A property I'm doing some work on has a B6 MCB which supplies two cables: to a stair lift (since removed after sale of property), and to the smoke alarms. The cable for the alarms is further protected by a 3A FCU next to the CU. I can't think of any purpose this fuse serves and am thinking of removing it and connecting the smoke alarm cable directly to a lighting B6 instead. Any reason why I shouldn't do this?
The 3amp FCU is common practice in the fire & security industry maybe it's come from that. The 6amp mcb offers little protection to the smoke alarm, downsizing through a FCU protected at 3amps is better imo.
When Wiring smoke alarms in HMOs I have installed a FCU to be able to isolate the alarms without disconnecting the lights to be able to test them on the batteries with the mains supply disconnected, service, repair or replace them.
