11
Interval Timer Operations
Interval timer is what keeps your pot fire lit while the thermostat is not calling for heat. You may need
a higher setting during spring and fall than you will in colder temperatures.
Set interval timer so that it runs about 2 minutes every hour. Ideally 40 seconds on time for every 20
minutes off time. This is just a suggested starting point. You will need to adjust to your setup. Chimney
draft and coal quality play a role in the required run time of your stoker. If your run time is too high your
distribution blower may turn on and distribute heat when thermostat does not have a call for heat. When
interval timer setting is to low, you will experience an outfire. When this happens you need to increase
the on time and decrease your off time.
The following list is on and off time for each Interval Timer Setting.
1. 20 Seconds On – 30 minutes off.
2. 30 Seconds On – 30 minutes off.
3. 20 Seconds On – 20 minutes off.
4. 30 Seconds On – 15 minutes off.
5. 30 Seconds On – 20 minutes off.
6. 40 Seconds On – 20 minutes off.
7. 40 Seconds On – 15 minutes off.
8. 50 Seconds On – 15 minutes off.
Winter Month Operation
During the heating season, the feed rate will need to be adjusted to provide sufficient heat for load
conditions. See chart 2 on page 10 for output settings. Interval timer settings should be about 30
seconds every 30 minutes for your peak heating season.
Out-Fire Situation
1. Is power indicator light ON? If light is ON this indicates that the furnace still has power and is
trying to function. If light is OFF this indicates that furnace has shut down due to pot out-fire
situation.
2. Check shear pin. If sheared, replace shear pin (part #SF250-SPIN) see page 4 Chart 1.
3. A stoker fired furnace must run periodically to maintain a pot fire even though there is no call for
heat by the thermostat. This is accomplished by the interval timer. A normal run time in the peak
heating season is approximately 30 seconds every half hour. This is a suggested start and times
may have to be adjusted to meet conditions and time of year. Due to the wide range in the quality
of coal, a timer setting of 2 minutes per hour may produce an acceptable burn. Its an
experimental process of timer run times, air and feed settings, with the two main objectives being
a proper ash ring (2 inches) and a fire that does not burn deeply into the pot. You may need a
spring / fall setting and a winter setting. It is recommended to record your settings for future
references.
4. An outfire in the stoker is a more prevalent condition during the spring / fall months. It can happen
even though you find nothing wrong with the stoker mechanically.
Snap Disc Function
1. The snap disc is located on the outside bottom of the main pot ring towards the front, behind the
front ash slide inside the ash door.
2. The snap disc will sense the temperature at the pot. If the temperature at the pot drops below 90
degrees Fahrenheit the snap disc will shut off. This will shut power off to the unit. You can push
the 60 minute timer button to override this snap disc for 60 minutes. This should provide enough
time to relight furnace and get the pot temperature above 120 degrees where the snap disc will
reconnect and the furnace should function. If it does not function see Out-Fire situation.
Note on Limit Switch settings:
The L4064B2236 limit switch has three settings
1. The High Limit Setting: This shuts the stoker off when the limit switch reaches the temperature
setting. It overrides all other controls. (Distribution blower will keep running, Stoker will shut down)
Factory setting is 215 degrees Fahrenheit.
ALL FURNACES MUST BE INSTALLED BY A NFI CERTIFIED SPECIALIST AND PLUMBED BY A
QUALIFIED LICENSED PLUMBER OR D.S. IS NOT RESPONSIBLE FOR WARRANTY
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