HomeRoast Digest


Topic: Airflow mod could be dangerous! (8 msgs / 197 lines)
1) From: Auctions
This is a multi-part message in MIME format.
Anyone wanting to change the roast temperature by choking off the =
airflow to the heater is playing with fire...literally.
The heater coils are designed with a predetermined airflow so that the =
coil and coil insultion do not burn up or oxidize too rapidly.  The =
airflow is for roasting AND for keeping the heater coil from getting =
itself too hot.
If you go to the extreme and eliminate the airflow altogether by just =
energizing the coil out of the fan's airflow path, as a test, you will =
see that the insulating materials around the coil will rapidly burn up, =
especially if there is any oil from popcorn, butter, or coffee beans on =
the surfaces.
I tend to lurk on this list, but when I see something like this, I like =
to chip in with my two cents.
Have any of the tinkerers out there ever tried modifying the heater coil =
circuit with a triac?  I have an old Poppery I  that cranks out a =
whopping 1500W but tends to slam the roasts after the chamber gets hot.
Roasting in Texas,
Martin

2) From: Mike McGinness
From: "Auctions" 
<Snip>
to the heater is playing with fire...literally.
<Snip>
and coil insultion do not burn up or oxidize too rapidly.  The airflow is
for roasting AND for keeping the heater coil from getting itself too hot.
Most discussions and usage for 'limiting' airflow where during the winter
months to compensate for cold temperatures and roasters not getting hot
enough. Since the roaster wasn't hot enough to roast, limiting the airflow
to increase temperature 'to normal roasting temperature' isn't a danger,
IMNSHO. Limiting air flow also can be used to a limited extent, to
compensate for low voltage and again too low a roasting temperature.
Increasing voltage is much more effective in this case though.
Have any of the tinkerers out there ever tried modifying the heater
coil circuit with a triac?  I have an old Poppery I  that cranks out a
whopping 1500W but tends to slam the roasts after the chamber gets hot.
A number of us, myself included, use a variac to control our input
voltage... with great results. No need to modify the roaster circuitry
itself, just modify and control the voltage given to the existing circuitry.
I use this method to increase and decrease roasting temps and times.
MM;-)
Home Ju-Ju Variable Variac Rockin' Rosto Roasting in Vancouver, WA USA
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

3) From: Dan Bollinger
This is a multi-part message in MIME format.
Good point.  If you monitor the heater's temperature just where it =
enters the roasting chamber you can avoid a fire and make a better =
roast.  Sivetz says that air roast temperature should be 530.  At =
545-550 the outer skin of the bean will char producing horrible =
roasts.  By monitoring this temperature you can prevent a fire and a =
lost batch.  Dan

4) From: AlChemist John
Sometime around 15:17 9/9/02, Auctions typed:
<Snip>
I assume you have, but did you measure this 1500 W.  I checked my WBI and 
only found about 800 W.  Do these things vary that much?
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

5) From: EskWIRED
<Snip>
John - 
Was that 800W WRT the whole system?  Or just the heater coil(s)?
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

6) From: AlChemist John
Sometime around 07:44 9/10/02, EskWIRED typed:
<Snip>
Whole system.
BTW, what is WRT?
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

7) From: EskWIRED
<Snip>
With Respect To.
So is the 800 watts with the chamber empty, or is it with the fan struggling
to force the air through a big mass of beans?  And maybe a 600 watt, off the
shelf dimmer could be used to adjust the heater coils if the fan is wired in
parallel?
And as an aside, I installed a transformer/triac to slow down the fan in my
WEPP and raise the temperature, but I also preserved the thermal fuse in the
system.  The original one burned out, and my first inclination was to simply
bypass it.  But then, in an uncharacteristic moment, I instead got one rated
higher and replaced the stock one.
So while I could still, in a careless moment, get very high temps in the
system, the electricity will be cut off if things get too far out of hand.
One thing that I still want to do is to replace the pot in the dimmer switch
system with a different value, and/or bypass it with a resistor.  As things
are now, I can only turn the pot about 1/4 turn before the fan becomes too
slow to be of practical use, and if I turn the pot too far, the fan stops
completely.  Obviously, if I had the heater switched on with no fan, my
popper (or hopefully, my thermal fuse) would soon be toast.
I'd like a lower value pot, so even if it were turned all the way "down",
the fan would nevertheless spin enough to prevent thermal problems. As an
alternative, I'm thinking of putting a resistor in parallel with the pot, so
even with the pot turned down (at its highest resistance) there would still
be enough current flowing, no matter what, to spin the fan.
Anybody got info to get me started?  Which mod sounds better and/or easier?
Any guesses as to the value of the existing pot in a 600 watt Lutron dimmer?
Any guesses as to the value of the resistor I should try first?
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

8) From: AlChemist John
Sometime around 09:30 9/11/02, EskWIRED typed:
<Snip>
Empty chamber.  It was too difficult to get the non alligator clip ampmeter 
leads on the terminals when it was full and upright.  I now have some 
alligator clips and will be checking with a full load.    With that low of 
a heater load, I have a 10a dimmer that I was going to try wiring in.
<Snip>
Smart idea
<Snip>
I have been trying to think this through before this thread started and 
determined I wanted to try the heater dimmer first and not worry about the 
fan variability.
<Snip>
Sorry no information from me
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast


HomeRoast Digest