Dehumidification Requirements For Large Grows

[Bmorrill]

I'm working on a design for a large flowering space and have found it difficult to get solid numbers on what i need to be pulling out of the room for water.

We've gotten feedback suggesting 95% of the water into the plant will transpire/evaporate into the space. Is 95% of the water that is introduced to a plant throughout the day a sufficient # to use to determine total dehumidification load?

Furthermore what % of that water is transpired during lights on and lights off? Is the water irrigated only during lights on?

The plants are hydroponically grown, with space circulation fans and 76F/45%RH room conditions. No outside air is introduced and the rooms are tight (no external humidity gains to space)

 

[1diesel1]

Use the K.I.S.S. Method. The flower room needs to hold humidity at 50-55%. Throughout growth.

 

[Bmorrill]

Temperature and humidity requirements in the room are set by the facility. We are designing to their setpoints, however that doesn't change the total water content we need to dehumidify as the amount of water going in will remain the same.

 

[DGP]

Look at the Quest site and se what they recommend. Their dehueys are the absolute best especially for larger rooms. If I remember correctly they have some information that help you choose the capacity needed for your grow or just call em up.

Dee

 

[Bmorrill]

It's not a matter of the equipment itself, its the calculated dehumidification load. This is a commercial operation and we have an idea of the amount of water we're thinking transpires into the space, but i want to make sure we have the correct #'s. Quest would be able to help us to identify how many of their units we'd need to maintain the conditions, but they need the load profile before then can do that.

That's why i want to make sure of how much and when the plants transpire, and what we should expect for watering for both lights on and off scenarios. E.G. if during lights on the plants transpire most of the water they're fed, the dehumidification load is higher because the rate per hour increases at those times. etc.

 

[Aqua Man]

Humidity is directly influenced by temperature. I suggest reading up on VPD (Vapor pressure deficit) to get a rough idea of transpiration rates. The amount of water transpired will depend on the VPD and the size of the plant. Fact is you can just increase or lower temps within optimal ranges to attain a certain humidity increasing or decreasing load on a dehumidifier and transpiration rates. To many variables to give you an answer.

 

[G gnome]

Figure on soaking up as much water as ur putting in. A quest 205 for every 6,000watts of light

 

[Aqua Man]

Figure on soaking up as much water as ur putting in. A quest 205 for every 6,000watts of light

Can't go wrong with that, better to have more than needed. I don't see the point in trying to calculate transpiration rates and its really complex.

 

[Bmorrill]

Our first thought was to go water in water out, but once we saw the irrigation #s we wanted to make sure we werent missing anything.

If we figure water in-water out, 1800 plants at 0.66 gal/day would net ~1200 gal/day.

That'd be 47 quest 205 units or 18 quest 506 units. Where $$ is a factor, we want to make sure we're not overkill on dehumidification equipment so i have to explore all calculation methods.

A question that still concerns me is, regardless of understanding VPD calcs to determine the potential #s, do the plants transpire more during lights on than lights off? If we want to maintain a space temperature during lights on and they give off a majority of the 0.66 Gals at that time rather than during the entire day (including night) then our per hour dehumidification load increases. If you say 85% of the 0.66 gals/day is during a 12 hour light block, then our dehumidification equipment has to do 84 gals/hour during that block as opposed to 50 gals/hour if its completely spread out over the 24 hours.

Thats a 67% increase in equipment capacity to maintain during those times.

 

[Aqua Man]

Yes during lights on transpiration is elevated. By how much depends on a whole host of factors. Light intensity, available Co2, wind, temp, humidity. I'm thinking you are waiting for an answer that your looking for more than one that is logical. Take G gnomes advice plan for the worst and hope for the best. The worst that can happen is you have a little to many and they run a little less, power consumption would be the same. They will run what they need to. Initial investment might be a little higher but how much more will it cost to have moldy plants because your calculations are out.

 

[Landscaper]

I can tell you that I have 2 quest 155's with a plant count between 120 and 140 ( strain dependent ) and they control my humidity quite easily.

 

[sixstring]

the most important,and hardest part of the cyle will be 2 hours after lights out.thats when the Rh spikes the most.
room temps,RH and co2 equipment will effect how much your equipment runs also.expect at least 90 % of the water in to be removed,the hotter the room the higher the number there.quest is fine if ya have unlimited funds,anden pulls more water at the same power(higher efficiency) and costs less.


i have this unit and love it

 

[Freshone]

I find it funny that all these people doing huge grows with tons of equipment and plants feel the need to come on the farm and ask for advice on anything.I honestly dont beleive a damn word they say and if they are telling the truth they are destined for failure.

 

[Aqua Man]

Also reducing temps slowly would reduce the load. So many ways to skin a cat some cheaper than others, some more efficient than others. You don't want hi Co2 at night anyhow so even a timed air dump cycle may help reduce load.

 

[PharmHand]

the most important,and hardest part of the cyle will be 2 hours after lights out.thats when the Rh spikes the most.
room temps,RH and co2 equipment will effect how much your equipment runs also.expect at least 90 % of the water in to be removed,the hotter the room the higher the number there.quest is fine if ya have unlimited funds,anden pulls more water at the same power(higher efficiency) and costs less.


i have this unit and love it

Nice units but weird voltages 208v and 277v are normally 3 phase, no? It says single phase. They cheaper than quest?

 

[PharmHand]

Ggnomes suggestion works out to be about 34 pints per 1k, which is what ultimately will drive transpiration/evaporation given a standard sized full canopy. I’d say 30-45 pints per 1k depending on many factors such as cooling methods,medium and pruning techniques to name a few

 

[sixstring]

Nice units but weird voltages 208v and 277v are normally 3 phase, no? It says single phase. They cheaper than quest?

The one I linked comes in 240v single phase and 208v but yes 277v is 3 phase.
Much cheaper than quest,when I compared mine with the same size quest mine ends up being 1k cheaper and more pints per kwh so it was a no brainier,plus the 5 year warranty.anden/aprilaire has been around for a while longer than quest also.these also have remote sensors,mine is hard wired but they have options for multiple wifi sensors and the unit will take readings from all and average the room.its a bad motherfucker :cool:

 

[PharmHand]

The one I linked comes in 240v single phase and 208v but yes 277v is 3 phase.
Much cheaper than quest,when I compared mine with the same size quest mine ends up being 1k cheaper and more pints per kwh so it was a no brainier,plus the 5 year warranty.anden/aprilaire has been around for a while longer than quest also.these also have remote sensors,mine is hard wired but they have options for multiple wifi sensors and the unit will take readings from all and average the room.its a bad motherfucker :cool:
View attachment 816652

Really nice. Aprilaire is a very good brand too

 

[PharmHand]

I never understood why quests cost so much. I can get a basic trane 5ton split unit for 2800 but a quest 225 is over 3k? Wtf these guys are just gouging us dope growers

 

[organicace]

I never understood why quests cost so much. I can get a basic trane 5ton split unit for 2800 but a quest 225 is over 3k? Wtf these guys are just gouging us dope growers

You are so right!!! I mean technically there is actually less there than a split unit, they basically just take an AC and put the outside condenser right after the indoor evaporative cooler to heat the cold air back up once the condensate has already built up on the evaporative cooler. Wouldn't it be feesable to build your own that way and get way more bang for your buck? anyone with more info that can chime in and let me know what i am missing?