HomeRoast Digest


Topic: Quest Amp Question (10 msgs / 312 lines)
1) From: Barry Luterman
I have been having difficulty nailing a roast with my new Quest. Today I
plugged it in empty turned it on opened the amp switch all the way  and the
meter went only to 11. This has me wondering if I am not getting enough
Amperage out of the socket. They are supposed to be 20 amp circuits in the
house. Do the other Quests behave the same?
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2) From: Mike Chester
20 amps is the maximum that the circuit will handle.  Your heating element 
draws 11 amps at full power.  That sounds correct.  Without getting 
technical, think of it as you have a gallon of water available, but your 
glass only holds a quart.  You can fill the glass with water left over. 
This is not a good analogy as electricity and water are quite different, but 
you probably get the idea.  Now more technical - The element has a 
resistance measured in ohms.  The voltage is relatively constant at 110-120 
Volts. the formula for current is I=E/R (amps = volts divided by ohms)  The 
resistance of the element changes as it heats up, but for practical 
calculations, you figure it as relatively constant.  If you have 110 volts 
and the heater is 10 ohms, you will draw 11 amps.  (110/10 = 11) When you 
adjust the rheostat to set the current, you are actually changing the 
voltage going to the heater.  Lower voltage results in lower current and 
higher voltage results in higher currents.  If you were to turn it down to 5 
amps, that would mean that you have lowered the voltage to 50 volts, etc.  I 
hope that I have helped.
Mike Chester

3) From: Hank Perkins
In the US, on a 110v it will stop at 10.  If you have a 220v version
it is different.
On Thu, Feb 3, 2011 at 3:00 PM, Barry Luterman  wrote:
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4) From: Rich
The current available is not determined by the circuit breaker rating. 
The max available is determined by the circuit breaker rating though. 
The current is determined by the applied voltage and the resistance that 
the voltage is applied to.  E
On 02/03/2011 03:00 PM, Barry Luterman wrote:
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5) From: Tom & Maria - Sweet Maria's Coffee
Just a comment: I tend to use about 7.5 amp setting, then use the air 
speed to shape the roast. I make adjustments to the amps on the fly 
and especially alter it for batch size, but I find that once the 
coffee is warm, higher air speed will accelerate the roast and lower 
will slow it down - I see it as my fine-tuning control. I use 125 
grams on average... Of course, there are many ways of approaching the 
roast, and since it is quite a manual machine, it allows you to do 
whatever you like! Even with extreme settings I have found it hard to 
scorch coffee in a Quest, although I am sure it could be done.
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-- 
-Tom
"Great coffee comes from little roasters" - Sweet Maria's Home Coffee Roasting
               Thompson & Maria -http://www.sweetmarias.com     Sweet Maria's Coffee - 1115 21st Street, Oakland, CA 94607 - USA
             phone/fax: 888 876 5917 - info_at_sweetmarias.com
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6) From: Barry Luterman
This afternoon roasts were better. I went back to my origional tools. My
nose and ears. I was trying to be too scientific relying on meters and
guages. It suddenly dawned on me the reason for the meters and guages are to
quantify the art of roasting and replicate a roast. First however, you have
to roast correctly. Now I think I am finally on the right track. This is not
a roaster for a beginner and I was approaching it like a beginner.
On Thu, Feb 3, 2011 at 2:43 PM, Tom & Maria - Sweet Maria's Coffee <
sweetmarias> wrote:
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7) From: sci
Further question:
If my line voltage is 125v and I turn my Quest to 10A, doesn't that mean I
am drawing 1250 watts? (don't have a Killowatt)
If so, am I not hurting the unit because it is rated at 1050 watts? I don't
want to burn out the elements.
Just for reference, my Quest will draw only 10.5A empty and cold. I run it
on a 20A (125v measured line voltage) circuit with nothing else running on
that circuit.
Also, I have been doing what Tom does. I set the amperage at a constant
based on the batch size. I typically do a 200g batch with a 7.5A setting
(charge at 200C). However, I have insulated the drum which seems to give the
whole unit a little extra ooomph! (that's a technical word that only
electrical engineers with Ph.D.s use :-)
Ivan
From: Barry Luterman 
To: "A list to discuss home coffee roasting. There are rules for this
       list,   available athttp://www.sweetmarias.com/maillistinfo.html"       
Subject: Re: [Homeroast] Quest Amp Question
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This afternoon roasts were better. I went back to my origional tools. My
nose and ears. I was trying to be too scientific relying on meters and
guages. It suddenly dawned on me the reason for the meters and guages are to
quantify the art of roasting and replicate a roast. First however, you have
to roast correctly. Now I think I am finally on the right track. This is not
a roaster for a beginner and I was approaching it like a beginner.
On Thu, Feb 3, 2011 at 2:43 PM, Tom & Maria - Sweet Maria's Coffee <
sweetmarias> wrote:
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8) From: Rich
Considering the heating element as a pure resistance and no reactive 
component then P = EI.  If the voltage at the heater is 125v while the 
current is 10a then the power is 1250 watts.
On 02/04/2011 06:34 PM, sci wrote:
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9) From: ricky carter
Ivan,
Are you measuring your ET?
I'm curious as to what you are getting throughout the roast with a 200 gram
load and 7.5A setting.
What time frame are you hitting 1st?
BTW, I think they changed the elements from the original and you should have
no problem running close to max setting (though it doesn't sound like you
are really getting anywhere close!)
On Fri, Feb 4, 2011 at 8:44 PM, Rich  wrote:
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10) From: Mike Chester
You are correct - 1250 watts.  You are not hurting your element. The 
nameplate ratings are only an average for many units.  They are built within 
a tolerance and your actual unit may be higher or lower within that range. 
Also, I am sure that the built in ammeter is only approximate.  You would 
need a more accurate meter to get the real reading.  The meter is there as a 
reference, not an absolute value.  As long as it reads consistently, it does 
not matter if it is correct unless you are giving your profiles to another 
Quest owner.  As an example, let's say that it was off by 50% (it is 
probably off by less than 10% but I am trying to make a point)  If would 
show 5 amps when the real current was 10 amps every time. Since your real 
concern should only be the roast results, you would dial in 5 amps every 
time instead of 10.  The beans would not know that your meter was wrong, and 
you shouldn't care.
If you really are running at 1250 watts, your element should be fine.  They 
are made heavy enough to handle a small over-power without any problems. 
Remember, the nameplate rating is only nominal and your actual results may 
vary.
I hope that I have explained this clearly.
Mike Chester


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