Dehumidifier causing wild fluctuations

[SpawnOfVader]

Installed a new dehumidifier inside my tent (humidity inside my house sucks). It's causing some heat however it still never goes over ~84 so I'm not worried about that.

My remote monitoring system has been seeing a TON of fluctuations though (see graph below).

I'm thinking these super short cycles are one of three things (or possibly all of the above)-

1. Humidistat on the unit sucks
2. Unit is too overpowered for space (30 Pint model in 4x4x7 tent)
3. Too much air exchange with my 6" fan

I already have an inkbird humidistat switch sitting around so I just turned off the humidistat control on the unit and moved it over to the inkbird controller w/remote sensor.

Anyone have similar issues/wild fluctuations with a dehumidifier in tent?

NOTE: I have tested my sensors at multiple positions in the tent and the same fluctuations show up. I have 2 oscillating fans at the top of the tent and one below canopy.
The same sensors in my veg tent (running humidifier off of an inkbird controller) do not have the same types of fluctuations.

 

[SpawnOfVader]

My fan is already running on the lowest setting- it's a ~400 CFM 6" fan. I'm thinking if this isn't enough maybe wrap it a few times in activated carbon cut-to-fit furnace sheets? That should help with the small amount of smell still being exhausted outside plus slow down the exhaust some?

 

[nc208]

Installed a new dehumidifier inside my tent (humidity inside my house sucks). It's causing some heat however it still never goes over ~84 so I'm not worried about that.

My remote monitoring system has been seeing a TON of fluctuations though (see graph below).

I'm thinking these super short cycles are one of three things (or possibly all of the above)-

1. Humidistat on the unit sucks
2. Unit is too overpowered for space (30 Pint model in 4x4x7 tent)
3. Too much air exchange with my 6" fan

I already have an inkbird humidistat switch sitting around so I just turned off the humidistat control on the unit and moved it over to the inkbird controller w/remote sensor.

Anyone have similar issues/wild fluctuations with a dehumidifier in tent?

NOTE: I have tested my sensors at multiple positions in the tent and the same fluctuations show up. I have 2 oscillating fans at the top of the tent and one below canopy.
The same sensors in my veg tent (running humidifier off of an inkbird controller) do not have the same types of fluctuations.

Why are you running that big of a dehumidifier in the the tent? Dehumidifier is blasting hot air when its on so thats why you see many fluctuations. Why don't you move the dehumidifier to the room outside of the tent and work on the air being pulled in vs dealing with it only in your tent.

 

[SpawnOfVader]

Why are you running that big of a dehumidifier in the the tent? Dehumidifier is blasting hot air when its on so thats why you see many fluctuations. Why don't you move the dehumidifier to the room outside of the tent and work on the air being pulled in vs dealing with it only in your tent.

No drain near my grow space so I needed a unit with higher capacity. The heat isn't fluctuating all that much, it's the humidity- spiking from 45-60 in a matter of a few minutes.

Going over my design, I think part of the "fluctuations" I'm seeing is that the intake for the dehumidifier is below the canopy where humidity is higher and the air is cooler. When the unit turns on at first it sucks in and circulates that damp air before kicking in. I'm going to try adding another fan below canopy.

 

[rmax]

A 40 pint is good for 2000 square feet

40 or 50-Pint Dehumidifier - This size of dehumidifier is recommended for areas up to 2000 square feet that smell musty and feel damp all the time.

You have 16 sq ft. Your dehumidifier kicks-on and extracts all the humidity within a minute. Can you return the dehumidifier and get one properly sized for use inside your tent?

Alternatively, can you place the dehumidifier outside the tent and somehow drain to outside? Like through a window or drill a hole through the wall for the dehumidifier hose?

My 44 pinter has a hose and catch basin. Does your dehumidifier have the catch basin? Can you return the dehumidifier?

 

[Merkn4aSquirtn]

Put the dehumid in the room your tents in. Your tent is exchanging air at a faster pace than what the dehum can keep up with. Tbh it's almost worthless to run one in a tent

 

[SpawnOfVader]

A 40 pint is good for 2000 square feet

40 or 50-Pint Dehumidifier - This size of dehumidifier is recommended for areas up to 2000 square feet that smell musty and feel damp all the time.

You have 16 sq ft. Your dehumidifier kicks-on and extracts all the humidity within a minute. Can you return the dehumidifier and get one properly sized for use inside your tent?

Alternatively, can you place the dehumidifier outside the tent and somehow drain to outside? Like through a window or drill a hole through the wall for the dehumidifier hose?

My 44 pinter has a hose and catch basin. Does your dehumidifier have the catch basin? Can you return the dehumidifier?

It's "New" for the tent, but not a new unit- it's on long term loan. I tried running it in the room around the tent but it makes very little difference since it's pulling straight from AC. Hopefully this all goes away once I get a vapor barrier installed under the house, it's up to 72 RH inside some days.

 

[SpawnOfVader]

Put the dehumid in the room your tents in. Your tent is exchanging air at a faster pace than what the dehum can keep up with. Tbh it's almost worthless to run one in a tent

So without my tent runs at 65-70RH. Even with the erratic swings the average is around 54RH with it on. That's a huge difference this late in flowering (first day of week 8 ).

 

[Merkn4aSquirtn]

If you're fighting high humidity... good air circulation from a couple fans work wonders. My humidity gets over 70% at lights off. Never no mold.

 

[SpawnOfVader]

If you're fighting high humidity... good air circulation from a couple fans work wonders. My humidity gets over 70% at lights off. Never no mold.

Will try that. I've got two tiny oscillating ones above the canopy and one small oscilating one below. I'll try scavenging a spare vornado from around the house and throw it below canopy as well.

I also got a random tip to stop exhausting outside and that the negative pressure created by my two tents is enough to draw in significant air/exacerbate my humidity issues in the house.

 

[Merkn4aSquirtn]

Negative pressure alongside constant airflow should calm your worries.
I was running 70-80s humidity while my tent was crammed packed. I chopped one 2 weeks ago and now it doesn't get above 65% at night. Hell i couldn't get it lower that 65 with lights on then.
I worried everyday that i was going to open my tent to see bud rot.
Keep the environment clean and have fans running and you shouldn't have anything to worry about.

I do live in a pretty decent controlled environment. I've never had mold issues outside my tent or inside so that could be why i never get it

I'm not even sure mold really even exists but i see it every day on here. I think it comes down to where you live and how muggy it can get.

 

[SpawnOfVader]

Negative pressure alongside constant airflow should calm your worries.
I was running 70-80s humidity while my tent was crammed packed. I chopped one 2 weeks ago and now it doesn't get above 65% at night. Hell i couldn't get it lower that 65 with lights on then.
I worried everyday that i was going to open my tent to see bud rot.
Keep the environment clean and have fans running and you shouldn't have anything to worry about.

I do live in a pretty decent controlled environment. I've never had mold issues outside my tent or inside so that could be why i never get it

I'm not even sure mold really even exists but i see it every day on here. I think it comes down to where you live and how muggy it can get.

Makes sense, well scientific method be damned I'm making a few changes at once today.

I've got a good weather station outside and multiple humidity sensors in my house spread out. Will watch the relationship between external humidity and average humidity in my house now that I'm no longer venting outside. Around 2 months of data are saved for the way it was configured so I have a good metric for comparison.

Also added another "S" curve in my exhaust to try and slow it down for now- the fan is already on minimum. If I need to slow it down further I've got 48" of carbon filter sheet coming in on Monday and I can wrap my filter a few times. My fan at max power is rated for 400 CFM. Doing some quick math my target fan should be around 87.3 CFM (112 cubic feet grow space x 30% additional (ducting) * 60% additional (carbon filter) * 50 % additional (heat from lights)/ 4 (minutes per cycle).

 

[SpawnOfVader]

Hindsight is 20/20. Before removing the drivers from my tent I was fighting a ton of heat related issues. Switching my intake to 100% from the AC vent and removing the drivers was the fix but first I went way oversized on my inline fan thinking the airflow would be enough.

 

[SpawnOfVader]

Random thought but what about cutting a few holes in the ducting on the inside of the tent after the fan? The new exhaust is running to a light proof box at the end so I wouldn't be introducing any light leaks. That should both reduce the amount that's being exhausted and up my air circulation? I've already got an excess of negative pressure so I could spare to lose some more.

 

[Spazz24]

I run my dehuey outside my tent along side a stand up AC. If you can’t get your humidity down inside the tent with the dehuey outside of it make your intake bigger to pump more dry air into the tent. I have a 16” oscillating fan above the canopy and a small little shit fan under the canopy.

 

[crazieglued]

Makes sense, well scientific method be damned I'm making a few changes at once today.

I've got a good weather station outside and multiple humidity sensors in my house spread out. Will watch the relationship between external humidity and average humidity in my house now that I'm no longer venting outside. Around 2 months of data are saved for the way it was configured so I have a good metric for comparison.

Also added another "S" curve in my exhaust to try and slow it down for now- the fan is already on minimum. If I need to slow it down further I've got 48" of carbon filter sheet coming in on Monday and I can wrap my filter a few times. My fan at max power is rated for 400 CFM. Doing some quick math my target fan should be around 87.3 CFM (112 cubic feet grow space x 30% additional (ducting) * 60% additional (carbon filter) * 50 % additional (heat from lights)/ 4 (minutes per cycle).

My only concern is if you artificially slow it down say with a HEPA carbon pre-filter cut is you're holding back the air. This could cause your fan to over work especially if your fan has a higher CFM even at its lowest setting. As an example, the air filter in your house should not go past a Merv 13 or else it inhibits the flow and can burn out the motor on your heat pump.

 

[SpawnOfVader]

My only concern is if you artificially slow it down say with a HEPA carbon pre-filter cut is you're holding back the air. This could cause your fan to over work especially if your fan has a higher CFM even at its lowest setting. As an example, the air filter in your house should not go past a Merv 13 or else it inhibits the flow and can burn out the motor on your heat pump.

So on that note- holes in the ducting after the fan would be less detrimental? I wish I had a good way to test as I go and quantify the change in airflow

Also- I figured out how to take a moving exponential average of my sensor data in Home Assistant so the "spikes" will go away on the graph and I'll just see a nice balanced/average.

 

[crazieglued]

I have better luck with a 4 inch fan the CFM is still on par much less noise and it's still delivers the suction of a 400 CFM 6in also know the four inch inline fan is so much quieter. I'm about down to 40 sones all said and done I just need to dampen the noise on my fan. That's said in line fans are the noisiest

 

[SpawnOfVader]

I have better luck with a 4 inch fan the CFM is still on par much less noise and it's still delivers the suction of a 400 CFM 6in also know the four inch inline fan is so much quieter. I'm about down to 40 sones all said and done I just need to dampen the noise on my fan. That's said in line fans are the noisiest

I've been debating down sizing the fan but that's more money into gear. If I can harness part of the power from the 6 inch fan to circulate air in the tent and reduce the amount that's actually exhausting I think I'll be solid. My tent is already stabilized some from 6 ~3/4 inch holes in the duct. A cycle from min-max humidity is every 5-6 minutes instead of every ~2. Depending on how this looks on the charts over the next couple days I will probably double the amount of holes in the ducting.

Also going to add a carbon filter for the dehumidifier (not currently running a filter)... hopefully that slows the flow through the dehumidifier a bit as well.

 

[crazieglued]

Good shit.