Portable AC venting into an attic?


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Old 04-23-20, 06:26 AM
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Portable AC venting into an attic?

Are there any portable AC units on the market which do not use the newer evaporative exhaust technology (which sends moist air out with the hot air exhaust)? I need to vent into an attic but do not want to send moist air into the attic. Would rather have one with the old technology - "just drain all moisture into a bucket and just empty it later".
 
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Old 04-23-20, 10:53 AM
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Welcome to the forums.

I don't know about old technology but I do know a single vent line portable A/C
is an energy waster as you are discharging cooled air with the heated air.

It would be more efficient to use a two line portable A/C.
However that unit could not use the attic for air exchange.
 
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Old 04-23-20, 02:22 PM
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I don't know your reason for wanting to exhaust into the attic but if you can give us some background as to what you are trying to accomplish we might be able to help.

Portable air conditioners send as much moisture out with the exhaust air as they can. They are designed this way to minimize how often you have to empty the catch bucket. The catch bucket is only there for the excess. So, any AC you buy will blow moisture up into your attic.

Next, please only consider two hose portable AC units. They are more expensive but they are MUCH more efficient and work MUCH better. Don't even consider a single hose unit. Two hose units operate similar to a regular AC where the inside and outside air do not mix. Single hose units draw the air that gets blown outside from inside your home. So, your single hose unit just worked hard to cool the air... which it then sucks in and blows outside... and because you are pumping air out of your home every gap around your doors and windows is allowing the same amount of outside hot, humid air into your home.
 
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Old 04-24-20, 04:50 AM
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Thanks for that input. Not sure I can use a dual hose unit because, as I understand it, they draw from the outside and vent to the outside. I don't have a way to do that. Here is my situation: I am trying to cool a bonus room in my house, which is being used as a bedroom for my child. It has no useable window for draw or exhaust. The house is one level, except for this upstairs bonus room, located over the garage. The slope of the roof is also the slope of the interior walls in the room, so that, for two of the walls, vent would have to pass through the actual roofing if I tried to vent through a wall to the outside. A third wall (to the front of the house) is brick - do not want to vent to the front or to mess with brick siding. The fourth wall is the only option, and it opens to the attic.
I have read in more than one source that venting to the attic is doable. But my concern is the moisture, which none of the manufacturers seem to want to address when they say using the attic is ok. So, that is why I was hoping to find a portable unit that drains into a bucket (much like a dehumidifier), rather than sending moisture out through the vent. I am now assuming those type of portable units do not exist.
 
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Old 04-24-20, 06:13 AM
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First, if the room has no windows and is over the garage it sounds like there is no second method of egress so the room legally cannot be used as a bedroom. If there is a fire someone can be trapped in the room and unable to escape.

All AC units will need access to outside air. The two hose models bring the outside air in with a second hose. Single hose models get the outside air by sucking it through the leaks in your house. If concerned about putting moisture into the attic a single hose AC is by far the worst. With either you still need access to the outside, not an attic. You might be able to run ducts through your attic for the AC. A couple straight runs of 6" rigid duct to go out the gable end of the house/roof might be an option.

I would also consider a mini-split system. It would by far be a better, more permenant solution. You could even choose a heat pump model so it can also heat the room in winter. Systems start at about $600 so it is more expensive than a portable unit.
 
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Old 04-24-20, 08:11 AM
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Thanks. But don't manufacturers recommend not extending the exhaust line beyond the length of the duct which comes with the unit?

I should have mentioned the room is being cooled by the central heat/air system in the home. Works fine most of the year, but not adequate in hotter months. We are in the south so hot months in all late spring and summer. So what I am trying to do is supplement the central AC system. Do you think a dehumidifier would help in this situation?

 
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Old 04-24-20, 08:47 AM
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No manufacturer recommends extending the ducting on their portable AC's. You'll have to use a bit of your own judgement in that regard. Mine has one 4" and one 5" hose. I had to go up about 6' and make a 90░ bend then go another couple feet to get outside. I used rigid 6" duct. The increase in size and smooth interior helped preserve good airflow. I just shoved the flexible hoses that came with the AC into the duct and used foam to fill the gap between the different sized pipes. The setup has worked well for several years so far.

Yes, a dehumidifier could help in that room. If the humidity is high then reducing it will make the room more comfortable. But, you don't want to just let a dehumidifier run in the room if it's not helping as the 600+ watts that it draws is all converted to heat and will act like a space heater in the room. So, you have to make sure the lowered humidity is more beneficial than the heating.
 
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Old 04-24-20, 07:01 PM
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I would also consider a mini-split system. It would by far be a better, more permenant solution. You could even choose a heat pump model so it can also heat the room in winter. Systems start at about $600 so it is more expensive than a portable unit.
I'd echo what Pilot Dane said. I've used a couple mini-split systems and they work great and are more energy efficient. The piping is small and makes it easy to go out a soffit or through a wall to the outside unit.
 
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Old 04-25-20, 04:14 AM
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An attic during airconditioning season is normally much warmer than outdoor temperatures.
In a properly vented attic the temperature can rise to 20 degF above outdoor temps. considerably more if not well vented.
If you try to vent a single outlet portable a/c into this space it would have little effect on the unit but would be raising the attic temperature making more work for the a/c.
If you connect a two pipe unit to circulate the attic air through the a/c unit it certainly would not work well or last very long.

Any addition to the supplied air hoses on a portable a/c will cause some restriction and increase in operating temperatures but considering how inexpensive these units are might be a worthwile modification.
 
 

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