The LDU11 valve proving system is designed for use with shutoff valves in connection with gas burners and gas appliances. In the event of inadmissible leakage, the system prevents the burner from starting up. The LDU11 system conforms to the requirements of EN 1643 covering automatic shutoff valves for use with gas burners and gas-fired appliances to EN 161, class A and pressure switch to EN 1854. The Siemens LDU11 gas valve leak test control checks for leakage through the shutoff valves prior to burner start-up and/or immediately after burner shutdown. The cost effective, easy to install LDU11 adds a substantial degree of safety to any combustion system. Checks both shutoff valves for leakage Improves system safety No inlet gas pressure limitations Global approvals Easy-to-read dial indicates progress of test program The LDU11 is designed for automatic gas valve proving (leakage test) based on the pressure proving principle. It is for use on gas-fired combustion plant with or without vent pipe to atmosphere. In the case of plants with no vent pipe where EN standards apply, the notes given in «Connection examples without vent pipe to atmosphere» must be observed. Used in connection with 1 or 2 commercially available pressure switches, valve proving is automatically initiated with every burner startup, either prior to burner startup during the prepurge time if it lasts a minimum of 60 seconds immediately after a controlled shutdown, or on completion of the burner control’s control sequence, e.g. at the end of the postpurge time The valve proving test is based on the 2-stage pressure proving principle: 1. The valve on the mains side is tested by evacuating the test space and by monitoring the atmospheric pressure in it. 2. The valve on the burner side is checked by pressurizing the test space and by monitoring the gas pressure. If the pressure increases excessively during the first test phase called «Test1», or decreases excessively during the second test phase called «Test2», the LDU11. will inhibit burner startup and initiate lockout. In that case, the lockout reset button will light up to indicate the fault. Remote indication of the fault is also possible. A program indicator, which stops whenever a fault occurs, indicates which of the valves is leaking. The LDU11 can be reset either on the unit itself or via an electric remote reset facility. Type of LDU:
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