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Topic: Power tolerances (8 msgs / 144 lines)
1) From: Victor Blackwell
This is a multi-part message in MIME format.
Commercial standard for the heating element industry is +10/-20 percent. =
 This means a 1000 watt heater could actually be 800 watts to 1200 watts =
and be acceptable and within commercial tolerances.  Would this effect =
you roasting?  So no wonder some of the manufactures provide a means to =
adjust the input power to their heating elements to provide reasonable =
consistency.
Vic

2) From: Victor Blackwell
This is a multi-part message in MIME format.
Sorry, I spotted my usual typo error.  The wattage range is actually 800 =
watts to 1100 watts for the example 1000 watt element.
Vic 
  Commercial standard for the heating element industry is +10/-20 =
percent.  This means a 1000 watt heater could actually be 800 watts to =
1100 watts and be acceptable and within commercial tolerances.  Would =
this effect your roasting?  So no wonder some of the manufactures =
provide a means to adjust the input power to their heating elements to =
provide reasonable consistency.
  Vic

3) From: Jim Schulman
On 30 Jan 2003 at 19:52, Victor Blackwell wrote:
<Snip>
That sounds like too much for roasting purposes: 
If a heater is 1100 watts at 110V, it would be 800 
watts at 94 volts. On my FR, I'd stall the roast 
either just before or just after the 1st crack at 
that setting. So if FRs varied by that much, some 
models would finish in 3-4 minutes, others never.
Perhaps, purpose built roasters are spec'ed a bit 
tighter, since I've never heard of that much 
variance. However, it would explain why the same 
popper models do so differently.
Jim Schulman
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4) From: Victor Blackwell
Yes, explains a lot.  Then if you had one on the low wattage end and low
line voltage you could never get the job done.   I have never heard of
anyone here measuring the line voltage and even mentioning how much current
the heating element drew.  An Amprobe like device could measure the current
then no trouble computing the wattage.  Might save a lot of fumbling.  You
can buy heaters with a much closer tolerance, but you will end up paying for
all the throw always.  Of course, you have to also specify the voltage.   A
little SCR circuit is dirt cheap compared to high tolerance heaters.
Vic

5) From: Mike McGinness
From: "Jim Schulman" 
<Snip>
Actually, it does sound like the heat variation encountered with Caffe'
Rostos though, my two are vastly different heat wise, 'bout 10v applied
difference for same heat... but not a problem with a variable transformer
and thermometer!
MM;-) aka Kona Konnaisseur miKe mcKoffee
Dual Variable Transformer Rosto Roasting
Rocky grindin' - Miss Silvia brewin'
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6) From: Victor Blackwell
Do these little roasters have thermostats to regulate temp?   Your home
cooking oven has one.  Of course, a good Robert Shaw thermostat would up the
roaster cost probably 50%.
My FR roast fast.  To darn fast, but I will try putting an inductor in
series with the heater after the warranty is up.
Vic
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7) From: Victor Blackwell
The picture is not as bad as it sounds.  The heater manufacture wants happy
customers and will make a hard effort to hold the wattage as close as
possible.  The application here really need for the wattage's to be on the
nose.  Practically ever thing done to a heater makes for variations of the
internal resistance.  Which changes with temperature.  If the wattage's seem
to be drifting off the user will feed this info back to the heater
manufacture to make some adjustments.  Or at least they should.  There also
gets into calibration issues.  Large companies or even the small companies
who need a high degree of consistency.  i.e..  medical equipment with a
heater application, will usually have a metrology dept.  who will tend to
other calibrations.  Test gear etc.
Some times the user will sort heaters themselves.  Cheaper than hiring the
vendor to do it.  I am glad people working to these tolerances did not make
my kitchen cabinets.  :-)
Vic
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8) From: Jim Schulman
On 30 Jan 2003 at 20:59, Victor Blackwell wrote:
<Snip>
They do, but they should act as safeties only, 
since random heating and cooling during a roast 
isn't a recipe for brilliant roasts.
My original FR cycled on and off towards the end 
of the roast, my FR+ never does even before the 
variac.
One reason the HWP roasts so nicely out of the box 
is that instead of switching the heat off, the 
thermostat kicks the fan up to high.
Jim Schulman
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