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Well, it’s not exactly fine home building but there’s alot of smart minds here who might be able to help me.
I was working on a small electric boiler yesterday. After fixing the thing, I went to turn it back on at the disconnect switch. I brushed against the switch for another boiler in the process and burned myself on the metal switch box. This is a 480V, three phase boiler.
so I shut that boiler down, opened the switch box and found the insulation burned off the wires within about 3″ of the switch and the plastic guard that covers the contacts looks like a Salvadore Dali painting.
The boiler draws 75 amps and the switch is rated for 100. The wires on both sides of the switch are 3AWG which is close to being at capacity but is big enough for the load.
I suspect corrosion at the terminals caused these to heat up but it’s burned badly enough now that I can’t see any. I didn’t check the resistance across the switch yesterday but I’m wondering what resistance should I expect as acceptable? And is there any way to check the condition of the wires withing the conduit feeding this part of the building to see if they’re burned too? Would a megger tell me the condition of the insulation? Is there some sort of fancy electronic device that can do this so I don’t have too pull all new cable?
Replies
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Well, it's not exactly fine home building but there's alot of smart minds here who might be able to help me.
I was working on a small electric boiler yesterday. After fixing the thing, I went to turn it back on at the disconnect switch. I brushed against the switch for another boiler in the process and burned myself on the metal switch box. This is a 480V, three phase boiler.
so I shut that boiler down, opened the switch box and found the insulation burned off the wires within about 3" of the switch and the plastic guard that covers the contacts looks like a Salvadore Dali painting.
The boiler draws 75 amps and the switch is rated for 100. The wires on both sides of the switch are 3AWG which is close to being at capacity but is big enough for the load.
I suspect corrosion at the terminals caused these to heat up but it's burned badly enough now that I can't see any. I didn't check the resistance across the switch yesterday but I'm wondering what resistance should I expect as acceptable? And is there any way to check the condition of the wires withing the conduit feeding this part of the building to see if they're burned too? Would a megger tell me the condition of the insulation? Is there some sort of fancy electronic device that can do this so I don't have too pull all new cable?