Disconnection time on TT system

[sparkywoman]

Can a Sunnyboy SB3800 inverter disconnect on a TT system fast enough to prevent injury through shock?

The installation has an RCD fitted and the inverter is connected to a 16 amp MCB.
With the inverter having simple separation, does this negate the need for an RCD to protect the cable between the inverter and the consumer unit?

 

[malcolmsanford]

The cable between the invertor and the CU will come under the regs and if you have buried the cable or run it under floors and it does not comply to regulations 522.6.5 and 522.6.6, then that cable will have to have additional protection by an RCd to reg 415.1.1

The RCD in the installation will ensure that the disconnection times are met.

 

[sparkywoman]

The cable will be clipped directly. If it does go under the floor, is it a standard RCD or does it need to be a Type "B"?

 

[malcolmsanford]

As the invertor as seperation then you don't need a type B RCD.

The trouble with TT installations are that becasue of the likelyhood of having a high value Ra, and therefore not being able to achieve a Zs low enough to achieve disconnection times of a Fuse/MCB, the use of a 30mA RCD is used as additional protection.

So for PV there is a chance of fitting a 100mA RCD if you do not bury the cable or run it under the floor without the protection of regs 522.6.6 and 522.6.5. ie completey run on surface, but there woulkd be very little chance of getting away without fitting some kind of RCD.