Download Flame Rectification

Technical Conference - Panama City Beach, Fl - 2002
Flame Rectification

Remember Ohm’s Law
E=IXR
Technical Conference - Panama City Beach, Fl - 2002
Alternating Current Sine Wave
+
+
+
Applied AC voltage
-
-
Technical Conference - Panama City Beach, Fl - 2002
Basic Electrical Circuit
SOURCE
CONTROL
CONDUCTOR
+
LOAD
Technical Conference - Panama City Beach, Fl - 2002
Flame Rectification circuit!
What devices are used for electrodes?
Flame rod
Burner
Technical Conference - Panama City Beach, Fl - 2002
Flame Rectification Circuit
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The Voltage Source is the Ignition Control
The “load” is the flame sensing circuit inside
the control
The conductors are the electrodes already
identified.
What acts as the “switch”?
The flame completes the circuit.
Technical Conference - Panama City Beach, Fl - 2002
Flame Sense Circuit
One electrode is larger than the other
causing electron flow to be greater in
one direction than in the other.
Compare the burner size to the flame
rod size.
Technical Conference - Panama City Beach, Fl - 2002
+
F
G
_
Current flow when flame rod
is positive
5a
+
0
-
Technical Conference - Panama City Beach, Fl - 2002
_
F
G
+
+
0
-
1a
Current flow when flame rod
is negative
Technical Conference - Panama City Beach, Fl - 2002
Effective Flame Signal
+
+ a
Effect = 4a pulsating DC
Applied AC voltage
-
a
-
Technical Conference - Panama City Beach, Fl - 2002
Flame Rectification Circuit
Remember Ohm’s Law ?
What happens in a circuit if
resistance increases and voltage
stays the same?
Technical Conference - Panama City Beach, Fl - 2002
Typical Flame Detection Current
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Need to measure AC A as well as DC A
Typical in-shot burner DC current is 2-5 A
with a 4-8 A AC leakage.
DC current is less than 1 A and AC current
is at or above 4A
1. Flame signal is weak
2. Corrective action is required
Technical Conference - Panama City Beach, Fl - 2002
DC Current vs. AC Current
DC CURRENT
30
25
20
15
10
5
0
AC CURRENT
AC DROPOUT
Technical Conference - Panama City Beach, Fl - 2002
DC Current vs. AC Current
DC CURRENT
0.5
1.0
1.5
2.0
2.5
3.0
3.5
AC CURRENT
3.94
4.37
4.88
5.45
6.20
6.95
8.29
AC DROPOUT
10.39
17.28
20.1
20.30
24.37
24.20
24.22
Technical Conference - Panama City Beach, Fl - 2002
Flame Rectification Circuit
Remember Ohm’s Law ?
What happens in a circuit if resistance increases
and voltage stays the same?
What can affect the resistance in the circuit?
What else can affect the flame signal?
Technical Conference - Panama City Beach, Fl - 2002
Increased circuit resistances
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Burner oxidation
Non-secure burner
Flame “lift off”
Loose wire connections
Contaminated flame sensor
Faulty grounds
No grounds
Reverse polarity