AS 3000 question about Safety Services 1

[AusLee]

Hi,

A building has both normal and 100% back-up generator power supplies. There is a service protection device on the normal side and a circuit breaker on the generator side. These breakers are connected to the busbars via one automatic transfer switch.

The question is:

Can this transfer switch then have connected after it (on the load side) the outgoing submains to fire and life safety items?

This (first) option seems to be compliant with the exception number (vi) of Section 7.2.2.3 of AS 3000 and is more resonable and cost effective. My understanding is that this clause is a waiver of the below.

Or is a second separate automatic transfer switch required to seaprate these items from the remaining items (power and lighitng), so that a single switch does not switch at the same time normal and safety services?

This second interpretation is more expensive and strict implementation of Section 7.2.2.1 of AS 3000.

Any votes?

Thanks.

 

[sibeen]

AusLee, have a look at Figure 7.1. I've always interpreted this drawing along with the associated clauses as meaning that having a standby generator connected to a board via an ATS doesn't mean that a separate ATS is required for the safety services.

Basically the ATS feeds your main busbars and you must ensure that the safety services are on a dedicated breaker fed directly from the main busbar. I've designed quite a few with this configuration and haven't as yet had any issues with an electrical inspector or with obtaining BCA compliance..