Air conditioner = dehumidifier?

[StaggeringGoat]

This is the time of year it starts getting humid in my shop. I like to keep it down to about 50%. I have been using an old 5000 BTU window air conditioner for this, just sitting on a work bench running constantly. I drilled a hole in the bottom of the AC for the water to drip out.

It works, but it's awful slow. The humidity goes down maybe 1% per hour, and I get about a quart of water. I'm wondering if an actual dehumidifier would work better? Would it be more efficient and use less electricity?

 

[philjafo]

Yes, a cresent wrench isn't a hammer but you can still hit a nail with one.

 

[Strouty]

I have a small dehumidifier and it takes a lot more water out of the air than that. I would invest in one quickly, you will probably save money on electricity rather than running the AC. They do create heat, but the AC should have as well. Mine has a place to put a hose, so I can put it up high and run the hose outside. This way you don't have to worry about emptying the water, just let it run.

 

[nehog]

One of the things that a dehumidifier does is it 'recirculates' the heat to the input which warms up the air going through. (In theory the air going in the unit is about the same temp as the air going out...)

I don't think you'll get good results doing what you do, and right now yard sales and CL should offer up some good buys for dehumidifiers.

 

[pseudorealityx]

Small dehumidifers are basically just window A/C's where the air streams are mixed. Dedicated units will do a little better because they try to run their coil cooler while not caring as much about overall airflow, but the process is the same.

I would also try and drain the water somewhere rather than having it drip out, as that's just too easy for it to be absorbed right back into the space.

 

[sands35]

As stated, dehumidifiers are just AC units that mix the condenser and evap air output.

Just get a bigger AC unit or a "proper" dehumidifier. (humidity pull down scales roughly linearly with AC BTU size).

The bonus of the AC unit is you can cool the garage in the summer. Dehumidifiers will act as a modest air warmer.

You might still find AC units on end of season sale at Lowes or Home Depot.

 

[StaggeringGoat]

What size dehumidifier should I be looking for to use in a 40x60 shop? It will get up to 80-90%+ humidity if I don't do anything. It is pretty well sealed, newer construction with insulation and drywall.

I already have a convenient hole in the wall to run a dehumidifier drain out of...the previous occupant of my shop grew a bunch of marijuana in here, and I'm pretty sure he had a big dehumidifier hooked up here.

 

[pseudorealityx]

Basically the biggest one you can afford. You've got 2400 sq. ft, so you're looking for "whole house" dehumidifiers, not little room versions.

 

[where2]

While you're at it, look at where your humidity is coming from. Is the garage so poorly sealed that you are exchanging air from the outside to the inside bringing more humidity with it? Is the surrounding grade higher than the garage floor, causing moisture to seep through the floor? Garage door seals, man door seals and weatherstripping to go around windows is all cheap. I used to run a 40 pint per day dehumidifier unit in my house 24/7, emptying it daily. After I replaced a bunch of windows and sealed things up tighter around the house, the humidity inside the house has been drastically reduced. If I run the dehumidifier 24/7, I get less than half a bucket in 24 hours.

I own three of the little "room" sized dehumidifier units. All purchased second hand, never for more than $25. The new "digital" variety are the ones I like the least. The old tried and true manual knob variety were great because they'd fire right back up wherever they were set when the power comes back on. In my own garage, I have an old 8k BTU window A/C, through the wall, plugged into a 15A appliance timer. The timer is set to run 1 hour per day to remove humidity from the garage each evening. I'm fortunate, because the old manual knob A/C controls fire it right back up every time the power switches back on via the appliance timer.

When asked why I have 3 dehumidifiers, I remind people that I loan them out after hurricanes. Two are currently out on loan to a co-worker who had water infiltration during tropical storm Issac and has been having his windows replaced. Running your whole house A/C to dehumidify a specific room is an expensive battle better fought with a "room" dehumidifier.