Suggested Cold Start (Thermal Shock Protection) Setup - Siemens LMV5 Series Technical Instructions

Technical Instructions
Document No. LV5‐1000
Properly adjusted PID values will result in the pressure / temperature staying within +/‐ 3% of
setpoint without constantly changing the load and modulating the actuators.
P‐Part (Proportional Band) ‐ Increases firing rate based on how far below setpoint the
temperature / pressure is. Smaller values cause a more aggressive P response to a drop in
pressure / temperature relative to setpoint. Values that are too small will cause hunting.
Typical setting: 10% to 30%.
I‐Part (Integral) ‐ Serves to eliminate steady state "droop" caused by the proportional band
setting. Thus, this works hand in hand with P‐Part to bring the pressure / temperature up to
setpoint. Smaller values cause a more aggressive I response (a setting of 1 is most aggressive).
Values that are too small will cause overshoot. Typical setting: 80 sec to 300 sec. A setting of 0
deactivates the feature, but this is not recommended.
D‐Part (Derivative) ‐ Serves to eliminate overshoot, and allows a more aggressive integral
setting. Larger values cause a more aggressive D response. D‐Part is not needed on many
steam boilers. If needed, small values of less than 20 typically work well. A setting of 0
deactivates the feature. Large values will typically cause hunting.
After the PID loop has been adjusted, it is possible that the load will still move up and down by a
8.
small amount (1‐2% load). If this is the case, adjusting parameter MinActuatorStep may help
eliminate this "micro‐hunting". This parameter can be found in the following menu:
Params & Display > LoadController > ControllerParam
MinActuatorStep is basically a dead band for the output of the PID loop. Typical setting: 1% to
4%. Values above 5% could cause hunting issues in some applications.
Suggested Cold Start (Thermal Shock Protection) Setup
The LMV51.1 and LMV52 have an internal load control and therefore have the ability to perform
thermal shock protection. Thermal shock protection only functions when the LMV5 is in an internal load
controller mode, namely IntLC, IntLC X62, or IntLC Bus (see chart on previous pages).
The cold start feature requires that the temperature or pressure of the boiler is measured by a sensor
connected to the LMV5.
For a hot water boiler (temperature‐based modulation), the same temperature sensor that is used for
modulation must be used for the cold start feature. For a steam boiler (pressure‐based modulation), a
temperature sensor is also highly recommended for cold start. Temperature sensors are highly
recommended since pressure does not always represent temperature in a non‐firing steam boiler,
especially when multiple steam boilers are piped to the same steam header. The paragraphs below will
only mention temperature‐based cold start, but the same ideas also apply to pressure‐based cold start.
Section 4 Page 24
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