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I am about to install a pv system , have done many before, but on this one I am feeding from the pv system back onto an existing submain and I was thinking is it necessary to provide lockable isolation at the source in the main building as well at the sub board or will the warning label regading dual supply and indicating where to isolate be sufficient?


Depends if you work to the 2nd or Draft 3rd edition of the guide, here's what the 3rd edition says:
2.3.2 a.c. switching device
Switching of the a.c. side of the installation shall comply with the requirements of BS7671,
An a.c. switch or combination of switches must be provided for isolation and maintenance in the installation.
A switch for mechanical maintenance shall be provided in close proximity to the Inverter and shall fulfil the following conditions:
* switch all live and neutral conductors
* be securable in the OFF position only
* clearly show the ON and OFF positions and be labelled as ‘PV system – main a.c. isolator’
An accessible means of isolation shall be provided to isolate the a.c. circuit . MCB’s, RCD’s and main switches installed in accordance with
BS7671 and in an accessible location can be used to fulfil the requirements for an accessible mea ns of isolation.
Note: At the point of installation of any a.c. switch-disconnector, the public supply should be considered the source and the PV installation the
It goes on to say:
Editors note – this section has been edited to match proposed G83/2 requirements – checks are underway with DNOs and ENA that we are OK to incorporate these changes prior to the release of G83/2
Now, the Draft G83/2 (still not yet published should have been in force for March 2012) says:

The installation that connects the SSEG to the Exit Point shall comply with the requirements of BS 7671. All wiring between the Exit Point and the SSEG shall be protected by a suitably rated protective device; and shall be of suitable size and type for the rating of the SSEG. The SSEG shall be connected directly to an isolation switch where for single-phase machines the phase and neutral are isolated and for multi-phase machines all phases and neutral are isolated. A secondary isolation switch may be required for remotely fitted invertors’ e.g in a loft. In each instance the manual isolation switch shall be capable of being locked in the ‘off’ (isolated) position.
(My emphasis)

Exit Point
Means the ends of the electric lines at which the supply is delivered to a consumer’s 434 installation.


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  • #3
Thanks thats very helpful .think Ill put one by the inverter in the remote building and one at the meter posititon (exist point) and label any boards in between
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