VESDA Metal Box HLI - Modbus Type 1

The recommended duty for a VESDA HLI is secondary monitoring, covering fire alarms and the other notifications a VESDAnet delivers. Primary reporting is suitable as well, provided the interface has first been integrated into whichever panel or reporting system takes it on, and approved or listed with it, to the fire standards and codes applying at the site.

VHX-1400 is the Wall-mounted ModBus HLI Type 1, a VESDA Wall-mounted ModBus High Level Interface. A Fire Alarm Control Panel (FACP), a Building Management System (BMS) or PC software monitoring tools that support the ModBus protocol are joined to a VESDAnet through it, and as the Type 1 build it returns to the host every character arriving on its RS232 link, together with reply message.

A single VESDAnet, served by one ModBus HLI, holds as many as 40 VESDA detectors, addressed on detector zone numbers between 1 to 200 across that network. The address range is split into 7 logical networks: the opening 30 addresses sit in network 1, the addresses between 31 to 60 in network 2, and so on across the range.

Smoke Level comes back relative to the Fire Alarm threshold on a full scale of 20, so the reported smoke value multiplied by the Fire1 Threshold and divided by 20 gives the actual smoke level. Secondary monitoring is the role recommended for a VESDA HLI; primary reporting is also suitable, whether it goes to a fire panel or to some other primary reporting system, and calls for the unit to be integrated and approved or listed with whatever panel or system receives the report, to the relevant fire standards and codes.