Solar Electric for Attic Gable Fan

Hi all.
I'd like to create my own Solar Electric Attic Gable fan by purchasing needed component and then connecting together!

The fan I will use requires 110 volts and draws 4 amps at 225 watts. This is the easy part!

Now I need to size a panel, charge controller, battery, and inverter. I will attempt to buy all these items used!

I envision the fan to go on when temp reaches 85ish degrees and go off at 70ish...

Any and all advise welcomed.

tx, frank

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar Electric for Attic Gable Fan

    Welcome aboard Frank,

    My first recommendation would be simply to open up more attic venting (both inlets and outlets).

    At least one person here, installed a solar powered attic fan (with its own panel, no battery) and was very happy with it. Then, after a couple of years, the fan motor failed--but the attic was still cool. The additional venting added when installing the fan was all that was needed.

    You are looking at a real AC attic fan--which has a lot more power and is probably more reliable vs the $300 DC Solar Fans that most people attempt to use.

    Again, my first recommendation would be for you to install venting and drop the fan.

    If you still want to use the fan, then first read this thread on sizing an OFF-Grid System for a cabin (my detailed post is near the bottom--last I looked). You will have to go through the same thing to size the array and battery.

    Next, for your requirements, I would recommend this inverter:

    wind-sun_2034_18479682Morningstar SureSine, 300 Watt Sine Wave Inverter 115VAC


    One reason is this is a True Sine Wave Inverter--20%+ more efficient than a MSW inverter when used with AC induction motors.

    Another reason is that this inverter has a DC on/off (inhibit) connection--that you can connect to anything (simple timer, temp sensor, etc.). Very low current draw when in "standby".

    You could also look for an AC switch that is used to control fans for chicken houses and such at www.grainger.com or McMasters, etc.

    Another reason to avoid using a battery based system is that batteries should not be discharged below 50% to for long life. An automatic system can do that easily (bad weather, failed charge controller, etc.) and you have toasted an expensive set of batteries.

    If this is an automated system and you want to protect your batteries, I would suggest the Xantrex Battery Monitor because it includes a programmable output that can shut down the system if the batteries go below 50%. However, these things are not cheap (~$250-$350 for the two below):

    wind-sun_2033_15065476Xantrex LinkLITE Dual Battery Monitor
    Xantrex dual battery monitor system

    wind-sun_2033_15080217Xantrex LinkPRO Dual Battery Monitor System
    Xantrex dual battery monitor


    If you still need a powered vent, you might look at using 12 VDC radiator fans from an automotive junk yard and connecting them directly to the appropriate solar panels. The fans only turn on if the sun is up and no battery/charge controllers/inverters required.

    You might still have to replace the fan motors every few years (don't know how long they would last in this application).

    Your temperature range is pretty low--the fans might be on most of the day. If you are doing this in a home--besides adding additional ventilation, you would probably be better off adding more ceiling insulation... This would help keep your home cool in both summer and winter.

    Questions?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Ecnerwal
    Ecnerwal Solar Expert Posts: 101 ✭✭
    Re: Solar Electric for Attic Gable Fan

    If going with PV fans, I would firmly suggest 12V fans (pick a style, there are many out there) and direct panel connection - if the sun shines, the fan runs, if it doesn't, it doesn't.

    Reliable, continuous duty 12V fans are very common in computer equipment - you can probably grab some for free from equipment being tossed out, or you can buy new ones.

    Eliminating the cost and waste of inverter and battery (and maintenance of battery) improves the effect and reliability of the system. If the attic is well-vented while the sun shines, there should be little need for venting after dark. Some large electrolytic capacitors might smooth things out a bit and provide a short run after dark, but they are also subject to fail with time, so not using them might be best.

    Now, if you care more about venting that about having a PV vent fan, put in a solar chimney - basically a tall cupola which is glassed in on its lower section to make solar thermal heaters, to heat the air in it and help drive it up and out. A plain old fashioned (all-vent) cupola might work as well. In either case, make sure that there is plenty of unobstructed eve venting to get fresh air into the attic.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Solar Electric for Attic Gable Fan

    As has been suggested, stay with 12vdc, even if you want a battery an controller. 12vdc computer fans can be had free or almost free, and car radiator fans which would move much higher volumes of air can be had from the wrecking yard pretty cheap.

    Also, adding either ridge or high gable vents, or roof vents will add considerably to the cooling. Remember to provide intake vents down low. With low intakes and high exhaust, fans are almost not needed if you have any breeze.

    Icarus
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Solar Electric for Attic Gable Fan

    Why reinvent the wheel ...

    http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&langId=-1&catalogId=10053&productId=100548465

    I found these 2 years ago at my local HD, they were at the time marked 50% off clearance. I added a second panel ( so the fan had two ) and installed a pair ( 2 fans and 4 panels ) in a building that was used for walk-in cooler, ice machine ect.
    Still works today and keep the temperatures in check

    For a house attic , they would work well IMHO
  • System2
    System2 Posts: 6,290 admin
    Re: Solar Electric for Attic Gable Fan

    Tx all.
    I already have the gable vents: 1 on one end and two on other but attic remains very warm to do location(Central Valley of Ca.) and lack of air flow.

    I think I'll go with 12v electric auto fans and a inexpensive panel. Keep it simple!
    When the sun is out the fan will run [above a certain temp] and at night it won't and that's ok......

    last year i put in a whole house fan and solar window screens and it reduced costs by 1/3 for summer months....attic vent fans should help even more....
  • System2
    System2 Posts: 6,290 admin
    Re: Solar Electric for Attic Gable Fan

    Solar Guppy: Home Depot does not have this item any longer.
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Solar Electric for Attic Gable Fan

    Yes they do, I still see them at the local stores ... just like the link says, not online
  • System2
    System2 Posts: 6,290 admin
    Re: Solar Electric for Attic Gable Fan

    Tx Solar Guppy. I was able to find HD fan after some mods to my HD search as link you sent wouldn't take me there!

    I like the idea of panel's to a car fan however. I found a solar system at harbor freight for 180.00 on sale. It's a 45 watt system with a controller. See http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90599

    Does anyone know what the watt ratings are for 12v car/truck fans?

    tx, frank
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Solar Electric for Attic Gable Fan

    Radiator fans are a poor choice, they are small, high rpm fans with very high current draws and quite noisy and not built for continuous duty. The link I proved is the fan you want, very low rpm but good cfm.
  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    Re: Solar Electric for Attic Gable Fan

    Look at this:

    http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94519

    A 10" auto fan will draw about 8 amps, then a 16" that will draw about 16 amps.
  • System2
    System2 Posts: 6,290 admin
    Re: Solar Electric for Attic Gable Fan

    Tx Wizard.

    Interesting Harbor Freight product...I think cfm is a little low for my application however but may buy anyway.

    In regards to auto fan amps: 12"/8amps 16"/16amps.....

    Given watts = volts * amps -- 12*8= 96 and 12*16 = 192 does this mean I need panels that generate 96 or 192 watts if I want a direct feed?
    Else would I use a battery to run fans and panels to charge battery? If so, how many watts are needed to keep battery charged?

    tx, frank
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar Electric for Attic Gable Fan

    Yes, you are correct--if you want "full" fan speed, then you need the watts (and panel current) to drive the motor.

    Generally, unless you need the batteries (fans run when the sun is down/cloudy)--stay away from them.

    Basically, the system price will just about double (charge controller + batteries + 20% or more larger panels), you loose ~20% more power just to charge the batteries, and if you don't closely monitor the system--at some point, you will run the batteries dead a couple times--and need to replace them years before their normal lifetime... If you want to run the fans more hours (panels+batteries), you will need to increase the panel size accordingly (more panels, more $$$)

    With a direct panel to motor connection--you have a nice, automatic/variable speed fan. When the sun is bright--lots of fan; when it is not bright--little fan.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: Solar Electric for Attic Gable Fan

    I have metal case gable type with 12watts, 12v for $ 220 including sh
  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    Re: Solar Electric for Attic Gable Fan

    I have a hub type attic fan and the ac motor has died after about 10 years I would like to replace it with a 20 or 50 watt solar pv and I'm trying to find a motor, to fit the exsisting housign which is around 6diameters. i guess i could rig it smaller, but does anyone knwo the replacemetn motor parts from the home depot solar fan? it would be a lot easier to use a product designed for that purpose than to try and rig a substitute?
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Solar Electric for Attic Gable Fan
    I have a hub type attic fan and the ac motor has died after about 10 years I would like to replace it with a 20 or 50 watt solar pv and I'm trying to find a motor, to fit the exsisting housign which is around 6diameters. i guess i could rig it smaller, but does anyone knwo the replacemetn motor parts from the home depot solar fan? it would be a lot easier to use a product designed for that purpose than to try and rig a substitute?

    Bummer, I only know of 12 diameter fans.

    here's one that looks to be about 8 diameters
    istockphoto_9896407-anti-frost-orchard-fan.jpg
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • raydias
    raydias Solar Expert Posts: 68 ✭✭✭✭
    Re: Solar Electric for Attic Gable Fan

    Found this fan the other day and ordered one. Not sure what the wattage needs are

    http://item.mobileweb.ebay.com/viewitem?itemId=290589272664
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: Solar Electric for Attic Gable Fan
    Why reinvent the wheel ...

    http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&langId=-1&catalogId=10053&productId=100548465

    I found these 2 years ago at my local HD, they were at the time marked 50% off clearance. I added a second panel ( so the fan had two ) and installed a pair ( 2 fans and 4 panels ) in a building that was used for walk-in cooler, ice machine ect.
    Still works today and keep the temperatures in check

    For a house attic , they would work well IMHO

    Assuming the picture of panel is correct in relation to fan size, the panel looks to be only about 20-25 watts.

    What is the motor DC voltage and what current does it take at full rated run voltage?

    I would like to put in active fan to push heat at peak of roof down a couple of ducts to couple of under eve exhausts. I really wanted roof peak 'J' outlet vents for passive ventilation but don't trust them during hurricanes. I have full hip roof with vents all around under eves.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar Electric for Attic Gable Fan

    From the EBay link, claims:
    MSRP on this fan is almost 200$

    This is a very powerful exhaust fan at 3000 CFM.This is not a fan you want running right next to your head all day, it is really, really powerful.I don't know the decibel rating but it is really quiet for the amount of air it moves but any 3000 cfm fan is going to be a little noisy.

    Diensions: 16 x 17 x 3.5 inches

    If you look at a generic 3,000 CFM exhaust fan... this unit runs ~5.34 amps at 115 VAC...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • raydias
    raydias Solar Expert Posts: 68 ✭✭✭✭
    Re: Solar Electric for Attic Gable Fan

    I bought one of these and will be testing to see if it is viable for my parents back porch. It get's very hot in the afternoon since it is on the west side of the house and has a lot of windows. I ran it for a short while connected to a battery and it was moving a lot of air. It was a short test.
  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    Re: Solar Electric for Attic Gable Fan

    this youtube video shows that the motor used is 38v and powered by a 12watt solar panel. See 2:00 mark
    http://www.youtube.com/watch?v=7c7bzeUmqcc&feature=player_embedded#at=125

    I'll call them on monday and see if they sell the MOTOR only as a replacement part.

    these other two companies uses a 36v motor
    http://www.solaratticfan.com/pdfs/gable_attic_fan_sheet.pdf
    http://www.atticbreeze.net/AB_literature/specifications/TDS-1001.pdf

    seems 36 to 38v is common motor voltage for this application., and NOT 12v like many including myself assumed.

    Armed with that information I found this on ebay;
    http://cgi.ebay.com/ebaymotors/Flxible-Bus-38-VDC-Condenser-Fan-Motor-70-1885-00005-_W0QQcmdZViewItemQQhashZitem587ceab957QQitemZ380052879703QQptZOtherQ5fVehicleQ5fParts

    not sure how much current it draws but it seems to be about the same size physically for a good replacement and more expensive than I though $110 !
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Solar Electric for Attic Gable Fan

    Had some interesting experience with an attempt at removing sun induced heat from part of a building where I once worked. We installed a 1/2 HP (9 amp/120 volt) "barn fan" at one end, with vents at the other. That thing moved a lot of air fast, but to my surprise, made only a relatively small difference in air temperature. Nothing at all like I had expected, the heat gain was just too much. With that in mind, I can't help but wonder what difference a little 12 watt fan would make to an attic. Probably not much different than the $150 Wood Stove thermocoupler-powered fan. They look nice, and they do turn, but for all intents and purposes are next to useless at moving air.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Solar Electric for Attic Gable Fan

    I disagree with Wayne about the thermo-coupled Ecofans on wood stoves. I have one on mine and it works better (and is quieter) than the built-in electric fan. Keeps enough air moving to heat the whole (small) house even at -35C.

    But it sure wouldn't work for a greenhouse or attic. That's the tricky thing about "just add a fan"; it doesn't always work, no matter what size fan you add. The efficacy of it depends heavily on how the air moves, not simply how much. If you can't get complete air change because there's a direct in/out path then stagnant air lurks in the edges, holding heat and negating any positive effect.
  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Solar Electric for Attic Gable Fan

    I made a couple of my own. The commercially available solar gable vent fans are prohibitively expensive IMHO.

    I started with a 5W panel, and a 12V muffin fan. Spun up nicely, but too small. Then used a 10" 12V camping fan (Walmart $12) and a 15W panel. Worked much better.

    I then put a couple of muffin fans in the attic access door, helping cool the garage, and get more airflow in the attic.

    Details of my setup here: http://2manytoyz.com/solar.html

    I wish I could say it made a big difference, but it hasn't yet. I plan on adding another gable vent to the back of the house, allowing some laminar airflow through the attic.
  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    Re: Solar Electric for Attic Gable Fan

    absolutely why does a regular 110v attic fan cost $100, but a solar one cost $400 to $500? A solar panel might add $60 to the cost.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Solar Electric for Attic Gable Fan
    I disagree with Wayne about the thermo-coupled Ecofans on wood stoves. I have one on mine and it works better (and is quieter) than the built-in electric fan. Keeps enough air moving to heat the whole (small) house even at -35C.

    Glad yours works far better than the one's I've seen in operation. Not joking, not sarcastic, but totally serious. The several I've seen in operation (I take an interest in such things) had any airflow they produced, overpowered and swept up and away by the normal convection currents around and over the hot stove, with no apparent forward breeze, or airflow that I could detect. Thus my opinion.
    Again, glad yours works and demonstrates that obviously not all of them are scams.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Solar Electric for Attic Gable Fan
    Glad yours works far better than the one's I've seen in operation. Not joking, not sarcastic, but totally serious. The several I've seen in operation (I take an interest in such things) had any airflow they produced, overpowered and swept up and away by the normal convection currents around and over the hot stove, with no apparent forward breeze, or airflow that I could detect. Thus my opinion.
    Again, glad yours works and demonstrates that obviously not all of them are scams.

    I bet it's along the same lines as the other air moving problem I mentioned; all has to do with the configuration! I know Tony (icarus) uses them with success too, albeit he has his on the back of the stove and mine works better in front. My stove is backed up against a corner; haven't tried it with the "free-standing" stove at the cabin yet. I suspect that may yield disappointing results.

    The stove design may play some role in this as well. Nothing is ever simple, is it? :roll:
  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    Re: Solar Electric for Attic Gable Fan

    home depot brushless motors are 17v dc 750 rpm and 0.6amp current.
    powered by v930503 (tps 105-10) solar panel
    rated pwoer pmax of 10w
    imax 0.6a
    vmax 17.8v

    i googled the motor part # and only got links to the chinese company that made it.
  • tonystewart
    tonystewart Solar Expert Posts: 54 ✭✭
    Re: Solar Electric for Attic Gable Fan
    Why reinvent the wheel ...

    http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&langId=-1&catalogId=10053&productId=100548465

    I found these 2 years ago at my local HD, they were at the time marked 50% off clearance. I added a second panel ( so the fan had two ) and installed a pair ( 2 fans and 4 panels ) in a building that was used for walk-in cooler, ice machine ect.
    Still works today and keep the temperatures in check

    For a house attic , they would work well IMHO

    I have 2 of these with an additional 30 watt panel installed in my attic, they move a substantial amount of air with the additional panel and temperatures are much lower.
    Today in Lake Worth FL it's 93, attic air temperature is 100 used to hover at 125 prior to the fans.
  • Sparkletron
    Sparkletron Solar Expert Posts: 71 ✭✭✭✭
    Re: Solar Electric for Attic Gable Fan

    I agree with those who say that plug-and-play solar attic fans are too expensive, and that it's significantly cheaper to build your own. But for many of us, these plug-and-play fans are the perfect first foray into the world of solar. They're easily within any homeowner's budget, can be installed without professional (expensive) assistance, address a specific need that is measurable and quantifiable, do not require any additional outlays to be useful, and, generally, give homeowners valuable experience and understanding.

    I purchased U. S. Sunlight Corp's gabled vent model from Costco. The first time I installed it, I didn't realize how much the sun varied from one season to the next. My panel, installed in one season, was in shadow by the next. Lesson learned. More importantly, I was able to correct my mistake in a way that might not have been so easy had I started with a 5-kilowatt system.

    As far as the company, I've got nothing but love for U. S. Sunlight Corp; I was easily able to reach human beings, request parts, etc. The support was superlative. The product is solid.

    The product is not cheap, but it is complete. You quickly realize how useless a panel is without the proper mount, without the proper angle to the sun, without the proper wiring that can withstand intense UV rays, etc. There's simply no skimping here. For those with experience--sure--roll your own. But for those of us trying to get experience, a plug-and-play solar attic fan is the perfect 101.

    Finally--it works. It blows hot air out of the attic. It cools the attic. How can you tell? Install a wireless temperature sensor in your attic. They're not expensive. They'll provide you with the metrics you need to evaluate the system.