11
2) When using Capacitance function, discharge capacitor(s) before
making any measurements. Large value capacitors should be
discharged through an appropriate resistance load
DC
A Current function
Inputs are made through the test lead terminals
COM
/
+
.
Application notes:
The
DC
A
function is designed especially for HVAC/R flame sensor
applications. The 0.1
A resolution is useful for identifying the minute
current changes in flame detector applications. Flame signal current
check should indicate steady flame signal of at least 2
A for a
rectification type, or 1.5
A for an ultraviolet type (8
A for self checking
systems). If a flame signal current with inadequate strength or
fluctuation beyond 10%, check the following to avoid the risk of
unwanted flame relay dropout :
For gas or oil flames (Minipeeper):
•
Low supply voltage
•
Detector location
•
Defective detector wiring
•
Dirty viewing windows
•
Faulty Minipeeper
For oil flames (Photocell):
•
Detector location & wiring
•
Smoky flame or poorly adjusted air shutter
•
Faulty Photocell
•
Temperature over 165
o
F (74
o
C) at photocell
For gas flames (Flame Rod):
•
Ignition interference (A flame signal current difference with the
ignition both on and off greater than 0.5
A indicates the presence
of ignition interference)
•
Insufficient ground (must be at least 4 times the detector area)
•
Flame lifting off burner head (ground), or not continuously in
contact with the flame rod
•
Temperature in excess of 600
o
F (316
o
C) at the flame electrode
insulator causing short to ground.
