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Air Change per Hour?

 
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mplaing




Joined: 03 Jan 2016
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Location: Canada


PostLink    Posted: Thu Dec 12, 2019 11:33 am    Post subject: Air Change per Hour? Reply with quote


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I posted a comment a while ago regarding condensation on my hood (6'x3'x1', vented in centre with vortex 600 fan, system 30 gallon kettles set up to brew +/-15 gallons with 5,500 watts elements). My basement is 20' x 26' and ceilings are 8.5' high.

I pretty much have the same set up Kal has and immediately at 205f, water starts to build up on the surfaces of my hood.

I have been trying to figure why this is happening, my basement temperature is usually 16C, I've opened the heat vents and it is now 19C and condensation has gone down a little bit, but is still not down to my expectations.

I was reading about air change per hour on a site talking about kitchen range hood calculations. Does any one factor in ACH requirements for their electric brewery set up? All the ACH information I am reading about applies to gas stove/ranges and suggest a rate of 16 ACH.

With this information and factoring in my basement size, it means I would need a fan rated for 1160 CFM not 450 CFM, does that look right?

An other option is to build a walled enclosure measuring maximum 12' x 17'-6" x 8'-6" to create air space (1785 cubic feet) that a 450 CFM fan can cycle the air volume 16 times per hour.

Has anyone had to factor in their brewery size in relation to ventilation fan size? Does an air change per hour rate of 16 (I got it off a site for kitchen calculations based on gas stoves) look correct or is it lower for electric based system?

Thanks in advance,

M

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kal
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Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Thu Dec 12, 2019 1:41 pm    Post subject: Reply with quote

Make sure you have adequate flow out and how you've done your make-up air. You haven't mentioned how that works. Unless you have enough air coming in to replace the air you're trying to push out, you won't get adequate flow. See my ventilation article for complete details: http://www.theelectricbrewery.com/ventilation

Based on previous pictures you've posted you're not using our products or design so it's probably best you ask your brewing system manufacturer for help on how best to use their setup. They should be able to help too.

Good luck!

Kal

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mplaing




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PostLink    Posted: Thu Dec 12, 2019 2:07 pm    Post subject: Reply with quote

Hi Kal, thanks for your reply. I have two windows open each are approx 2' x 2'. I cannot see how things can be different based on different products that function the same way. My system is back to back, but I have only tested it using one 5,500 watt element running at 100% power until the water begins to boil then I reduce it to 80%.

My duct work is insulated all the way to the fan, 6" from hood and is reduced to 4" at the wall output similar to yours.

What is the the foot cubic size of your brewery room, just to compare my size?

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kal
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Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Thu Dec 12, 2019 2:37 pm    Post subject: Reply with quote

Two windows that size open for make up air is lots. It can support considerably more airflow than what you're pushing out. So you're good there.

My brew room is about 13x11'. But that shouldn't matter, as long as I have my make-up air vent open the air coming in matches the air out since my hood/vent is directly above my boil kettle so the steam goes straight out. My make-up air 6" pipe is very short, shorter than the output so there's less restriction coming in than out which is good so I'm not limiting my output flow. If my brew room door is open then it's open to the rest of the house and some air will come from there too of course. I prefer not to do that as then I'm evacuating either heated (winter) air or cooled (summer) air. I try and minimize this by keeping the brew room door closed (it has a seal) whenever the hood fan is running. This is simply to minimize home energy usage.

My brewery isn't filling up with moist air from the kettle. In fact, in the winter it's very dry/cold air which really helps offset the heat from the kettles. I love brewing in the colder months because the room drops to the mid 60s (F) and is very comfortable to work in (plus the ground water's a lot colder). In the summer when it's hot outside the room is a good 20 degrees (F) warmer.

Kal

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701pilot




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PostLink    Posted: Thu Dec 12, 2019 6:34 pm    Post subject: Reply with quote

What is happening is the steam is condensing on the hood before it can be removed by the fan taking it outside to condense in the air. So you can either use a bigger fan to get it out faster before it has a chance to condense on the hood or you can use a hood designed to collect the condensation in a trough and channel it to a drain. I suppose you could heat the hood and insulate it so the steam doesn't condense on it in the first place. Seems to me using a properly designed hood is probably the best bet.
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mplaing




Joined: 03 Jan 2016
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Location: Canada


PostLink    Posted: Fri Dec 13, 2019 11:25 am    Post subject: Reply with quote

kal wrote:
Two windows that size open for make up air is lots. It can support considerably more airflow than what you're pushing out. So you're good there.

My brew room is about 13x11'. But that shouldn't matter, as long as I have my make-up air vent open the air coming in matches the air out since my hood/vent is directly above my boil kettle so the steam goes straight out. My make-up air 6" pipe is very short, shorter than the output so there's less restriction coming in than out which is good so I'm not limiting my output flow. If my brew room door is open then it's open to the rest of the house and some air will come from there too of course. I prefer not to do that as then I'm evacuating either heated (winter) air or cooled (summer) air. I try and minimize this by keeping the brew room door closed (it has a seal) whenever the hood fan is running. This is simply to minimize home energy usage.

My brewery isn't filling up with moist air from the kettle. In fact, in the winter it's very dry/cold air which really helps offset the heat from the kettles. I love brewing in the colder months because the room drops to the mid 60s (F) and is very comfortable to work in (plus the ground water's a lot colder). In the summer when it's hot outside the room is a good 20 degrees (F) warmer.

Kal


With your room size, it is within your fan ratings (13' x 11' x 8.5'(?) = 1,215.5 cubic feet and to factor in air cycles at a rate of 16 times per hour 1,215.5 x 16 = 19,448 cfh divided by 60 for minutes = 324 cfm fan required.

This may explain why you do not see a lot of condensation in your hood.

With my room it is 20' x 26' x 8.5' = 4,420 CF x 16 ACH = 70,720 CFH / 60 = 1,179 CFM fan required

Pretty much power rating 5,500 watts kettle, exhaust hood, fan is the same so the only variable I see is room size and the ACH rate of 16 is from looking up information on kitchen exhaust requirements.

And for humidity in my basement, it is a very dry one, usually in 20% relative humidity, and goes up to 30% when I do tests with my brew system.

Right now I am trying to come up with inexpensive test walls to create a temporary room approx. 8' x 9'-6" to test the theory of ACH and the impact of room size in relation to exhaust systems, but was hoping someone else here has dealt with something similar to me and figured room size has an impact.

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mplaing




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PostLink    Posted: Fri Dec 13, 2019 11:31 am    Post subject: Reply with quote

701pilot wrote:
What is happening is the steam is condensing on the hood before it can be removed by the fan taking it outside to condense in the air. So you can either use a bigger fan to get it out faster before it has a chance to condense on the hood or you can use a hood designed to collect the condensation in a trough and channel it to a drain. I suppose you could heat the hood and insulate it so the steam doesn't condense on it in the first place. Seems to me using a properly designed hood is probably the best bet.


Thanks for your comment, you mention steam condensing on the hood before it can be removed - I completely agree which comes to my room space question. It the room was smaller, the fan wouldn't need to remove as much air and with my calculations to properly cycle air out of my basement - aka brewery I would need a fan with 1,179 cfm rating.

I am going to build another test condensate hood, this time approx. 36" x 36" x 15" deep that will only target the brew kettle to see if that will manage steam/condensation better and of course I am including gutters to catch water build up, if that doesn't improve I will revisit the room size in relation to air cycles theory.

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kal
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Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Fri Dec 13, 2019 2:09 pm    Post subject: Reply with quote

mplaing wrote:

With your room size, it is within your fan ratings (13' x 11' x 8.5'(?) = 1,215.5 cubic feet and to factor in air cycles at a rate of 16 times per hour 1,215.5 x 16 = 19,448 cfh divided by 60 for minutes = 324 cfm fan required.

This may explain why you do not see a lot of condensation in your hood.

No, as when I brew with my doors open my "room" is huge, it's my entire house. Using your logic, a brewer should have issues with condensation on their vent hood if their brewing room gets larger or if they open their brewery door. But that is not the case with a properly working ventilation system.

You don't need to turn over the entire room (or house) so many times every hour to make this work. That's incredibly wasteful in terms of energy. A condensate hood like the ones we use in our breweries is specifically meant to capture the steam directly coming out of the brewing kettles (mostly the boil) and evacuate it out. It's localized. It's purpose is not to evacuate or turn over the entire brewery room air.

IMHO you're confusing the issue with bringing in air exchanges per hour into this and going down an illogical rabbit hole. You don't need to evacuate the entire room. If you do need a much larger fan it's not because of those room turn over calculations you're doing, it's because your ventilation system is not working correctly in the first place.

From my ventilation article:

Quote:
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.

John makes no mention of room size that's not relevant. No hood fan sizing calculator does because hoods are localized, meant to exhaust from a single device or location (like a kitchen stove, soldering station, pre-wash sink, etc).

I don't know why you're having condensation issues but something certainly isn't right. I don't know where your hood exhaust port is in relation to your boil kettle, but directly above the boil kettle is the best as it doesn't allow steam to rise and collect on the horizontal ceiling surface of the hood. You could have a cold basement (affecting dew point) or a cold hood because of how it's positioned. No idea I'm afraid.

As 701pilot mentioned going with a larger fan may solve your issues to for the reasons he mentions. But that has nothing to do with the turn over calculations you're doing. You don't need to turn over the entire room on a properly designed/working ventilation system meant for a specific purpose. You don't WANT to do this as it's wasteful. This is not a HVAC / air quality issue (where usually the discussion of turn overs per hour come up). The exact same is true for a kitchen stove hood. Building code dictates the size of your stove vent hood based on stove BTU output, not based on the room size. Room size has nothing to do with it and isn't used in the calculations because a stove hood's sole purpose is to evacuate from the stove only. It's not a room/building exhaust.

Installing baffles in your hood can also help - see my ventilation article for how/why. I didn't have to do this myself, and I've yet to see any brewer need them too but since I don't understand where your issue is, it's a possible option.

Kal

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mplaing




Joined: 03 Jan 2016
Posts: 13
Location: Canada


PostLink    Posted: Fri Dec 13, 2019 3:29 pm    Post subject: Reply with quote

Thanks for your inputs - I am currently working on a new hood prototype with rigid insulation.

This one will be a square (36" x 36" x 15") and entirely focus on the brew kettle and have a look at how my fan is located (am thinking of placing it horizontally and directly connected to the hood with the rest of ductwork hooked to the output to see if that makes a difference) I will also design baffers to be added to divert condensation in case this design still develops a lot of condensation. Of course there will be channels around it to collect water and drain into a bucket or sink.

Kal, in one of your photos I noticed you reduced the output from 6" dia. from 4" dia. ductwork to exhaust through the exterior wall. I am doing the same, but could that be slowing down or preventing the correct amount of air being exhausted?

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kal
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Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Fri Dec 13, 2019 3:42 pm    Post subject: Reply with quote

mplaing wrote:
Thanks for your inputs - I am currently working on a new hood prototype with rigid insulation.

Good idea. That's what I did originally when testing: http://www.theelectricbrewery.com/ventilation?page=8

Quote:
Kal, in one of your photos I noticed you reduced the output from 6" dia. from 4" dia. ductwork to exhaust through the exterior wall. I am doing the same, but could that be slowing down or preventing the correct amount of air being exhausted?

I did that at my previous house. Yes, it did slow things down a bit. I never measured how much as my tests (link above) showed that it still worked fine.

If you want to do some tests now to check out restriction to see if your ducts are causing issues, try measuring the airflow from the fan not installed (running in open air) vs what you get when installed at the end of your vent line. There are cheap devices to do this: https://amzn.to/35jNfqA
One (free but not as accurate) way to do this is time how long it takes to inflate a garbage bag.

Kal

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mplaing




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PostLink    Posted: Tue Feb 11, 2020 11:12 am    Post subject: Reply with quote

Thought I would post an update - prototype hood with bafflers works as expected, vortex fan was adjusted to be mounted horizontally, first few tests there was so much condensation building up in the pipes post fan and in the fan. Someone suggested using HVAC mastic, with some hesitance I gave in, spread mastic around the entire piping post-fan, then wrapped it with mesh fiberglass tape, covered the mesh tape with more mastic.

I also drilled a bigger drain hole in the screw hole that I removed (to control water leaking from fan) by letting excess water drain in to a collector, but after applying mastic it looks like no water is coming out of the fan (weird).

So far everything seems to be working perfectly. Currently the hood is pretty low due to spacing limitations for the fan, so I might do another prototype hood where the pipe connects by the side instead of top to see if things still work fine enabling me to have my hood raised at least 18" higher.

Has anyone utilized HVAC mastic to their ventilation system? I'll try to post photos when I have a chance.

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kal
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Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Tue Feb 11, 2020 12:54 pm    Post subject: Reply with quote

mplaing wrote:
I also drilled a bigger drain hole in the screw hole that I removed (to control water leaking from fan) by letting excess water drain in to a collector, but after applying mastic it looks like no water is coming out of the fan (weird).

With the various coatings you've done you've insulated the pipes so the steam stays warm and doesn't condense. Insulating is what I recommend in my ventilation build instructions if you want to reduce the amount of condensation. See: http://www.theelectricbrewery.com/ventilation

Kal

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