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Topic: New member and variac (3 msgs / 83 lines)
1) From: George Miller
Hello one and all, 
I'm a new member here.  I've been reading the digest for about a week now 
and this will be my first post.  In no way am I an expert, maybe not even a 
novice yet...but working on it.  My equipment, bought about 3 months ago 
consists of a Zach and Dani's roaster, a Bravi roaster, digital scale, and 
almost a dozen ways to brew the coffee from the single serve Swiss Gold unit 
for cups, drip, espresso, vacuum, French press, aeropress, and others (read 
a perc machine in there also)and a couple of so so grinders - nothing really 
great. 
Besides introducing myself here, I have a question. 
Having noticed my roasters slowing down and up during roasting due to other 
things on the circuits I use for roasting, I have purchased and received a 
variac from Sweet Marias.  Now for the question.  What is the ideal voltage 
to set it for?  I have noticed that the dial when set on 100v shows 110v on 
the meter.  I would think that I should determine the set the voltage to the 
meter and not by the dial.  But what voltage?  110v, 115v, 120v?  None of 
the roasters give any idea of the "ideal" voltage to roast at. 
Anyone have any suggestions.  Oh, I'm in Central New York and I got the 
variac as we do have a fair amount of "natural" voltage flux especially in 
the summer months. 
Thanks for any suggestions.

2) From: J.W.Bullfrog
George Miller wrote:
<Snip>
Start at around 100 volts, then change it based upon how long the roast 
takes.

3) From: Michael Wascher
Geirge,
Go by the meter, the dial setting needed to achieve a given output voltage
will change depending on the line voltage de jeur. The product you are
plugging into this should have a placard or a manual that defines the safe
range of line voltage. That said, any sane engineer will design in a safety
factor, especially if he has a justifiably paranoid company attorney lookin=
g
over his shoulder.
Long answer:
I don't have an SM variac, but the dial is usually calibrated as a
percentage, not as a voltage.
Variacs don't actually regulate the input voltage, they modify it by a
constant factor. If the input changes the output changes. The description
says that you'll get 0-130V out with 110 V in. so at the top stop it will
multiply the input by 130/110 = 1.2.
Many of these have a dial that ranges from 0-100, for 0-100% of max output
(of 130V if you have 110V input to it). A few I have seen have a scale that
reads 0-120 meaning output is 0-120% of the input voltage.
I presume you have one of the later, if not, your line voltage is
approaching dangerously low levels In this case, when set at 100 the output
voltage is the same as the input voltage.
--MikeW
On 4/29/06, George Miller  wrote:
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--
"Life is just one damned thing after another."
  - Elbert Hubbard


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