I want to put a dehumidifer in my crawl space with a direct drain line connected to it. It is a very tight crawl space with an access door(window actually) that isn't easy to enter and exit, so, I'm wanting to leave it there over winter when it won't be needed. It is a regular home-use unit that would normally be used inside the home or a basement. Question: Would the low winter temps damage this dehumidifer? I know they make units designed for low temperatures that would probably work better, but they are costly. I want to know if a standard home dehumidifier would be rendered useless if left in freezing temperatures. Thanks for your time with my question.

Depends on how cold it gets in winter... if its below 50 F... its not going to work very well if at all... and if it is anywhere near that warm or warmer... you are in dire need of insulation.

Since average winter temperatures vary drastically....where would this be? South Florida or Homer Alaska?

I would not leave any device desinged to be used inside the home...sitting in the dirt in a crawlspace. THey aren't designed for that type of enviroment. and will corrode heavily. Both the aluminum coils and the steel components.

Clients of mine who have installed the entire package (termite treatment, new insulation, sealing the crawlspace, dehumidifier, remote monitor) in the temperate coastal Southeastern U.S. have reported recouping the outlay in about six years just in savings on their utility bills. A household unit probably won't last a year unless the other factors are installed as well. By the time you get new insulation and crawlspace sealing figured in, a heavy duty unit's cost won't be a factor.

I'm in northern Indiana. It wouldn't be necessary to run the unit during winter since humidity is quite low here during that time of year. The summer, however, is a different story, but an air conditioner does a good job of taking it out of living areas, but I'm thinking a dehimidifier in the crawl space would really assist the a/c since in this way. I just wanted people's input on whether I should yank it out of the crawl space before winter--if freezing temps would damage or ruin it. I did find some reasonably-priced (less than $1000) crawl space dehumidifiers after searching more on the net. Might have to go this route.

Clients of mine who have installed the entire package (termite treatment, new insulation, sealing the crawlspace, dehumidifier, remote monitor) in the temperate coastal Southeastern U.S. have reported recouping the outlay in about six years just in savings on their utility bills. A household unit probably won't last a year unless the other factors are installed as well. By the time you get new insulation and crawlspace sealing figured in, a heavy duty unit's cost won't be a factor.

My crawl space appears to have what looks like a sprayed-on foam type of insulation. It covers the entire underside of the floor, the furnace pipes, you name it. It's everwhere down there except that the dirt has not been sealed or anything. I plan on sealing up the four outside vents that are in the foundation. Don't know about termites, so I should have someone look for that. There is a definite musty smell down there too, and it's damp but the dirt isn't wet or anything, even after it rains hard. But it is damp.

My next home will have a basement rather than a crawl space...

I should think the sprayed insulation without a vapor barrier is a DIY attempt at protecting the wooden joists. I've not dealt with it but it seems like a good idea except leaving the ground bare seems counterproductive. ALL the moisture in a crawlspace (well 95%) comes from the ground.

That said, at least half of your work has already been done. All that's left is a termite check (you may not need a treatment), a vapor barrier, and the dehumidifier. As I said, clients have reported a 10 - 20% reduction in their utility bills, so how fast could you start showing a profit from doing it?

Is radon gas a problem in your vicinity? The attached map shows moderate to high levels in N. Indiana.
Map of Radon Zones in the United States based on Environmental Protection Agency (EPA) data (http://www.city-data.com/radon-zones/)