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owen44138 07-05-2012 07:01 AM

Doing it right - Dehumidifier Sizing
Hi, I am fairly new around here. I'm going to post in the introductions shortly. However I joined at the moment because I need some advise on this subject.

I have a Victorian-era farmhouse. Its been added onto a couple of times over the years. I am in need of a dehumidifier. Our last one conked out after 7 years of service. I have decided that I'm going to do it right this time and spend the money on a good one instead of the crap they sell at Homer Desperate, Sears, etc. To make sure I go about this in the right way I've been trying to do some research with regard to sizing.

Given the age of the home, our duct work layout is not exactly what one might call modern. While we have return air "drops" from the first floor to the basement, the returns are not connected to the intake on the furnace. "Open returns" Ive heard this called. There isn't much that can be done about this due to the layout of the basement, ceiling height, placement of the furnace in relation to the return drops, etc. The basement itself is about 900 sq. ft. unfinished. The rest of the house is about another 2700 sq. ft. two stories.

So here's my question that I came here for: Since the furnace is essentially drawing ambient air from the basement do I need to get a dehumidifier that is designed to handle the entire 3600 sq. ft. of the house incl. the basement or can I get away with something smaller? This is pretty important because the price difference between between one that can handle the whole thing (Santa Fe Max Dry) and one just for the basement square footage (Santa Fe Compact 2) is nearly $1000. Or could I get away with something in between?

I sincerely appreciate any advice on this subject.

scottmcd9999 07-05-2012 07:09 AM

You'll need one for the entire space, including the basement. If your returns were connected directly to the furnace, then you could dehumidify only the top space, and that would very likely be a good thing to do. Trying to cool with very moist air is difficult at best, and you really should be returning air directly from the conditioned space, not the area where the furnace is installed. You mention that the basement is unfinished, so in many cases routing return ducts directly to the furnace is not terribly expensive.

owen44138 07-05-2012 07:22 AM

Perhaps I should have been more clear about its intended use. Our dehumidifier has always lived in the basement. We generally don't have above moisture problems, just an occasional seep when we get super heavy rain, never really a mildew smell or anything. According to local history the house was moved in about 1915 but even so what can you expect for an almost 100 year old basement? Then too, my mom thinks its a good idea to run one in a basement anyway even if there's no musty smell.

Also we had our furnace replaced about 18 months ago. When the contractor was doing the install they said they could do direct routing for about another $2500 on top of the $4000 we paid for the furnace. We were hesitant not so much because of the price but because the contractor said the only efficient way to get from one of the return drops to the intake was to cross the ceiling right at the bottom of the stairs with 12 inch round which due to the ceiling height would have made the last two steps into the basement rather awkward.

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