Exhaust Vent Length

[Spartan1979]

I'm starting to plan my electric brewery. The first thing I'm trying to figure out is the exhaust venting as it will affect the layout of the room.

The room is in the basement at the front of the house. The front of the house is brick veneer. I don't think I really want to punch through that if I can avoid it.

So I was thinking about placing the brewery on the other side of the room and running the exhaust out of the back of the house. There already is an old unused dryer vent running from that room out to the back. I know I'd need to upgrade it to 6" but it is a 20 foot run.

I was looking at this fan: https://www.amazon.com/dp/B00GYG0MH0/?tag=skimlinks_replacement-20

This fan has a small enough diameter that it will fit between the floor above and the ceiling tiles of the existing drop down ceiling while still moving 420 CFM. The Vortex brand fans have too big of a diameter.

Is this fan big enough to push enough air 20 feet? If not, can I use two fans? Can the first fan (or only fan if it's big enough) be placed about 6 feet from the hood? Where would the best place to put the second fan (if necessary)?

Thanks.

 

[BrunDog]

I have no experience with an exhaust system like many on this forum, but I imagine if I were building one, I would be as concerned with incoming air for replacement as much as exhaust air. That will be a limiting factor if you create negative pressure. If your air comes from elsewhere in your house, is it going to be heated air that gets pumped outside and gets back-filled by outside air, making your house colder and HVAC work to replace that lost heat? Or reversed if in summer and you have air conditioning (haha I am ASSuming you are in MI from you avatar and name!).

Ideally, the perfect system has two vents, running in parallel. One exhausts, the other intakes. The exhaust is up top, the intake is at the level of your kettles.

The key with exhausting steam is mixing as much dry air as possible to avoid/reduce condensation. As soon as kettle steam, which is saturated air cools, water wants to condense out. So big fans are needed to reduce the blend of steam air with ambient air. But if you just backfill with warm humid air, you don't get much headroom for sub-saturated air to exist. Cool dry air from outside has lots of capacity to take on vapor as it heats up.

 

[Aeverman123]

You didn't mention if you are using gas or electric but gas will definitely need return air. I brew on an electric system in my insulated garage in Denver and am using two homer fans for my set up. View attachment ImageUploadedByHome Brew1482118074.785837.jpg. At 300 com each they move plenty of condensation. They're also on sale locally for 99 bucks. Check online and I can show you what I have done.

 

[augiedoggy]

Ideally, the perfect system has two vents, running in parallel. One exhausts, the other intakes. The exhaust is up top, the intake is at the level of your kettles.

Thats exactly what I do in my super low budget foamboard exhaust hood/dual window fan setup.... I just crack open the lower part of the window to let air in while the exhaust fans remove the steam from the hood... Works pretty well. I recently had one of the fans fail and had issues with condensation but just rewired the fan to bypass the switch to correct that.

Honestly I am looking for a more cosmetically appealing setup but since it works so well it keeps getting pushed back..

 

[Spartan1979]

All of the input on supplying air is great. It's something I hadn't really considered and I need to. However, no one has addressed the questions I actually asked.

Is this fan big enough to push enough air 20 feet? If not, can I use two fans? Can the first fan (or only fan if it's big enough) be placed about 6 feet from the hood? Where would the best place to put the second fan (if necessary)?

 

[BrunDog]

420 CFM is pretty good. Sorry, I was implying it was but replacement air would limit it.

It doesn't matter too much where it is but I would put it as close to the hood as practical.

 

[angrybits]

420 CFM is pretty good. Sorry, I was implying it was but replacement air would limit it.

It doesn't matter too much where it is but I would put it as close to the hood as practical.

Does the replacement air need to be forced? And am I reading correctly that you vent at the top and feed replacement air from the bottom?

 

[BrunDog]

It doesn't need to be forced but then some of the replacement air will come from elsewhere in your house. May not be a deal breaker.

Ideally fed from bottom but that may not be practical.

 

[ryane]

do you really need 420CFM? that seems like quite a bit of air movement??

in a 6in flex duct that thing is gonna howl especially if you add in a non-sweep 90 or two

The fan says 420CFM at 0 DP, so you'll never get that much airflow. To figure out how much you would gett you need to measure out the length of flex and add up 90's etc. Then using this info you can estimate the losses through the flex, then all you need to find out is the capability of the fan (eg max output pressure in inwc)

 

[timdillon36]

I would recommend against using flex as that is not a smooth ID and will create turbulent air flow and slow down the flow of air. There is also going to be condensation in the duct work. I would make sure there is a slope downward from the hood to the exit of of the duct. A smooth bore will allow much better drainage.

If you are concerned with leaks you can do the plumbing with pvc. Think of it as a hot water drain. The distance can be over come but it introduces other factors that need to be considered.

When I get around to moving my brewing to the basement I think I am going to build what I would call a collection hood. It won't vent at all, I will keep the hood cool from the outside, not sure exactly how yet but I have a few ideas. Then on the inside it will be sloped steep enough that the condensation runs down into a drip ledge and runs out into a drain or bucket.

 

[Kmo4040]

John Blichmann wrote an article for the November 2012 issue of BYO magazine that summarized ventilation requirements as follows:

Electric based brewery: Divide the element size (in watts) by 17.6 to obtain the required CFM (cubic feet per minute). In our case we use a 5500W element in our boil kettle. 5500 / 17.6 = 312 CFM. We therefore require a fan that can move a minimum of 312 CFM in order to ventilate our electric brewery properly. Fans this size are readily available and reasonably inexpensive.
Gas based brewery: Divide the burner’s BTU/hour rating by 30. Because of the inefficiencies, a 80,000 BTU burner produces approximately the same amount of heat in the kettle as a 5500W element. 80,000 / 30 = 2666 CFM. We would therefore require a fan that can move 2666 CFM in order to ventilate a gas setup properly. A fan this size is not readily available. A commercial restaurant exhaust fan is likely required.
Because of the enormous ventilation requirements of a gas based brewery (8.5 times higher than an equivalent electric setup), an indoor gas brewery is not easily achievable. It requires a massive amount of air evacuation as well as an equally substantial make-up air system. Large fans with ducting larger than 16" in diameter may be required, making safe indoor gas brewing very expensive. It is not uncommon for the ventilation and make-up air system of a gas based indoor brewery to cost more than the brewing setup itself.
• Use large ducts and minimize turns
• In‐line duct silencers are worth the money!!
• Make sure your fan is rated for at least 140F
• Each sharp 90 deg elbow = 10ft of straight duct
• Each 45deg elbow=5ft of straight duct
• 10” dia duct will handle 400 CFM
• 12” dia duct will handle 700 CFM
• 14” dia duct will handle 1100 CFM
• 16” dia duct will handle 1500 CFM
This assumes a MAX of 100ft of equivalent straight duct length. So for a system with (4) 90 deg elbows you could have up to 60 ft of straight duct.

 

[steveoatley]

Spartan

I have a 6 inch fan - 460 cfm ( i started with a 4 inch & 4 inch duct that was worse !! )

https://www.amazon.com/gp/product/B005XNNYMU/?tag=skimlinks_replacement-20

the distance from the top of my pot to the vent out - threw a glass block window
is 5 ft total - see pic

And I get drippage - water condensing in the duct and fan - and dripping back down

The longer your run - the more the water vapor has time to condense
Then you will have to deal with water management

Best case - Shortest distance possible to get the water vapor OUT side your house - it can condense out there ~ and water your plants outside.

Water vapor will start to condense the second it hits a cold metal duct
You want to move that as FAST as you can and the SHORTest distance to get it out of your house

Otherwise you have to set up a whole "drip tray/hose" system

I insulated the duct in the pic, by wrapping it
AND I still get water out of my fan & duct! ( depends on the humidity in the air as well )
I need to run a drip line form the fan, to the sink
It totals about 8 oz per brew day...... ( depending on the temp in my basement, and the air temp, and outside air temp )

Get the water out, and as fast as you can

My 2 cents