sealed room intake placement

[doctor.dank]

Hey guys, I need a little help on intake placement.

I have a 100x60 warehouse space, I am building rooms within that space. I am about to frame up 2 10x10 flowering rooms and 1 10x20 veg room. total space is 10x40.

I have external res's outside each room (plus ballasts) so Im going to frame up a 5x40 space for rez's/ballast. They have to be framed up because someone else uses the rest of the warehouse space and doesn't want to see anything.

Heres a picture for you visual folks.

(first one is a top view, second one is a side view)

The ceilings are 12 feet, I have to frame up the walls to 12 feet to hide the exhaust duct work but the grow rooms are only going to have 8 feet ceilings. im not going to put a ceiling at 8 feet over the res space. So I will have a pretty large "dead space"

I'm going to run sealed rooms for the most part. Exhaust will be piped directly outside. I was thinking 12" inline fans for each room. Turned on at night to control humidity/reduce co2 levels. I'm running CO2 burners and worried about off gassing issues from the burners so I'm also going to exchange the air maybe 10-20 minutes every 3-4 hours when the rooms are sealed.

Now because I live in a cold climate I'm going to be able to get away with not running air conditioning during certain parts of the year and just do active air exchange. that is where I'm lost. I don't know where and how I should do the intake in order to have enough airflow/exchange to not need AC when its cold out.

I probably don't want to intake from the main warehouse space because it will waste heat in the rest of the building. I don't think I want to have an intake directly into the grow rooms from the outside due to condensation from 10 degree 20% humidity air hitting 80 degree 70% humidity air.

Should I intake from outside into my "dead space" then have an intake for each room?

Above the 12 foot ceiling (just a drop ceiling) the building has a large attic space. Should I add in a passive intake in the attic and then have a passive intake duct from the attic into my dead space instead of an intake directly from outside? Should all of my intakes be passive or active? Does anyone have suggestions on intake ducts for passive intake so CO2 doesn't leak out of the room when im running it sealed? And how big should my intakes be? I heard 1.5x of exhaust so each room would need 18 inch vents? What about the lung room intake, how big should that be?

thanks for any and all help and input.

 

[Alaskan_Ice]

fwiw,

It's going to be difficult if not impossible to control temperature and humidity with the same externally vented loop. However, you might be able to take advantage of the warehouse's volume of conditioned space for humidity control. Draw air from the warehouse through a carbon filter, a set of louvers, and exhaust outside.

When using cold air, you have to control where the condensation occurs. You need enough surface area, and time for this to occur. The more of this heat exchange that takes place in the room you are trying to cool the better. The condensate can be drained into your reservoir.

You will need 2 sets of controllable louvers on all outside penetrations. One that operates with the fan; and one that operates when the heater turns on, or when the low temperature alarm comes in.


AI

 

[doctor.dank]

thanks for the response. what do you mean by the same externally vented loop?

the only issue I have with intake from the warehouse space is wasting all of the heat in the warehouse space. and I dont want to vent the heat from the grow rooms into the warehouse space because of the high humidity.

 

[olekingkole]

The saturation water vapor pressure at freezing is about 1/8 of what it is at 30C. In other words, the cold air you are bringing in will be very dry relative to the air already inside. If you have a condensation problem it won't be because of the air you are bringing in. But the warm moist already inside might condense in the ceiling cracks. I've never had condensation problems caused by the air coming inside. I bring it in low, where the room is coolest and I use greenhouse fans high up in the room to create a circular air circulation pattern. That causes negative pressure so that cool air is drawn up and gradually moistens without condensation. I believe that's how it is done in most commercial greenhouses. Commercial greenhouse fans are different than what you see in most grow rooms. They are very well made and should last for years. One problem though, your rooms are going to be a little small to establish good circular air circulation. 12x 24 works well with just 2 fans high up along the long walls pointing in opposite directions. I don't know if you can do it in a smaller room.

 

[Alaskan_Ice]

A loop refers to a segment of the heating/ humidification/ air exchange system you are building. It would most likely be best to separate the (de)humidification, cooling/ heat, and air exchanges (mostly) into their own controllers, fans and vents.

Lights off (air exchanges), you are not generating any waste heat, you will have to use heated air for the exchanges. Considering the heat loss from the overall size of the warehouse, and the amount of volume changes you are suggesting, this will be a rounding error on your gas bill.

Lights off (supplemental heat), Assuming the back walls of your rooms are exterior, you may need heat. Warehouse, or in room heaters?

Lights off (dehumidification) If you are using a humidity controller with a large'ish dead band, I wouldn't expect this to be much of an additional heat load on the building. You could use in room dehumidifiers.

Lights on (hood cooling). In the winter you may have to temper (warm up), and/ or significantly reduce the volume of air coming into your light hoods so that any uninsulated surface doesn't drip.

Lights on (room cooling sealed) in the winter you may have to run your AC unit. In the summer you will have to run your AC unit. You can get commercial AC units with economizers in them to significantly reduce energy usage.

You can do what you are trying to, and it will end up being "sealed for the most part" once you get everything sized properly for your application.

A bit of advice on your fans. Unless you are going to run 3-phase fans with temperature controlled variable frequency drives; don't assume you can buy the biggest fan you will need in summer, and use it during the winter. You most likely will need a temperature controller with 2 or 3 stages of cooling, running different size fans to accommodate outside temperature swings. For my hoods I use 3 stage temp controllers that have 2 variable stages, and one fixed stage.

The somewhat complexity of getting all of this stuff to work nicely together, is why you see guys buying air handlers with everything built in.

 

[doctor.dank]

I'm going to be running vertical bulbs so no air cooled hoods.

I plan on getting 2 9k btu mr slims for each room. heating and cooling model. set on a thermostat with day and night settings. So it will heat and cool as needed

I will have a humidifer and a dehumidifer both on seperate controllers so I wont need to use only air exchange to control humidity spikes at night

the reason I dont want to run sealed rooms 365 is mainly because it can get pretty cold here in the winter time. especially at night. The mini splits I am looking at only cool down to like 5 F degrees (they heat down to -15 F though). I have seen units that cool down to -40 F but a lot of them seem to be discontinued or much more expensive and way less efficient. It hardly ever gets below -15 so I should be all set with just using them for heat in the winter. the second reasons is I think it will cost a lot less to run active air exchange in the winter time instead of trying to use an air conditioner year round.

so are you saying for the lights off air exchange I should be intaking from the warehouse space and exhausting outside? That would work for lights off but when lights are on and Im doing active exchange I dont think that would be a good idea.

 

[Alaskan_Ice]

Um,

What exactly are you trying to do?

Are you planning to use the splits, for heating and cooling until the ambients get too cold, then switch to temporary backup unsealed system?

Or are you planning to run unsealed all winter?

Are you able to use the warehouse as a lung, if not why?

Using sub freezing outside air to cool a room is fairly straight forward. I use heavily insulated intake ducts with multiple diffusers at the ceiling; and 2 variable speed exhaust fans on a temp controller. As olekingkole pointed out, cold air is very dry, you may have difficulties maintaining humidity using outside air.

What you seem to be looking for is 2 complete heating, cooling, humidifying, air exchange solutions; one for sealed, one for vented? With the right controls you could possibly share some of the equipment. But way? If you look at your total energy consumption for a 12 month cycle, I'm not sure it's worth the added complexity?

If you want to decrease the AC usage during the winter, you should look at something like the ice box air to liquid exchanger, or a home brew air to air exchanger. You will still need 100% back solutions for when your AC/ heater stops working.

AI

 

[olekingkole]

To cool 10K lights I use a 1.5 ton mini-split and active exhaust with a large ceiling fan. The split is set for 75 and the fan for 80. Air comes directly from the outside. Temps rarely go over 82 in the room, even in mid-summer when outside temps run up to 100. Outside temps drop fast here on summer nights and are usually under 70 by 10 pm. The big problem with this hybrid system is keeping sufficient moisture in the room. The best solution seems to be to pack it full of plants. Condensation is not an issue.

 

[doctor.dank]

I plan on running mini splits for most of the year. I would run them 365 if it didnt get too cold in the winter time for them to cool however, they will be my heat source year round because they will still heat in -15 F outside temps. so come winter time I want to have an exhaust system that is powerful enough to cool during lights on since I cant use the minisplit for cooling.

I am also going to be using the exhaust (preferably just one for each room) year round at the beginning of lights off (to get rid of co2+humidity) and I also plan on running the exhaust maybe 1 to 4 times (maybe 10-15 minutes) during lights on because I'm going to be running a CO2 generator and have read about a lot of people having off gassing problems so I want to pump fresh air into the room periodically so I don't have any issues.

I can't use the rest of the warehouse space because the person I am renting it from has people in and out from time to time and doesn't want to see anything.

I agree, keeping humidity up when i'm running it active air exchange in the winter will be difficult, especially with bare bulbs. I am going to get the hydrofogger that puts out 2 gallons of water an hour for each room so I'm hoping that will be enough. I could also add another one to the dead space if I end up using that as a lung room.

But is that what I should do? Use the deadspace as a lung room with a passive intake from outside and than passive intakes for each room? Put self closing grates over the intakes in each room that will open up from all the pressure once the exhaust kicks on? What about the main intake for the lung space?

and again I want to say thanks for all the input I do really appreciate it.

 

[Alaskan_Ice]

Yes, use lung room with passive intake with an exhaust fan(s). Use 2 normally closed louvers on wall penetrations. One of the louvers is opened when the fan turns on, the other closes with loss of power, or low temp alarm. Put the lung room exhaust fan(s) on its own variable speed temp controller. Keep in mind that you could experience icing that will cause your louvers to stick open, and collect on your fan. You will also want a LARGE electric unit heater in the lung room for when something breaks.

Each room gets its own passive intake, exhaust fan, single louver, and variable speed temperature controller ducted to the lung room.

Set your grow rooms at the desired temperature set point (80F?), and lower the lung room temperature just enough so the rooms can reach their set points. When your AC is working, the room fan(s) are off, lung room fan(s) are off. AC stops temperature increases louvers open, and fans start circulating to the lung room. The lung room warms up and reaches its set point, louvers open fan(s) turn on. This may sound easy but, even with the variable speed temperature controllers, it can be challenging getting the proper size fans.

I am in know way recommending this; I use 2ea. Phason TVS, 3-stage temp controllers for this exact purpose. Each controller has 2 stages of variable speed (triac), 1 fixed, and one alarm. Start and stop temps, minimum idle temp and speed, adjustable ramp rate. The variable speed stages run the fan(s), the fix stage runs louvers. Fan speed controllers, type of fan motors, humming, spontaneous fan explosions, all have their own koolaid. I use shaded pole motors with the snubbed triacs in the TVS's. I size the fans so they don't need to idle down past 50% speed. Next time I will drive single phase to 3-phase inverter VFD's for speed control.

I'm not so sure I wouldn't look for a different AC/ air handler solution, KISS. In my experience when dealing with -15 degree cooling air, there is zero margin for error.

AI

 

[Alaskan_Ice]

PS you'll have to put a ceiling over res room, and seal, and insulate the lung, your lung room temps could easily go below freezing, when you are trying to balance humidity loss.

AI

 

[doctor.dank]

So to avoid having to worry about louvers freezing up should I just run a pipe up into the attic and intake from there instead of directly from outside? The attic is a huge space.

Why would I need a separate exhaust for the lung space? Couldn't I just have exhaust in each room with intakes for each room and cycle from lung room (intaking from attic) into the rooms and then out thru the rooms exhaust fan?

 

[doctor.dank]

Is there an alternative to running active exchange in the winter? I really want to run mini splits for how efficient they are (I'm looking at 30.5seer units) and how they can heat and cool so it's really going to be hands off most of the year. It doesn't get below 15 degrees here that often. Average temps for Dec Jan and Feb are like 25 degrees but it's just those few nights that it will get colder I don't want it to fail or stop working. Although im having my sparky wire up high temp shutoffso plants won't fry if the mini splits cut out I just don't want to damage the mini split. Can I build a shed type setup around the condensors for winter time? Obviously it has to allow enough airflow but something that will at least keep temps about 20 degrees if outside temps go below 0?

 

[Alaskan_Ice]

I have not done this but it should work;

Since the AC's are a pain in the ass outside in the winter anyway, packed with snow, ice, frost, continuous defrost cycles etc... I would build a small building, insulate it, put the condeser / heat pump thingy inside of it. Install external temperature controled louvers, supply and return duct from the warehouse with fans, and temp controller, set temp controller at 0F?. With some tweaking you could probably match the external louver area, and warehouse heating loop to balance the thermal load from the AC. When in cooling mode, the AC units will be removing heat from the grow room, and adding heat to this building. The warehouse will proved heat when AC is off, and temperatures are below set point. You need good airtight louvers, one smallish set of temperature controlled, and several sets of large manual ones for summer operation. It should work fine as long as you keep air circulating through the "lung" shack?

Comercial AC can use separate cooling loop filled with glycol. There is a big radiator outside, a big radiator inside, a pump that circulates glycol between the 2. The inside air and the outside air never mix, heat is tranfered through the glycol. Sized properly this will cool anything very in expensively when the outside ambients are cold.

I would wager that a comercial airhandler that has an economizer built in, will have greater overall system efficiency then the splits, with a work around. You would be using the economizer all winter until ambients warm up enough that it wouldn't handle the heat load, then AC would take over. This is a little simplistic explanation, there are comercial air handlers, and chillers being marketed to growers now. Installation cost are higher, bit more duct work.

Unless someone knows a reason the lung shack wouldn't work? I wouldn't be afraid to try it!?

Best solution is to purchase an AC designed to run in the conditions you are asking it to. Even though your current model may have a higher seer, it doesn't mean that the overal efficiency of your system when operating in low ambients is going to be better, it might actually end up being worse?

ymmv

AI

 

[Alaskan_Ice]

^Inexpensively

 

[Alaskan_Ice]

Do you have the budget to move to a chiller/ airhandler set up? With your cold weather it may pay back fairly quickly.

AI