The monitoring diode is installed to provide fault monitoring across the actuator outputs. Even if the actuator output is not used the diodes need to be installed. If they are not installed a FAULT condition will occur as the panel thinks the output is either disconnected or short circuit.
Under the Construction Products Regulations (CPR) it is a legal requirement to use only certified products for smoke ventilation. It is the responsibility of the installer to ensure installations meet the relevant standards. For more information see SCS Group’s Technical Bulletin.