Siemens LMV5 Series Basic Documentation page 264

264/278
Siemens Building Technologies
HVAC Products
18.11 Commissioning the O
18.11.1 Setting ratio control
First, adjust the ratio curves as with the LMV51... system. The excess O2 rate
must be selected high enough, ensuring that, irrespective of ambient conditions
(combustion chamber and fuel pressure, temperature and pressure of the combustion
air), the O2 level will not fall below the O2 setpoint of O2 trim control.
Parameterize the loads at the curvepoints proportional to the effective fuel rate (amount
of fuel). For that purpose, ascertain the load with the help of the fuel counter.
The curvepoint identifies the smallest load where O2 trim control is still possible. In
normal situations, this is the low-fire position. Point 1 defines the curve for reducing the
air rate below point 2. If, in the low-fire position, no further air reduction is possible (e.g.
because the air damper has already fully closed), curvepoint 1 must be selected as the
low-fire point. In that case, O2 trim control will only be performed up to curvepoint 2.
The O ratio value between the curvepoints should be linear. When O
2
activated, precontrol will transfer any nonlinearity to the actual O
adjusting the load, the actual O
linearity of the O progression by approaching the loads between the curvepoints. If the
2
O ratio value has such nonlinearities, they can be corrected by setting intermediate
2
curvepoints.
The more thoroughly the ratio curve is set, the easier the subsequent adjustment of O2
trim control, and the more accurate O2 trim control will be.
If the ratio curves are changed later, the O2 trim controller must also be
readjusted.
18.11.2 Setting the O
Next, the O monitor must be adjusted. When making the adjustment for the first time,
2
the O monitor should remain deactivated to avoid undesired responses. When
2
changing settings later, it can stay activated.
Set the O2 min. value as low as possible to ensure a high level of availability. The O2
min. value marks the boundary between the permanently non-harzardous range and
the potentially hazardous range.
Above or at the O min. value, hazardous conditions must not permanently
2
occur.
Guide values: CO = 2,000 ppm, soot number 3.
The values can vary, depending on the type of plant.
After setting all O min. values, the O
2
The setting can be made in 2 different ways.
Basic Documentation LMV51...
18 Addendum 4: LMV52... with O2 trim control and O2 module
2
trim control system
value fluctuates about the O2 setpoint. Check the
2
2
monitor
monitor can be activated.
2
trim control is
2
value. When
2
CC1P7550en
01.10.2003