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Flame
Signal
Flame Safeguard
Amplifier
R7247A
BC7000L; R4140G,L,M; R4138C,D;
R4075C,D,E
a
R7247B
BC7000L; R4140G,L,M; R4138C,D;
AMPLI-
R4075C,D,E
CHECK™
R7257A
R4150
R7289A
R4795
R7847A
RM7800E,G,L,M; RM7838A,B;
RM7840E,G,L,M; RM7885A;
RM7890A,B; RM7895A,B,C,D
R7847B
RM7800E,G,L,M; RM7838A,B;
AMPLI-
RM7840E,G,L,M; RM7885A;
CHECK™
RM7890A,B; RM7895A,B,C,D
None
RA890F, R7795B,D,F,H; R7023B,
R485
b
None
R4181
a
Set W136A selector switch to SPL (damped) position to read current.
b
Press test button while reading current.
Measure the flame signal for the pilot alone, the main burner
flame alone, and both together (unless monitoring only the
pilot flame when using an intermittent pilot, or only the main
burner flame when using direct spark ignition). Also measure
the flame signal at high and low firing rates and while
modulating in between (as applicable). With the detector in its
final position, all required flame signals must be steady (or
stable) and as specified in Table 1.
If the signal is unstable or less than the minimum acceptable
current, check the flame rod installation and circuitry:
• Check the supply voltage at terminals L1-L2 on the wiring
subbase or terminal strip for the flame safeguard control.
• Check the wiring for defects including:
— wrong type or size of wire.
— deteriorated wire.
— open circuits.
— short circuits.
— leakage paths caused by moisture, soot, or
accumulated dirt.
• Make sure:
— there is enough ground area.
— the flame rod is properly located in the flame.
— temperature at the flame rod insulator is no greater
than 500°F (260°C).
— ignition interference is not present (see Ignition
Interference Test below).
• Make sure that the flame adjustment is not too lean.
• If necessary, reposition the flame rod.
If you cannot obtain proper operation, replace the plug-in
amplifier if applicable. If you still cannot obtain proper
operation, replace the flame rod.
Table 1. Flame Signal For C7005A,B.
Minimum
Acceptable
Steady Current
Control
C7005A,B GAS PILOT AND FLAME ROD ASSEMBLIES
Maximum
Expected
Current
(uA)
(uA)
2.0
5.0
1.25
2.50
2.0
5.0
2.0
5.0
2.0
5.0
8.0
15.0
Pilot Turndown Test
If the flame rod is used to prove a pilot flame before the main
fuel valve can be opened, perform a Pilot Turndown Test.
Follow the Instruction procedures for the appropriate flame
safeguard control, and the burner manufacturer's instructions.
Ignition Interference Test
C7005B
Test to make certain that a false signal from the spark ignition
system is not superimposed on the flame signal.
Ignition interference can subtract from (decrease) or add to
(increase) the flame signal. If it decreases the flame signal
enough, it causes safety shutdown. (The flame relay will not
pull in and the flame safeguard control will act as though the
pilot or main burner, if using direct spark ignition, has not
been ignited.) If it increases the flame signal, it could cause
the flame relay to pull in when the true flame signal is below
the minimum acceptable value.
Test
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
0.5 microamp, or 0.25 Vdc with 7800 SERIES controls,
indicates ignition interference.
To Eliminate Ignition Interference
Make sure there is enough ground area.
Be sure the ignition electrode and the flame rod are on
opposite sides of the ground area (Fig. 1).
7
Minimum
Maximum
Acceptable
Expected
Steady voltage
Steady voltage
(Vdc)
(Vdc)
1.25
5.0
1.25
5.0
60-2033—3
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