HI guys
I recently landed a a comercial job where we were to subdivide a large floor in an old ofiice building to make two offices, and rear entrances to a fire hallway. They had an electrician to do the rewiring, so we ewere not to touch any wiring. However, he was grumpy and slow, and we ended up with wires that we were told to move by the client, who also told us they were disconnected…
I had to pull a cable out of a metal box. It used to switch something, and I checked it by flipping the switch…nothing happened to any lights. Unfortunatly, I did not have my meter handy as we were told we were not to do any wiring. As you can guess, the line was live and as I pulled it through the clamp,the hot grounded to the box. Nothing changed lighting wise, so I figured it was an end run switch line no longeer connected to any lights.
The client eventually complained of some circuits not working two floors down, And asked me to look if any breakers were tripped in any of the numerous panels. All OK.
Turns out that this floor’s panel was fed from another panel and my little short blew a 60 amp bus fuse so that one phase of the three phase was now dead.
would anybody comment on how the 15 amp breakeer on the circuit, the 30 Amp fuse on the sub panel did not blow yet this 60 amp main fuse did. The client was unhappy and wanted to hold back some of the payment, claiming we were negligent.
Thanks
Stemreno.
Replies
First of all there are different types of breakers and fuse and they will have different time constants.
But being otherwise similar a fuse will go before a breaker.
The breaker has mass to move vs burning out of a realatively small link.
But we have no idea of what kind of load might have been on the 60 amp fuse before the short. It might already have a 55 amp load on it.
"The client was unhappy and wanted to hold back some of the payment, claiming we were negligent."
Tell him fine. He will need to money, plus some more, or OSHA fines for maintaining an unsafe work area.
But being otherwise similar a fuse will go before a breaker.
The breaker has mass to move vs burning out of a realatively small link.
That's not an accurate statement, in general. While a breaker does have more mass, it has nothing to do with trip rate.
Conventional breakers and fuses both trip/blow based on thermal heating. Generally, breakers are designed to trip with less heating than a fuse, so they will generally trip faster than a fuse will blow. However, there are many different types and designs of both fuses and breakers, and the actual trip speed will depend on the specifics.
It's essentially impossible to accurately make a blanket statement about which will trip/blow first.
Hard to understand why he is unhappy.
HE said the lines were disconnected
HE said to do what you did.
Not that I always listen to my clients when they have a good chance of being wrong.
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His electrician, his hire, his problem.
You had to hire his electrician, back charge him for any payment held back and your time for trouble-shooting a problem he caused.
You might also think about billing the buildings owner for your time if it was a problem caused by a person he hired. (won't build any good will though)
You might rather take the approach with your client that you have had problems with the electrician (one that could have resulted in an injury). He has not been responsive to your supervision, (if you are supposed to supervise & schedule him), he has cost you money and you would like to hire your own electrician.