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I like to keep things at around 118VAC throughout the roast. Without the Variac, the voltage will drop down into the 111-113 after about 7.5 minutes. The voltage with no load at the outlet I'm using is around 122VAC.
The Variac is not a "set and forget" device. The voltage in my house seems to fluctuate quite a bit and the load of the roaster changes throughout the roast cycle. To keep things at 118 I have to keep an eye on the Kill-A-Watt and make frequent small tweaks to the Variac.
With consistent voltage I can predict C1 & C2 within a few seconds for a given coffee. I keep fairly detailed log which makes it easy to compare crack times between batches. P2 seems like the best profile to me, but it's important to do a couple of P1 roasts so that you know when to expect C1 to start.
I set things up with P2 so that the temp drop occurs right after C1 gets rolling, otherwise it seems like the first crack is either very brief or very late.... makes me wonder if the coffee is baking in those cases.
3 Comments:
Thanks for this post. I have a Behmor, an old house w/ very low voltage at certain times, and can only do about 12 ounces at a time (and still get to 2nd crack).
This is very helpful. Where did you get your variac? it looks like a lot of the usual sources (sweet maria's et al.) don't carry them any more.
Thanks for the comment. I got lucky and got a good deal on the Variac from a guy on CoffeeGeek who was giving away a bunch of roasting related stuff for the cost of shipping.
You might want to try eBay, or perhaps post a "Want To Buy" in the CoffeeGek forums.
Sorry for the late reply--thanks for your answer. Nice blog!
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