DC Ceiling Fans Worth It?

PorkChopsMmmPorkChopsMmm Solar Expert Posts: 189 ✭✭✭✭✭
We are finishing up the build on our off-grid cabin and I have started to look at ceiling fans. My original intention was to just use AC fans that have lights in addition to the fan component and use LED bulbs for efficiency. I have since found some neat looking DC fans but I have a few concerns about going with them. Namely, the extra cost per fan and if the fans can have lights added to them and if they need a dedicated DC switch box on the wall.

We have not yet closed the walls of our cabin in so I can add the DC wiring and if needed the dedicated DC wall switches but if the fans do not have lights I will need to rethink how we illuminate the room. For the additional cost and headache do you think they are worth it? I was going to have 3 ceiling fans and the costs of these fans over cheap AC models really add up. Here is an example of a DC fan (thanks MtnDon).

I was thinking of the Vari-Cycle model. The wall switches are so expensive!
http://www.thesolar.biz/RCH%20Fan%20Works%20DC%20Fans.htm

Comments

  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: DC Ceiling Fans Worth It?

    I have both, and given the choice, I would go with the AC only. The ubiquitous availability of AC fans makes options so much easier. Both of my fans use just about the same amount of power at similar speeds.

    If you are worried about inverter loses when the fan is the only thing on line you might have a argument for the DC, but using the 300 watt Suresine it really isn't much of an issue.

    Tony

    PS I generally dont think that ceiling lighting is a very efficient way of lighting, I personally prefer table and dedicated work/task lighting
  • PorkChopsMmmPorkChopsMmm Solar Expert Posts: 189 ✭✭✭✭✭
    Re: DC Ceiling Fans Worth It?

    Icarus, thank you for the reply. I have asked quite a few off the whole questions on this forum and I have always valued your response. AC ceiling fans it is! This saves me quite a bit of time and money.
  • PorkChopsMmmPorkChopsMmm Solar Expert Posts: 189 ✭✭✭✭✭
    Re: DC Ceiling Fans Worth It?

    Ok, quick update. I found these fans on backwoods solar that are only $108 a piece for the 12V version and they come with a battery powered remote control. This price is what I was looking for. Do you think we these prices it makes sense to go with DC? I will just need to run DC wiring to each fan location. Any recommendation for wire size to reach across a 32 ft wide cabin?

    http://www.backwoodssolar.com/catalog/fans.htm

    12v-ceiling-fan.jpg
  • BB.BB. Super Moderators, Administrators Posts: 32,018 admin
    Re: DC Ceiling Fans Worth It?

    Assuming a 45' run, 1.5 amps maximum, and 1 volt drop, the generic voltage drop calculator gives:
    • 45', 1.5 amp, 18 AWG -> 1.0 volt drop...
    If you run 14 AWG Romex (marked/tagged for DC at this time)--You can probably do whatever you want (fuse/breaker for 18 or 14 awg wire).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: DC Ceiling Fans Worth It?

    I have that exact same fan, from the same vendor in fact. I would not buy it again however (if I had 120 vac available, I bought mine before I had a real inverterand we were all 12 vdc). The battery remote is a pain in the ,,,,. Even with new batteries it either has to be nearly dark, or I have to stand on a chair to get it to respond. The vendor was good, and shipped me a new remote and the controller but it was no better. The fan also makes somewhat of a growling noise on slow speed.

    My concern with the remote is what happens when either the remote or the sensor fail? There is no way to field repair it. It does move plenty of air, and reverses fine.

    I wired mine with #12 romex with but # 14 would be fine.

    T.
  • Peter_VPeter_V Solar Expert Posts: 226 ✭✭✭
    Re: DC Ceiling Fans Worth It?

    FWIW I bought some DC ceiling fans (designed for RVs) that included a switchpate control that allows reversing and 3 speed adjustment.
    The switchplate mounts in a standard outlet box.

    I got mine on Ebay for about $20 each so it was worth it for me. I don't think I'd pay over $100 for DC fans though.

    This is similar to what I've got:
    12V Ceiling Fan
  • MichiganOffGridMichiganOffGrid Registered Users Posts: 11
    Re: DC Ceiling Fans Worth It?

    While these fans arn't real cheap, they do appear to be very energy effcient. http://www.gossamerwind.com/ This might not fit your application, but if someone else is looking for effcient AC ceiling fans, these would be an option.
  • SCharlesSCharles Solar Expert Posts: 123 ✭✭
    Re: DC Ceiling Fans Worth It?

    I bought one of the Vari-Fans a few years ago and we liked it so much I got another one. They run either 12 v. or 24 v. In 12 v. operation [as in our house], they use 0.4 amps or so. Very quiet, very efficient. Don't know how they'll hold up as we've only had them for two years. I have both 12 v. and 120 v. wire circuits run all through my house, so hooking them up was simple.
  • 2manytoyz2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: DC Ceiling Fans Worth It?

    Maybe I'm missing something...

    I just went to the Gossamer website to look at the power consumption of their fan, with the light off.

    Low, 16W
    Medium, 34W
    High, 68W

    Compare that to a fan I bought at Lowes (120VAC):

    fanwatts.jpg

    Low, 9.5W
    Medium, 26.3W
    High, 66.4W

    I've been using this fan for several years. Quiet, no hum, used nightly.
  • PorkChopsMmmPorkChopsMmm Solar Expert Posts: 189 ✭✭✭✭✭
    Re: DC Ceiling Fans Worth It?

    Robert, I am glad you posted. After checking out quite a few AC fans on the internet I saw that there really isn't a saving's in wattage -- at least that I can see. Maybe you gain efficiencies at the inverter that would you save you 10% to 20% (at least in my case with an older Xantrex 2.5 Prosine) but the cost of purchasing, wiring, and switches for DC fans is extremely prohibitive. I need 7+ fans in our cabin and I have found a sold one from Lowes for ~$60. To do the same thing with DC fans would cost quite a bit and would be money better spent on additional panels or a newer inverter.

    BTW Robert I have used your site as a reference guide for building my solar set up for the past year. Thank you for posting your projects -- it has helped immensely!
  • SilverbulletSilverbullet Registered Users Posts: 2
    Re: DC Ceiling Fans Worth It?

    My solution was to buy automotive type radiator cooling fans. I bought three. One for up/down flow for winter or summer and a second for cross flow and a third for redundancy. All three cost me $60.00 total on Ebay and were new in the package. They can move a LOT of air! Next, buy a simple control, usually available on Ebay, for about $25.00 each. You will have to buy your own box at Radio Shack to put them in. No wiring, just simple connections. Mount the fans with rubber grommets to eliminate any vibration.
    I have no clue why the 'Solar' ceiling fans are so expensive. I have been watching them for years and waiting for them to come down in price. When that didnt happen, I went with what I felt was the next best option. If you really want to get fancy, buy the automotive type fan and discard the blades, just using the motor to drive a set of ceiling fan type blades from a junk ceiling fan. Or, mount both ac and dc fans on the ceiling and use whichever you want/need. That way you have all the options. Running an inverter for any single source appliance makes no sense when you add up those lost watts over time.
  • BB.BB. Super Moderators, Administrators Posts: 32,018 admin
    Re: DC Ceiling Fans Worth It?

    Welcome to the forum Silverbullet,

    What kind of fan control did you use? I would guess you are not running the radiator fans at full speed.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: DC Ceiling Fans Worth It?

    Too bad they don't make 3 phase AC fans.......Or do they ??
    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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    Lots of DIY Renewable Energy Projects on ETSY : Solar Panel builds, Wind Turbine builds, Rain Barrel build,etc.  
  • BB.BB. Super Moderators, Administrators Posts: 32,018 admin
    Re: DC Ceiling Fans Worth It?

    They do--But apparently it is getting difficult to find used fractional HP three phase motors (many are being scrapped for copper/steel these days). Also, you may not find many that operate below 208/240 VAC.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • monolocomonoloco Solar Expert Posts: 103 ✭✭
    Re: DC Ceiling Fans Worth It?

    We are using Emerson Eco Midway fans and have been extremely happy with them. They claim to use only 17.5 watts on high speed, remote control, reversible, 6 speeds, super quiet.
    http://www.emersonfans.com/pages/Fan.aspx?Fan=Midway%20Eco
  • FanGuyFanGuy Registered Users Posts: 2
    Re: DC Ceiling Fans Worth It?
    SCharles wrote: »
    I bought one of the Vari-Fans a few years ago and we liked it so much I got another one. They run either 12 v. or 24 v. In 12 v. operation [as in our house], they use 0.4 amps or so. Very quiet, very efficient. Don't know how they'll hold up as we've only had them for two years. I have both 12 v. and 120 v. wire circuits run all through my house, so hooking them up was simple.

    I'm glad those Vari-Fans are working for you. I'd be interesting in hearing some of the pros and cons about the DC Vari-Fans.
  • FanGuyFanGuy Registered Users Posts: 2
    Re: DC Ceiling Fans Worth It?

    I know I'm late to the party here (by 3 years or so) but I'm curious about your power supply for this stuff. You mentioned solar on the roof, how is the dc solar getting to the appliances? Do you use batteries or MPPTs? The fan setups I sell are directly connected from solar but I'm interesting in learning about other ways to bring in the power and work it in for an entire house. This forum in very informative!
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: DC Ceiling Fans Worth It?
    FanGuy wrote: »
    I know I'm late to the party here (by 3 years or so) but I'm curious about your power supply for this stuff. You mentioned solar on the roof, how is the dc solar getting to the appliances? Do you use batteries or MPPTs? The fan setups I sell are directly connected from solar but I'm interesting in learning about other ways to bring in the power and work it in for an entire house. This forum in very informative!

    Welcome to the forum.
    You might need to read a few thousand posts to get the hang of things. :D

    Normally off-grid systems use batteries. The batteries supply the loads and are recharged by the solar when available. MPPT is Maximum Power Point Tracking and refers to a type of charge controller which charges the batteries. The point is to mitigate the time when power is produced (sunlight hours) and when it is needed (which may be any time). Batteries do this well. :)

    Sometimes it helps to familiarize yourself with all the terms. Here's some of them: http://forum.solar-electric.com/showthread.php?6136-Glossary
  • BB.BB. Super Moderators, Administrators Posts: 32,018 admin
    Re: DC Ceiling Fans Worth It?

    FanGuy,

    More or less, there are three ways to bring electric power to an off grid home:

    1) Simply connect a solar panel to a DC capable motor
    2) Solar panels charging a battery and using the battery bus power to a DC motor
    3) Use battery+AC inverter to an AC capable motor

    The all have their pluses and minuses.

    I like to look at the loads/needs first. So the motors in this case.

    DC motors fall into to a couple of camps. The universal/brush motor. Cheap, work, take variable voltage pretty well, and you can get things like a Linear Current Booster to better match the solar panels (sort of) higher voltage/lower current to the DC motor's lower voltage/higher current needed to get started, run at slower speeds in low light (LCBs are done mostly for water pumping). LCB's are not cheap, but they do work and no battery needed if you only need the fan/pump/motor to run when there is sunlight available. And brushed motors require brush replacement every X,000 of hours (and commutator cleaning/turning once in a while too).

    The second DC motor type are those with electronic commutation. Basically, the "brush/commutator" function is replaced with electronics. DC computer fan motors are a good example. Cheap, reliable, and simple to use.

    From what I have seen/designed, if you can get away with daylight only operation (water pumping, fan/swamp cooler, even now some A/C systems), your solar power costs will be about 1/4 of that of a similar off grid system with battery bank (losses, more panels, battery costs, etc.).

    If you need the power 24x7, then you are looking at a battery bank. And you have even more options.

    If we drop universal/brushed motors as being unreliable for long term use--Then we are looking at brushless DC motors and AC motors.

    The simpelist is an appropriate AC inverter driving an induction motor. The AC inverter may be around 85% efficient (if sized correctly) and all you need to do is make the solar array+battery bank ~1.18x larger to support the extra losses. Not a huge hit for the better reliability, the ease of sending 120 VAC vs 12 VDC longer distances, etc.

    AC induction motors however have about 20% extra losses because of the way they work--"Induction" of the magnetic field in the rotor of the motor. If you replace the rotor with permanent magnets, use a poly phase windings (typically three phase), and a poly phase inverter of some sort (H-Bridge as in DC computer fans, or VFD--Variable Frequency Drive in larger motor applications), you can save ~20% of losses that and induction motor would have wasted.

    Is it worth the time/money to go with the battery based "hi-tech" solution--It all depends. What is available (are PM fans available at reasonable prices), do you need the variable speed/soft start of a VFD, is the cost of a VFD worth it, etc.

    You pretty much have to do the research and go through the paper designs to see what will work best.

    In general, for specific applications, there are some neat tricks that can be done to make low cost Solar->VFD->3 phase motor applications very cost competitive (being done for water pumping).

    For the average off grid home, there are some DC fans out there that are very nice for small cabins with DC battery systems. As I recall, they generally are not cheap.

    But, once your power needs get over ~1,000 Watt*Hours per day, many times, it is better to just go with a 120 (or 230) VAC AC inverter. The reduction of current at the higher voltages just makes AC wiring so much easier. Plus deep cycle battery bank voltage can vary a lot over the day (from ~10.5 volts to 15-16 volts for a "12 volt system")--Which many DC appliances really have problems with.

    Putting an AC inverter (even a smaller 300 Watt TSW inverter like this one) will power most of the loads a small cabin/RV will need pretty efficiently.

    Just run everything on AC power. Most modern AC appliances with the Energy Star regulations are getting just about as energy efficient as native DC appliances. You only need larger AC inverters and battery bank when you start adding heavier loads (typically, installing a refrigerator is the break point between "small" and medium/larger off grid power systems.

    And, if you are interested in the whole AC/DC motor application--Take a look at these water pumping threads:

    WELL PUMP and Inverter QUESTION
    Wind/solar for large scale pumping etc (out of my depth!)
    could use knowledge - using Gould jet pump - transfering from 230vAC to ? DC (new link/thread 10/27/2012)
    Help required to design off grid system (information on possibilities to connect "standard VFDs direct to solar panels) (new link 1/13/2013

    And, general FAQ about Solar RE/Conservation, this thread:

    Working Thread for Solar Beginner Post/FAQ


    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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