Wednesday, February 9, 2011

Lust for gold or born neutral?

A series of unfortunate events led us to suspect that our 240v oven outlet was borked. Trying to measure if it was alive with a multi-meter proved frustrating as it's very hard to get the tiny multimeter prongs to make a connection without pulling the outlet off the wall and touching the wires directly. To make matters worse we weren't quite sure what results we should get (other than that probably some of them should not be zero!).

A quick trip to Home Depo (thankfully quite close!) yielded a nice explanation, a diagram of what our results should be, and two reusable multi-meter prong extensions. Just ram into 240v outlet, grab both at once, and enjoy the ride! Hopefully by recording this on the blog we'll have a nice reference in case any of our other appliance outlets seem borked.

Multimeter with Optional Prong Extenders

Apparently these are the results one should get from a 240v outlet:
Expected Results

Despite some degree of nervousness about ramming wires into a 240v outlet, we decided to try to test our outlet. Using our shiny new prong extenders we found that our outlet gave the right results between live/live, live/ground, and gave about 7v between live/neutral. We neglected to measure neutral/ground. The correct live/live result may explain why our electrician thought the outlet was operational - he probably didn't check every pair.

We chatted with the Home Depo electrician once again and speculated that neutral might be charged, that wires might be stripped too far and arcing, or ... something. If neutral was charged we'd expect to see 120v neutral/ground. Once home again we tested again and this was our final result:
Actual Results

Neutral to live OR ground giving roughly zero seemed to strongly suggest that the neutral wasn't connected to *anything*. To confirm this we finally took the step we'd been avoiding all along and ripped the damn outlet out. As one might have expected we discovered a white wire (std color for neutral) kinda chilling on it's own:

The multimeter results are 100% correct if you touch the white wire directly when neutral is desired. Sadly we didn't quite manage to fix it as the screw to loosen to slide neutral in seems to be completely stripped. Fingers crossed the electrician makes it in today to fix the bloody thing and we actually have a working oven (gas range part is fine) again soon!!

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