Exhaust and effects on central a/c?

[Gil Tokerson]

Hi
I'm using a spare bedroom in the house with 3 600w hps, plus some t5s for vegging. I live in a hot climate. I'm trying to figure out the most efficient way to cool the room.
1. I've tried so far a small 13000 btu portable ac with the exhaust hose going out the window. This works, but bumped my electric bill up quite a bit. And I only have a 20 amp breaker (120v) to work with. This would push me down to 2 600w's.

2. I haven't tried just exhausting out the window with no portable ac. Would this be better? My gut says no due to the fact that besides the central ac vent in the room, and the gap under the door, I can't really install an intake. And if I'm exhausting hot air out, my central ac is going to have to keep running to keep up with the exhaust?

-So what's my most efficient option? Is there another option that I'm over looking? I'm not trying to be Mr commercial. I just want to run 1800 watts in a bedroom!

Thanks in advance for any advice!
-gil

 

[Granger2]

Seal the room and install a mini-split AC. Your electric bill will go up no matter what kind of AC you use, but mini-splits are very efficient unlike portables. Good luck. -granger

 

[Gil Tokerson]

I have considered this, however to run a sealed room, you must use co2...right? That's not out of the question, but I'd rather not have to use co2 if possible. I see plenty of people running several thousand watts without co2, so I'm sure I can get around it.
Thanks. Any other ideas?
-gil

 

[Eureka Springs Organics]

Is there a crawl space? You can suck in air from the crawl space, and send it out the window, or through the ceiling into the attic. You would obviously need vented hoods, but it would make it so that you might be able to get away with an 8,000btu unit.

 

[Gil Tokerson]

There is insulated attic space above the room, however during the summer that air is somewhere in the 130°f range. I didn't think air that hot would be able to cool a vented light. Perhaps?

 

[Gil Tokerson]

Sorry. "Un-insulated", not insulated. It's freaking hot!

 

[Eureka Springs Organics]

There is insulated attic space above the room, however during the summer that air is somewhere in the 130°f range. I didn't think air that hot would be able to cool a vented light. Perhaps?

You don't suck from the attic. You suck from the crawl space(if there is one) and exhaust in the attic, or out of a window.

What's funny is if you drive around Denver you can see so many god damn people venting out of their basements it is unreal.

 

[Gil Tokerson]

Ohhh, I see. I guess there is a space between the 1st and 2nd floor. I don't really know how to get to it though. I'd rather not cut a hole in the floor if I can avoid it. I would think the air in there wouldn't be that much cooler than the attic? I don't know much about houses and hvac though, or else I wouldn't be asking for help!
Thanks

 

[Eureka Springs Organics]

You can always suck in from another room, and then blow it up into the attic. I assume that the other room would be about 72F which would be fine to run through your hoods.

It is very easy to cut a hole in the wall, and almost as easy to patch.

 

[Gil Tokerson]

Well that was what I was wondering about. Is exhausting my central air out the window gonna be more or less efficient than running a portable ac in the room?

 

[Ez Rider]

Well that was what I was wondering about. Is exhausting my central air out the window gonna be more or less efficient than running a portable ac in the room?

Portable a/c's are JUNK! Get an energy-star window unit, or even better, a small mini-split. A good 12K btu a/c should handle your room, especially if you pull outside air through the hoods and into the attic(it should help cool your attic too).

You can always water-cool your lights...I do.

 

[Holdin']

You are almost inevitably going to have to cut some sort of hole... so you have to accept that!

I'm an HVAC professional, and to answer your question, regarding exhausting air vs. running a portable... well one thing that many people don't realize, is that if you are running a single-hose portable unit, you are continuously exhausting air. There is an intake, usually in the bottom/back area that pulls in air from the conditioned space, draws that air across the condenser coil inside the unit, then dumps the rejected heat outside through the a/c's exhaust.

You're going to see an increase in your bill regardless, but properly exhausting the heat from your lights with a closed loop design is a good idea - unless, you want to use adequate air conditioning and run sealed. But with that, you still must supply fresh air to your plants one way or another.

What about pulling outdoor air through your hoods and dumping into the attic? Or pulling air from another space in the home, another room, etc, and dumping into the attic? Or, have the lights as an open ended exhaust, keep one end of the hoods open, pull air from the growroom and dump it out the window. It's not going to cause a huge drop in efficiency in the cooling of your home. This way you'll be bringing in new air for your plants, as well as dumping heat. Additional cooling shouldn't be necessary if you do this...

And just so you know, if you're running your lights on standard 120v and not 240v, you are already maxing out your circuit. Amps = watts/volts, therefore 1800 ÷ 120 = 15 amps. It's not recommended to go over 80% of the circuit size. And there could be other power drawn from that circuit if you are in a regular bedroom, unless you do have a dedicated 20amp circuit. Even if you do have a dedicated circuit, anything else drawing power in addition to your 15amp load from your lights will start to cause the wire to heat up and wear the breaker, or trip the breaker, or in worst case, start a fire.

As Tim Allen would say, "more power!!!"

 

[Ickis]

Hey there Gilot!

IMHO even if you are in a hot climate using outside air would still significantly cool your lights that it would make the room air much easier for an a/c unit to cool the room air. That air would still be way cooler than the light bulb.

You could pull air in one window. No real modifications needed. It could be as simple as a piece of wood with a round hole equal to the diameter of the vent hole on your reflector. The vent pipe/tubing needs to be the same size too. You can not reduce the diameter anywhere along the intake or exhaust.

So now that your intake is hooked up to the first light reflector connect the two lights with pipe/tubing. Then connect the other end of the second reflector to the other window. Same way as intake window.

There can be no leaks. The reflectors have to be the sealed kind with glass. There will be no need to filter the exhaust because it does not draw stinky air from the plant room. You won't need some huge exhaust fan on this system because you are only drawing air through 8 inch or 10 inch vent tubing and sealed reflectors. It could be a 360 cfm inline booster fan or get a 240 cfm panasonic whisper fan. It needs to be reliable more than powerful.

If this room is connected to the central a/c you might find it stays cool enough. Or draw air from another room but have the fan drawing the air in connected to a temp controlled plug adapter so it only runs when the temp gets to 80 and turns off at 75.

If this worked you would not see a huge jump in the electric bill.

 

[Gil Tokerson]

Thanks holdin'! I saw your signature in another thread, and I was actually going to send you a pm about this.

So I'm thinking open ended cool tubes exhausted out the window might be my best option.
As far as my breaker, it's a 20amp at 120v. So:
120 X 20 = 2400
2400 X 80% = 1920watts....right??

I'm going to alternate between 1 600hps for 12 hours and a double stacked 600 cooltube vertical donut for the other 12 hours. So at most 1200 watts at a time, leaving 700ish for pumps and fans and shit.
Does this sound correct? I don't want to burn my house down!
Thanks everyone, for the advice!
-gil

 

[Ickis]

I forgot to mention you need an exhaust fan and filter to empty the room air and that fan would need to be of a size to exchange the air in the room 5 x an hour or so. There are threads to figure that out based on your rooms cubic feet. You probably already know.

You have a plan now so the added info doesn't matter. There is more than one good way to do it. So you will get it done.

 

[Ez Rider]

Thanks holdin'! I saw your signature in another thread, and I was actually going to send you a pm about this.

So I'm thinking open ended cool tubes exhausted out the window might be my best option.
As far as my breaker, it's a 20amp at 120v. So:
120 X 20 = 2400
2400 X 80% = 1920watts....right??

I'm going to alternate between 1 600hps for 12 hours and a double stacked 600 cooltube vertical donut for the other 12 hours. So at most 1200 watts at a time, leaving 700ish for pumps and fans and shit.
Does this sound correct? I don't want to burn my house down!
Thanks everyone, for the advice!
-gil

Assuming there are no other loads on the circuit...you are correct. The math is simple, and you can look at the nameplates on your equipment for amp ratings, if not watt ratings. Follow the 80% rule, and no fires should result. You are right on the edge though, and odds are, something else will come up which requires more power.

What size wire is coming from the breaker? If it's at least awg 10, you can safely upsize to a 30A breaker. The awg # is usually printed on the wires insulation.

 

[Gil Tokerson]

I didn't even consider upsizing the breaker. That would be much better. Everything in my house is cheap "builder grade", so I'm guessing they used the smallest wire they legally could. Where is the easiest place see the wire so I can check? I'm thinking take off an outlet cover in the room?
Thanks again!
-gil

 

[Ez Rider]

I didn't even consider upsizing the breaker. That would be much better. Everything in my house is cheap "builder grade", so I'm guessing they used the smallest wire they legally could. Where is the easiest place see the wire so I can check? I'm thinking take off an outlet cover in the room?
Thanks again!
-gil

I'd be checking at the main panel, you should have the most exposed wire there. The print can be small, I take a pic with my phone, then blow it up to read.

You also need to determine what EXACTLY is running off that breaker. Overloading circuits is a BAD idea. Worst case, you can run a new circuit for your grow(if you have room for a new breaker in your panel).

I ALWAYS put the grow on its own dedicated circuit, w gfic protection. Materials would be about $150 to run an entirely new circuit. It's a very easy thing to do...usually. Either myself or one of the pros can walk you through it.