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I want to work on ventilating our shop in this heat. Probably will be 90-100 degrees the next few days with hair wrecking humidity. Our shop is about 4000 sq ft. 14' ceiling. right now the guys just kind of drag around drum fans to where they are working. We have 2 huge garage doors on one side, then really nothing but a man door on the other end, sort of in a hallway and an exhaust fan in that same corner by the man door.
I think the first thing i need to so is jimmy the flaps on the exhaust fan open, which will at least let more air in or out. they normally only open when the exhaust fan runs. The exhaust fan makes a ton of noise when it runs, so we dont really like to put up with it running for too long. I was thinking about putting a drum fan up next to the exhaust fan to bring air in.

Is it best to focus on pushing air out of the shop, or bring new air in? I think one of the big issues is with the garage doors on one end, and a much smaller opening on the other end, we are just kind of swirling the air around in the shop. I tried once to put a fan by the man door blowing air into the shop, but that fan got scooped up to put in someones work area.

Should i put fans up high to try to get the hot air close to the ceiling out of the shop? We have 2 solar powered vent fans that were "supposed" to take care of that, but i knew from the get go those two little fans werent going to do much.

Anybody have one of those "big a** fans"? Our waste oil heater guy was pushing one on me last year. kind of expensive. And we had ceiling fans before, and pretty much knocked them all down with forklifts, dumptrucks, backhoes, etc.
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Depending on how often the man door gets used I think i would put as big a fan as possible in that door sucking air out of the shop. That way you will get some cross flow.

That being said you should seriously consider planning for putting in AC. I cannot imagine not having it and most of the better auto repair shops I deal with have installed it too. It will be a big initial hit but the boost in productivity will pay for it pretty fast. My shop is 1800 sq ft and it adds about $150 a month to the electric bill during the summer. If you work 20 days a month that is only $7.50 a day. It was 95 here yesterday and is supposed to be even hotter today but it will be right around 75 in the shop :) :)
 

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Unless you have the shop so airtight there are no ways for air to infiltrate then exhaust air out. Replacement air will come in through all the different nooks and crannies. And the higher you install them the better. Gets the hottest air out first. my $.02. They make 'barn fans' that go in the wall and have louvres on them that blow open when the fan starts. Might be a quick fix or at least help.
 
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Discussion Starter #4
Depending on how often the man door gets used I think i would put as big a fan as possible in that door sucking air out of the shop. That way you will get some cross flow.

That being said you should seriously consider planning for putting in AC. I cannot imagine not having it and most of the better auto repair shops I deal with have installed it too. It will be a big initial hit but the boost in productivity will pay for it pretty fast. My shop is 1800 sq ft and it adds about $150 a month to the electric bill during the summer. If you work 20 days a month that is only $7.50 a day. It was 95 here yesterday and is supposed to be even hotter today but it will be right around 75 in the shop :) :)
The way things come in and out of here during the day, basically we wouldnt be able to shut the doors more than a few minutes at a time. it would kind of be fruitless.
 

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The way things come in and out of here during the day, basically we wouldnt be able to shut the doors more than a few minutes at a time. it would kind of be fruitless.

Funny because I just had this discussion with one of my repair shop customers. I had them check something on my Tahoe before I went on a trip a few weeks ago and I was commenting on how nice it was in his shop. He said he thought the same thing when he first decided to do the AC but said that they quickly learned a routine to keep the door openings at a minimum. He is a very busy shop so he also has cars coming in and out all day.
 

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My shop is a concrete tilt up with a well insulated flat wood roof. Ceiling is about 18’. I have two whirley fans on the roof that draw hot air out by convection.
I find that if I keep all the doors shut it’s liveable inside @ about 80 degrees for about three days of over 100 outside temp. After that, the concrete has just absorbed to much heat.
At our home we keep it closed up all day too and we don’t have AC. Once the temp drops in the evening, I use a whole house fan and one open window at the opposite end of the house to suck all the hot air out and cool air in. Our whole house fan is huge.
 

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Dean, your first diagram is a classic illustration of a poorly designed system. I saw this all the time on indoor generator set installations.
By locating the air intake and discharge so close to one another, the air flow is “short circuited”.
With air intake and discharge located properly on opposite sides of the room, preferably air-in down low and air-out up high, drawing air out is far better than blowing air in.
 

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If you pull it out, you're going to get unfiltered air coming in, as well as possibly sucking in water around your door and window openings during a rain.

If you push it in, you have the option too filter it if you'd like, and it will push the water away from the leak points.

*I'm a door & window guy, not an HVAC guy*
 

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blow the heat out the top suck it in on the shady side of the building, or leave a ceiling vent open and blow it in at floor level. Either way, make actual inlet locations that you can add filters to if you want.
 
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blow the heat out the top suck it in on the shady side of the building, or leave a ceiling vent open and blow it in at floor level. Either way, make actual inlet locations that you can add filters to if you want.
To control where the air is entering in a big shop would be impossible to do though.
 

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As Dean says, need to be carefull with fuel appliances for sure. Best is a balanced system, not too negative pressure or a positive pressure. if you exhaust 500 cfm then you should bring in 500 cfm. Just a water heater running probably not an issue. But if you are mainly concerned about removing heat then remove it! and let the outdoor (supposedly cooler) air find its own way in to replace it. As far as filters go if your doors are open as much as you say it wont matter if you blow or suck as far as dust goes anyways.
 

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I worked for many years in unairconditioned shops in Maryland, suck it up and get to work!!
 

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Cooling is the removal of heat. Heat rises. Moving air feels cooler. You need ventilation. I'd figure out a ventilation plan that creates circulation and exhaust through a high spot. You've got to bring in as much air as you exhaust. Next step would be to add cooled air. If the humidity is not too high, you can use an evaporative cooler.
 

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I was told by a few AC techs that air conditioning was designed to dry air not cool it. What ever the temp is without it running, lower the thermostat by one degree from that point and leave it there.. That usually does it..

Its been my experience exhausting air from a room will make it hot, pumping air in from the outside will usually cool it provided the outside air is cooler..

Ceiling fans pulling the cool air up from the floor usually will cool a room, ceiling fans blowing down will warm a room but this is not gospel, there are times when I think blowing the fan air down makes it cooler..
 

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Air conditioners are designed to cool. Dehumidifiers are designed to dehumidify. Having said that part of the byproduct of cooling is dehumidifying. That is where you get the comfort and why you dont oversize a/c's as they will short cycle. Then you will get cold air but clammy, cold air. Sorry, getting off topic. Bottom line is as another posts suggests, 'cooling is removal of heat'. Using fans on people might feel better as you are getting air movement but you are still blowing 90 degree air. As always just my 2 cents for what its worth.
 
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by a drum fan do you mean a squirrel cage fan like from a home furnace??my dads shop we had 3 or 4 of em and they worked great,but they were pretty general area specific.if you weren't in the air stream it kinda sucked.my garage i do most of my work in is 24x30 and as long as the doors are closed the concrete keeps it pretty nice in there,until you open the 16 ft double door,
 

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I was told by a few AC techs that air conditioning was designed to dry air not cool it. What ever the temp is without it running, lower the thermostat by one degree from that point and leave it there.. That usually does it..

Its been my experience exhausting air from a room will make it hot, pumping air in from the outside will usually cool it provided the outside air is cooler..

Ceiling fans pulling the cool air up from the floor usually will cool a room, ceiling fans blowing down will warm a room but this is not gospel, there are times when I think blowing the fan air down makes it cooler..
Air conditioners are designed to cool. Dehumidifiers are designed to dehumidify. Having said that part of the byproduct of cooling is dehumidifying. That is where you get the comfort and why you dont oversize a/c's as they will short cycle. Then you will get cold air but clammy, cold air. Sorry, getting off topic. Bottom line is as another posts suggests, 'cooling is removal of heat'. Using fans on people might feel better as you are getting air movement but you are still blowing 90 degree air. As always just my 2 cents for what its worth.
We're getting off of the thread topic subject of the best way to keep the Techs cooler in a 4000 sq. foot commercial shop with high ceilings and no air-conditioning here but yes, in residential air-conditioning sizing, keeping in mind de-humidification is just as important as removing heat.

Actually in the particular setting mentioned by the OP, probably the best way is how they are doing it now. (fans blowing on them, since an exhaust fan will do nothing)
 
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