's needed here is Ridge Vents on the Apexes of your roof line. Older homes usually do not have any insulation on the pitches inside. Newer ones like mine are blown in insulation with styro foam baffles every 4-5 rafters. The circulation goes from Vented Soffits through the baffles and out the ridge vents. Ridge vents are like thicker scrubbing pads found on professional floor scrubbers only 1' wide and in 20' - 100' lengths found at Menards or Lowe's. These vents are covered by ridge shingles with longer nails to keep from crushing the vents.

    Another plus for doing this might land you a 30% federal tax credit for next year, just save your receipts. Form 5695, I believe, IRS.

    Would also suggest using the energy for something else much less demanding, like an independent string of lights in the house, if not utilized already.
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #7
    Re: attic fan project

    Another thing to consider is that battery life is counted in "cycles" - the more times you discharge/recharge them, the sooner they will wear out.

    You need to figure out how deeply you will be discharging those batteries, so you can figure out how many cycles they will last (the deeper you discharge them, the lower the number of cycles they will last) and if it is worth it to wear them out for household use.

    Depending on your cost per watt it's probably a lot cheaper to just use grid power than to wear out your batteries.
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