negative pressure, am I loosing air?

[yamaha_1fan]

Got a pretty well sealed room, built from scratch, and drywalled. All outlet boxes, ducting, or anything coming through the drywall is caulked or sealed with expanding foam. Door is an exterior door with weather stripping.

When entering the room (door opens out), you have to pull against the suction and it is pretty strong.

Air cooled lights by 2 12" can fan max fans, pulling from a passive intake

Central A/C ducted by metal ducting. All outlets were sealed and caulked with plywood. New outlets were cut and 6" round duct (like on the hoods) was used. The boxes were sealed with silicone where attached to the main A/C trunk line.

My concern is if we have a suction on the door, we must be loosing air somewhere? To have suction, we have to be pulling more air out, than is being pushed back in? Is it possible we didnt add enough ducts to compensate for the ones we sealed?

The unit is a 3 ton I think and we have 8 6" ducts

The reason this is an issue is obvious. We are loosing cool air, which is Co2'ed, then we are leaking odor too.

 

[nnnnghhhhgnnngh]

Since air pressure inside room is lower than elsewhere in the house, any openings in the walls, around doorframe et cetera will serve to pass air INTO the room. Which is exactly what you want for scent control. Sounds like you did a good and very thorough job planning/building.

 

[SkareCrow]

Yea thats exactly what you want I used to have the opposite problem because my intake was too strong.

 

[Hydro-Soil]

IF you're losing air with odor in it..... You should be able to smell it.

Is there any place it could be going that you can't get to and 'smell' to see?

 

[asher1er]

you have the 3 ton air handler in the room or it's elsewhere and you just have the ducts running to the room?

 

[guest 77721]

Too much negative pressure is a lack of intake space.

Static Pressure is caused by blocked intakes or exhausts which results in a reduction in airflow.

 

[dongle69]

Sounds like your air cooled hoods aren't sealed completely.
Those 2 Max fans are surely taking advantage of that.

 

[hoosierdaddy]

From what I am reading, you have exactly the same surface area for intake as you have exhaust. Add one more 6" intake duct and I bet you are golden. (a good system will have at least 10% over on intake vs. exhaust)
I always recommend not using the same air to cool the lights as the rest of the room. Seal the lights best you can, and dedicate a duct in and out, plus a small fan, to cool the lights only. If you get smell at the room exhaust after sealing and separating the lights, then you need to address your scrubber. Maybe too small scrubber and too powerful an air draw?

 

[DiscoBiscuit]

^^^+K^^^^ can't give it to you myself until I pass around a little more. You just made air flow a little less of a head scratcher, thanks. at least 10% extra intake? good to know.

 

[asher1er]

^^^+K^^^^ can't give it to you myself until I pass around a little more. You just made sealed room air flow a little less of a head scratcher, thanks. at least 10% extra intake? good to know.

sealed room air flow? a sealed room has no intake n no exhaust, his lights are vented on its own circuit, like stated above first thing to check is the glass closure on the hoods.

you shouldnt have a prob using foil tape to seal them up real good its just a PITA if your one that likes cleaning the glass on the hoods pretty often

 

[yamaha_1fan]

negative pressure would be good in a non sealed room without Co2. Its not good in a sealed room with Co2. I tested it yesterday and after one day, my propane tank is almost empty. I went from 1300PPM, to 600PPM in 20 minutes when I shut the Co2 off.

My lights are not connected to the A/C. They have 2 fans, teed into one 16" intake. Air comes from outside of the room, through the lights, then outside of the room

I played with it yesterday. With the A/C off, I still have negative pressure, because the door still closes on its own. Not as strong as when the A/C is on. Around the hoods, I can feel air leaking, so combined oer 24 hoods, I guess that is alot of air.


At this point, we dont really have an odor issue. The plants just went into 12/12 and the scrubber isnt even hooked up, due to a fan problem we are trying to replace


I am dealing with 2 seperate systems here, the air cooled lights, then the A/C. The A/C air handler is on top of the room, and has a 40-50 foot long duct line, that had several 8x12 (roughly) openings. We sealed all those openings and added the 8 6" ducts.


My thought was to add more exhausts to relieve the pressure the A/C is creating. If anything, by blocking the existing ducts, we have created less exhasut area, than before. Thoughts on this?

I am going to foil tape every hood, A/C joint, etc. I thought the A/C was pretty well sealed when the ducts were put in with silicone but I am going to go over it with tape.

 

[asher1er]

yamaha you said the air handler is on top of the room, now do you mean its hanging on the roof INSIDE of the room or as in its outside on top of the roof?

if its outside of the room how is the return duct into the ac?

 

[yamaha_1fan]

The air handler is hanging from the roof of the building (inside) and has ONE return duct hanging down. We simply built the room around it.

So the air handler is outside of the room and the return is roughly 24x24 and the grill is flush with the ceiling.

I am going to go by tomorrow and start taping, I'll snap some pics for this and CCC

 

[Lapides]

Around the hoods, I can feel air leaking, so combined oer 24 hoods, I guess that is alot of air.


I am going to foil tape every hood, A/C joint, etc. I thought the A/C was pretty well sealed when the ducts were put in with silicone but I am going to go over it with tape.

I'm gonna go with Dongle on this. I'll bet ya dollars to donuts you're losing a TON of air through them hoods. I was a bit baffled by my room as well with negative pressure. Taped up the hoods and everything is nice now.

(sorry if the pic's huge, i dont know any other way)