DC isolator arcing when turned off

[fourtytwo]

Not wishing to be controversial BUT I had never heard of the DC last shutdown sequence and I am not sure the average person attending a fire would either, certainly there is no prescribed site labelling indicating this.

Going back to the OP's now resolved problem his breaker looks in the manufacturers catalogue strongly as a re-rated 3-phase AC design and as such possibly has slow contacts ? In any case it's voltage rating of 450V is inadequate to break a 400V string and faulty transformer less GTI backfeeding 350V so that would explain the arcing/burning.

As my experience has/will only be with transformer based GTI's I had not thought of this problem before seeing the OP's post and I think maybe something should be adjusted in the safety requirements regarding transformer less inverters that I must admit personally I have always viewed as unnecessarily unsafe just to gain a few percent in efficiency and save a few pounds in cost.

Rant over

 

[fourtytwo]

It is unfortunately impossible for someone such as myself to access the actual standards documents BUT I did find this reference about Australian standards doubling the voltage requirement of the DC breaker when a transformer less inverter is used (vs transformer type) so this generally supports my feelings.