Ignition interference test (all flame rods) – 2nd Ave. Honeywell Relay Modules 7800 Series User Manual

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12. Close the master switch to recycle the burner and stop

the sequence in the PILOT period by using the Run/
Test Switch.

13. Increase the pilot flame size by increasing its fuel flow

until a smooth main flame is accomplished.

14. Reposition the flame scanner sight tube or use orifices

until the pilot flame signal voltage is in the range of 1.25
to 1.50 Vdc.

15. When the main burner lights reliably with the pilot at

turndown, disconnect the manometer (or pressure
gauge) and turn up the pilot gas flow to that
recommended by the equipment manufacturer.

16. If used, remove the bypass jumpers from the subbase

terminals, limits/controls, or switches.

17. Run the system through another cycle to check for

normal operation.

18. Return the system to normal operation.


Ignition interference can subtract from (decrease) or add to
(increase) the flame signal. If it decreases the flame signal
enough, it causes a safety shutdown. If it increases the flame
signal, it could cause the FLAME LED to come on when the
true flame signal is below the minimum acceptable value.

Start the burner and measure the flame signal with both
ignition and pilot (or main burner) on, and then with only the
pilot (or main burner) on. Any significant difference (greater
than .5 Vdc) indicates ignition interference.

To Eliminate Ignition Interference

1. Make sure there is enough ground area.
2. Be sure the ignition electrode and the flame rod are on

opposite sides of the ground area.

3. Check for correct spacing on the ignition electrode:


6000V systems—1/16 to 3/32 in. (1.6 to 2.4 mm).


10,000V systems—1/8 in. (3.2 mm).

4. Make sure the leadwires from the flame rod and ignition

electrode are not too close together.

5. Replace any deteriorated leadwires.
6. If the problem cannot be eliminated, consider changing

the system to an ultraviolet flame detection system.

Hot Refractory Saturation Test
(All Infrared Detectors)

Start the burner and monitor the flame signal during the
warmup period. A decrease in signal strength as the
refractory heats up indicates hot refractory saturation. If
saturation is extreme, the flame signal drops below 1.25 Vdc
and the system shuts down as though a flame failure

If hot refractory saturation occurs, the condition must be
corrected. Add an orifice plate in front of the cell to restrict the
viewing area, lengthen the sight pipe or decrease the pipe
size (diameter). Continue adjustments until hot refractory
saturation is eliminated.

Hot Refractory Hold-in Test
(Rectifying Photocell, Infrared Detectors,
Ultraviolet Detectors)

This condition can delay response to flame failure and also
can prevent a system restart if hot refractory is detected.

Infrared (lead sulfide) detectors can respond to infrared rays
emitted by a hot refractory, even when the refractory has
visibly ceased to glow. Infrared radiation from a hot refractory
is steady, but radiation from a flame has a flickering
characteristic. The infrared detection system responds only to
flickering infrared radiation; it can reject a steady signal from
hot refractory. The refractory steady signal can be made to
fluctuate if it is reflected, bent or blocked by smoke or fuel
mist within the combustion chamber. Be careful when
applying an infrared system to verify its response to flame

The ultraviolet detector can respond to hot refractory above


F (1371



1. Operate the burner until the refractory reaches its

maximum temperature (Infrared Only).
If the installation has a multi-fuel burner, burn the
heavier fuel that is most likely to reflect, bend or
obscure the hot refractory steady infrared radiation

2. When the maximum refractory temperature is reached,

close all manual fuel shutoff valves, or open the
electrical circuits of all automatic fuel valves.

3. Visually observe when the burner flame or FLAME LED

goes out. If this takes more than three seconds, the
infrared detector is sensing hot refractory.

4. Immediately terminate the firing cycle. Lower the

setpoint to the operating controller, or set the Fuel
Selector Switch to OFF.

Do not open the master switch.


Some burners continue to purge oil lines
between the valves and nozzles even though
the fuel valves are closed. Terminating the
firing cycle (instead of opening the master
switch) allows purging the combustion
chamber. This reduces a buildup of fuel vapors
in the combustion chamber caused by oil line

5. If the detector is sensing hot refractory, correct the

condition by one or more of the following procedures:


Add an orifice plate in front of the cell to restrict
the viewing area of the detector.


Resight the detector at a cooler, more distant part
of the combustion chamber. Make sure the
detector properly sights the flame.


Try lengthening the sight pipe or decreasing the
pipe size (diameter).

For details, refer to the detector Instructions and the
equipment Operating Manual. Continue adjustments until hot
refractory hold-in is eliminated.