Duct mounted twin fan unit for internal use, with a high efficiency forward curved centrifugal impeller, sensors fitted in each scroll monitor air flow, detect and signal flow failure. Direct drive motors fitted with thermal protection and manufactured to BS5000. Class B insulation and sealed for life bearings. Air is discharged into a common outlet plenum chamber through separate shutter system which prevents blow back through the standby fan. The casing is manufactured from galvanised steel, internal faces of the case are lined with flame retardant acoustic material.
The fan unit incorporates an integral auto-changeover controller which provides 6 hour duty shared operation and automatic selection of the standby fan should the duty fan fail. Fault indication to a remote fail indicator (supplied) is provided via volt free contacts of a relay. The integral run-on timer allows the fan to run-on for a pre-determined time after the initial source (eg. coupled light switch) has been switched off. The run-on period is adjustable between 1 and 60 minutes.