king 8500 ?s

Is this a US Stove? Couldn't find the manual on-line. It is possible that variation in fans is not available when on auto...

https://www.usstove.com/index.php?route=product/download/download&download_id=63 (manual_part 1)

https://www.usstove.com/index.php?route=product/download/download&download_id=64 (manual_part2)

I could not locate anything when I glanced at the manual, sorry.

Page 12 - fans will automatically adjust to heat setting. In auto, should be able to adjust draft fan but doesn't mention if you can override automatic adjustment in relationship room fan and heat setting.

Are you burning pellets or corn?

Changing the settings is highly frownded on by the 'powers that be' that being said . . .
To adjust the feed rate;
press AUX down and Heat range down to change the low limit
press AUX up and Heat range up to do the high limit

draft fan;
same as above but replace 'Heat range' with draft

press the on button after changing settings.

Copied from 'iburncorn.com'
C- 1 - Reset to defaults (hold Mode and Auger Delay buttons for 3 seconds to
reset all to defaults)
C- 2 - Fuel Lbs Per Hour HR 1 (0-20.00) - This is the fuel rate in pounds per hour
for a heat range setting of 1. The default is 5.00lbs.
C- 3 - Fuel Lbs Per Hour HR 9 (0-20.00) - This is the fuel rate in pounds per hour
for a heat range setting of 9. The default is 13.lbs. The fuel rates used between
settings 1 and 9 are linearly interpolated between these two settings.
C- 4 - Agitator On Percentage HR 1 (0-100) - This is the Percent On time for the
Agitator for a setting of 1. The default is 25%.
C- 5 - Agitator On Percentage HR 9 (0-100) - This is the Percent On time for the
Agitator for a setting of 9. The default is 50%. The percent on time for the
Agitator used between settings 1 and 9 are linearly interpolated between these two
settings.
C- 6 - Draft Fan Level HR 1 (0-500) - This is the Draft fan output level for a draft
fan setting of 1. The default is 150/500.
C- 7 - Draft Fan Level HR 9 (0-500) - This is the Draft fan output level for a draft
fan setting of 9. The default is 400/500.
C- 8 – Fuel Rate Type Compensation (50%-200%) – This parameter affects how
much the auger runs to produce a given fuel rate. The default fuel rates are based
on corn. This is the default setting for this parameter, or 100%. If the parameter
is adjusted up, the auger rate is increased proportionally. If the fuel being used is
less dense than corn (wood pellets for instance), it may be necessary to raise this
parameter to compensate. This makes the programmed lbs per hour correspond to
the particular fuel type. Typically, wood pellets need to be run at 120% to
compensate for their lower density and slower travel through the auger system.
C- 9 - Ramp Seconds for Increasing Level (0-300) - When the heat range setting
is adjusted, the control will ramp from the current setting to the target setting to
avoid abrupt changes in the outputs that could cause problems with the flame
quality. The Ramp Seconds value sets the amount of time to spend on each heat
range setting (1-9 pseudo ranges not 1-5 user ranges) as the current setting is
ramping toward the target. If the current setting is ramping down toward a lower
target, the ramp value is half this number. The default value is 120 seconds.
C-10 - Startup Minutes for Detecting Warm Furnace - (10-60) This is the amount
of time the control will wait for the furnace to reach the warm temperature (110
Degrees F) after the furnace has been started before shutting down and reporting
an Error condition Err3. The default is 30 minutes.
C-11 – Overtemp Setpoint - (0-700) This is the measured flue gas temperature
that will cause an overtemp condition. In this condition, the control will stop
augering fuel until the temperature returns to a safe operating point. The default
is 575 degrees F.
C-12 – Cutback Setpoint - (0-700) This is the measured flue gas temperature that
will cause a cutback condition. In this condition, the control will ramp the heat
range down based on the ramp seconds described above divided by 2 until the
temperature falls below the cutback setpoint. The default is 550 degrees F.
C-13 – Room Fan On Setpoint - (0-700) This is the temperature that the measured
flue gas can reach before a the flue controlled foom fan turns on. If the measured
temperature is higher than this setpoint, the control will turn on the flue controlled
room fan. This variable also serves to indicate to the control that the stove is
warm. If the measured temperature is higher than this setpoint, the stove is
considered warm and will not create an Er 3. Whether or not the stove is warm
also determines if the unit will recover from a power failure. If the stove is warm
when power is lost and cold when it returns, it will shutdown with an Er 4 error.
The default is 200 degrees F.
C-14 – Cold Stove Setpoint - (0-700) This variable is used to determine when the
furnace is cold and ready to be shut down. If during the shutdown sequence the
measured temperature is less than this value, the furnace will stop running the
fans to cool it off. The default is 120 degrees.
C-15 – Low Temp Vent Heatrange – (0-9) This variable is used to control the
vent controlled room fan. If the pseudo heat range (1-9) is greater than this
number, the vent controlled room fan will turn on. If the pseudo heat range is less
than this number, the vent controlled room fan will turn off. The default for this
parameter is 3.
C-16 – High Temp Vent Setpoint – (70-400) This variable is used to limit the
maximum vent temperature. If the measured vent temperature is greater than the
High Temp Vent Setpoint, the furnace will reduce the heat range by 1. If the vent
temperature falls below the setpoint – 5, the heat range will ramp back to normal.
The default for this setpoint is 225 degrees.
C-17 – Auger Period in Seconds – (5-20) This is the fixed auger period. The ontime
is calculated based on the setpoint fuel rate in lbs and the full on rate set in
C-18. The default is 10.00 Seconds.
C-18 – Full On Fuel Rate in Lbs/Hour – (7-40) This is the fuel rate that would be
delivered if the auger was turned 100% of the time. This definition is for corn
only (see proportional offset parameter CCool. The default value for this parameter
is 36 lbs of corn per hour.
C-19 – Ignore Sense Errors (0-1) When this parameter is set to 1, the sensor errors
including Interlock, and all fuse detection errors are disabled. The default is 0
(sense errors enabled).
C-20 – Ignore Vacuum Switch (0-1) When this parameter is set to 1, the vacuum
switch is ignored. The default is 0 (do not ignore the vacuum switch).
C-21 – Bump Rate in Lbs (0-0.5) When the furnace is in shutdown, this parameter
can be used to force a small amount of fuel to be pushed through the auger to
keep the fuel in the auger from getting hot. The default is 0lbs per hour.
C-22 – Purge Seconds (0-120) After shutdown, the auger can be run for a fixed
amount of time to dump any fuel that may have become hot in the auger. By
default, the auger will run in this purge mode for 30 seconds after shutting down.

The 2nd fan won't kick on until the heat range is higher then 3 (4 or more).