T-D2-IN / T-D2-OS Service Manual
Ver. 1.00
52
CONFIDENTIAL
12-4. AFR rod function
<Function>
The AFR rod checks flame conditions during combustion. When the AFR rod detects unexpected flame
conditions, the computer board of the T-D2 adjusts the fan motor speed to ensure that air and fuel are
always at a proper mixture ratio, minimizing emissions.
<AFR normal range of values>
Model
T-D2-IN
T-D2-OS
Gas type
LPG
Natural gas
LPG
Natural gas
Combustion
mode
MAX
8.8 to 32.5
12.5 to 35.0
2.5 to 50.0
9.0 to 38.0
MIN
1.5 to 13.2
2.0 to 11.5
3.5 to 18.5
2.0 to 10.5
・
If the detected AFR value is higher than the normal value, the FM speed is increased.
・
If the AFR value is lower than the normal value, the FM speed is decreased.
・
These values are read with the front cover close.
・
Measure the values after burning the water heater for ten minutes.
*The AFR stage can be confirmed in “Diagnostic Mode”. (Section 12-1)
<The relationship between the AFR stage and the “10” and “99” error codes>
16
15
6
0
(Unit:
μ
A)
(Condition of AFR stage)
・
0 to 5: Air-rich
・
In order to solve the “air excess” problem, the fan motor
speed is automatically decreased and AFR combustion
stage goes down.
・
6: Default
・
7 to 16: Gas-rich or Air shortage
・
In order to solve the “air deficiency” problem, the fan
motor speed is automatically increased and AFR
combustion stage goes up.
・
15: “101” error code
・
16: “991” error code
・
When the “101” or “991” error code appears, see section
12-3.
+15%
FM
0%
-9%
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+13.5%
“101” error code
“991” error code
Default condition
Stage
・
・
・
・
・
・
・
・
・
・
・
・
・
・
/
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