Dehumidifier causing serious issues in closed grow

When constructing a medical grow we decided to go with a closed room setup. Read up a lot, asked a lot of questions but in the end designed an excellent room. Unfortunately due to time restraints we were not able to dial equipment in before moving in our genetics.

So one week goes by and plants three wks old are thriving in the environment but humidity is a little high so we begin to utilize our dehumidifier. After two days of this plugged into our CHHC4 set on 65% RH our plants foliage dried up completely overnight in odd patterns across the room and began to spiral. Temp, nutes, air circulation, C02, PH, PPM and every other facet was perfect so we knew it was the dehumidifier. It was the right size for our room but maybe we just needed to mount it so five days later after letting the plants recover we ran it again mounted and in 24 hours the plants looked the same.

We immediately ordered another one sightly smaller 60 pint dehumidifier. Once it arrived I mounted it and ran it with the fan set on low plugged into CHHC4 and it nearly killed all plants never dropping RH under 65%.

At this point we were completely unsure of what to do because RH gets to be 98% at night so we ordered yet another dehumidifier but smaller 40 pint one. We have ran this one for one week now with no problems and just last night it began to slightly show spiraling on the tops of a few plants in close proximity. Being in Cali we have spoken with many growers and even had a friend drop the question for the people at Oaksterdam but nobody had any clue.

So my question is what are we missing? Has anyone else ever ran a closed room and experienced dehumidifier issues?

Specs:
7'x14'
5000 watts HPS
12,000 BTU A/C
40 Pint Dehumidifier
1300 ppm C02
3 wall fans
Advanced Nutrients with organic tea supplementation and Fox Farm Soil
6.4 PH and currently hitting them with 950 ppm week 1 for Flower
Soil PH is 7
Temp during day is 78-82 F

Vegging plants like high humidity...I don't have one in my grow room...bud room yes, but not grow room.

Yep certainly know this but in a closed room our humidity can get to 98% RH and we had powedery mildew from such moisture. So not running one is not an option

do you have an intake pu;;ing frsh air in at all?

*pulling/pushing

Nope. Designed the room to be closed so no ins or outs. Control temp with AC/heater; dehumidifier for excess moisture and C02 for them to breathe all running off a CHHC4.

Worked out perfect until dehumidifiers were brought in. We have excellent air circulation inside as well. Determined to make this closed room work. I've never seen plants grow quite like they have in these conditions.

Yep certainly know this but in a closed room our humidity can get to 98% RH and we had powedery mildew from such moisture

Click to expand...

then a fan needs to be aggressive...tight room or not, you need fresh air...recycling inside air isn't enough.....you might think so but the plants may say otherwise...listen to them...my old partner wouldn't listen and his results wasfailure...

and apparently the plants are tellin you they need fresh air. if you sealed off a room completely, and are acheiving a 98% RH, then its pretty close to airtight like you like it and its like your slowly suffocating a plant. They breathe in carbon dioxide and release oxygen, it stands to reason that soon they wont have much to breath because what they are looking for is not there. basically.

Agree completely.

Thank you for the help and suggestions.
After reading tons and talking with many people concerning this issue fresh air is not needed for a room when you supplement adequate C02, have good air circulation and control the environment completely. I do believe this is optimal for indoors. Plants look amazing when dehumidifier is not running and have grown at an exponential rate with these conditions.
Specs:
7'x14'
5000 watts HPS
12,000 BTU A/C
40 Pint Dehumidifier
1300 ppm
3 wall fans
Advanced Nutrients with organic tea supplementation and Fox Farm Soil
6.4 PH and currently hitting them with 950 ppm week 1 for Flower
Soil PH is 7
Temp during day is 78-82 F

Really want to dial this room in. Creating intake/exhaust to vent the room will be our backup but we would only use this to control humidity which will not be very efficient for C02 or RH. Basically am really hoping someone has ran into similiar issues with their closed room setup.

lets see a pic. with and without dehumidifier. if youve got em, dont go stressin your plants.

i have never heard of a dehumidifier hurting plants, even when the rh drops to single figures, if the rh is 60+ with the dehumidifer on i am most certain that it is not this causing it, how sure are you?.

i have heard from several people who employ cge growing methods that have very similar problems to the ones you are describing, it is caused by the high levels of co2. the plants can take up to 3 weeks to get used to the high ppm of co2 they claw and can shrivel up.

it is very hard to help without pictures of the plants in question, as i said earlier i really can't see how the dehumidifer is hurting the plants.

i am interested in doing a sealed room grow in the near future so i will subscribe to this thread to se if you find the answer to the problem, good luck with the growing.

Won't have pictures up till later tonight. But this is certainly related to the dehumidifier.

Plants loved the environment, had been growing amazing in this environment. At one week marker in dixie cups we ran our dehumidifier since RH was in the high 80's. It wasn't till the next morning that we noticed it had greatly affected our plants. The leaves were dry and different ones across the room were spiraling. Also certain ones in close proximity had soil dry up like a rock.

So we let a week go by fo plants to recover and decided to mount the 75 pint dehumidifier in the corner of the room to see if this really was the culprit because everyone else said otherwise. We ran it and the next morning all plants were looking awful.

Sought after help from others who have closed rooms and they all said they never heard of this. We ordered a 60 pint that lowered RH well but it made every plant spiral and feel brittle in 24 hrs. We then ordered a 20 pint dehumidifier that did nothing bad but also didnt lower humidity very much.

Now we are running a 40 pint on lowest fan setting. Unfortunately this wont lower RH below 60% so we may have to upgrade and now we are 1 week into flower and are still dialing in the rooms. Also saw small signs of spiraling on healthy 4ft plants directly next to it

Thanks for the help. Will have pics of the before and after running dehumidifier later tonight.

I run a closed room with a CHHC-4, CO2, and a dehumidifier, it's worked acceptably for my first two grows. However my dehumidifier is stand alone and not controlled by the CHHC-4. The humidity not dropping at all sounds fishy to me, have you checked your CHHC-4 readings with another device? I know mine isn't reading temps right.

Thanks ghb for the info. Only things I've noticed with C02 is since they are utilizing such high & constant amounts is the need for higher nutrients. All plants directly under the lights were slightly yellowing until we increased their nutrients. Fixed all problems regarding this. They have grown at an unreal rate and have stalks like trees so I don't think its C02 stress. Definitely not with the foliage dryness and spiraling. The pics I'll post on here later are 100% directly related to the dehumidifiers.

Ive got a thermometer right above the plants that I use for my check. But it isn't RH, just general moisture reading and temp. Temp is on point night and day. My CHHC4 is hung up on the wall to avoid getting splashed with water so its not the best gauge for these readings but yes humidity is really really high

We ran the 60 pint for our third attempt both off CHHC4 and with its own sensor. This is the one that really messed things up but did get RH right at 50%

The only dehumidifier that didnt really affect anything was the 20 pint. Couldnt get RH under 85%

Now we are running 24 hrs a day the 40 pint that won't get RH under 70% but after almost a week is showing the same signs of stress that existed before. Thought we had solved the problem. But this one has three options for fan speed so we are trying them all out. Thanks pimpernickel for taking time to help out. Will have before and after shots later tonight and shots of our deadly dehumidifiers.

are you relying on hygrometer for reading RH? or just assuming it didn't go below 65% because that's what the controller was set to?

maybe you controller is bad?

i run a setup similar to yours and have no problems with my dehumidifier, although i run a small burner for CO2 gen and it lowers the RH as well.

Yeah unfortunately I've spoken to quite a few people who are running similiar designs but have not encountered this specific problem. Most have much larger dehumidifiers then ours and say it works great. But there is no further questioning the issue in our room, cause and effect is always the dehumidifier always within 24-48 hrs. Wish it weren't the case. We've increased air circulation, let temps rise to 82 F to maximize C02 use and also lower RH, mounted in different locations, set the fan speed lower and have tried to alter things to make the dehumidifiers work for us. But to no avail...

The CHHC4 sensor is unfortunately giving proper readings and controlling equipment the way it is supposed to. The hygrometer in the room is just a backup for readings above canopy and is not giving bad info either. We even installed a third one the other night to check the readings at both ends of the rooms. When not running our polyfilm will be covered in a mist by the morning. So this will become a much more serious issue in the weeks to come if not properly handled.

Have any issues similiar to this occured in ur closed grow murfy? Or anything else I should be aware of for that matter? Thanks for the help

Here is what the room looks as of now after not running dehumidifier for almost 4 days. Most things have recovered. Before anyone else says it I know the room is was too crowded. But because of inadvertent stress we had to veg out these girls way too long. I'll move a few of the weaker ones out tomorrow. In the second photo the only thing missing is our dehumidifier which is usually mounted in the top right corner next to our little heater for night. Welcome to our sanctuary

Before anyone starts talking defiencies, please note these plants were 100% healthy 24 hours before these pics were taken. There was no spiraling, all healthy green and thriving. Almost have to be here to believe it.
This is back 3-4 weeks ago when we ran our first two dehumidifiers. The photo with small dixie cups was our 24 hr control to dial in the room before we moved all plants in. It ended up really hurting the foliage and dried soil up terribly all overnight. So we figured if we moved in more plants in their 3 gallon bags, raised it things would work out alright. They did not and we have done this with four different dehumidifiers now. Thank god for return policies.