But the 110v was measured after I completed the initial check and at that point, everything indicated that the isolation switch was switched off. I could have been working on the circuit when this intermittently powered up again. I was fortunate that I noticed the dim light on the switch before I was about to work on the circuit.
Hence me question on best practice, whether I should always isolate at the breaker or is it acceptable to do this as the isolation switch. I must say after this near miss, I am inclined to reach for the breaker every time but wasn't sure if this was just very unusual and as @terryplumb suggested, perhaps I should have been more attentive to the operation of the rocker switch.
