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Building Technologies Division
CC1N7696en
20.04.2016
Use
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
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during the prepurge time if it lasts a minimum of 60 seconds
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immediately after a controlled shutdown, or
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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 moni-
toring the gas pressure.
If the pressure increases excessively during the first test phase called «Test1», or de-
creases excessively during the second test phase called «Test2», the LDU11.... will in-
hibit 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.
Warning notes
To avoid injury to persons, damage to property or the environment, the following
warning notes must be observed.
Do not open, interfere with or modify the control unit.
All activities (mounting, installation and service work, etc.) must be carried out by
qualified staff
Before making any wiring changes in the connection area, completely isolate the
plant from mains supply (all-polar disconnection). Ensure that the plant cannot be in-
advertently switched on again and that it is indeed dead. If not observed, there is a
risk of electric shock hazard
Ensure protection against electric shock hazard by providing adequate protection for
the valve proving system’s connection terminals
Each time work has been carried out (mounting, installation, service work, etc.),
check to ensure that wiring is in an orderly state
Press the lockout reset button only manually (applying a force of no more than 10 N)
without using any tools or pointed objects
Do not press the lockout reset button on the unit for more than 10 seconds since
longer presses will destroy the lockout relay
Fall or shock can adversely affect the safety functions. Do not put such units into
operation, even if they do not exhibit any damage
Mounting notes
Ensure that the relevant national safety regulations are complied with
