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Need AC advice - cooling a finished garage

Posted on 7/10/17 at 6:29 pm
Posted by Huey Lewis
BR
Member since Oct 2013
4641 posts
Posted on 7/10/17 at 6:29 pm
TLDR question:
Anybody have first-hand experience with using a portable AC unit compared to a window unit and what are your thoughts on them? Do portable units work as well as window units and are they worth the cost? I'm looking at dual hose units though I've read some articles claiming dual hose and single hose end up with virtually the same results.



Full story:
My house's garage was turned into a bonus room by the previous owners. It's a little over 400 square feet. The house has two AC units that are sized for cooling the house minus the bonus room and the main unit is being overworked due to cold air flowing into the bonus room from the hallway. We spend most of our time in and around the bonus room all summer since it's basically a combination play room/TV room for the kids so keeping the door closed and letting the temperature in there skyrocket isn't feasible.

AC guy recommends a ductless mini split and I think that probably is the best solution overall. But my concern there is that it requires a dedicated line and the breaker panel was already (seemingly) maxed out and rearranged by the previous owners so the cost may end up going above the ~2500 for the ductless.

My other option is to use a window unit or a portable unit for however many years it takes for one of the house's split systems to need replacing, then just upgrade to a larger unit capable of including the bonus room. Is this feasible or will a portable or window unit fail to give me the results I want? In the future I think I'd rather have larger units rather than two undersized units + a mini ductless, or is that dumb?
Posted by Clames
Member since Oct 2010
16529 posts
Posted on 7/10/17 at 6:37 pm to
A window unit will cool better than a portable version, btu for btu. At least the portable you can put away when not needed and not the eyesore a window unit is. Pros and cons for each.
Posted by Da Hammer
Folsom
Member since May 2008
5750 posts
Posted on 7/10/17 at 7:14 pm to
I went mini split. Researched how to DIY did it all myself had an AC giy check vacuum and freon. Total cost was about 1550.
Posted by bbvdd
Memphis, TN
Member since Jun 2009
24916 posts
Posted on 7/10/17 at 7:24 pm to
I bought a portable to go in my garage a few years ago from Costco. It crapped out in less than a year. Never replaced it.

ETA: returned it to Costco and used the money on gas.
This post was edited on 7/10/17 at 7:51 pm
Posted by QuietTiger
New Orleans
Member since Dec 2003
26256 posts
Posted on 7/10/17 at 7:35 pm to
Been hearing a lot of negative things about the splits lately, like repair issues with parts and such. If possible I'd go with what I call a zone-air like in a hotel, usually under a window in a hotel. Those things work super well for both heat and cool.
Probably a 30 amp line.
Posted by Maniac979
The Great State of Texas
Member since Jan 2012
1904 posts
Posted on 7/10/17 at 9:11 pm to
Get the dual duct portable unit but don't connect the supply duct. This way you'll be recirculating the already cooled air similar to the recirculation feature in a car. Check Friedrich Zone Aire units
Posted by Milk
central
Member since May 2010
1042 posts
Posted on 7/10/17 at 9:54 pm to
I had an LG window unit with heat for my garage mancave. It worked well in both the summer and winter. I believe it was 7500 btu.

Before i had a no named 5000 btu that cost a fortune and never caught up. Electricity bill dropped 75 a month by switching from a 5000 to a 7500 and going from a mini frige to a full size.
Posted by lsu xman
Member since Oct 2006
15511 posts
Posted on 7/10/17 at 10:13 pm to
I have a LG 15000 BTU for a 400sqft enclosed garage.. It's loud but certainly does the job during the summer. Works on a standard 120v outlet.

$400 from HD.
This post was edited on 7/10/17 at 10:15 pm
Posted by brew400
West side Best side
Member since Sep 2009
575 posts
Posted on 7/11/17 at 7:36 am to
Go window unit until the big AC on that side of the house craps out and you replace it with something a little bigger. Then just run a couple drops to the "bonus" room and throw a 12x12 return and youre golden. Mini-splits are a headache, and portables are nice because they are portable, you just want it for this room, that window unit will come in handy during a storm as well.
Posted by Huey Lewis
BR
Member since Oct 2013
4641 posts
Posted on 7/11/17 at 1:53 pm to
quote:

Get the dual duct portable unit but don't connect the supply duct. This way you'll be recirculating the already cooled air similar to the recirculation feature in a car. Check Friedrich Zone Aire units


Wouldn't this be the same as running a single hose system? I've read conflicting info on the single vs. dual hose dilemma. Alot of people say single hose is less efficient at cooling and therefore takes longer to cool, in addition to the negative pressure issue and that dual hose systems are therefore superior in all circumstances. But I've also seen claims that dual hose systems actually draw inside air to cool the unit down as well as air from the intake hose and therefore also create negative pressure. I've also read that dual hose systems are actually less cost efficient from a power consumption standpoint even though they may cool air more efficiently. And then I've read that it may be a mixture of both scenarios - dual hose systems may be better depending on ambient temperature and humidity in the room, sun exposure, outside temp and humidity, etc.

Hence my confusion. The room itself is in the low 80's during the day right now with colder air from the hallway coming in, or technically I guess heat from the bonus room is able to escape into the cooler hallway thus cooling the bonus room a little. I'm trying to wrap my brain around whether negative pressure in the bonus room created by a single hose setup will pull cooler air from the hallway, warm air from the door and windows, or have virtually no impact and if that would be definitely better or definitely worse than a dual hose setup given how hot and humid it is outside.
Posted by X123F45
Member since Apr 2015
27321 posts
Posted on 7/11/17 at 2:14 pm to
I have twin 12k btu window units in our sub 600 square foot mini house.

I can keep it 60 degrees in there in the dead of summer. But more importantly, I can cool it from 90 to whatever temperature I want mid day.

I cannot stand the portable units.

Strategically planted fruit trees or hedges are a great way to hide window units and keep leaves our or the units.
This post was edited on 7/11/17 at 2:15 pm
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