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Honeywell C7076D Product Data page 13

Adjustable sensitivity ultraviolet flame detectors
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Adjustments and Checkout
WARNING
Fire or Explosion Hazard.
Can cause serious injury, death or equipment
damage.
Consult the burner/boiler manufacturer instructions
and sequence of operation for the burner
management system before initial burner lightoff.
Flame Signal Readings
The final sighting position of the C7076A or C7076D Detector
may be most readily determined by using a Honeywell W136
Test Meter connected to the Flame Current meter jack on the
plug-in electronics chassis. This output is the unprocessed
flame signal from the detector and is intended as a diagnostic
aid. Readings taken at the detector will facilitate installing the
detector in the best sighting position by pinpointing the region
of greatest UV intensity for a given flame.
Fig. 16 illustrates the relationship between the detector and
amplifier readings. Detector saturation (the point at which an
increase in UV intensity does not product a noticeable
increase in flame signal strength) occurs at point A. Point B
represents the point at which the amplifier is saturated while
the minimum UV sensitivity required for system operation is at
point C.
6
5
4
3
2
1
C
6
ULTRAVIOLET INTENSITY
Fig. 16. Comparison of UV intensity, amplifier saturation
and detector saturation.
The linearity of the detector output curve shows that a unit
increase in UV intensity is accompanied by a corresponding
increase in flame signal strength. This condition facilitates
pinpointing the location of the most intense UV radiating from
a flame. Thus, by locating the optimum flame signal with the
detector, the peak UV signal, and therefore the most reliable
reading, is obtained.
The minimum acceptable stable flame signal readings are:
a. C7076A and C7076D Flame Detectors: 1.4
microamperes.
b. R7476A Flame Signal Amplifier: 2.5 microamperes.
c. R7886 Flame Signal Amplifier: 1.2 Vdc.
C7076A,D ADJUSTABLE SENSITIVITY ULTRAVIOLET FLAME DETECTORS
AMPLIFIER
DETECTOR
SATURATION
SATURATION
B
A
M20761
Sensitivity Adjustments
General Considerations
1. If a single detector is required to supervise both the pilot
and main burner flame, verify the flame signal for each
flame individually.
2. Make sure the minimum acceptable stable flame signal
(1.4 microamperes at the detector, or 2.5 microamperes
at the R7476 Amplifier, or 1.2 Vdc at the R7886 Ampli-
fier) is obtained throughout the entire turndown range of
the burner.
3. Parallel detectors may be required if a single sighting
angle will not provide a proper flame signal for both the
pilot and main burner flames throughout the entire
turndown range of the burner.
Single Burner System Using the C7076A Detector
1. Loosen the four captive screws in the rear cover plate of
the C7076A and remove the plate.
2. Adjust Sensitivity Control A for maximum sensitivity.
a. If the remote sensitivity selection feature is used,
make sure the external selector switch is open for
Control A adjustment.
b. Loosen the setpoint locking nut on Sensitivity
Control A.
c. Turn the control clockwise to MAX position.
d. Tighten the setpoint locking nut 1/4 turn past hand
tight. Do not over-tighten.
3. Read the flame signal in microamperes at the Flame
Current jack.
a. Use a Honeywell W136A test meter with the
selector switch at the SPL position. (If a W136 is not
available, a microammeter with a 0 to 25
microampere dc range, shunted with a 50
microFarad capacitor, may be used.)
b. A 117053 Meter Connector Plug is needed (supplied
with the W136A, or it may be ordered separately).
Connect the red spade tip to the red (+) meter lead
and the black spade tip to the black (-) meter lead.
See Fig. 17.
c. Insert the plug into the Flame Current meter jack
and allow a few seconds for the meter reading to
stabilize.
d. Read the average stable current, disregarding the
peaks due to shutter operation.
4. Optimize the flame signal.
a. Observe the flame signal while varying the line of
sight of the detector.
(1) Swivel the detector if it is mounted on a
Honeywell 118367A Swivel Mount, or
(2) Adjust the angle and/or position the sight pipe
(which was only tack welded as previously
instructed).
b. Try several sighting angles until you obtain the
highest and most stable meter reading possible. (If it
is less than 1.4 microamperes, refer to the
Troubleshooting section.)
c. Repeat step b for both the pilot and the main burner
flame. Do not sacrifice the main flame signal to
obtain an unnecessarily high pilot flame signal.
5. Repeat steps 2 and 3 for Sensitivity Control B, if used.
Make sure the external selector switch is closed while
adjusting Control B.
13
95-8269—1

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