Siemens LMV5 Quick Start Manual page 132

Oxygen Monitor / Trim / Efficiency Calculation
The LMV52 has the capability of integrated O2 trim and / or O2 monitoring. The O2 trim system
includes the PLL52 module and the QGO20 O2 sensor as well as optional stack / ambient
temperature sensors that can be used for an efficiency calculation. Common problems and the
related solutions include:
O2 sensor is not reading
Displayed as "XXXX" on the AZL screen, or is reading incorrectly check the following:
1) Ensure that the QGO20 O2 sensor is activated.
This can be done under:
Params & Display > O2 Module > Configuration > O2 sensor.
2) If the QGO20 is activated, check the temperature of the QGO20 sensor.
The sensor will not sense % O2 if the sensor is below 1202
The PLL52 module controls the QGO20 sensor's heater to achieve a sensor temperature of
approximately 1292
The temperature can be checked under:
Params & Display > O2 Module > Displayed Values > QGO SensorTemp.
The sensor heating load can also be viewed under the Displayed Values menu.
QGO Maximum heating load is 60%. If the heating load is at 60% and the QGO20 is not at
least above 1202
sensor. Maximum stack velocity is 33 ft / second.
(See Section 2 for mounting restrictions on the QGO20 Sensor)
Note: The QGO20 sensor can take up to two hours to achieve operating temperature on
the first start-up.
Anytime the LMV5 system / PLL52 has power and parameter O2 sensor is set to
activated, the PLL52 will try to maintain the QGO20 at approximately 1292
O2 sensor reading grossly high or low
Check the following:
1) The milli-volt signal from the QGO20 to the PLL52 could have interference.
Ensure that the high and low voltages wires that run from the PLL52 to the QGO20 are in
separate conduits.
2) The wires for the QGO20 heating element are high voltage (120 VAC),
and the wires for the O2 signal and thermocouples are very low voltage (200 mV max).
Interference is almost sure to result if the high and low voltages are run in the same conduit.
Note: The QGO20 sensor reads %O2 wet.
Most combustion analyzers read %O2 dry, so the O2 number that appears on the
AZL5 is typically at least 1% O2 lower than the combustion analyzer.
See table in Section 6 for approximate values.
LMV5 QSG Rev 4
o
F.
o
F after initial heat up, stack velocity may be too high, thus cooling the
Sec 5 Pg 6
o o
F (650 C).
www.scccombustion.com
o
F.