dbuckley
Senior Member
- Location
- Canterbury, New Zealand
Going to relate a tale from a job where I was an IT person, and the data centre was dead. The (three) electricians were under "some pressure" to get the power back on. Eventually, I couldn't just hang around in the office, I needed to go and have a look.
As I got there they were about to hand us back the facility, they'd done some creative bypassing of failed contractors and were confident that all was well. Which was excellent news.
So, the first breaker was thrown, and then the second, and then there was a loud bang from a rack. A few colleagues and I look at each other nervously, hoping that was just a one off anomaly. The third breaker thrown and another bang. STOP we shout.
I ask the sparky nicely to measure the voltage out the end of an IEC connector in a rack, and it's swinging all over the shop. "Power not acceptable" I advise the sparky. "But it reads fine in the panel" he growls.
It's about this point when its getting distinctly frosty, we're doing the "Labor rate 75 per hr straight labor, 100 per hr you watching, 150 per hr you helping." type thing.
So sparky hauls me off to the panel, bungs the black probe on the metalwork, and prods the red probe onto each phase, and the voltage is indeed pretty much exactly what it should be. "Do it again with the black probe on the neutral not the metalwork" I ask. At which point I am reminded by EC that the metalwork and the neutral are bonded at the source of supply. "Please, just humour me" I ask, and he acquiesces, the measurement made, and the wildly swinging voltage is observed. "Odd" he declares...
I eventually manage to get him to measure ohms between metal and neutral, and it's open. "Lost neutral" I declare.
The rest is just an everyday tale of burned out switchgear due to lack of preventative maintenence, boring, but there is a moral to this story - when troubleshooting never assume, as thats where you get caught out.
Everyone who does this long enough falls for this sort of thing at least once, and it's hardest to stay on the logical path when there's pressure on top.
As I got there they were about to hand us back the facility, they'd done some creative bypassing of failed contractors and were confident that all was well. Which was excellent news.
So, the first breaker was thrown, and then the second, and then there was a loud bang from a rack. A few colleagues and I look at each other nervously, hoping that was just a one off anomaly. The third breaker thrown and another bang. STOP we shout.
I ask the sparky nicely to measure the voltage out the end of an IEC connector in a rack, and it's swinging all over the shop. "Power not acceptable" I advise the sparky. "But it reads fine in the panel" he growls.
It's about this point when its getting distinctly frosty, we're doing the "Labor rate 75 per hr straight labor, 100 per hr you watching, 150 per hr you helping." type thing.
So sparky hauls me off to the panel, bungs the black probe on the metalwork, and prods the red probe onto each phase, and the voltage is indeed pretty much exactly what it should be. "Do it again with the black probe on the neutral not the metalwork" I ask. At which point I am reminded by EC that the metalwork and the neutral are bonded at the source of supply. "Please, just humour me" I ask, and he acquiesces, the measurement made, and the wildly swinging voltage is observed. "Odd" he declares...
I eventually manage to get him to measure ohms between metal and neutral, and it's open. "Lost neutral" I declare.
The rest is just an everyday tale of burned out switchgear due to lack of preventative maintenence, boring, but there is a moral to this story - when troubleshooting never assume, as thats where you get caught out.
Everyone who does this long enough falls for this sort of thing at least once, and it's hardest to stay on the logical path when there's pressure on top.
