A/C Question Regarding Negative Pressure

Evening green thumbs,

Currently tired from working and building out a new site in between the tasks of life. Running a single 4k flower room with vented 8 inch hoods. Have a portable whynter double hose 14k btu portable as the location won't permit the use of an outdoor mini split. Problem is, I have a full set up for co2 enrichment but when the a/c pump turns on, it starts bulging out the 6 mil poly walls tighter than I prefer with the hvac aluminum tape as a seal. Any ideas or suggestions on how to equalize the pull from the a/c unit but still allow me to run a sealed room? Everything else has been overlapped, taped, foamed or caulked. Much love everyone!

I just went through the exact same shit. I have the Whynter ARC-14SH 14,000 BTU. Don't listen to anyone else on here saying the problem is something else, it is the unit. Everyone claims that dual-hose units create no negative pressure, but the design of these Whynter units have MANY air leaks. Mine was blowing out twice as much air as it was sucking in. Just go stand outside and you can feel for yourself. You will lose a lot of CO2 using this thing, and mine was even causing damage to my floors. Negative pressure can seriously build up, especially if you don't visit the grow room every day. If it's not too late, return it and maybe try a different brand. I have no experience with other brands, but I heard Whynter creates the most negative pressure.

There is a fix, if you're willing to void your warranty and risk creating a potential fire-hazard if done improperly. You can open up the unit and modify it, using caulk to seal the air leaks. Here is a link to my thread from when I was going through this: Portable AC, Bad Negative Pressure and here is the guy who discovered this fix: Modifying Portable AC for Use in Sealed Grow Room w/ CO2. His is an actual tutorial he made. I will make one soon with more detailed pictures when I get the time. Him and I both rerouted the water drain outside of the unit. Normally, the water will drip into the hot coils to help cool it more instead of relying on the intake air only. But you need to add ducting and stronger fans if you go this route. Personally, I think just sealing the insides is enough without rerouting the water drain. The small hole that it drips through shouldn't be leaking too much air through as long as you upgrade your intake. I did an 8 inch duct just to be safe, with a 745CFM fan, and an added 400CFM to the exhaust. In my thread, I tried using a 240CFM booster to the intake but it's nowhere near strong enough. FYI if you do reroute the drain system, just note that it will be pulling a lot of water from the air. Normally it evaporates from the hot coils but the way I have it now, I'm filling up a half mop bucket a day.

Jsisko01,

Appreciate you taking the time to reply back in the utmost fashion. I feel as if the unit it about a 75/25 percentage in regards to air flow difference between the intake and exhaust side. Knew it was going to be an issue a few minutes after the condenser kicked on and was running. I will not run co2 until I know the room is completely sealed and no air is being pumped out. Frustrating thing is I don't and can't really put a mini split option outside as the neighbors/hood are shitbags. I will look into an amazon return on a large unit like this as it "won"t meet my needs". Now I have to find an option to keep my room cool and at least flip some girls while finishing out the room.

Cheers

How big is your room? Are you using a tent inside of that room? I've heard of some people putting the minisplit in the attic or inside a wall but you have to have a condensate drain. Or maybe just use a window shaker unit. If you're using a tent you would have to build some type of frame to hold the weight. I know it sucks cutting any walls open but if you already cut holes for that dual-hose portable then it wouldn't be so bad just cutting out those to fit the window unit.

Those portable AC units are crap. I had one in my garage and it was worthless. You really need a window unit or a mini-split.