Make-up air for roaster

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Milligan
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#1: Post by Milligan »

I watched a great video by Matt Risinger about make-up air systems for powered ventilation units in newer construction homes.
It had me thinking about the roaster drawing interior air and venting it to the outside. I wouldn't think a typical home roaster draws too much CFM but I've roughly calculated that my 5kg roaster draws 300CFM at the end of the roast not including the cooling bin. Definitely a situation that should use make-up air.

It has me thinking of adding a passive damper for my smaller unit which I use in my basement so that I reduce the negative pressure effect on the rest of the house. I wouldn't want back draft so I'd put it on an opposing wall, conveniently cracking a window on the other side of the room should negate a lot of the effects.

I remember reading an article by Rao saying they were striving for a completely sealed roasting environment. I'm not sure how that is possible without drawing air from the outside. I'm betting larger commercial roasters have outdoor air intakes with some type of humidity and temperature sensor in the inlet pipe to adjust the burners for the external air environment. Then use some sort of recirculating hot exhaust gases exchanger/scrubber to preheat the incoming charge. That seems to be more efficient and consistent.

Anyway, anyone else have "cracking a window" as part of their indoor roasting process? If not, maybe it is something to consider.

PBJ
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#2: Post by PBJ »

I have my roaster (1K MCR) in my walk out basement. The furnace is about 8 feet away from the roaster. Any furnace installed after about 1980, by law, should have a combustion air intake. That would be enough to replace what is used by the roaster.
Curly

Milligan (original poster)
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#3: Post by Milligan (original poster) replying to PBJ »

Depends though. As the video showed, you need 3x the size of the exhaust vent pipe for your passive damper to get near a pressure equilibrium. My furnace intake is only a smaller 2in intake pipe so not even as big as the 4 in vent pipe I use on my cormorant.

Houses are leaky so air will find its way in, the point of make up air is to 1) control where the air comes in 2) filter that air 3) make sure we aren't back drafting 4) preheat/cool the air in some cases.

Capuchin Monk
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#4: Post by Capuchin Monk »


PBJ
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#5: Post by PBJ »

Milligan wrote:Depends though. As the video showed, you need 3x the size of the exhaust vent pipe for your passive damper to get near a pressure equilibrium. My furnace intake is only a smaller 2in intake pipe so not even as big as the 4 in vent pipe I use on my cormorant.

Houses are leaky so air will find its way in, the point of make up air is to 1) control where the air comes in 2) filter that air 3) make sure we aren't back drafting 4) preheat/cool the air in some cases.
Code in my area is minimum 4" combustion air which is about 4 times the area of a 2" intake. Combustion air is mostly used to replace oxygen used by the gas appliance

Milligan (original poster)
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#6: Post by Milligan (original poster) »

PBJ wrote:Code in my area is minimum 4" combustion air
I don't see how this has to do with the roaster venting air? Are you saying the hole in your house envelope for the furnace will suffice? When the furnace is on it draws air in via a fan. We are talking about a separate roaster that draws air out of the house and needs to "make-up" the air being drawn out with fresh air. On modern furnaces the inlet air and outlet air are separated from the air in the house. It draws into the unit, burns, and is directly piped back out. So I'm not sure how that helps?

Milligan (original poster)
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#7: Post by Milligan (original poster) »

Capuchin Monk wrote:Remember this post? :arrow: My 5kg USRC Roaster, I took the the plunge :wink:
Yes! I actually have that heat exchanger concept on my list for my permanent set up. Do you do anything like that for your home roaster?

PBJ
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#8: Post by PBJ »

Milligan wrote:I don't see how this has to do with the roaster venting air? Are you saying the hole in your house envelope for the furnace will suffice? When the furnace is on it draws air in via a fan. We are talking about a separate roaster that draws air out of the house and needs to "make-up" the air being drawn out with fresh air. On modern furnaces the inlet air and outlet air are separated from the air in the house. It draws into the unit, burns, and is directly piped back out. So I'm not sure how that helps?
I'm saying that you have a 2" combustion air intake for your furnace. I have a 4" intake, which is 4 times the area of yours. If your furnace works with the 2", then 4 times that area will supply enough for my roaster. Again, the combustion air intake is for resupplying oxygen that is used when gas appliances are used. It's not just replacing the air that is going out of your exhaust. It is always supplying air, not just when the burners are running.

Capuchin Monk
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#9: Post by Capuchin Monk »

Milligan wrote:Do you do anything like that for your home roaster?
My roaster is small enough (400g capacity) to let the window / door infiltration to balance out the exhaust pressure.

There are many sites showing the (larger CFM) vent make up air methods.
Here's one :arrow: https://www.prolinerangehoods.com/blog/ ... ke-up-air/

Combustion air intake for furnace is not the same as make up air intake. I remember seeing some basic house mechanical system calculation sites.

Capuchin Monk
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#10: Post by Capuchin Monk »

Milligan wrote:I watched a great video by Matt Risinger about make-up air systems for powered ventilation units in newer construction homes.
Passive method can work better if the intake opening and louver is very close to the exhaust hood but that would require opening up the exterior wall of kitchen area which is not feasible for most homes.