Humidity swing help

Hey guys new to the pulse forum, hoping I can get some help. I recently purchased a larger AC then I previously had and it has made keeping humidity consistent almost impossible. I have 2 scynce raging kush LED in a 8×8 tent with co2. I had a 10,000 btu window unit prior to this run, but I purchased a 12000btu unit thinking I would be helping myself out but all it did was make my humidity swings out of control. At first I had my dehumidifier in my tent and the swings were completely out of control… from 55-80% every swing. I battled that for 2-3 weeks then I decided to move my dehu outside the tent and just pull dry air into the tent as needed. That has helped drastically. I’m able to keep a 10-12% range now. Is this an acceptable range? I attached a photo of my pulse readings so you can take a look. If you have any other advice or ideas please let me know. I’m mentally exhausted from trying to figure this out. Wishing I hadn’t purchased the larger AC at this point but its a little late to change that.!
The first pic is before moving the dehu outside the room. The last 2 pics are the current readings. My plants def seem happier with the change. But I’m going for perfection… not just acceptable.
Screenshot_20190918-125759_Brave|281x500 Screenshot_20190918-125642_Chrome Screenshot_20190919-151538_Chrome

1 Like

Seems like your dehumidifier has a pretty big threshold , maybe find the sensor that’s taking the reading and move it away from the unit . Someone was just talking about this on Instagram with their air conditioner , just routingthe sensor made a big difference for them.

1 Like

I’ll look into that and see if I can figure out where the sensor is. Do you think 10% swing is ok tho? Or is something that needs to be remedied right away? I wish I could maintain 5% but I think my AC alone drops it about 10% when it kicks on

Where is the sensor in relation to the dehu? It could be that the air in your space isn’t circulating well and therefore causing the dehu to run short cycles instead of long ones. 10% swing is not a big problem (compared to temp at least) but all of your readings are during lights on. You can expect much higher humidity when the lights are off (both lights and A/C will not be removing moisture).

What type of A/C is the 12k that you added? Another window banger or a portable? Is it a dual hose?

The AC is a window unit. I pulled out the interior and sealed the unit up with foil tape. I’ve def got plenty of air circulation inside the tent. I solved the issues by moving my dehu to outside the 8×8 tent (the room it’s in is 10×10) so I’m keeping the outside room at 50% humidity and I have my inkbird hooked to my exhaust fan. So now when my humidify gets to 74% (in veg) the exhaust fan kicks on and pulls in dry air from outside the tent and exhausts the humid air from inside the tent. I’ve been able to keep it within 6% swings now (68-74%). Much more acceptable for me. I’m going to use a bit more co2 now as I have to keep the 10×10 at 1200ppm instead of the 8×8 but I’m good with that. Small price to pay to keep things stable and keep VPD steady. I’m moving to a less humid state in a few months so I’m going to have to re design everything again when I get there but for now this will work for my last run at this location.

1 Like

Do you make sure to re-calibrate your CO2 sensor every few months?

1 Like

Lol to be honest I didnt kno I had to… how do I do that?

I’ve been using it a year, I didnt kno they had to b recalibrated!

Yeah pretty much every CO2 meter needs to be re-calibrated. Usually the calibration involves placing them into a non-enriched environment for a certain amount of time. Different CO2 monitors have different calibration procedures.

Yea I re calibrated, it was off by 100ppm. Thanks for the info I appreciate it!

Set yourself a reminder on your calendar to do it again in 3-6 months!

If I may ask, how large of a dehumidifier are you using? (holding capacity and liters / pints per hour?) and how much rh are you able to strip off your room running at full?

My friend struggles with high RH in his growspace and I’m trying to get an idea how large a dehumidifier he would need. My psychrometric chart seems to indicate a 70-90 pint machine would be required for a 448 running at 300cfs to lower rh by maybe 15-20%… But it’s real tricky to know.

Great work figuring out how to balance that all! Using your room to buffer the swings is useful information for everyone. Thanks :slight_smile:

1 Like

I have a 95pint and it has absolutely no problem keeping up. I’m also in a hot state so my AC definately helps quite a bit. Even without the AC I think the 95 pint is plenty for my space

1 Like

I know this thread is older but what I’ve experienced might help someone reading now or in the future.

I am having the same issues. I am running twin rooms both with the dimensions of 6‘ x 12‘ x 9‘. Until I got my pulse monitors (one per room), I had no idea that my swings we’re that radical. Since then I’ve been able to flatten them out a little. Like the OP I installed much larger AC, one per room, than I probably needed. I did that because I didn’t want my minisplits to run all the time or at least that was my thinking. I use a much more sensitive humidity controller than the one that comes with my dehumidifier. The dehumidifiers that I run are woefully insufficient. My current dehumidifiers are the standard Amazon 90 pint garbage that I have to replace every year - year and a half. I’ve tried them all except the one that I thought I didn’t have space to use. I finally broke down and called Quest. I talked to Mike the sales agent and he told me about a smaller 70 pint unit they have that is extremely efficient with energy. It’s the Quest 70.

Besides saving money on my electrical bill having these much more efficient dehumidifiers should keep my air conditioning from cycling as much. My current inefficient dehumidifiers produce more heat for the same amount of dehumidification. That equates to more cycling of my AC. Every time my AC flips on I have a major drop in RH and a corresponding increase in VPD. Now having said all that, I haven’t bought the quest 70 dehumidifiers YET. They are more expensive to get in with but in the long run they should be much cheaper and do a much better job from what I have gathered from everybody who’s ever had one. Not only that but these dehumidifiers are small with a really good warranty. They are 12” x 12” x 21” in size. And the intake and exhaust is set up in such a way that they are breathing better so I can get a more uniform delivery. Now I just need to come up with the $1200 per unit times two in my case.

I thought I would just add what I’ve experienced so far. And hopefully I’ll be able to but you know how they work out. And no-I’m not involved with Quest or Pulse other than as a customer basis.

Now back to the original problem - rapid cycling. Another thing that I have been doing that helps is I use a much more sensitive humidity controller made by Inkbird. It has two outlets one for dehumidification and one for humidification. I plug in my current dehumidifier in the one and I plug-in a humidifier in the other. The humidifier turns on right after a cooling cycle starts. I have found this level things out a little bit more. I hope I won’t have to use much humidification once I get these new dehumidifiers.

I’m a nerd when it comes to my grow. It keeps me ticking. One of the smartest decisions I’ve made in the last six years of growing has been to buy these Pulse monitors. They helped me find and fix a problem that I didn’t realize was that bad. I LOVE THESE THINGS MAN LOL. Pete really helped me get it lined out. Thanks Pete for a great product and great service.

1 Like