do DBs need isolators

Dean Williams · Aug 14, 2011

Hi Folks.

Do all DBs require isolators?, is there a regulation for this?

the reason i'm asking: I'm testing a theatre and they have a series of maintained boards dotted around the theatre supplying lights and sockets. Its a dual supply system, mains and generator. All the boards are the old MEM type with BS88 fuses, where normally, a seperate isolator is fitted. These boards have no isolator, therefore, no local isolation. To isolate a board, you would have to go into the switchroom under the stage and pull out a fuse in the submains board.

can anyone shed a little light on this please.

thanks

IQ Electrical · Aug 14, 2011

Dean Williams said:
Hi Folks.

Do all DBs require isolators?, is there a regulation for this?

the reason i'm asking: I'm testing a theatre and they have a series of maintained boards dotted around the theatre supplying lights and sockets. Its a dual supply system, mains and generator. All the boards are the old MEM type with BS88 fuses, where normally, a seperate isolator is fitted. These boards have no isolator, therefore, no local isolation. To isolate a board, you would have to go into the switchroom under the stage and pull out a fuse in the submains board.

can anyone shed a little light on this please.

thanks

Do you consider an increased danger to be present because the DB does not have integral isolation?

A BS 88 fuse is classified as an isolation device so technically, the distribution circuit (and DB) plus the sub-circuits (from the local BS 88 fuses) are covered for isolation.

Then there is 132.12 regarding arrangement of devices for isolation and switching.

If any possibility exists of the means of isolation being compromised, some form of locking should be applied. Regulation 537.2.1.5 requires the means of isolation to be locked off where it is placed remotely from the equipment being isolated by it's operation.

As usual, it's your decision as the inspector, Code 2 or Code 4.