We built our cellar earlier this year, with a through-the-wall ductless split cooling unit that we were lead to believe would work well for our needs. Unfortunately, it does not, so now we are trying to figure out what our other options are (ideally without tearing out large parts of wall or ceiling in the cellar to modify the design).
We have a kind of unusual (apparently) installation in that the back end of the cooling unit opens into our unconditioned crawl space. We were told this would be fine, but in hot and humid Tennessee, it turns out that the entire back of the unit sweats all spring, summer, and fall. We’ve tried every remedy the manufacturer has suggested, to no avail. I really would like to avoid surface-mounting because the room is not designed well for it (the cooling unit would be right in your face as you walk in, if it’s surface-mounted).
Do any of you have through-the-wall units in a similar situation, and they work without sweating? I’d love to hear about those.
Alternatively, are there any good and reliable but very slim surface-mount units we could consider? How much it protrudes forward from the wall is the main consideration.
I don’t think going to a ducted system is practical without massive modifications to the cellar, so that is really a last resort.
My understanding, and my experience, is that the vent of the cooling unit needs to be conditioned space. You can’t vent into an unconditioned space because the cooler can’t handle 100 degree air input.
Exactly. If the coils are in hot, humid, static air and hence cannot dissipate the extracted interior heat, the compressor may overheat and fail. It would be akin to keeping a refrigerator in a hot garage.
At the very least, the crawl space may need a fan, but even that would be insufficient in a prolonged heat wave.
BTW throughout this the manufacturer has claimed it should be fine, they have people who do stuff like this all the time, they’ve never seen an issue like this before, etc. etc. etc. At no point have they admitted that it just won’t work (which would have been preferable early on, so I could have wasted less time and money trying to get it working).
Unfortunately, the sale seemed to override the design, as priority. You may wish to ask the business how other customers have handled your problem type.
While I’m no HVAC system expert, I don’t know why the manufacturer would tell you it won’t sweat. Anytime a cold item meets warm air it will sweat. It’s very similar to a cold glass of tea sitting in a warmer environment. In your case the blower unit is cold, which is what you want, and behind it is warm.
My only suggestion is to well insulate behind the cooling unit and try to make it part of the conditioned space.
I think the part that gets cold needs to be in the cellar’s insulated space, not just the vent but also the coils. Or at least like your air handler in your house’s HVAC system, fairly well insulated and sealed.
I had a Mitsubishi ductless mini split and coolbot in humid NC for 7 years. Never any issues or condensation. The air handler was surface mounted inside the cellar above the door. Entire cellar was closed cell foam insulated. Nary a drop of what other than what the condensate pump caught. Like others I think the issue here is the thru wall install which I am not familiar with but allows a temp gradient and extra condensation. Also is there a condensate pump installed? Seems like something a good commercial refrigeration guy/firm could address.
There is a condensate pump. We have had two HVAC companies out. One is my builder’s normal HVAC sub, one is the commercial HVAC company the manufacturer chose and said they have worked with before. They both said that it appears to be installed correctly, the condensate drain and pump is working, etc. And that it should work here so they don’t know why it’s not. Most recently the mfgr has suggested that we spray foam the back side of the unit, which seems unwise from a maintenance perspective…
WhisprKOOL claims that the WhisprKOOL Extreme line can be installed through-the-wall to outside air with no issues as long as the outside temp doesn’t exceed 110F. But I’ve been burned on this claim once, so now I am skeptical. I’d want to hear from people who have actually done it.
I have no doubt that surface-mounting, either the unit I have now, or some other split system, would solve the problem. However, the design of the space makes that very difficult without significant modifications to the room. So I am exploring other options before going down that expensive and disruptive path.
Wait, so this is a split off a window unit in another room? Assuming it has adequate cooling capacity, it seems like you’re just stressing the unit to the extremes?
I have a self-contained through the wall unit (WhisperKOOL Extreme) here in Houston, so not the same setup. My system does have an exterior drain line and the flow can be noticeable at times.
I wonder what’s the real issue with the “sweat” or condensation, as long as it’s on the back of the unit and not inside the wall. Since it’s in a crawl space, wouldn’t just managing any dripping be the simplest approach? Is installing flashing, a drip pan and drain line possible?
No, it’s a ductless split system. Meaning there is an outdoor unit with the compressor, and an indoor unit with the coils and blower. It is WELL under its capacity. It runs about 15 minutes per hour, which the manufacturer say (and I quote) is “ideal.”
There is a drain pan, drip line, and condensate pump, all of which have been confirmed (by manufacture’s instructions on a phone call where they walked us through it as we did it, with their chosen HVAC contractor there also) to work correctly. The issue is that the entire outside of the unit gets covered in water, which then drips onto and into the wall and everything around it. There is no containing it because there is so much water all over the unit, and the wood on the back side of the wall where it is installed is getting soaked. Sometimes there is so much that moisture starts dripping out the TOP vent on the front of the unit (not the bottom where the drain pan is). This has then caused discoloration on the finish on the interior of the cellar from the water running down it (again, drip pan and drain line confirmed to be set up and working as per specification).
On the spray foam on back idea, I think that may be how mine was done. I did not watch them install but on the back of the air handler side was closed cell foam. Sorry I don’t know more and I don’t have any photos.
Instead of using spray foam, is there enough room to make a sleeve out of insulating pink foam board that would slip over the back of the unit? You could then easily remove it for maintenance.
I’m hesitant to comment on items like this because I don’t want to jinx myself …
I live in the Houston area, so definitely hot and humid, although relatively few days with triple digit temps. I built a well-insulated “wine room” in one of the bays in my un-airconditioned garage and have been cooling with through an exterior wall WhisperKool units for more than 20 years. My current cooling unit is a WhisperKool Extreme 8000 that I installed in 2009. It replaced a 1-year-old Extreme 8000 that started acting up (I don’t recall the details). I do remember getting a replacement unit under warranty was pretty painless, other than the physical work of removing the old unit and installing the new one. Prior to that, I had a “normal” WhisperKool 8000, as the Extreme versions didn’t exist until around 2008.