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Long duct run for indoor brewery ventilation

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I poked around the forms a bit and could not find an answer to this question.

I have my electric brewery up and running. On my first brew day, all went well except I am getting a serious amount of condensation in my condensate hood.

The hood is 5' long x 2' wide x 1' tall. It is 2 ft. from the top of my pots. I have 6" ducting setup. There hole in the hood is centered in the top and there are two 90 degree elbows to get the exhaust to fun to my duct run. The overall length of run is 25 feet. I am using a 347 CFM 6" inline fan.

I am guessing that the 347 CFM is not sufficient for removing all of the steam, but I'm trying to figure out what CFM I need to prevent the excessive condensation and/or if there is anything else I should be doing in order to help prevent this excessive condensation.

Lastly, does anyone know if I add another fan in line with the current fan, will that boost the overall ability to remove the steam? or is the CFM not additive?

The only fans I can find with a high CFM are larger diameter, so I'm wondering if I should install reducers in the duct line (6"->10") and install a 10" fan in a small section of the duct run?

Any advice is greatly appreciated!
 

jddevinn

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CFM is dependent on pressure drop in the line (and is not additive). 90°s are going to push the pressure drop up a good bit.

Any "low points" are going to collect condensate!
 
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Thank you for feedback.

I know it is not 100% additive, but do you happen to know how to calculate equivalent CFM of two fans in series with one another?

Also, technically the opening in the hood is the lowest point in the entire system. Is that a bad design?
 

doug293cz

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Two fans can help overcome the pressure drop due to the long duct run and 90˚ turns. I would think it would work best with the fans at least 1/2 the total duct run apart. If you put them close together, you won't get much benefit.

Condensation can collect in any point where the duct sags from a positive slope from the inlet to outlet. Any such sags that can't be eliminated should have weep holes drilled (1/8" is enough) and a way to deal with the drips from the weep holes.

Brew on :mug:
 

lschiavo

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Is the steam escaping the hood? If not, I'd think that you are probably moving enough air.

Do you have a source for makeup air? Fans work far better when they aren't pulling a vacuum.

Condensation happens with temperature difference. Is your hood or vent piping insulated? That could help a lot.

I would expect to see at least some condensation on a "condensate" hood. What method are you using to drain it away?
 
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Thanks for feedback all!

There is a lot of condensation in the condensate hood. So much so, that it is dripping off the hood and back into my kettles. I do not have any baffles on my condensate hood, it is a simple stainless steel box with a vent hole at the top.

What I'm wondering is if I get high CFM, will that suck the steam out faster and minimize the amount of condensation that is occuring?

For makeup air, I do not have a separate intake, but there is a double door opening with both doors open in the brewery and I left the back door of my house open, so I think there was sufficient makeup air getting into the room.

I have not insulated my ducting, but will try doing so. The condensate hood has a drain built in and a small lip/trough running around the bottom to channel condensate to that drain. The thing is that the condensate is just dripping off the top surface and not making its way down the sidewalls.

For the weep holes, is it just a small hole in the ducting with a collection vessel underneath?
 

doug293cz

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For makeup air, I do not have a separate intake, but there is a double door opening with both doors open in the brewery and I left the back door of my house open, so I think there was sufficient makeup air getting into the room.
Should be plenty of makeup air.

I have not insulated my ducting, but will try doing so. The condensate hood has a drain built in and a small lip/trough running around the bottom to channel condensate to that drain. The thing is that the condensate is just dripping off the top surface and not making its way down the sidewalls.
If the top of the hood is horizontal, then condensation will collect and drip. This is why most hoods have sloped tops, so that condensation will run to the walls, and then down to the drip trough.

For the weep holes, is it just a small hole in the ducting with a collection vessel underneath?
Yes.

Brew on :mug:
 

lschiavo

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I'm not sure that moving more air will solve the dripping problem. It sounds like you have plenty of air flow and makeup air.

I would probably start with modifying the hood to collect the condensate better and try to insulate it somehow. Lowering one end of the hood so it's not completely horizontal could help direct the water to the low end.

Post a few pics if you can.
 
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Here are some pics.

I added aluminum duct tape to the inlet hood joint in order to make it a smoother transition. I also tilted the hood to slope toward the drain to promote condensate running to that location. Going to give it a try again in a week or so and see if any of that helped.

Thank you for all the advice. Please chime in if pictures help you think of some other possibilities.

Ventilation Hood.jpg


90 degree elbow at top.JPG


90 degree elbow to fan.jpg


duct hood inlet.jpg


straight duct run.jpg
 

lschiavo

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Nice rig. Beautiful hood. How could it possibly drip?....okay, upside down pics.

I can understand not wanting to ugly things up with insulation. I would suggest some reflectix for the pipe and foil faced foam maybe on the inside of the hood if still necessary. With some careful cutting and some more foil tape, you could probably pressure fit the foam inside the hood and also build in some slope for better drainage.

You don't have to wait to brew. Just boil some water if you want to test your modifications.
 

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Very nice hood, unfortunately preventing condensation on the hood is like trying to stop a cold beer from sweating on a hot day! I have sprayed the inside of hoods with rubber sealant and had success to a limited degree. That said fresh air is key.
 

ScrewyBrewer

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A 90 degree elbow will add up to 10 feet of restriction per elbow to the duct run. So a 25 foot run with 2 elbows really becomes a 35 foot run. My hood uses a 780cfm fan and has less than 3 feet of of 6 inch flex connecting it to a wall vent. Even though it hangs 36 inches above the top of the kettle, the hood drips condensation in winter and summer. What saves me it the fact that the hood is mounted to the wall on a swivel mount, allowing me to swing it off center so the drips don't land inside the kettle.

brewday-13-sml.jpg
 
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