Negative Pressure Causing Damage

they sell thermostats for about 50 bucks plug it in and plug your fan into it . can just suck the cold air up from out side and the thermostat does the rest . I have it set up like this. never in the summer bugs

for winter months...i shut my split down. Just retarded to run ac in the winter when there is free cold air outside. I run a motorized louvered duct with fan connected to a thermostat. My ambient bottled co2 levels (1200 ppm at peak) take a slight hit from December to early March....bit it doesnt take a hige chunk out of my yields. A little...not very much. Worth it to shut down the a.c. and less of a electric bill.

Can anyone tell me if this is bad? It looks like the coils are leaking coolant or something. It's a white hard substance that I can scrap off with my fingernail, but it is quite difficult to get off. Almost feels like paint, but obviously it's something else.

jsisko01 said:

Can anyone tell me if this is bad? It looks like the coils are leaking coolant or something. It's a white hard substance that I can scrap off with my fingernail, but it is quite difficult to get off. Almost feels like paint, but obviously it's something else.

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Honestly it looks like paint. A refrigerant leak would leave an oily residue and you unit wouldn't work very well

So I've been in the process of sealing this unit inside. Today I picked up the AC unit and didn't realize my arm bent this copper pipe. It's very small and feeds off of the larger pipe. Like just 4 inches sticking put in the air. Now that I've bent it, I'm sure it will block the flow of anything passing through. It literally bent down in half. I'm assumingthis little thing is to relieve pressure? I hope I'm not screwed now. Here's some pics

jsisko01 said:

So I've been in the process of sealing this unit inside. Today I picked up the AC unit and didn't realize my arm bent this copper pipe. It's very small and feeds off of the larger pipe. Like just 4 inches sticking put in the air. Now that I've bent it, I'm sure it will block the flow of anything passing through. It literally bent down in half. I'm assumingthis little thing is to relieve pressure? I hope I'm not screwed now. Here's some pics

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It's a process tube, not to worry and just leave it alone so you don't break it, nothing flows through it.

you ever get your issue under control ? with the pressure .

I finished the modification of the AC unit last night. I'm gonna let it sit and dry for a couple days because I used this stuff by DAP called Seal N Peel. It's a clear temporary weather sealant. That way the seal isn't permanent in case I ever have to take it back apart. It says it's only a 30 minute dry time but this stuff gives off some major fumes. It says breathing the vapors can cause brain damage and nervous system failure lol. Scary. I'll wait until I can't smell the chemicals anymore before I lock it in my sealed grow room.

I cant wait to hear about the results! I also have the same AC and would like to eliminate the negative pressure.

Hey all. Yes sealing the inside of the unit completely solved the negative pressure issue The only problem I'm getting is since I rerouted the the water drain, which used to drip over the hot coils, now the unit runs much hotter. 240 CFM of extra air flow to the intake isn't enough, so I'm going to buy a stronger fan and show you guys the outcome. The exhaust is literally hot enough to almost singe your hairs lol. But the unit doesn't shut off so I'm assuming it's not reaching a dangerous level (it's supposed to shut down automatically at given temp).

Thanks for the update.

I got a couple question if you don't mind

1.Do you find that it as reduce the cooling effectiveness having more heat coming out of the exhaust?
2.I am also wondering if i would try like a 400/500 CFM blower and force that into the intake would that help with the negative pressure issue? with out having the need to seal it?
3. Do you find having eliminated the negative pressure as helped you cool the room faster?

Thanks.

sounds like a major issue to me an ac that gets burning hot . its will shut off when your not around and toast your plants .

Yes I agree that it getting so hot is not good! But according to the other tutorial on how to do this, he upgraded to 6 inch ducting out the back of the unit, and added extra fans for intake and exhaust, and that is enough to keep it cool. The cold water that drips onto the coils probably doesn't cool it off much (but I do lose the benefit of auto evaporation). This thing catches so much water it filled 1/4 of a mop bucket up in a couple hours.. but it was 95 in my room though lol. I've been running a single hose unit until I can figure out how strong of a new duct fan I want. I'm thinking around 800 CFM on the intake and then add my 240CFM fan to the exhaust as a booster and I won't have to worry about overheating anymore.

DGTAL said:

Thanks for the update.

I got a couple question if you don't mind

1.Do you find that it as reduce the cooling effectiveness having more heat coming out of the exhaust?
2.I am also wondering if i would try like a 400/500 CFM blower and force that into the intake would that help with the negative pressure issue? with out having the need to seal it?
3. Do you find having eliminated the negative pressure as helped you cool the room faster?

Thanks.

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Hey DGTAL,

1. I don't believe it will affect the cooling power. The hot and cold side of the unit are also completely sealed from each other now. If the unit gets too hot it will shut off automatically, but should not reduce the coolness.

2. Yes, technically that would solve the issue. That was I wanted to do initially, but that only solves negative pressure. All the air leaks inside of the unit, it really pushes out a LOT of the grow room air. If running CO2, you would be wasting a lot of money. Also, you want to invest in a filter for the intake. A bug screen does not stop dust, small bugs, etc. When I first opened the unit, the hot coils were filthy with all that stuff plus that cottonwood shit. So with an added filter, you might need a stronger fan. Like 800CFM. That exhaust is pretty strong to keep up with.

3. Eliminating the negative pressure will definitely keep it cooler. The unit exhausts way too much inside air. I hooked up a single hose AC unit to compare the negative pressure and they literally seem to create the same amount. My vinyl flooring raises up like a parachute lol.


The only problem I'm having now is its getting so hot out lately that this unit isn't even strong enough to keep my 12x20 room under 90. The room is in direct sunlight and I'm running a couple lights and an air pump.. I would buy a mini split if I could afford it.. maybe next harvest I will get one. All-in-all portable air conditioners are shit unless you have a smaller room. I need to figure something out :/

I am still using the 4 inch hoses that came with the unit. I don't want to cut bigger holes in the wall, but with a strong enough fan I think 4 inch is fine. 240CFM is not nearly enough of an extra boost, so I'll add different fans when I can. I put duct reduces on this 6 inch fan so it will fit into the unit and on the hose. The back of the unit is a 5 inch opening (or your reference). I haven't sealed anything on the outside yet because I'll be replacing that but here's the fan propped up onto the intake leaning on my heater lol. NO negative pressure anymore though. And I didn't even tape the seams of the outer casing like the other guy did.

now you have all these not so proven mods done . not proven to work for longevity or reliability . now your going to have to go out and buy a different ac unit after all this . should of listed this working unit on craigs list got 200 bucks and could of bought a unit that would be cooling your room like you want . I am not ripping into you I might of done the same thing in the past when I was young and stupid . sorry it is not keeping it cool .