FIRST Grow Room... finally!

Welcome to the forum! Let me see if I can help without missing anything. No promises ha!

That’s a great light, but its probably a little bigger than you need. You could pretty easily do 260 xl kit and have really good results. And you won’t need lens kit either.

I’m not aware of a ran that will do that. You can fans with speed control and start/stop them with a different controller though. Or there are a few fans that will work by themselves on temp sensor. But I’m not aware of anything ready to setup that will run on both rh and temp setpoints.

There’s a few devices that will allow remote monitoring, the one I know of is sensor push.

You can use a series of duct bends, 90 degree fittings. Or something like a dark room vent for your intake. But you want it coming in low on opposite side of your exhaust if possible.

Your sensor push from above monitor temp and rh.

If you get a humidifier or dehumidifier, get them large enough to control the room that intake air comes from. That solves floor space issue, and will actually do the job in most cases.

Just give the walls a solid coat or two of flat white paint. It does a pretty good job reflecting and is easy to keep up with, without any hot spots.

Buy a relatively inexpensive tds meter. Its important, but not so important you need to spend a ton of cash on.


@dbrn32. Thank you so much for responding. I was hoping you might drop by. :smile:

I’m getting the 320 because a) I can turn it down to run it at max efficiency/lower heat, b) it has the BLE/Android controller option monitoring/automation, c) series wiring is “safer”, and finally… if/when I decide to seal it up with a mini-split and start injecting CO2, there will be headroom to supplement the additional needs.

No lens kit… check. :slight_smile:

Vent fan(s) and controller: Going to use active in/out fans… always on minimum with rampu up control for temp. Both fans in attic for stealth/quiet.

Sensor push and a backup temp/RH meter en route from Amazon.

Ducting: Intake will go from patent room ceiling pre-filter, 90 to inline Vortex vtx400 to 90 to grow room ceiling, ducted down in one corner to near the floor opposite corner from exhaust to minimize short circuit. EXHAUST: from vertical mount carbon at ceiling out via plate junction in ceiling, to 45, to inline vtx400, to duct ending in a gradual downturn or backflow flapper.

Both fans will be on a Titan controller, that controls fans, (de)humidifier, et al.

GREAT idea about controlling RH of supply air in parent room, BUT… this MAY lead me back to needing to dual control the fans for RH, too… I am pretty sure that IF I can find the right relay setup, that I can put it in the AC busbar line between the Titan Controller and the fans… Rig the RH controller to switch from Fan always ON (LOW) to a RH HIGH side of the relay which will switch the fans to full mains.

There are a number of other ways to do this to… Ideally, I’d like to rig up BOTH the Titan’s Fan and RH controller AC outputs in PARALLEL (either/or) fashion such that whichever output is putting out most pwr (voltage), then THAT is the part of the Titan that controls the fans…

Walls: Are you saying NOT to use the MYLAR I already have on-hand? To paint instead? Hotspots in reflection? Hmmm…

Plus for paint is that if I use a bathroom enamel vs. Mylar, I don’t have to worry about any mold/mildew issues behind mylar on sheetrock walls.

pH meter - I went ahead and ordered an Apera PC-60 5 in 1 (pH, TDS, EC, et al.) with cal kit and case. This is a pretty decent piece for the price and does all measurements at once on each sample. I’ll keep my PH-60 as a backup pH meter in case bulb gets broken.

Thanks again?

Any recommendations for a particular 4" flanged carbon filter?

I’m cleaning out the closet right now, and getting the vents plumbed in is high on the list.

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Dropped order for the HLG 320 XL light kit with BLE module.

Working up exact specs for ventillation parts.

Fans: 2x VTX400 200CFM, 1 each inlet and exhaust
Carbon Filter: >/= 200 CFM
Anyone have a suggestion on specific make/model for filter?

Controller: Looking at the Titan Controls Spartan Series Basic Digital Environmental Controller (Temperature, CO2 Timer and Humidity)

… BUT, on reading the instructions for it, I can see it doesn’t do what I want it to. I may have to use separate controllers until I find/build what I want.

I will be running a humidifier or dehumidifier in the PARENT room to the grow closet to control supply air RH.

Here’s what I need to do:

Fans on at minimum set speed all the time.
If temp rises above setpoint, fans speed up or go to full speed.
IF RH exceeds setpoint, fans are kicked on full speed until RH returned to some setpoint below max.

This is getting interesting…

@dbrn32 @MattyBear

I figured you would eventually run into that. You pretty much need a programmable controller, software, and all of the devices to measure environmentals. To my knowledge, the separate controllers available as plug and play aren’t available as plug and play stackable

Yep… OK… let’s start over and define the problem and the conditions. Then figure a solution that won’t break the bank. High tech control system would be cool, but not needed here.

Problem: Control the temperature and humidity inside a small volume using only the ventilation fan(s) .


  1. Approx. 64 cu.ft volume likely to experience temp and RH shifts routinely throughout the day.
  2. Active ventilation system capable of changing entire volume of air roughly twice per minute at max speed.
  3. Supply air temp and humidity will be controlled by HVAC and on demand humidifier/de-humidifier. Avg. current supply air temp Summer: 74-76 F, Winter: 68-74, but will be managed to optimum for this application.


  1. Constant airflow change-out to prevent CO2 starvation, thus fans must run at some minimum speed 100% duty
  2. Fan speed must be increased IF/WHEN temperature or RH rise above max set-points and remain on until returned to some point below max set-point.

Discussion: Fan min speed would ideally be set for required air swap rate.

Temp: Temp needs to be maintained at/near air supply temp to keep crop happy. HVAC is never off, except during rare power losses, so the temperature can largely be managed with minimum fan speed setting. BUT, there’s the issue of ON/OFF lighting changing the temp inside. Thus, temp adds TWO new cases… temp DAY, temp NIGHT. So, min fan speed should be set for speed to maintain temp at NIGHT.
A HIGH Temp override is required to kick the fans up in speed OR simply 100% when temp exceeds setpoint. Controller hysteresis should be able to be used to assist in not rapid cycling right at setpoint.

Humidity: Never done this before, but I’m guessing that RH will fluctuate mostly around light switches. During day, the lights keep it warmer, so air holds more total vapor. When temp drops on lights out, the RH increases. When temp rises again on lights on, the RH decreases, but transpiration should rapidly pack the air again up to the RH setpoint.

BUT, we are hopefully controlling the air temp inside the volume as close to constant as possible or withing a small range, thus the air vapor holding capability should not change a lot… So we are dealing MOSTLY with the vapor SUPPLY inside the volume which is going to be highest with lights on. So, we need a controller that monitors RH and then kicks the fans higher or 100% when RH exceeds setpoint… which I am guessing will be during lights on.

So… We set fan min speed to handle the larger of air swap rate and lights off temp management.
Then we need to monitor temp and kick fans up/on full if temp exceeds max setpoint.
Then we need to monitor RH and kick fans up/on full if RH exceeds max setpoint.

Dispense with the fans speed ramping fantasies and we’ll simplify this to simple on/off events.
We need TWO different fan voltages: <100% variable and 100%.
We need monitored temp and monitored RH tied to each of the two 100% voltage supplies.

OK… I have an idea… If I simply parallel connected the min speed controller, temp controller, and RH controller’s AC supply lines to the fans, then the fans would run at the speed of the highest voltage… All three AC supplies would be drawn from same AC circuit to insure same frequency and phase.

It would not matter if BOTH temp controller and RH controller were “ON” at the same time… same voltage, same frequency… the fan only sees one voltage and no current flows from controller 1 to controller two on AC supply lines

Problem here is that the fan speed controller is running at LESS voltage than the 100% voltage on the other two. Thus, without intervention, ANY time either temp or RH controller kicks ON, there would be a current flowing from those controllers BACK into the fan speed controller.

So, we need a way to block that AC current flow, and/or disconnect the min fan speed supply whenever either of the other two controllers kick on…

Time to go do some circuit research/drawing. That Titan controller or a kludge up of some eBay Chinese boards might do this for less than the Titan Controller plus a fan speed controller cost.

Back later…

Figured out the Controller!!! This is how you can have fan (s) on at slow speed 100% duty for air-swap/temp lights off, and then kick the fan up to 100% if EITHER the temp OR Relative Humidity goes out of range.

Fan Low-Speed Controller (FLSC): This guy right below will be used to set the “Always ON” speed for the fan:

This little guy lets you control speed with the rheostat, and you can set the voltage range with that little trimmer screw on the blue trimmer. :smiley:

Low-Speed Interrupt Relay (LSIR): In the HOT wire on the OUTPUT side of the FLSC (above), we insert this Normally Closed relay (120 VAC ctrl voltage, </= 240 VAC switched voltage):

Temperature/Humidity Controller (THC): The controller below will allow basically ANY setpoint temperature/humidity and hysteresis level to be set.


Powered by 120 VAC. When the temp/RH exceeds the setpoint, it triggers the respective power out relay (120 VAC OUT) to whatever you have hooked to it. Simply connect BOTH the relay outputs to the ventilation fan AND the LSIC INPUT. (Does not matter if both are on at same time, as they are both powered at same voltage from same source.)

In THIS way, when the fans are kicked up to 100% to address a high temp and/or RH, the power out to the fan(s) ALSO activates (opens) the LSIR, which cuts the LSFC (at < 120 vac) out of the circuit. Thus, the fans speed up, but no reverse current shows up and smokes the FLSC or does other bad things.

When the temp and/or RH are back in range, the THC cuts the power to the fan AND the LSIR. The LSIR closes and powers the fan BACK on instantly at the lower voltage… switching is so fast that it will just look like the fan is slowing down. :smiley::sunglasses::nerd_face:

Not bad for a TOTAL of $33.43

Oh… and I figured out how to do it with ONE fan in the attic and no down tube inside closet to get supply air from one room to the next. Will put that in a separate post.

@dbrn32 @MattyBear


BELOW is how I figure to SUPPLY nice cool/dry air to the grow room WITHOUT using a second fan in the attic, ducting from the parent room, and a down tube from closet ceiling cluttering up the place. :slight_smile:

Here is a pic of the closet:

That big white space is the wall between the grow closet and the master bedroom. That wall is HOLLOW. If I take a PAIR of theseguys, appropriately sized of course…

… and put ONE of them low down on that back wall, and the second one in the MBR wall up a little higher, then I have essentially created a room to room air duct of an appropriate size to provide a PASSIVE air supply. BONUS: The one in the MBR will be mostly hidden from view by a piece of furniture.

Gotta make sure the louvers are facing down and offset is sufficient to stop light infiltration, but it sure simplifies things, delivers cooler air from one room to the floor in the closet (breaking possible flow short-circuit), and keeps the space-consuming clutter in the closet down.

Now, to calculate the grill size I need to meet the needs of the 200 CFM fan on a 4" negative pressure duct through the carbon filter. No idea how to calculate that with any precision.

Thank you @TommyBahama It was YOUR idea about the floor vent that led me to this solution!! :smiley:

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@dbrn32 @MattyBear @TommyBahama

NOTE: I made a mistake in my circuit logic for the controller hack… I was trying to use the THC controller’s AC output DIRECTLY to power the fan AND activate the LSIR to disconnect the LSFC from the fan.

There’s a PROBLEM doing this. The LSFC output and THC outputs would be connected together at the fan, thus current could flow from the LSFC output to the fan, to the THC output, AND THENCE to the INPUT of the LSFC… At best this would cause the circuit to NOT WORK or chatter, as even the reduced LSFC voltage fed BACK into the LSFC INPUT might be enough to activate the LSFC coil… thus, an on/off/on/off chatter until it burned out.

It MIGHT also eventually cause issue at the THC outputs…

SO… I found a solution. Use the THC AC outputs to drive a PAIR of AC to AC Solid State Relays (SSR) to drive the fan.

The SSRs inputs and outputs are optically isolated. Thus, the THC outputs will drive the INPUTS of the LSIR and the SSRs. The OUTPUTS of the SSRs will drive the fan(s).

With this arrangement we eliminate the backfeeding from the LSFC into the other control loop(s).

Glad I drew it out again before I tried to hook it up… I HATE seeing “magic smoke”.

EDIT: Oops… another “mistake”. Looks like I only need ONE SSR… I can bridge both outputs to the single SSR input. Oh well… a spare SSR just in case I need to drive a separate device and/or need a spare at some point.

A single 4"x10" floor register should be just fine. Factoring in the sidewalls and the louvers, that 40 square inches becomes more like 25 square inches. Your fan is designed to push air through a 4 inch diameter duct, which is just over 12 square inches.

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I get 12.5664 sq in. area in a 4" duct. Most references I see call for at least 3 to 4 times the size of exhaust for passive intake, so that would be around 50.2656 sq in. @ 4x exhaust. That would seem to indicate something larger than a 4 x 10 even at 100% efficiency.

I’ll go to the home stores and measure some today to see what I need…


You can just run the one output, and have two inputs in parallel to create “or” logic right. So temp sensor or hygrometer send relay to high state.

That is what I would do anyway.

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Yep… pretty much exactly what I am doing… I’m bridging the temp/RH relay outputs, because it’s a logical OR. And thus that’s why only need one SSR to isolate the output from the fan drive.

I’ll try to put up a circuit diagram and real life picture once I have it working.


You have to bridge the input right, because paralleling outputs would create short circuit if both go true.

@QST_59 love my sensor push. tried a couple cheaper environmental sensors this one is the best.

I’ve been up all night, so I am not saying things right… the temp/RH output relays are in PARALLEL… because even if BOTH are engaged, you can parallel AC IF it is the same voltage, frequency, and phase. These are both on same circuit, so you will just see line voltage.

It will make a LOT more sense when you see the circuit schematic…

@DankGunslinger. Welcome to the party… yep, it’s a neat bit of kit. I’ve got it running right now in the grow area to build a before history and hunt problem areas.

Hopefully, I can spring for the wifi gateway at some point, so I can keep up with things while away from the house.

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My first unit came not working. Sensor push sent me a replacement two days over a weekend super fast email response communication etc. And someone at amazon accidentally sent me a second I emailes them and they said keep it.

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Think I have all the major items on-hand or on-order to outfit the grow room… fan, vent tunes, clamps, filter, etc, etc. Grabbed some 6" x 14" wall/ceiling registers at one of the home stores… Measured the effective openings and totaled the effective area, and it’s just over 57 sq. in… which is better than 4x the 12+ sq. in of the 4" ducting cross-section.

Grabbed several kinds of gasket seals for the door and one of those under door light/draft blocking deals with the 2-pocket bag and foam rods to try and seal up the leaks.

STILL need pretty much ALL of the germination, seedling, containers, catch trays, et al. supplies… and of course media.

Sure does add up!!

I would LIKE to be ready to start BEFORE my order from ILGM shows up, but I’m not sure I am gonna make it. :grimacing::beer::beers:

@DankGunslinger @dbrn32 @TommyBahama @MattyBear


Got the first Fresh Air Supply vent cut in to the closet today… It’s a 6" x 14" ceiling/wall register with measured effective area at full open of 57-58 sq in.

Slight issue… the vent on the other side of the wall is going to be less hidden than intended… a lot less. Like plain view… 3 feet from where the boss rests her precious head. If she balks at the location and visibility, I’ll have to go UP the wall, build a bypass fillet in the top back corner and rock , tape, float it in. THEN, I’ll have to build a box in the shape of a “C” to come up from the fillet, over two joists and back down around a register in the parent room. Simply not enough headroom in the attic for 8" insulated duct work.

Silver lining IF I have to do it the hard way… Simply burying the new box in the existing insulation will keep it cooler and make it virtually invisible.

MAN, I hope she lets me cut it into the wall… It’s hot (and tight) up in that attic…

Vortex fan, 4" flex duct, relays, Low Speed Fan Controller, filter and ProMix HP all showed up at once in a big pile today… Fortunately, piles of boxes are not unusual here. :wink:

Still need to buy an air pump, hose, and stone to aerate the nutrient mixes…

Any suggestions as to brand and size? They’re a lot more expensive than the last time I bought one.

@MattyBear @Hogmaster @Drillbit @DankGunslinger @TommyBahama @AAA @dbrn32

Oh… and the gaskets on the door ain’t gonna work… no way to get zero light AND be able to latch the door. I’m going to pull them off and custom mould some using silicone and Vaseline on the door. It’ll cure to the frame. Squish out when door is pushed to, and the Vaseline will allow the door to open after cure.