electricalelectrical-panelsafety
I recently replaced our main load center with a larger one. I was planning to use the old, smaller panel as a sub panel in an addition we are building.
After removing the breakers from the old panel, I noticed some discoloration on the bus bar, where the breakers attach. The panel and all breakers were Square D QO brand. The contacts on the breakers don't seem to have this.
Is this panel still safe to use? What causes this? Should I use some electrical contact cleaner on the bar?
The panel you have pictured is a grounded panel but originally designed for just 12 branch circuits. There would be no problem if you added an extra ground buss as long as it is screwed securely to the metal box and bonded to earth ground with a piece of 10 or 8 AWG. Knowing you want to add kitchen circuits, looks like you have plenty of capacity. Minimum of two 20 amp convenience receptacle circuits (GFIC), one for the fridge, one for the dishwasher, and one for lighting. Looks good to me. I'd pass it on my inspection.
Yes, you can add an insulated ground bar in the can (you should be able to get one specifically designed for your particular can, but here's what they look like):
.. and then connect it to the other ground bar using a piece of #4 AWG (solid bare copper, or stranded THHN insulated) assuming you're still at 200 amps. This guarantees that the green bonding screw that's actually bonding your neutral on the other bar will affect both bars if it is removed. It's common to add these for isolated grounds, where they're connected to a different ground altogether instead of the other bar.
Note - the one you buy may come with its own bonding screw, and the appropriate tapped hole to receive it - so check for that prior to connecting the two together (IOW, read the installation notes that came with it).
Best Answer
Are you sure that the brownish color is not due to some contact grease? It may have come originally from the breaker(s). Try to see if it will wash off with a Q-tip and some isopropyl alcohol.
Be careful to not scrape the bus bar with any sharp metal tool because the silver colored plating on them is quite thin and you risk exposing the underlying copper.