Coffee Roasting     Bypassing the Nordfab Y duct tie in

2020-06-17 19:28

Bypassing the Nordfab Y duct tie in

I've done this on my roaster mainly because I didn't have any space restrictions and didn't mind having two exhausts exiting the building - It's fantastic. I'm helping some friends set up a 6 kilo, the have the complete Nordfab kit and are looking at separating the cooling tray from the drum exhaust due in part to the Nordfab butterfly valve being difficult and potentially broken. Anyone else doing this or having issues with the Nordfab ducting?

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2020-06-17 21:16

Hi Ben,

It's not totally uncommon to keep the exhaust lines separate to termination - I probably have about 10% of our customers request Line 1 & 2 from our kit but then handle the rest themselves. I actually suggest keeping the lines separate for roasters that have longer runs and/or multiple elbows to reach termination outdoors -or- roasters in spaces with low ceilings that don't allow the height of the kit & clearances and also for whom horizontal ganging doesn't make sense. The downside is running the lines separately is more expensive as you're essentially designing, sourcing and installing two lines to termination outdoors and, if you have combustibles in your building envelope, your permitting official might want to want to talk about the heat in the cooling line or worse, require to you to have a clearance-to-combustible rating on both lines. But if time, cost, penetrations, etc. are not an issue, running two lines prevents any chance of backflow which sounds like might be an issue for your friends if you're referencing the function of the butterfly valve.

For most people, that butterfly valve is at most a modulating device that is a "set it and forget it" damper just to offer enough resistance that the roast air finds it's easier to flow outside than to back up through the cooling fan/tray. If your friends are having to actively open/close that butterfly valve with every drop/charge, it's worth a conversation to figure out why that air is slow in the line to termination to begin with- especially if the plan is just to reroute the cooling but leave the chaff collector exhaust line as it exists. We may find a minor change in that main line could also improve air flow capability in the drum over what they experience now (different cap, exposure, etc.). We should also be talking anyway if their valve is broken and they bought it from us. If they are on a Mill City Roaster, maybe suggest they (or you) give me a call at the office. I'm happy to talk through this.

Angie Davis | Mill City Roasters
Ph: 612.886.2089 E: Angie@millcityroasters.com

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