Design for fan control help please?

Ok, I am planning on having a 4" inline fan pulling about 110CFM out of a 50CFM grow tent.

I would like to control the fan 2 ways. #1 I would like it to be plugged in to a Air-3 Heat/humidity controller that will turn it on for exceeding atmospheric conditions.

I would also like to control the fan by a periodic timer so the tent gets alot of fresh air.

Can I just take 2 extension cords plugged 1 into each controller and pigtail all the black and white connections together with the fan and have it turn on if either/or timer goes on?

My concern is that what happens if both timers go on at the same time? I am a newbie electrician...

probably. maybe?

If both controllers are relay (DPST) output instead of triac, shouldn't be a prob. If a triac output, I'd have to ponder that a bit. Not sure if backfeeding would be a prob or not.

Thank you for taking the question seriously. I will dig up as much as I can find on the timers.

Is there an easier way to do this? I figure that I could buy another inline fan but the good ones are $100-$150 and it would add impetence to one duct line or require a separate ductwork etc...

My current plan is going to allow me to use a basement for my first grow but I will soon be using a 2x4 tent and want to make sure that I have the proper equipment to do this right.

Thanks again.

NLXSK1 said:

Thank you for taking the question seriously. I will dig up as much as I can find on the timers.

Is there an easier way to do this? I figure that I could buy another inline fan but the good ones are $100-$150 and it would add impetence to one duct line or require a separate ductwork etc...

My current plan is going to allow me to use a basement for my first grow but I will soon be using a 2x4 tent and want to make sure that I have the proper equipment to do this right.

Thanks again.

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Yeah. use a couple of relays and wire them in a XOR configuration. Would need a pair of DPDT relays. With the controls feeding the coils through the XOR.

BigBudBalls said:

Yeah. use a couple of relays and wire them in a XOR configuration. Would need a pair of DPDT relays. With the controls feeding the coils through the XOR.

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After spending about an hour searching through info on DPDT relays I figure that it will be much safer and more practical to just buy another fan.

Thanks for the info though. Maybe once I have a few grows under my belt I can concentrate on the advanced electrical systems.

NLXSK1 said:

After spending about an hour searching through info on DPDT relays I figure that it will be much safer and more practical to just buy another fan.

Thanks for the info though. Maybe once I have a few grows under my belt I can concentrate on the advanced electrical systems.

Click to expand...

No Prob. I do electrical controls as part of my job (so its old hack)

But I know that feeling about get a few grows done first.
I've already gone overboard.

As long as both the controller and the timer are using the same circuit, your original plan would work. Even if they both call for the fan to come on,as long as they are on the same circuit,you'll be ok. Different circuits,and you'd have a direct short.

spark1 said:

As long as both the controller and the timer are using the same circuit, your original plan would work. Even if they both call for the fan to come on,as long as they are on the same circuit,you'll be ok. Different circuits,and you'd have a direct short.

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No. Not a given. If the 2 controlers have the same phasing, it can create a direct short also. (of both fired at the same time. And L and N need to be in sync.)

And if the first controler fired, it can easily backfeed into the second and possibly create issues (hence my Q about triac or relay output on the controllers)

And different circuits doesn't mean direct short. Different phases *might* be a direct short.

BigBudBalls said:

No. Not a given. If the 2 controlers have the same phasing, it can create a direct short also. (of both fired at the same time. And L and N need to be in sync.)

And if the first controler fired, it can easily backfeed into the second and possibly create issues (hence my Q about triac or relay output on the controllers)

And different circuits doesn't mean direct short. Different phases *might* be a direct short.

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Buy a seperate fan. Sometimes as enlightened stoners we tend to overthink things. If would suck ball to start a fire because we wired something wrong.

FatSalad said:

Buy a seperate fan. Sometimes as enlightened stoners we tend to overthink things. If would suck ball to start a fire because we wired something wrong.

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Oh I stand behind my wiring and design work. Work with up to 25KV. @ 1.5A