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Whole house fan

Post in 'DIY and General non-hearth advice' started by maverick06, Apr 7, 2010.

  1. maverick06

    maverick06 Minister of Fire

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    Hi All,
    I grew up with a whole house fan, boy did I miss it when I moved! I am now about ready to install one in my house and am looking for some tips.

    I already have ordered the fan,
    [​IMG]

    30" fan blade
    Belt drive
    34" x 34"
    5700 CFM
    1/3 HP, 525W High, 4.1 amps - 400W Low, 2.8 amps
    2 speed wall switch
    Cools 1900 sq. ft. max
    34-1/4" x 29" shutter opening

    I will end up running some new wire to the attic space for it. Thats a hassle, but not a big deal. I am looking for tips for instalation. I am suppose to cut a joist for the instalation. i am a bit concerned about that. The house was built in the early 1950's with 16" center joists. Most places i read say to just cut the joist then frame it out. That doesnt sound right. Any suggestions! Sure dont want to cause any nail pops or worse doing this.

    Also any tips to minimize the vibrations? Or tips in general?

    I love having a whole house fan, but have never put one in before.

    Thanks
    Rick

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  2. vvvv

    vvvv New Member

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    Support the joist/rafter you're cutting with 2 2x4 pieces screwed to the nearby rafters so when you cut the rafter it wont sag.
  3. fbelec

    fbelec Minister of Fire

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    the way that i've seen them done is cut the joist. cutting one joist won't be any support problem. then use the same size lumber as to go from the the joist on either side of the cut one. nail to those two joists with a double piece of 2 by what ever size the joists are 2 x 6 or 2 x 8 or 2 x 10. do this on both size of the cut joist and nail the cut joist to the cross pieces you just put in. thats it. there is nothing you can do if the fan has a vibration or hum. normally they use a motor that is quiet. and as you know the fan blade makes enough noise that you wouldn't here the motor if it was humming. as far as circuitry for that fan, depending on the size it is, as in the amount of air that it pushes, will take anywhere from 4 to 8 amps. you can get by with a existing bedroom circuit if it takes 4 amps but if it takes 7 or 8 amps depending on the circuits existing load you might have to run a new circuit. a 15 amp circuit will be fine. if you have to run a new circuit the code is that the circuit be arc fault type. and the arc fault breaker should be the same brand as your circuit panel.
    oh, make sure that you have sufficient attic venting or the fan will make more noise than it should and won't push the air that it should also. i've seen it happen where the fan got installed into a small vent or ventless attic and didn't work right or not at all. if there is not enough venting to compensate for the air that the fan is pushing you will get a certain amount of air feed back thru the fan that you get air from the attic into the living space. you'll be able to tell. on a hot day run the fan. if you have feedback air you should be able to smell it. it will smell like your hot attic in and around your fan. good luck. whole house fans are great.
  4. fbelec

    fbelec Minister of Fire

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    btw if you didn't have one on you old fan there are companys that make a thermostat for whole house fans so if it were to cool the house off to much it would shut the fan. i've seen the on some older fans installed but i have not done the install so i don't know the brands. i could make one but it might be hard to explain.
    if you see one of these thermostats get it. well worth having for over night runs. by the time you wake up it's so cool you don't won't to get out of bed to shut it :bug:
  5. maverick06

    maverick06 Minister of Fire

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    Thanks for the input. That was my plan, its surprising how many manuals differ (I have been reading online) Most do not have you make a bridge piece. Most do not have you use double headers. Most dont have you reinforce the remaining joists...... I plan on doing all that though... wood is cheap. Do it right the first time. Thanks for the input. I am thinking about (prior to instalation) Welding together the bolted frame and taking the propeller blad off and balancing it. I have a MIG welder in the garage and balance my RC airplane propellers, so that should help minimize some vibration. it should be easy to do and a little effort ahead of time might save a lot of agrevation later.

    I have been looking for a switch that lets me select speed and hours to run, cant find it. The fan specifies no rheostats either. Unfortunatly the box I plan on putting the switch in is only large enough for a single size switch, but I have to run new wire (high/low/ground/neutral).
    Thanks for the input

    Rick
  6. Tony H

    Tony H New Member

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    I don't know if anyone mentioned it but before you cut the joist but haver it measured and marked put a 2x4 across the span where you are cutting to take up any load and keep it aligned while you build the inner frame.
    The other thing for vibration isolation between the fan frame and mounting install some hi density foam it will help a bit.
  7. fbelec

    fbelec Minister of Fire

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    tony i'm not sure of the foam your talking about, but wouldn't the foam get eaten up from the vibration of the fan?
    i've tried a tire tube between a noisey bath fan and a joist and there was very little difference. if it's vibrating and the foam gets eaten wouldn't the frame rattle?
  8. maverick06

    maverick06 Minister of Fire

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    I've thought about that.... rubber may help better than foam. I am inclined to think that if I install everything with screws, not nails, that should prevent vibrations... And making sure everything is very tight together should help.... I think....

    It will make noise regardless, but I would like to go in making the best decisions I can.

    Thanks for the input so far!
  9. semipro

    semipro Minister of Fire

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    I've installed and used a few of these. A few thoughts:
    - If you're installing in a hallway the walls on either side will likely support the joists well. You many not need to worry about the one you cut for louver clearance.
    - Belt driven fans like the one you chose are really good about not vibrating. I wouldn't worry about vibration unless you experience it.
    - A timer or thermostat is real nice on one of these. Its better to get up in the morning with this thing already off.
    - Find ways to latch your bedroom doors open. When this thing is running and a window is open in a room the door can slam shut and knock you out of bed.
    - Consider filtering the air entering the house though windows. The airflow created by this thing will bring in a bunch of dust.
    - Make sure you have adequate attic ventilation either by continuous soffit vents, gable vents, or ridge vents.

    Good luck.
  10. Czech

    Czech Minister of Fire

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    Does anyone know if these can be mounted through the wall? I've always thought one of these would take care of most of our cooling needs during the summer months, split level upper floor is all open with cathedral ceiling, thought one up in the peak through the wall may be a good investment? If so, are they filtered at all?
  11. vvvv

    vvvv New Member

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    The science of this application is simply to create a wind in the house so you feel the cooling effect. The fan should be located centrally enough so that it draws equally from each opened window opened so to feel the breeze & yes you can install an exhaust fan anywhere but exhausting to the S & inhausting from the N sounds more ideal. Factors to consider are indoor temp vs outdoor temp, outdoor pollutants & pollen +, etc.? A well insulated/vented attic doesn't need mechanical ventilation I think.
  12. fbelec

    fbelec Minister of Fire

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    you wouldn't want to put one of these in your familyroom. they are to big and loud. they not super loud but because they're 30 inches square they make a lot of wind noise. and in the winter it would be a source of great draft. these are made to be installed in a central hallway location. they are great. makes it seem like a breezy night.
    there is no way to filter the air that comes in unless you put filters in every open window or door.
    if you are just one person or a couple it might be cheaper to run a small window air conditioner. air conditioner 5 amps when the room reaches temp the 5 amps drops to about 1 amp. until the temp in the room goes up and then 5 amps again until the room cools
    running the fan all night or say 5 or 6 hours might be more electric burnt. the fans that i wired are in the 5.5 to 6.8 range constant draw until shut off.
  13. Czech

    Czech Minister of Fire

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    It just dawned on me, call me thick. These push air OUT! Now I got you! Could not figure out why you'd want all the hot summer attic air in your house.....
  14. LLigetfa

    LLigetfa Minister of Fire

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    If you look close at the inside trim, you can see there is a notch in the middle. This is to allow the joist to be notched out slightly and not cut out entirely. The fan is then mounted above the joists in a boxed curb.

    To eliminate vibration sound travel through the joist, you could hang the boxed curb from the rafters and couple it to the joists with EPDM rubber.
  15. semipro

    semipro Minister of Fire

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    I believe the motor on this unit is isolated with rubber mounts and since its driven by a belt, vibration is minimal. We've used a similar unit installed in a hallway and vibration was not a significant issue. The units that are direct-drive are much more prone to vibration.
  16. woodsmaster

    woodsmaster Minister of Fire

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    If you cut a cieling joist, by code you are suppost to double the joist on each side of the cut one. The boards supporting the cut joist should also be doubled. You may want to consider an insulated hood to cover the fan in the attick to control unwanted heat loss in winter.
  17. Hunderliggur

    Hunderliggur Minister of Fire

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    Just make sure if you cut you are cutting a joist, not a truss. Trusses do not like to be cut! If there are diagonal braces from the "joist" to the rafter, attached probably with flat plates, it is a truss.
  18. fbelec

    fbelec Minister of Fire

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    yep thats right those things are like leaving a window open a crack. easy to make. 2 inch foam panel, glue, done.
  19. maverick06

    maverick06 Minister of Fire

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    Well i got it installed!

    I ended up having to cut 2 joists. I believe I framed it out pretty well. Boy the old joists in the attic must have been made from endagered hardwoods back in the 50's Had to use a lot of screws becuase a lot of the attempted naiils just bennt on the first hit! The fan works well, the manual says not ot use a rheostat, the switch has a high /low setting though. High produces a modest amount of noise, rumbly, not a typical high speed fan noise. The low speed is awesome and really quiet! I have a split level and was unable to install it in the upper hallway due to stuff in the attic, but installed it on the center level, workes great, pulls a lot of air. The fan is quite nice (4 blades, not 6 though). I will have to build the foam box before winter though.

    I now have to figure out a way to latch the bedroom door open about 2 inches... enough to allow for airflow... but not enough for the cat to get in! but one thing at a time. This is great, i really expect for it to make a wonderful difference (I grew up with one and am excited to have this in the house)!

    The installation wasnt fun... but it is in. I am also pretty confident that the house is massively overbuilt... should really help keep us cool without running hte AC. On high it pulls 530watts, and on low it pulls 390 watts. That is really cheap to operate! The centeral air is on a 40amp breaker.... and a window AC is about 1200 watts. While those would cycle on and off this is definitly the eay to go, at least for where I live in the country!

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]


    Rick
  20. fbelec

    fbelec Minister of Fire

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    nice job. looks like it's around cthe corner from the bedrooms. that should be good for sleeping
  21. daveswoodhauler

    daveswoodhauler Minister of Fire

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    Placement is great as well, as you are going to pull up the cooler air from the lower level of the house.
    Looks cool.
  22. vvvv

    vvvv New Member

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    I'm wondering if you have enough gable venting to suit the fan's cfm. If not the attic will become pressurized & push the heat down?
  23. LLigetfa

    LLigetfa Minister of Fire

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    To latch the door open, you need a door stop that holds in both directions like this.

    [​IMG]
    ...or one of these.

    [​IMG]
  24. maverick06

    maverick06 Minister of Fire

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    Oh, no worries there. Lots of attic space, so there are 2 gable vents and soffet vents. Arguably there might not be enough venting space there, but the entire roof has a ridge vent (70 to 80 ft)! So that should be massively adaquate. Thanks for making sure of that, it wouldnt be any fun to have that problem!

    Love the ideas to stop the door halfway! I will have to see if homedepot has something like that!

    Already had it on for about 30 min today, so nice. Today wasnt for cooling the air, but just bringing fresh air in.

    My wife is excited too, apparantly the matha stewart magazing just had an article saying a whole house fan can save up to 90% AC costs (my guess is that is awfully generous where I live), but point taken, its cheap and socially acceptable. So thats good! Might think about seeing if you can find that article if you are interested in selling the idea to your other half!

    Thanks a lot for the assistance guys!
  25. begreen

    begreen Mooderator Staff Member

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    Nice neat job down below, now get some staples in that romex and neaten it up in the attic. Seriously, those loose wires can be a hazard and are not to code.

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