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Building Technologies Basic documentation LMV37.4... CC1P7546en
12 Fan control 17.12.2018
Trim range test via PLC
Once the curve setting or commissioning is complete, a trim range test must be carried
out to check the influence on the application.
The test is initiated by the PLC, which provides both the output specification (via
Modbus) and the trim specification (via 4...20 mA).
Test sequence:
1. Starting point:
The PLC delivers a stationary output specification
( no modulation during the test sequence)
2. Lower trim limit test:
The PLC delivers the minimum current setting (4 mA)
Verification of the flue gas values if minimum trim influence is active
3. Upper trim limit test:
The PLC delivers the maximum current setting (20 mA)
Verification of the flue gas values if maximum trim influence is active
Steps 1...3 must be carried out at least for low-fire and high-fire to guarantee a correct
trim setting.
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