so we added the third switch to the stack. it turns out that there was only one stacking cable installed on the original 2 switches in the stack so we technically did not have to "break" the stack to add the new switch.we first plugged the new switc...

so i called Meraki support and they told me to follow the procedure @Philip D'Ath described and suggested that there should be no downtime. i will report back once i have add the switch.chris

When you say short disruption what do you mean? Will the two existing switches stop forwarding packets?thanks

I have the wiring part down, lots of experience with Cisco classic stacking. I was hoping for a way to just add to the stack like you can with Cisco classic switches so i would not have to take the network down or risk it going down.