Exhaust fan timed and temp controlled

In my veg room I have an exhaust fan on a TMP-DNe temp sensor so it kicks on when it gets hot in the room and turns off when the temp drops to a set level. Outside temps have been low recently so it's not turning on as often as it was when I set it up. I'm concerned that my babies may not be getting enough CO2. Is there any way to turn it on every hour for 15 minutes and also have it respond to the temp sensor?

I would just switch to a standard timer instead.

Punk said:

I would just switch to a standard timer instead.

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But if it's 90 degrees outside you don't want to pull in a lot of hot air and burn up the plants, so you have to adjust the timer based on the day to day temperature? Or vice versa, if it 40 degrees outside you don't want to pull in a lot of really cold air and slow down growth either, right? You have to pull in some air for CO2 but depending on the temp of intake you might want to limit the amount.

A seperate intake fan (motorized shutter) tee`d off your main intake duct could be an option.
Add a cycle timer and set it to run the fan once every X hours for 30 seconds or whatever the minimum duration would be for a single airchange of your room. The outside air temperature wont matter as its only enough to refresh the co2.

KnowledgeSeeker said:

In my veg room I have an exhaust fan on a TMP-DNe temp sensor so it kicks on when it gets hot in the room and turns off when the temp drops to a set level. Outside temps have been low recently so it's not turning on as often as it was when I set it up. I'm concerned that my babies may not be getting enough CO2. Is there any way to turn it on every hour for 15 minutes and also have it respond to the temp sensor?

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I had this exact idea the other day, but then I thought whenever the fan shuts off it wont be exchanging the air anymore as it has 2 functions to exhaust heat AND spent air. please tell me how you sorted this problem? 8P

Atomizer said:

A seperate intake fan (motorized shutter) tee`d off your main intake duct could be an option.
Add a cycle timer and set it to run the fan once every X hours for 30 seconds or whatever the minimum duration would be for a single airchange of your room. The outside air temperature wont matter as its only enough to refresh the co2.

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True. I'm trying to avoid the cost of another fan. i would like to solve this for both my flower and my veg room and if there was a more efficient way rather than purchasing two more fans that would be great.

you should wire a motor speed controller up with your thermostat, when the temp gets down to where you want it, it runs at a slow speed, when it gets above it runs full speed.

nordowell said:

you should wire a motor speed controller up with your thermostat, when the temp gets down to where you want it, it runs at a slow speed, when it gets above it runs full speed.

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Now that sounds like a good idea. Can you give a bit more detail for the electrically challenged? Any idea where I can get an appropriate motor speed controller? Specs for the controller? Is there any way to check if my fan is variable speed capable? (It's a Dayton 463 blower.) My thermostat is the TMP-Dne.

KnowledgeSeeker said:

Now that sounds like a good idea. Can you give a bit more detail for the electrically challenged? Any idea where I can get an appropriate motor speed controller? Specs for the controller? Is there any way to check if my fan is variable speed capable? (It's a Dayton 463 blower.) My thermostat is the TMP-Dne.

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Lol, talk about ironic - just hooked up my TMP-Dne to my fans in my Sun Hut today and was having the exact same thoughts as to when it got cold.

Doubly problematic for me is that because my intake and exhaust fans are so powerful, I'm not using an oscillating fan in there.

I'm subscribed for this answer, whatever it may be.

Straight up G said:

I had this exact idea the other day, but then I thought whenever the fan shuts off it wont be exchanging the air anymore as it has 2 functions to exhaust heat AND spent air. please tell me how you sorted this problem? 8P

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Or you could just do nothing.

I "somewhat" solved the problem by removing the 6" inline that I had air-cooling my 400W and using only a 6" inline for cooling my light and room exhaust.

Makes it so it gets hotter in there quicker than before with a dedicated 6" cooling my light by its lonesome.

Ha, I will use a 4" inline so temps will be that bit higher and buy a huge 1 for nxt. summer, thanks for the response thought I had selected an invisible font there for a minute. 8P

+Rep'd

i found dirtysteves post that answers your question. the pic is also here. https://www.rollitup.org/newbie-central/200093-fans-making-my-head-spin.html thanks steve.

Simple,
You need
1. 1 attic thermostat, they keep it near the attic vents and roofing supplies.
2. 1 5 Amp or better rated fan speed controller. In the ceiling fan section
3. 1 2 recepticle gang box
4. 1 Male plug
5. 1 switch/outlet cover combo
6. 1 duplex outlet rated at least 15 amps
7. A few feet of minimum 14g wire. I just had some 14/2 w/ ground laying around and i used the male end of an old extension cord for the male plug. You could probably get a cheap 6' or so extension cord and use it for your wire and plug. Just make sure it is rated at least 15A.

The speed controller and thermostat both have 2 black wires coming out of them. You take your Hot (Black) wire from your plug and connect it to one black wire each of the speed control and the thermostat. Then connect a piece of insulated 14g wire to the other black wires from the speed control and thermostat. Connect the loose end of the 14g wire into the "HOT" side of your outlet. The white (Neutral) wire from your plug will connect to the "neutral" side of your outlet. The outlet is marked so it is easy to figure out. Then connect your ground wires. Then put it all together in the gang box. I fastened mine to a piece of 3/4" plywood to keep it all neat. The photo has different parts but the same wiring is used. I just put an outlet on mine for ease of operation. Any fan I plug into that outlet will be run by the speed control/thermostat. In case I needed another fan. Hope this helps. If not, just let me know.

Thanks, that's actually very helpful.

And thanks to Steve for initially posting that.

bob you end up building one? i have 2 they work perfect.

nordowell said:

bob you end up building one? i have 2 they work perfect.

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Nah, doesn't seem like I'm gonna need it, truthfully - until it gets down to under 50 degrees in the garage (if ever), the exhaust fans run enough for my liking in my veg tent.

Once it hits 75 they turn on and turn off at 68 or 69, then turn on again in a bit when the temp goes back up.

If it gets cold enough that they don't come off as often as I'd like, I can just lower the differential on my TMP to three degrees instead of five (might do that anyways just to keep my temperature "band" a little more narrow).

I have an electrician about to be finished wiring me up for 60 amps in the garage, so I'm gonna put a portable AC/heater in there to always keep it at right about 68 degrees.

Plus I'd probably electrocute myself.

I have used a small PC fan that runs 24/7 along w/ a larger fan hooked to a thermostat.
you could also add a small passive vent at the top -heat rises so it will draw fresh air in