Pushing heat back down 16' ceiling

[trackwelder]

Guys here is my problem I currently rent a shop space aproximately 30'x50'x16' with no insulation and block walls. This shop is heated with a 150,000 btu waste oil heater and the bottom half rarely gets warm enough to be comfortable. Just wondering if a few ceiling fans would make any difference.

 

[rickairmedic]

Yes but you actually want to run them backwards ( I know sounds crazy ) but this will pull air up off the floor and spread it across the roof and down the walls . Then it hits the floor and starts all over again .


Rick

 

[trackwelder]

Rick, is there any distance from the ceiling that would be most effective?

 

[rickairmedic]

Now that is a good question and I dont have an answer for it . I would say you would want them within a foot of the ceiling to be most effective at pushing the air out towards the walls .


Rick

 

[930dreamer]

I have a HD industrial fan, I used one of the rods that came with it(longest) I believe. I have it set to push/pull air down from the ceiling.

 

[Racecarl]

My Dad used to work in a shop heated with forced air and it would be 40 degrees on the floor and 90 on the ceiling. They had a sheet metal shop make some ducts that ran from the center of the peak, down the sidewall, and vented on the floor. The shop had 5 or six bays and I believe they installed four of these units. They made a TREMENDOUS difference.

The shop I work in has ceiling fans and they don't seem to help alot--still pretty cold on the floor and hot on the ceiling.

 

[Vincenthdfan]

I used to have (ex-wife and her boyfriend have it now ) a 30 x 40 pole barn with a double barrel woodstove I built.

That stove got nice and toasty in no time, but all the heat went up in the rafters.

Solution? Two ceiling fans running backwards...they pulled that heat right back down where it needed, really worked great!

I put extended length pull chains with handles on the ends down to arms reach (but above head height) so that I could reach up and adjust the fan speed with a quick tug.

Simple but very effective.

 

[LocoCoco]

Now that is a good question and I dont have an answer for it . I would say you would want them within a foot of the ceiling to be most effective at pushing the air out towards the walls .


Rick

I would say the opposite and would think that the fan would be best 2-3' from the ceiling. Reason being is in order for the fan to blow air down it needs to receive air from above.

No different than a boat propeller having to be below the bottom of the boat. If it were above the hull but still under water it may work at idle, but anything more and it would just create negative pressure and go nowhere.

Also, looking at commercial buildings where headroom isn't an issue (malls, arenas, the lobby in the office building I'm in right now), from what I've noticed the fans tend to be a few feet from the ceiling.



LC.

 

[Cast Iron Nuts]

Track

Try looking into Canarm prop fans most likely 36 inch with an 18 inch downrod. You can then wire them individually to a speed controller mounted on the wall ( which will give you complete control over the the speed you require ) or hook them up to one speed control all at the same speed but still controllable . I would look at installing at least 2. Take a look at the model that is reversible and has a forward function this way you have options in the summer months.

 

[Charles (in GA)]

Yes but you actually want to run them backwards ( I know sounds crazy ) but this will pull air up off the floor and spread it across the roof and down the walls . Then it hits the floor and starts all over again .


Rick

This I will disagree with. In a room (small, in a house) with an 8 or 9 foot ceiling, it might be helpful to do it this way, but simply put, the most efficient way to make the heat go back to the floor, is to simply blow it down there. If the fan is set to blow up, it will not **** cold air from the floor, it will **** moderate air from the area two or three feet below the fan, and the air will circulate up at the top of the room. The floor area will stay cold. If you FORCE the air to the floor with a down blowing fan, it will be much more effective.

In fact, I don't even think the Big *** Fans can be reversed, not sure, but I believe they only blow down, and this is one of their claims to fame, is in tall areas (warehouses, etc) that they can get the heat back to the floor.

As far as fans, you have an area large enough and tall enough to justify some powerful fans. THIS THREAD discusses 60" Home Depot ceiling fans and will be worth looking at. (these are only reversible by getting up to the fan and loosening a set screw and raising the cover on the down rod directly above the fan to access a reversing switch, not something you want to do very often)

The fans shown above are the HD 60" "industrial" fans. They come with a 4 speed plus off, controller. The controller will only work one fan, it will burn up if you try to run more than one on it. The fans come with 6" and 18" downrods, which I threw in the junk pile. I fabricated 4 ft downrods from USA made 3/4 galvanized water pipe, drilled the cross hole for the pin that goes thru the pipe and ball, and drilled and tapped for the ground wire connections, works perfectly. There is also a safety cable inside the downrod, as is specified by the manufacturer. They are mounted about 15 ft above the floor.

The lower switch box on the right is the fan controls. Master switch on the far right, supplies power to all three fan controllers (the white sliders) and then to each fan.

Charles

 

[rickairmedic]

CHarles that makes sense looking at it . My area is residential ( dont do much commercial work . ) True in a home situation where you have lower ceilings the fan blowing on you will make you feel cooler but in a shop situation such as this I believe you are right .


Rick

 

[kbkna]

Charles, How tall are your ceilings and how far apart are the fans? How big is that gangbox? Looks really sharp!

 

[sneezer41]

the most efficient way to get the heat off of the ceiling is to not let it get there to begin with. direct the air out of the heater down, use a sheet metal duct if you can. My work building has a home type hot air furnace hung high on the wall, ducted 10 feet off of the floor with just little elbows pointed down. Ceiling temp was 85, floor was 60. ran flex 6 inch duct from mcmaster down to the floor[as in to the floor!] and now there is barely noticeable temp difference.

 

[Cast Iron Nuts]

Check out canarms web site you can get a general idea from there what size you want and how many cfm you want to move. Selecting the correct speed controller by the amount of amps your going to use you can wire in multiple prop fans to these controllers without worrying about burning them up. Plus the basic fan 36 inch one direction including speed control is about $ 65.00.

Big *** fans come withe big *** price tags

 

[Charles (in GA)]

Charles, How tall are your ceilings and how far apart are the fans? How big is that gangbox? Looks really sharp!

The upper box is a formed, welded box, 5 space, with 3/4 and 1" knockouts alternating. When I went to get the other one (from another supply house, I was pee'Oed at the first one), I got a drawn steel 5 space, same 3/4 and 1" knockouts. I had to use reducer washers to install the 1/2 EMT, they work surprisingly well.

Switch face plate was pre stamped for five switches, I just blanked off the outboard two. The lower box I got a blank face and scribed out and cut and filed out the switch and fan control positions. Those 5 space boxes are EXPENSIVE, something like $40 each.

Top one is mounted on spacers to make the 1" ****** that goes to the panelboard align with the knockout. The fan box is mounted on some thin Unistrut pieces that hang down from the same bolts that go thru the spacers. Its very solid.

The peak of the building is 21 ft on the outside, 16 ft eave, which is about right as the fans have 4 ft downrods and are 15 ft off the floor and then you have the thickness of the purlins and sheetmetal, makes about 21 ft.

Cannot remember the spacing off hand, I have a sectional garage door that made it impossible to evenly space the fans 20 ft apart (and ten foot from each end) so the three fans are fairly evenly spaced in a 40 ft area. I put the closest fan near the garage door opener, but with enough swing room in case something happened, and put the fan down at the end of the building far enough from the wind braces to again, prevent any accidents if the fan were to swing around.

Charles

 

[Charles (in GA)]

This shop is heated with a 150,000 btu waste oil heater and the bottom half rarely gets warm enough to be comfortable.

What brand of heater? Did you install it or was it already installed? Do you like it?

Charles

 

[Charles (in GA)]

Fan downrod closeup.

Fan mounting

Fan mounting and 4" box cover.

Fan 4" box

4" box is attached to the unistrut with two 1/4" bolts into unistrut nuts in the channel. In addition, a metal strap passes over the unistrut and has two long 1/4" bolts that pass down thru the box, thru the cover and thru the fan mounting bracket and secured with large washers and self locking nuts. The fan bracket is attached to the cover, and the cover is attached to the 4" box with the usual two corner screws. In addition, a safety cable from the fan comes up thru the downrod and passes out and is secured around the unistrut mounting. It can be seen in the second pic (fan mounting) Not a big cable, but hopefully stout enough to hold if something comes apart.

Charles

 

[trackwelder]

What brand of heater? Did you install it or was it already installed? Do you like it?

Charles

It is a Cleanburn. I bought it off craigslist last winter with the hope of getting away from the salimanders. After about 5-6 hours of run time the bottom half of the shop temp gets into the fiftys.

We had Cleanburn units at work that got replaced with energylogic and the guys that maintain them do not like them. They say that cleanburn furnaces are easier to maintain. I personally would stay away from any heater that has a compressor on the unit. The compressor running is extremely annoying to me from being in other shops that have that style. I just ran a drop of my hard line.

I really like it and highly recomended it.

 

[nickleone]

I rember seeing a fan(circular) with a long plastic tube(light weight like plastic drop cloths)
hung in the rafters with the tube venting at the floor. It sucked hot air in and pushed it down to the floor. A couple of cheap window fans and some plastic sheeting would be a DIY project.

Nick

 

[Charles (in GA)]

I rember seeing a fan(circular) with a long plastic tube(light weight like plastic drop cloths)
hung in the rafters with the tube venting at the floor. It sucked hot air in and pushed it down to the floor. A couple of cheap window fans and some plastic sheeting would be a DIY project.

Nick

Not so sure the window fans would do it. but a trip to a HVAC place would probably yield a squirrel cage or two from smaller home furnaces. make a restrictor plate to keep from overspeeding the fan and as mentioned, some plastic sheeting formed into a duct with some kind of metal ring at the bottom to give it shape, and weight.

Couple of squirrel cages mounted in the rafters probably would throw the air down to the floor without any help.

Charles

 

[fatboyf150]

http://www.bigassfans.com/

 

[trackwelder]

I plan on mounting a few home depot fans and see how they work.

 

[kbkna]

Thanks again Charles for the info and pictures. Add another project to my list.

 

[bmwpower]

14+ foot ceiling. Forced air from the ceiling.
2 ceiling fan set on push mode.
Works for me.

 

[pdham]

I recently worked on this issue at work and found good info in the graingers catalog

 

[Charles (in GA)]

Looking in the Grainger catalog, I find several fans that are quite similar to the Home Depot industrial fan. The HD 60 industrial fan, according to the box moves 10,000+ CFM of air. Similar Dayton 60" fan (both are three blade) supposedly moves in excess of 40,000 CFM. The Dayton fan draws just under one amp (.96 amp) and I seem to recall the HD fan draws close to that same amount. Same size, similar amperage, four times the CFM????? Not possible. Dont know who is right and who is wrong, but one of them is fibbing or one is being right conservative. (Personally I think the 40,000 is way too high) To move more air, you will need more amps, all other things equal. There simply isn't that much difference in efficiency (both electric or physical blade design, etc) possible.

Grainger Catalog #401 page 3947.

Go HERE to see the "How to select" section. Problem is, I think their information is based on the apparently bogus CFM information. Use the "Go To Page" box at the mid right side of the screen.

Charles

 

[56nash]

I have a couple of Dayton fans that I removed from my production facility when we shut it down, they had less than 6 months use, they are just taking up space. If you are interested, I will make a screaming deal.
http://www.grainger.com/Grainger/DAYTON-Commercial-Ceiling-Fan-4C854
this is the fan I have, 2 of them. New were $199 each, take them both and you can have them for $50 plus shipping

 

[wbrian63]

I'll take 'em. PM on the way.

 

[Charles (in GA)]

I have a couple of Dayton fans that I removed from my production facility when we shut it down, they had less than 6 months use, they are just taking up space. If you are interested, I will make a screaming deal.
http://www.grainger.com/Grainger/DAYTON-Commercial-Ceiling-Fan-4C854
this is the fan I have, 2 of them. New were $199 each, take them both and you can have them for $50 plus shipping

Commercial Ceiling Fan, Blade Diameter 56 Inches, Voltage Rating 120/120 Volts, Frequency 60/50 Hertz, Fan Speed 265/245 RPM, Full Load Power 110/93 Watts, Full Load Current 1.00/0.90 Amps, Air Delivery 25500/23500 CFM, 1 Speed

You most certainly will need a speed control with this fan. direct wiring it and running it full speed, it will produce a BLAST of air that is almost annoying in the summer, and not workable in the winter. I'm basing this on my HD fans which, judging by amperage/wattage and diameter probably are not as powerful.

Charles

 

[mt_spiffy]

I have a couple of Dayton fans that I removed from my production facility when we shut it down, they had less than 6 months use, they are just taking up space. If you are interested, I will make a screaming deal.
http://www.grainger.com/Grainger/DAYTON-Commercial-Ceiling-Fan-4C854
this is the fan I have, 2 of them. New were $199 each, take them both and you can have them for $50 plus shipping

I'm interested in these if you still have them.

 

[soapii]

I'm interested in these if you still have them.

You do realize that post was almost 4 years ago

--Joe