question about dehumidifiers

hey rollitup,

i have a question on sizing dehumidifiers.

im building a room and im having difficulty picking the right dehumidifier for the room here is some information on the the build so far. the room is 9x12. i have the capacity to run 4000 watts of light, i have a 24,000 btu minisplit, a natural gas co2 generator. id like to use promix in 25 gal fabric pots. i have a 4 plant limit so id like to grow the plants on the larger side under a net im hoping to not exceed 4-5 ft in height trained under a net. im hoping to find an appropriate sized dehumidifier that i can connect to a controller and will survive a power outage and come back on if im out for the day. thanks for the help!

My only advise is to plumb the dehuey outside or into a larger container if you're going to use the water. Or both with a valve.

It gets really old really fast dumping out a little built-in catch tank.

22elar said:

My only advise is to plumb the dehuey outside or into a larger container if you're going to use the water. Or both with a valve.

It gets really old really fast dumping out a little built-in catch tank.

Click to expand...

i plan on plumbing it to a sump pit and pumping it to waste water i forgot to add that in my post ill need one that i can either connect a hose or pvc to.

22elar is right. Mine drains to a basement floor drain. Peak use, mid-summer the thing ran straight through. Like two months. Dumping a bin every 10/12 hours would be for someone else, not us.

I just use the $300 one from Lowes. I put some tubing on it where it drips into the catch tank, that goes to pvc and outside to a valve to a large tank or runoff. 12x12 room and I'm in the SE US, pretty humid.

what brand is it and what size? i dont have lowes im in canada. are there lots of plants that are a decent size i think dehumidifiers have alot to do with the size of the plants that are perspiring water that they drink as well as the room size. is it possible to buy too large of a dehumidifier ? (with the exception of crazy large commercial ones)

xox said:

what brand is it and what size? i dont have lowes im in canada. are there lots of plants that are a decent size i think dehumidifiers have alot to do with the size of the plants that are perspiring water that they drink as well as the room size. is it possible to buy too large of a dehumidifier ? (with the exception of crazy large commercial ones)

Click to expand...

Sounds like a question for @Renfro

xox said:

i plan on plumbing it to a sump pit and pumping it to waste water i forgot to add that in my post ill need one that i can either connect a hose or pvc to.

Click to expand...

You can't use it outside to water?

Many of the commercial dehumidifiers that are used to dry homes after a flood, have a built in condensate pump. This is handy if your drain is not below the dehumidifiers drain port. These models also tend to have the "auto restart after power outage" feature that is required if you are going to plug it into a controller. They often have an hour meter to show how long it has run over it's life.

So you may want to consider one of those. Phoenix, Dri-eaz Drizair are two that I have used and have only positive things to say about them. You can often find them used on craigslist with big savings. These units last a LONG time. Never had one die honestly.

Of course there is always Quest, Anden and others that all make good dehu's. I have a Quest dual thats really nice.

You can even get split style dehus that place the condenser coil outside like a split AC unit. These actually offer some cooling capacity since the hot air is outside. I know Quest makes these, I am sure there are others. I honestly wish I had purchased one of these when I picked up my quest but I was in a pinch and didn't have time to wait for a order.

I would avoid the home units because they tend to last a year or two and shit a brick.

Also, with a dehu plugged into a controller, you not only want a dehu that auto restarts after an outage but you want a controller that has a "delay on break" feature. This will delay from when the unit was turned off to prevent short cycling the compressor. So if the unit is shut down and the humidity reading quickly rises the controller will wait (from the time the unit was shut down) for a preset time before restarting the unit. If enough time has passed since the unit was turned off then there is no delay. This prevents rotor lock/hard start condition caused by back pressure on the high side of refrigerant loop that will quickly fry the compressor. Given a little time this pressure bleeds off through the orifice and the system equalizes. Some units have a delay on break feature built in but most do not (quest doesnt). Generally a 2 minute delay is enough but 5 is safer.

I build my own high amperage controllers for such devices, using a delay on break timer on the contactor coil. I can plug this controllers trigger cord into my autopilot, plug the power feed cord into a different dedicated circuit (120 or 240v) for the device (AC or dehu) and then plug the device into the power out of the high amp controller. It's a very simple build and it allows for the delay feature plus it allows for switching the power from another circuit. Otherwise you are stuck powering the dehumidifier from the same power source the humidity controller is running on, in many cases there isn't enough power especially if the controller is an environmental controller with other devices running on it and if you are switching 240 volt power.

Inkbird controllers have the delay option BTW.

Renfro said:

Many of the commercial dehumidifiers that are used to dry homes after a flood, have a built in condensate pump. This is handy if your drain is not below the dehumidifiers drain port. These models also tend to have the "auto restart after power outage" feature that is required if you are going to plug it into a controller. They often have an hour meter to show how long it has run over it's life.

So you may want to consider one of those. Phoenix, Dri-eaz Drizair are two that I have used and have only positive things to say about them. You can often find them used on craigslist with big savings. These units last a LONG time. Never had one die honestly.

Of course there is always Quest, Anden and others that all make good dehu's. I have a Quest dual thats really nice.

You can even get split style dehus that place the condenser coil outside like a split AC unit. These actually offer some cooling capacity since the hot air is outside. I know Quest makes these, I am sure there are others. I honestly wish I had purchased one of these when I picked up my quest but I was in a pinch and didn't have time to wait for a order.

I would avoid the home units because they tend to last a year or two and shit a brick.

Click to expand...

i was planning on wiring an outlet on the ceiling and sitting the unit on a shelf using gravity to feed the water to the sump pit outside the room. i dont necessarily need a controller on the unit either i havent purchased one yet mostly just having a hard time figuring out how many gallons/pints/litres to get for the size. also im hoping to just run all the fans and co2 generator and dehu on one 15amp circuit if that helps.

You can put the delay on break timer into a lighting controller as well. To give HPS bulbs time to cool before restarting them after a power outage. I do this to all my lighting controllers so I don't have to worry if I am not around when the power goes out for a second and comes back on. I use a 10 minute delay when doing this with a lighting controller.

Here is a 120 volt 15 amp version i use on a dehu thats plugged into an autopilot environmental controller.

xox said:

i was planning on wiring an outlet on the ceiling and sitting the unit on a shelf using gravity to feed the water to the sump pit outside the room. i dont necessarily need a controller on the unit either i havent purchased one yet mostly just having a hard time figuring out how many gallons/pints/litres to get for the size. also im hoping to just run all the fans and co2 generator and dehu on one 15amp circuit if that helps.

Click to expand...

When sizing a unit you have many factors involved. Ambient RH% & biomass being two big factors.

How big a unit will you need? I can't say. I have seen some things... lol for one, I did a coco run and RH% was fucking out of control, had to run 3 or 4 dehu's in one of my rooms and could barely keep up with the RH%. Insanely high RH. Same amount of biomass and soil grow I don't have any issues with just one dehumidifier. Only difference was the medium being coco. I ran DWC with less RH% issues. For some reason the coco run made for massive RH% problems. I got away from the coco. I still can't say why the coco was pushing the plants to transpire so much, I mean even if I water soil plants right before lights out I don't get the RH% #'s that I did with coco. So when sizing a dehumidifier I am left with that in the back of my mind.

that is excellent information, i plan on using promix its a mix of peat, perilite, vermiculite much like soil. as far as size of plants i was hoping to do 4 plants one under each bulb trained under a net prolly do 3x3 or possibly 3x4 due to how the ceiling is in the room. im hoping to finish at 5’ under a net. 70 pint maby? maby 100 pint?

the humidity isnt to bad where i live its just super cold and dry. id say rh% normally in the basement is typically around 55%

xox said:

that is excellent information, i plan on using promix its a mix of peat, perilite, vermiculite much like soil. as far as size of plants i was hoping to do 4 plants one under each bulb trained under a net prolly do 3x3 or possibly 3x4 due to how the ceiling is in the room. im hoping to finish at 5’ under a net. 70 pint maby? maby 100 pint?

Click to expand...

Chances are that a typical 70 pint home sized unit would get the job done. I won't promise that it will though.

If you can find a good deal on a commercial unit on craigslist then you may wish to go that route for reliability/longevity reasons. I just have terrible experiences with the typical "Kenmore" or "LG" home grade dehumidifiers. They just don't seem to last. The ones you could get back in the 70's and 80's would last forever but sometime in the 90's the quality started to drop off. Back in Missouri I bought a home that had a basement, never grew there, it was just a place to live. The house came with a dehumidifier running in the basement to keep it at 50%, it would kick on and off. It was an old 1970's model, old school. It was every bit of 30 years old when I bought the house and it was still going strong 8 years later when I sold that house.

well ill prolly roll the dice with a 70 or 100 pint dehu and if its too small ill sell it online used and get a larger one lol. your right appliances just dont last anymore i have a beer fridge that was manufactured in 1947 just after the war and it still is running on the original hermetically sealed compressor its built like a tank id be happy to pay a premium for appliances if i knew they would last oh well throw away society these days

xox said:

well ill prolly roll the dice with a 70 or 100 pint dehu and if its too small ill sell it online used and get a larger one lol. your right appliances just dont last anymore i have a beer fridge that was manufactured in 1947 just after the war and it still is running on the original hermetically sealed compressor its built like a tank id be happy to pay a premium for appliances if i knew they would last oh well throw away society these days

Click to expand...

It's all about bearing quality. As you pointed out with your beer fridge, we humans have long known how to make quality bearings that will last nearly forever. The Germans currently make the best bearings out there but they aren't cheap. Unfortunately most modern appliances are built with bearings made in China or India. I saw a demonstration once where two bearings of the same size and type, when spun up with compressed air the high quality bearing would just keep spinning long after the other one stopped. Friction is the enemy of bearings and the cheap bearing had plenty of friction lol.

xox said:

hey rollitup,

i have a question on sizing dehumidifiers.

im building a room and im having difficulty picking the right dehumidifier for the room here is some information on the the build so far. the room is 9x12. i have the capacity to run 4000 watts of light, i have a 24,000 btu minisplit, a natural gas co2 generator. id like to use promix in 25 gal fabric pots. i have a 4 plant limit so id like to grow the plants on the larger side under a net im hoping to not exceed 4-5 ft in height trained under a net. im hoping to find an appropriate sized dehumidifier that i can connect to a controller and will survive a power outage and come back on if im out for the day. thanks for the help!

Click to expand...

I have a sealed room that’s 8x16 and a 110 pint struggles sometimes. Also you need one with a pump, so you don’t need to empty it all the time. Trust me, don’t cheap out on it and make sure it has a pump! Only way one from Lowe’s or Home Depot will work is, if you special order it. The $300 ones, they have in the store, wont make you happy! Bud rot or WPM isn’t fun!