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2 - Each lead-to-lead resistance should be the same.
If the measured resistance is greater than 20 ohms, replace
the motor and control module.
Test B
FIGURE 13
C-Heating Components
Heating component locations are shown in figure 14. Make
note the cover plate for the -090XV60C model only. The
cover plate is removed for LP/Propane conversion only.
1. Ignitor
The SureLight
®
ignitor is made of durable silicon nitride. Ig
nitor longevity is enhanced by controlling voltage to the igni
tor. The integrated control provides 120 volts to the ignitor
for a consistent ignition. Due to this feature of the control,
voltage measured with a digital meter will be slightly lower.
To measure correct voltage use a true RMS meter or ignitor
can be ohmed. Ohm value should be 39 to 70.
2. Flame Sensor
A flame sensor (figure 14) is located on the left side of the
burner support. The sensor is mounted on the flame rollout
plate and the tip protrudes into the flame envelope of the
left-most burner. The sensor can be removed for service
without removing any part of the burners. During operation,
flame is sensed by current passed through the flame and
sensing electrode. The SureLight control allows the gas
valve to remain open as long as flame signal is sensed. To
check flame sense signal use the push-button found on the
integrated control and go to Field Test Mode. The menu will
display the flame signal. Table 18 shows the flame signal for
the SLP99UHV unit.
TABLE 18
Flame Signal in Microamps
Normal
Low Drop Out
2.6 or greater 2.5 or less 1.1
NOTE - A much higher than normal micro amp reading (15
for example) may appear when checking flame signal.
3. Flame Rollout Switches
Flame rollout switch S47 is a high temperature limit located
inside the burner box. Each furnace is equipped with two
identical switches. The limit is a N.C. SPST manual‐reset
limit connected in series with the primary limit S10. When
S47 senses rollout, the circuit breaks and the integrated
control immediately stops ignition and closes the gas valve.
If unit is running and flame rollout is detected, the gas valve
will close and integrated control will be disabled. Rollout
can be caused by a blocked heat exchanger, flue or lack of
combustion air. The switch is factory set to trip (open) at
210°F and cannot be adjusted. The switch can be manually
reset. To manually reset a tripped switch, push the reset but
ton located on the center of the switch.
4. Burners
All units use inshot burners. Burners are factory set and re
quire no adjustment. Always operate the unit with the burner
box front panel in place. Each burner uses an orifice that is
precisely matched to the burner input. Burners can be re
moved as a one piece assembly for service. If burner assem
bly has been removed, it is critical to align center of each burn
er to the center of the clamshell when re-installing. See more
detail in Section VII- MAINTENANCE..
5. Duralock Plust Heat Exchanger (Figure 15)
SLP99UHV units use an aluminized steel primary and
stainless steel secondary heat exchanger assembly.
Heat is transferred to the air stream from all surfaces of
the heat exchanger. The shape of the heat exchanger en
sures maximum efficiency.
The combustion air inducer pulls fresh air through the burn
er box. This air is mixed with gas in the burners. The gas / air
mixture is then burned at the entrance of each clamshell.
Combustion gases are then pulled through the primary and
secondary heat exchangers and exhausted out the exhaust
vent pipe.
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