Please critique my air cooled lighting design... pics within

[mikeross]

I am looking for any insight or comments good/bad regarding this design. I really like the manifold idea but am still not sure of the sizes in regards to the intake and exhaust manifolds. Only thing set in stone is the 6" flexible duct work connecting the hoods.

I want to know If I should keep both manifolds 10" or keep the exhaust manifold slightly smaller than the intake.

Also want to know if I should up the sizes of the manifolds to either 2-12" manifolds or 1-12"intake and 1-10"exhaust?

Would you suggest round duct work or squared plenum for the manifolds?

The hoods have 600w by the way...

I have seen a similar design in action and looks to be working great... just want to fine tune the original design.

thanks

 

[LlamaSchool]

Nice design. I am also a fan of heating houses with air-cooled lighting. Where do you duct the air in? Is it near the furnace? Are there any safety issues with ducting high pressure (from a 10" fan) air into a home heating system? Issues with pushing carbon monoxide into the house or anything when the furnace blower is off? I've done it on a smaller scale ducting directly up to floor registers but I'm considering doing this with a setup more like yours now.

The manifolds are very cool but are you sure they are much better than a piece of Y-duct at either end? Maybe with flow-testing you could find something better but I have a hard time believing that arbitrary size/shape manifolds could give better performance than a simple Y since the restrictions (8"/10") are the same.

Consider insulated 6" ducting between the lights for maximum cooling. I made this mistake recently and I'm really heating up the room with my long runs of uninsulated 8".

 

[mikeross]

Nice design. I am also a fan of heating houses with air-cooled lighting. Where do you duct the air in? Is it near the furnace? Are there any safety issues with ducting high pressure (from a 10" fan) air into a home heating system? Issues with pushing carbon monoxide into the house or anything when the furnace blower is off? I've done it on a smaller scale ducting directly up to floor registers but I'm considering doing this with a setup more like yours now.

The manifolds are very cool but are you sure they are much better than a piece of Y-duct at either end? Maybe with flow-testing you could find something better but I have a hard time believing that arbitrary size/shape manifolds could give better performance than a simple Y since the restrictions (8"/10") are the same.

Consider insulated 6" ducting between the lights for maximum cooling. I made this mistake recently and I'm really heating up the room with my long runs of uninsulated 8".

This grow will be in my basement. Above the Intake side of the manifold is a small closet. I planned to just cut a 10" hole in my sub-floor and connect it to the intake manifold. The 10" opening in my closet will have some type of intake filter like a hepa filter or maybe something home made.

The furnace is located in the basement as well. Right behind the exhaust manifold is a big 12"x12" plenum that is connected to my furnace. That large plenum goes up to the first and second floor of my home and dissipates the heat to all the rooms. I just planned to connect the grow room exhaust to that large 12"x12" plenum.

I am not sure about the carbon monoxide. I know a lot of members on here are doing similar setups. I haven't read anyone having issues with carbon monoxide flowing.

I don't understand what you mean about the "furnace blower being off"? I know nothing about furnaces but would appreciated some info about the blower being off and possibly have carbon monoxide flowing into the upstairs areas of the home.

Good question about the wye pipe. From my research when cooling lights in a sealed room pressure is not a concern... the concern is moving large amounts of air. I figured the manifold idea would be less restrictive than a large manifold. I could be wrong though... that's why I made this tread in hopes to fine tune this setup. I was hoping to have a little more discussion about the setup but doesn't look like anyone wants to put in there .

Yes, after a little more research I am going to use all insulated duct work between the hoods. Not only will it not allow the heat in the duct work to warm up the room but it also makes the large amounts of air flowing through the duct work a lot more quitter.

 

[LlamaSchool]

Mike,
I'm no expert, but as I understand it, a furnace runs a pilot light all the time and then when your thermostat determines that heat is needed, both the heating flames (better terminology?) and a blower (fan) are turned on. When the furnace blower (fan) is turned off, not only will your grow-heat be escaping through the HVAC registers, but there will also be some pressure on the furnace end potentially causing air to leak out around the area that the furnace blower would usually pull air from.

When the furnace blower is on, I imagine the furnace end of the system will produce enough pressure that none of your grow-heated-air will escape out through the furnace. However, since furnaces are not designed to see any pressure in the HVAC system with the blower off, I'm wondering if there may be some issue here. I'd love to hear any thoughts on this.

I'm still not sold on the manifolds, but it's a cool idea and I doubt it would hurt anything unless it created some serious turbulence between the in and out sides of each manifold, hurting air flow. Also, the air will slow down as it goes through the manifold and since the manifolds have more surface area than a simple Y-pipe, there may be some slightly increased heat exchange between the exterior surface of the manifold and the surroundings.

 

[mikeross]

Mike,
I'm no expert, but as I understand it, a furnace runs a pilot light all the time and then when your thermostat determines that heat is needed, both the heating flames (better terminology?) and a blower (fan) are turned on. When the furnace blower (fan) is turned off, not only will your grow-heat be escaping through the HVAC registers, but there will also be some pressure on the furnace end potentially causing air to leak out around the area that the furnace blower would usually pull air from.

When the furnace blower is on, I imagine the furnace end of the system will produce enough pressure that none of your grow-heated-air will escape out through the furnace. However, since furnaces are not designed to see any pressure in the HVAC system with the blower off, I'm wondering if there may be some issue here. I'd love to hear any thoughts on this.

I'm still not sold on the manifolds, but it's a cool idea and I doubt it would hurt anything unless it created some serious turbulence between the in and out sides of each manifold, hurting air flow. Also, the air will slow down as it goes through the manifold and since the manifolds have more surface area than a simple Y-pipe, there may be some slightly increased heat exchange between the exterior surface of the manifold and the surroundings.

I totally understand what your saying. I hope someone here can chim in with some knowledge.

 

[Lazyman]

HI Mike, I used to be an appliance repair guy and installed many furnaces.

I like your plenum/manifolds, gonna be doing something similar in mine. I think it will be easier to use regular round 8-10" metal ductwork, with a metal tee where I need them. Cheap and easy to get at Home Depot. From there yes insulated ducting to the hoods and another manifold, be sure to leave room on both ends for a fan in case you need to add a pusher/puller fan on the other end to help.

You can't blow into a furnace ducting, because as soon as the furnace turns on it will vastly overpower your hood fan and blow the air back in (with very hot air too.) Only way to do this is to vent into the return pipe of the furnace, but also keep in mind that if your furnace reads 110* air coming in, it won't ever kick on the burners and will likely stay off, which won't help distribute the air in your house very well.

I've jerry-rigged a switch to manually kick the furnace blower on and off in this situation, but you better be handy with reading schematics and a voltmeter to do so. A lot of furnaces have the ability to run a "fan-only" mode, just gotta figure out what wires make that work and splice something in.

 

[mikeross]

HI Mike, I used to be an appliance repair guy and installed many furnaces.

I like your plenum/manifolds, gonna be doing something similar in mine. I think it will be easier to use regular round 8-10" metal ductwork, with a metal tee where I need them. Cheap and easy to get at Home Depot. From there yes insulated ducting to the hoods and another manifold, be sure to leave room on both ends for a fan in case you need to add a pusher/puller fan on the other end to help.

You can't blow into a furnace ducting, because as soon as the furnace turns on it will vastly overpower your hood fan and blow the air back in (with very hot air too.) Only way to do this is to vent into the return pipe of the furnace, but also keep in mind that if your furnace reads 110* air coming in, it won't ever kick on the burners and will likely stay off, which won't help distribute the air in your house very well.

I've jerry-rigged a switch to manually kick the furnace blower on and off in this situation, but you better be handy with reading schematics and a voltmeter to do so. A lot of furnaces have the ability to run a "fan-only" mode, just gotta figure out what wires make that work and splice something in.

Thanks once again for all the help... you seem to be around every corner helping me out lol.

voltmeter isn't an issue... its the reading the schematics. Were do I find them? I assume they should be someplace on my furnace? Am I just looking for the wiring schematics which turns the blower on and just wire it up to some switch allowing me to turn the blower on when the furnace is off?

 

[mikeross]

Can I blow into the furnace ducting if I never plan to turn my furnace on?

Do you think the hot air coming off 8-600 watt lights would be enough to heat my house up in the evening? Winters here get slightly below freezing.

During the day when the lights are off I was thinking using some type of shut off valve... I believe you hvac guys call them dampers. In the morning when the lights go out I would close the damper shut and use the furnace as usual? Does this make sense? will it work?

 

[Lazyman]

Hey buddy, yeah I live here. I'm thinking of renting a cave right over >there.

So yeah, open the front of your furnace, be careful, and look at the inside of the front covers, you should find a schematic that shows thermostat connections. Figure out what two wires you would use to run FAN ONLY or FAN and you can just move the 2 wires from your regular thermostat to that, and it will kick the fan on and off with the temperature. It's all millivoltage so those wires can't zap you (everything else can) but don't short them out.

Your hood fan doesn't move enough air to heat your house, your furnace probably moves 3-4K CFM, WAY more than any centrifugal we use. Like I said, if you hook into your return, hotwire your furnace, and you can make it work, but I don't think you'll get a lot of BTU's out of it, it will probably be cold by the time it gets to your bedrooms. Furnaces put out 50-300K BTU of heat and your lights put out around 12K BTU.

Yeah you could use a N/C damper inline right before it gets to the air return pipe for the furnace and hook it to your light timer, but I don't think it will be the solution you think it is. Not enough heat in the end, unless you live in Florida or Hawaii.

Hope that helps.

 

[mikeross]

Hey buddy, yeah I live here. I'm thinking of renting a cave right over >there.

So yeah, open the front of your furnace, be careful, and look at the inside of the front covers, you should find a schematic that shows thermostat connections. Figure out what two wires you would use to run FAN ONLY or FAN and you can just move the 2 wires from your regular thermostat to that, and it will kick the fan on and off with the temperature. It's all millivoltage so those wires can't zap you (everything else can) but don't short them out.

Your hood fan doesn't move enough air to heat your house, your furnace probably moves 3-4K CFM, WAY more than any centrifugal we use. Like I said, if you hook into your return, hotwire your furnace, and you can make it work, but I don't think you'll get a lot of BTU's out of it, it will probably be cold by the time it gets to your bedrooms. Furnaces put out 50-300K BTU of heat and your lights put out around 12K BTU.

Yeah you could use a N/C damper inline right before it gets to the air return pipe for the furnace and hook it to your light timer, but I don't think it will be the solution you think it is. Not enough heat in the end, unless you live in Florida or Hawaii.

Hope that helps.

Thanks for the speedy reply... I understand what you mean. I honestly had no clue that the blower in a furnace puts out that much cfm

 

[LlamaSchool]

Good info, Lazyman. +k. So would you say it's a bad idea to try to duct into the out-ducting of a furnace that regularly cycles on? Or would it still be worth it to get some heat into the house while the furnace is not blowing? It wouldn't destroy my 10" centrifugal fan when the blower comes on, would it?

In a small house, I really feel like 3000w would heat the place up somewhat significantly if I could get the air into the system.

Another alternative to the OP - I've previously found a duct that goes straight to a floor register on the floor above the grow. You could always send all the air out one register.

 

[Lazyman]

Hey Llama, I like your last idea best, but no, your 10" centrifugal would be overpowered by your furnace fan in the first scenario you mentioned. Which would result in MUCH hotter air being blown over your lights, lol. Has to blow into the air return of the furnace if at all.

 

[Lazyman]

Oh and Mike, don't use a Phason with the hood fan, not needed and would be a waste of an expensive controller. Just a manual speed controller is all you would need, after the lights have run a while just modulate the fan speed until the final output temp is around 100*f.