Crawlspace Dehumidifier issues.

Hello all. I recently had a company to come in to do a major overhaul on my crawlspace. I had them to do an encapsulation of the space and also install a crawlspace dehumidifier to address any humidity in the space to keep mold and termites from returning (I also had a complete termite treatment around the entire house prior to having this done). The crawlspace is extremely cramped and difficult to maneuver around. My crawlspace is L-shaped (garage on cement pad completes what would be a rectangle). They installed a Sante Fe Edge dehumidifier and I've put some remote humidity sensors down there to keep track of how it's doing. The part of the space which was the worst is the very back corner which happens to be furthest away from the dehumidifier unit. Due to the tight space, they couldn't put the unit back there. I've got a sensor in the back corner and one beside the unit and the one beside the unit reads about 50% which is excellent but in the back corner it's 65%. If I installed a remote humidistat and placed it in the back corner area would that fix my issue so the unit measured from that and ran until that area was in the 50% range, or do I need some kind of fan or something to stir the air?

As part of the encapsulation did they cover all the ground with 6 mil plastic? With it encapsulated I assume the vents are now closed and the exterior walls are insulated. Are you putting any heat into the space or just the warm output of the dehumidifier?

They covered all the vents with 2" insulated foam board which went from the joists down to the ground on the foundation walls. The 6mil vapor barrier completely covers the ground and then goes up the side of the foundation and is secured to the foam board insulation. There is no heat or ac venting to the space.

Johnboy2978 said:

They covered all the vents with 2" insulated foam board which went from the joists down to the ground on the foundation walls. The 6mil vapor barrier completely covers the ground and then goes up the side of the foundation and is secured to the foam board insulation. There is no heat or ac venting to the space.

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I'm not an expert but the humidity level seems pretty high. Typically when a crawlspace is encapsulated you condition it as well by putting HVAC into it. You don't need to bring it to the same temperature as the house but it is heated and cooled.

I would run a 5" duct into that corner with an inline fan and figure out how to have the fan run when with the Dehumidifier. I think it supposed be a conditioned space but if the humitity in the house is greater what are you winning?

How long ago did you have the humidifier installed? it may take a little time for equilibrium to be reached, and an overall drop to happen.

That being said, maybe increase the circulation like Neal said.

I would agree, try to get some sort of circulation maybe.
I was lucky on mine because our HVAC unit (Plenum and Furnace) is in my crawlspace so all I had to do was simply install a vent into the Plenum and viola, instant conditioning.
It stays between about 65-70 degrees under there with humidity under 50% all year now.
It used to be 20 degrees in the winter and up into the 80++ with humidity in the summer so high that it was literally raining, I could stand in the middle and hear drip, dripdrip, drip all over the whole crawlspace.

Now it is like any other room in the house.

I would think that it being "tight" would actually be an advantage for the Dehumidifier as there is less square footage for it to squeeze water out of.

slownsteady said:

How long ago did you have the humidifier installed? it may take a little time for equilibrium to be reached, and an overall drop to happen.

That being said, maybe increase the circulation like Neal said.

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The work was completed just over 2 weeks ago so it should've had time to stabilize. I'm thinking the humidistat on the unit isn't working as it should. Even the remote sensor I have right beside the unit is reading in the mid 50's and I have the unit set to come on around 20%.

Is the unit sized large enough for the volume of space you're trying to dehumidify?

Also, where are you located? How warm is the crawlspace now? Dehumidifers don't work that well in cold temperatures.

I just checked the online manual for a Santa Fe Compact (never found an "edge") but they are probably all very similar anyway.
It said not to run it in "dry" mode if the temp in the crawlspace in less than 65 degrees as it will result in long periods of dehumidifier run time for basically no reason, plus it will frost up and the defroster has to come on using even more electricity.
So Sparky is probably correct that it could be a Low Temperature thing.

Also it appears that the dehumidifier should have a built in fan to circulate air.

I am located in SW Va. The temps have not been to extreme yet. Right now it's 50° outside and 59° in my crawlspace. The humidity outside is about 90% while it's 59% right beside the unit and 70% in the area I'm most concerned about in the corner of the space.

The unit is designed for a space up to 2200 sf and I have roughly 1200sf of crawlspace.

I would check the operating temperature range of the unit. 59F may be too cold for it work optimally. Adding circulation may help since the unit can't be centrally located in the space.

Are you getting any icing on the coils? Is the unit piped directly to a drain? Any idea how much moisture you're getting out of the air in a day?