DC Vent Fan with Therostat Switch?

StevenB
StevenB Solar Expert Posts: 71 ✭✭✭✭
Can someone point me in the right direction, for getting an inexpensive little DC vent fan with some sort of thermostat switch, for my battery barn? I should call it a battery shed.....6 wide x 8 long x 8 high. Houses batteries, inverter, controller, breaker boxes etc.
Since I have AGM batteries, it's more to cool it down a little, then vent fumes.

Thanks
Steven

Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    they really don't need vented because they are warm, but only vent when voltages are exceeded beyond the manufacturer's recommendations. this is an overcharge and is usually minor even for eq charges. problems will occur if no regulation is present so always have a controller on an agm battery even if the panel is small in comparison to the ah rating of the battery. have a battery temperature sensor to compensate for small voltages differences needed for proper charging when temperatures change. this is a must imho.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    Go to your local computer recycler/repair shop and you can get dozens of fans for next to nothing. Wire in a simple bi-metal on on rise t-stat.

    Although I agree with Neil,, unless it gets too much solar gain for example,

    Tony
  • StevenB
    StevenB Solar Expert Posts: 71 ✭✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    Sorry I wrote to quickly.
    The "it" in "it's more to cool it down a little, then vent fumes"...refers to the shed itself. I want to locate a 12v fan with frame to mount in the wall of the shed............it's summer and the shed is hot inside.

    I don't know if a computer fan would move enough air.

    I don't know what a simple bi-metal on on rise t-stat is, I'm afraid.
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    The bimetal tstat is just a basic/simple thermostat that uses a bimetal strip instead of mercury bulb or other switching mechanism. I work in the HVAC field, we use them often for unit heaters, ventilators for mechanical rooms, and such. "on on rise" means the switch contacts close when the tstat gets hot. There are a lot of these that are "on on fall" because they do tend to be used primarily for heating. There are models that have three terminals, and can do heat OR cool.

    They are also commonly called "snap action thermostats". If you do a search for that on Grainger.com or Kele.com (two places I use at work) you can find some examples. I tried posting a link to one at Kele, but they use some funky scripting that doesn't let the link work...

    I have a few computer fans that move a ridiculous amount of air. But a couple of those also pull a ridiculous amount of current! So be sure to watch that as well. Don't bother with the 3" fans, common on smaller home computers. Look for the 4" or even 6" models. They move a LOT more air and are a LOT quieter. They also can be found in low-power versions.

    My Dell server had one of the ultra-powerful fans in it. The thing could move a lot of air, but it pulled a whopping 2 AMPS! Couldn't believe it. Loud too, I could hear it throughout the house. I found another fan that still effectively moves the same amount of air, but is whisper quiet and only pulls about 200mA! Can't produce the suction of the other one, but I didn't need that anyway.

    Another idea I got from another forum (fieldlines.com) is to go to an auto salvage yard and get a radiator cooling fan from a wrecked car. The newer front wheel drive models use 12V motors for the fans. They'll move a lot as well, although they are probably going to pull a whole lot more juice too. Reducing the voltage some (or maybe putting two in series) would reduce the speed and thus make them run quieter - they can be pretty noisy at full tilt.

    I used to have a squirrel cage blower from an auto AC system, relatively light on power but lots of airflow! It was from a '71 VW bug of all things, I don't know if current vehicles use that style fan or not... (Yeah, AC in a bug. Blew my mind when I first saw it! :D )
  • StevenB
    StevenB Solar Expert Posts: 71 ✭✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    Great lead to Granger....tech support was very available.
    Best I could find was .2 amps @24 volts Axial Fan. I've got tiny starter system right now, that I will be building on....but I want to keep the battery draw way down obviously.

    What do you (or anyone) think of .2 amps @24 volts? I'm a beginner with very little perspective on this stuff.

    I hope it's ok to list these products...pretty obscure hard to find stuff. Here's links to fan and thermostat.
    http://www.grainger.com/Grainger/items/4WT39
    http://www.grainger.com/Grainger/items/4E116
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: DC Vent Fan with Therostat Switch?

    To be honest--if you can, use natural convection (vents into the shed down low, peak roof vents and/or large dia plastic pipe from top of box thru roof, etc.), roof top wind turbine, and other no-power methods to extract the heat and the fumes...

    All of this power adds up:

    24 volts * 0.2 amps * 10 hours = 48 watt*hours

    That represents, very roughly, the entire output of a ~24 watt solar panel for most people.

    If you have a large system, then the DC fan does not represent much load--but if you have a small system--you probably don't even need the fan as the batteries will not self heat, and hydrogen gas will want to rise and be vented anyway by natural means if given the chance.

    I would measure the temperatures the battery bank actually reaches before I would install a power vent. Installing the bank at ground level, and in contact with the ground, is probably enough cooling.

    People that live in areas with very cold temperatures (hard winters)--probably more often need an insulated battery box to keep the batteries "warm" to prevent freezing (a problem as the batteries become discharged) and prevent to capacity loss from the extreme cold temperatures.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    What about just a simple solar power (no battery) fan, unless you do a lot of late night equalizing. Sun ON=fan ON
    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 ,

  • StevenB
    StevenB Solar Expert Posts: 71 ✭✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    jeez Bill....the math is pretty sobering. Again, I see I need to concentrate on learning the basics better to "play the movie ahead" for myself.
    Mike, I've seen vents with their own little panels to operate, but too expensive so far. I've got the Home Depot version with Halogen light for inside.

    I believe I'll check the lube oil in the chain saw, put on my blindfold, and take a running start at the side of the shed......first place the saw hits will be perfect.

    Thanks Bill. As newbie, this stuff gets so intoxicating....it's easy to miss the obvious.
  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    Re: DC Vent Fan with Therostat Switch?

    I concur with Bill try and using passive cooling and heating when designing new projects.

    I applied this from the beginning when I designed my solar shed. vents low for incoming cool air and at roof top to create a thermal flow .

    Batteries are located on the rear back wall where the higher vents are

    Considering the Black Solar Panels are the roof you can imagine how much Spanish summer heat they absorb.

    Proof is in the pudding, I ve just recently got three kittens Smudge , Tiger, Bandit, who were relocated and kept in the Solar shed 4 a week, they have now been let out now via a catflap at will and guess where they are during the day, yeah in the solar shed. (Still have vermin problem :grr not 4 long though)

    Passive Cooling works KIS To prove the point its 4 oclock here sunny day outside its 34 c or 93 F Ive just gone in the Solar Shed where my XW 60 CC reports the batteries are in Absorb stage at 37 c or 99F . Ive also just taken this picture (no 4) in the Solar Shed to prove it the kittens are cooler in here

    So a couple of low grills and a roof vent or 2 should be better that small fans

    HTH
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    Put the venting on the 'shaded' side of the building, and insulate the roof. You'd be amazed at the difference that will make. Insulation can keep heat out as well as in.
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    I must be doing something wrong. Or there's something I'm just not considering here... I do like the idea of passive cooling, but I'm just not getting any success with it. In particular, with my attached garage, where the battery bank and other gear lives.

    So hot air rises, my very roomy attic with steep-pitch roof is (so I thought) well ventilated - gable vents on north and south ends, two of those wind-powered turbines at the peak, lots of eave vents all the way around the house. But the attic is a blast furnace in summer, and if I open the ladder to the attic, I will get hot air flowing DOWN the ladder into the garage! Even if I all the doors are closed, so not like there's a bunch of airflow in the room. Similarly for any other hole in the ceiling.

    What's up with that? Do I need more vents at the peak? (I figure a ridge vent would probably be best - and will probably do that when I reroof, but that's not going to be for a while.)

    It would be nice to be able to just vent into the attic and draw fresh air through an outside door, but right now I'm more likely to be heating the garage...! Thus I've been more focused on low-power fans to try to ensure the air moves the direction I intend.
  • StevenB
    StevenB Solar Expert Posts: 71 ✭✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    Well one of my Carpenter friends essentially told me "you idiot, why don't you put louver vents in the peak, like your house, then see what else you need?! So we are doing that. Duh. Like I say all this for a newbie like me is intoxicating, and hard not to over think sometimes.........especially when I should be spending all my time on the basics.
    By the way don't post anymore stuff about moving cats to the battery barns.....my cat happen to be reading over my shoulder....he's been pretty depressed since that.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: DC Vent Fan with Therostat Switch?
    RandomJoe wrote: »
    I must be doing something wrong. Or there's something I'm just not considering here... I do like the idea of passive cooling, but I'm just not getting any success with it. In particular, with my attached garage, where the battery bank and other gear lives.

    So hot air rises, my very roomy attic with steep-pitch roof is (so I thought) well ventilated - gable vents on north and south ends, two of those wind-powered turbines at the peak, lots of eave vents all the way around the house. But the attic is a blast furnace in summer, and if I open the ladder to the attic, I will get hot air flowing DOWN the ladder into the garage! Even if I all the doors are closed, so not like there's a bunch of airflow in the room. Similarly for any other hole in the ceiling.

    What's up with that? Do I need more vents at the peak? (I figure a ridge vent would probably be best - and will probably do that when I reroof, but that's not going to be for a while.)

    It would be nice to be able to just vent into the attic and draw fresh air through an outside door, but right now I'm more likely to be heating the garage...! Thus I've been more focused on low-power fans to try to ensure the air moves the direction I intend.

    1). Those roof turbines are worse than useless.
    2). Yes, a ridge vent is the best way to go - along with full eave venting. You need a lot of opening to let the air out once it gets hot as it increases in volume.
    3). The heat blows down out of the attic because the hot air is pressurizing up there - a sure sign of insufficient venting.
    4). How's the insulation? It keeps heat out as well as in.
    5). Don't vent the garage into the attic, just vent it.

    Air movement isn't simple. The gable end vents are nearly never adequate, and without sufficient outlets the eave vents don't do much. Ideally you want the air coming in low at the eaves and exiting at the highest (hottest) point, i.e. the ridge. End vents rely on pressure build up or stray currents to draft air - not very efficient.

    Does this help?:D
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    Great photos of the shed, I don't think we've seen them before.

    Are the panels the roof, or is there roof structure under them?
    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 ,

  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    Re: DC Vent Fan with Therostat Switch?

    They are the roof, theres twelve now, and opps have i shown them b4, well threads get repeated, and i think pictures help, the puddy cats was a new photo:p

    I expect buddys to question thier idiot mates dooh :p

    For clarification your my buddy Im the idiot;)
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: DC Vent Fan with Therostat Switch?
    1). Those roof turbines are worse than useless.
    ...snip...
    Does this help?:D

    Yes, actually, it does! I had long wondered about those turbine things. They are everywhere around here, so I figured they must do something, but apparently not. I'll have to think about what to do up there. I've also thought about radiant barrier, all the other stuff, but I think getting the ventilation up to snuff might be more important first.

    Insulation is decent, I was about to say "very good", and it is compared to most houses around here, but compared to "proper" insulation not really... 6-8" blown-in rockwool, covers the joists plus a bit in areas. Certainly the house feels nice, and the AC doesn't run a lot (again, compared to other houses I've been in!) but can definitely be better. I have to compromise though - I use the attic for my ham radio antenna cabling and other hobby purposes so can't just bury it in feet of insulation! (Well... Don't want to... It's nice having so much room up there!)
  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    Re: DC Vent Fan with Therostat Switch?

    Mike Ive edited my last post Im not perfect;)
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    Run a length of 6" flexible drain tile in the attic, put all your antenna wires inside it,, along with a pull string,, then insulate the hell out of the attic. 6" of blow in rock wool, cellulose or fibreglass is pretty marginal,, ~r15-20 max. Most modern codes require R-40. There really is no such thing as too much,,, as long as you have proper venting,,, both for heating load,,, as well as cooling load,

    Tony
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    This type of kit works GREAT. I've installed a few and I was impressed (and I'm not easily impressed). They are less than half the cost of the plastic "solar powered roof ventilators"...and they don't need a big hole in the roof.


    This is the exact kit I've personally installed.

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

    It comes with a 10w PV and they are pre-wired to add a second PV. When I bought them, they were sold Fan and PV as seperate units, now it looks like they are selling them together. On one house I installed 3 of these, so naturally I had to try one of them with two panels hooked up.

    The second panel definitely made it go go go - but it wasn't worth it since the gable end vent had a screen on it and it seemed like with two panels the fan was producing more than the vent could flow. With 1 PV the fan-vent flow seemed like a perfect match.

    When I installed these, I cut a piece of 1/2" plywood to cover the vent, and cut a hole in it for the fan. Then screw the fan to the plywood, and screw the plywood over the vent. That is what the instructions recommended, and I tried it both ways and it did flow more with the plywood (subjective impression standing outside the vent with a ladder - still it was noticable).

    With three of these, we ended up having to add some more intake vents because the attic crawl hole in the hallway of the house was whistling as air was sucked past the crawl hole door.



    Here's a similar kit.

    http://www.lowes.com/lowes/lkn?action=productDetail&productId=41125-228-SG8&lpage=none
  • StevenB
    StevenB Solar Expert Posts: 71 ✭✭✭✭
    Re: DC Vent Fan with Therostat Switch?

    In my battery barn I used 3/4 rigid foam with reflective surface turned outward....because I wasn't going to want fiber residues floating around.

    ....but I also started this thread asking for help eliminating heat....so obviously it's not adequate without the ventilation put in.
  • StevenB
    StevenB Solar Expert Posts: 71 ✭✭✭✭
    Re: DC Vent Fan with Therostat Switch?
    niel wrote: »
    they really don't need vented because they are warm, but only vent when voltages are exceeded beyond the manufacturer's recommendations. this is an overcharge and is usually minor even for eq charges. problems will occur if no regulation is present so always have a controller on an agm battery even if the panel is small in comparison to the ah rating of the battery. have a battery temperature sensor to compensate for small voltages differences needed for proper charging when temperatures change. this is a must imho.

    I just installed the battery temperature monitor cable onto the Xantrex a few minutes ago.
    Battery temp compensation is set for .108 V/C
    Hot day and I havent put the battery barn vents in. XW Config says my batteries are at 31C - 90F (I put it on the one connected to the positive lead to Inverter)...

    It exceeds the spec for the normal operating range for the battery...is this just an issue of slightly less efficiency, or more concern than that?

    Below is the battery spec:
    Capacity 100 Ah @ 20 hr. rate to 1.75 volts per cell @ 77°F (25°C).
    85 Ah @ 10 hr. rate to 1.80 volts per cell @ 68°F (20°C).
    Operating Temperature Range Discharge; -40°F (-40°C) to +160°F (71°C), Charge; -10°F (-23°C) to +140°F (60°C).
    (with temperature compensation)
    Nominal Operating Temperature Range +74°F (23°C) to +80°F (27°C).
    Float Charging Voltage 13.5 to 13.8 VDC/unit Average at 77°F (25°C).