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.
Table 9.
Signal Strength
Good
Marginal
Inadequate
Pre-Purge and Main Flame Ignition (20:1 Turndown, 1250-2400 MBh)
With the manual gas cocks closed move the manual disconnect switch in the heater vestibule to
the ON position. The system should energize, and the combustion blower motor should start,
indicating that all of the safety/limit contacts are closed:
•
•
•
•
The combustion airflow switch (CAFS1) should close, starting the purge timer, the green power
light should illuminate on the flame-relay panel, and the prepurge cycle should begin. The
combustion air blower should run for approximately 90 seconds to evacuate the heat exchanger
of any combustible gases before the ignition sequence. This prepurge cycle is initiated before every
startup.
At the end of the purge cycle, the ignition transformer and automatic gas valves will energize. With
the manual gas cocks closed, the burner should go into a safety lockout condition. The flame
safeguard will have to be reset manually. Turn the manual disconnect switch in the control panel
to the OFF position.
Note: Prior to opening the manual gas cock make certain the modulating gas linkage is set to
1. Turn the manual disconnect switch in the control panel to the ON position. After the prepurge
2. At initial start up, air may be trapped in the gas lines so more than one attempt to light off may
3. Once flame is established run the mod motor to position the modulating gas valve wide open.
4. The amber Main Flame light should illuminate on the flame relay panel after the ultra-violet
5. Check the flame-signal strength from the flame rod. A 0 to 15 Vdc, 1 megohm/volt (minimum)
6. Insert the positive probe of the voltmeter into the positive (+) flame-signal test point on the
7. Connect the negative probe to the negative (-) test point on the flame relay cover. Flame signal
8. Allow the burner to ramp up to full fire.
CLCH-SVX08A-EN
Signal strengths
HLI1: high-temperature limit
AI1: airflow interlock
HPGS1: high-pressure gas switch
LPGS1: low-pressure gas switch
operate in all positions without binding.
sequence is complete the ignition transformer will energize providing ignition spark and the
main automatic gas valves will open. With the ignition spark energized and the automatic gas valve
open, slowly open the manual gas shut off cocks. Flame should be established. (Make sure the
modulating gas valve is adequately open).
be required. Do not allow unburned gas to accumulate in the combustion chamber.
flame sensor has detected the main flame. The flame can be observed through the larger sight
glass under the burner. Normal flame color is blue; abnormal color is yellow, indicating a need
for adjustments by a qualified technician. Note that smaller sized heaters have the sight glass
on the side opposite the piping connection side.
meter is required.
flame relay cover.
strength should be a steady dc voltage between 1.25 and 5.0 volts.
Ultra-Violet Sensor
5.0–11.0 Vdc
1.7–5.0 Vdc
0.0–1.7 Vdc
Operation
29
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