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Siemens Building Technologies
HVAC Products
17
Engineering notes
17.1 Requirements placed on burner design
The mechanical connection between actuator and actuating device must be rigid with
no mechanical play.
This means that the transmission of forces may not take place due to friction.
Rigid mechanical connections are:
·
Key groove with key
·
Split pin
·
Spindle with flat surface and matching member
·
Gear wheels
The mechanical link between actuator spindle and feedback potentiometer must also
be rigid, with no mechanical play.
Where possible, slipper valves should be used.
They allow the actuator to be fitted directly to the valve, thus eliminating the need for
intermediate linkage.
The total running time of the actuators (corresponding to DC 0...10 V at the feedback
potentiometer) must be in the range between 20 and 120 seconds, but the running
times of the individual actuators may vary.
It is of advantage to use valves and dampers with a characteristic as close as possible
to equal-percentage.
The ramp time (corresponding to the full speed range from standstill to maximum
speed) for the fan motor must lie between 60 and 240 seconds.
The ramp time must be at least twice the running time of the slowest actuator.
Position
Equal-percentage
damper
78731d04e/1001
Fig. 35 Air damper characteristic
If should be noted here that the positioning accuracy is 40 mV.
If, for example, the gas damper has an extremely unfavorable characteristic, the po-
sitioning accuracy (neutral zone) will lead to inaccuracies in terms of gas flow rate.
Electronic Air / Fuel Ratio Control System
17 Engineering notes
Unfavorable damper
Load
53/69
CC1P7873.1en
15.10.2002
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