Portable A/C in garage - safety issues.

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Old 05-07-15, 08:53 AM
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Portable A/C in garage - safety issues.

I had an AC guy suggest a portable AC unit for my garage. It's a fairly large unit and I had to cut a whole for the exhaust (not sure if I'm using the right term). It's a two car garage.

My concern is the fact that I have a gas water heater in the garage and I'm afraid the unit may be sucking the water heater exhaust out of the flue and into the garage.

When I turn the unit on my garage door gets sucked in a bit. Also when I open the door to the house you can feel it being pulled shut and you can hear air being sucked in through the opening in the door.

The guy told me that I shouldn't be concerned because any carbon monoxide that gets pulled out of the flue would quickly be sucked out of the garage by the AC unit. Since it seems to be creating suction it seems like the AC unit is pulling more air out than it's putting back in causing negative pressure.

I don't want my family to be on the news because their idiot dad set up a dangerous situation in the garage leading to carbon monoxide build up that seeped into the house and killed them all. Is this a concern or no big deal?
 
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Old 05-07-15, 09:06 AM
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Welcome to the forums!

If you just bought the AC unit I would suggest taking it back and buying a duel hose model. Single hose units creates a negative pressure in the room because it uses room air to cool the unit and exhausts it outside. This is very inefficient. A duel hose mode will use outside air so there is no change in room pressure, and is more efficient.
 
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Old 05-07-15, 11:03 AM
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I would not use a single hose AC in a garage with a gas appliance. You are correct in thinking that it might be sucking exhaust gasses into the room.

I tried a single hose portable AC unit in my toy car garage and it was largely a waste. The one hose is blowing the hot exhaust air out so just as much outside air must leak back in. I'd let it run for hours and not get much cooling. I did a DIY hack to convert it to dual hose and it works much better.
 
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Old 05-07-15, 11:04 AM
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I appreciate the suggestion. Unfortunately I really couldn't afford to buy a new unit and got this one slightly used. I could take it back if there's a safety concern but I wouldn't be able to easily replace it.

Does it sound like what this one is doing is cause for concern?
 
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Old 05-07-15, 11:21 AM
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I could take it back if there's a safety concern
If it is single hose that is a safety concern (along with not working well).. If you can't or don't want to return it you may want to ask Dane to post how he modified his to two hoses.
 
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Old 05-07-15, 02:41 PM
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How about building a room or box around the AC unit and somehow building some ductwork for the cool air for the garage. Then add a vent hole to the outside for the unit to suck air from outside. Be sure to add a tube for the condensation.
 
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Old 05-07-15, 05:00 PM
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I used aluminum trim stock, you could also use aluminum flashing stock, to make a box that fits over the air intake that brings the air in that gets blown out the tube. If you are lucky you might even find a box that fits. Screw, rivet or duct tape it to the unit and attach a large hose. I used 6" duct and ran it to the outside. Keep the ducting as short as possible and as smooth and straight as possible to minimize resistance. This separates the air being re-circulated and cooled in the room from the air used to cool the coils. For $20 you can convert a single hose unit into a much more efficient dual hose.

Just make sure you understand what's going on with the unit. The one hose blowing out is easy as is the vent blowing cold air into the room. You need to look at it and determine which air intake takes the air that gets recirculated back into the room and which takes in the air that get's blown outside through the hose. Build your box and intake plenum around the intake for the air that gets blown outside.
 
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