B4T
Senior Member
- Location
- Long Island, N.Y.
A sign that maybe they do know a little about what they are doing.
No.. more luck than anything else.. IMO..
A sign that maybe they do know a little about what they are doing.
No.. more luck than anything else.. IMO..![]()
Well they are definately not afraid to operate things at a higher temperature than we do indoors. And with things being in free air most of the time the ratings are not the same as they are indoors anyway.
Take a look at differences in ampacities between T310.16 and T310.17. 2008 NEC. 310.17 is for conductors in free air - they are rated for higher ampacity than similar conductors in 310.16 - but not to extent you sometimes see POCO allowing them to be loaded.
I'm sure that's true.
But it just doesn't excuse the the horribly untidy state of the wiring in my opinion.
Butt connectors are bad enough but just having them hanging it mid air - ghastly.
You make a very good point. I don't know what the size of the conductors are in the quad-plex shown in the photo but if we assume (conservatively) that they are 1/0, the 90 degree column of 310.17 says they're good for 205 amps. The quad-plex is connected to (6) 3-phase 120/208 services that are protected at the least 100 amps each. One store is a Snap Fitness (6 arc trainers, 8 tread mills, 4 bikes, all have TV's attached, 1 tanning bead. There's also a hair salon, Chinese restaurant, dry cleaners, vitamin store and 1 currently vacant space. All have A/C units. Not sure what the max draw is during the summer but I'd bet they're pushing the envelope at 205 amps.Well they are definately not afraid to operate things at a higher temperature than we do indoors. And with things being in free air most of the time the ratings are not the same as they are indoors anyway.
Take a look at differences in ampacities between T310.16 and T310.17. 2008 NEC. 310.17 is for conductors in free air - they are rated for higher ampacity than similar conductors in 310.16 - but not to extent you sometimes see POCO allowing them to be loaded.
One real problem due to above is the lack of co-ordination in the operation of protective devices installed by the POCO with those inside a building.The protective devices of a building designed in accordance with NEC are invariably of higher rating than those of POCO with the result that the POCO's protective devices operate faster than those in any of the buildings whenever there is a fault inside and this may cause considerable inconvenience.POCO is not designing things to same standards as we do inside buildings.
I have. This is a piece of tri-plex I cut away from a drop that burnt. It was attached to (2) residences and a sewer pumping station. One of the crimps corroded and failed, began to arc and melted the insulation.Their biggest drop is 1/0 AL for any overhead size service.. but to be fair.. I have not seen one of their drops melt..![]()
I have. This is a piece of tri-plex I cut away from a drop that burnt. It was attached to (2) residences and a sewer pumping station. One of the crimps corroded and failed, began to arc and melted the insulation.
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One real problem due to above is the lack of co-ordination in the operation of protective devices installed by the POCO with those inside a building.The protective devices of a building designed in accordance with NEC are invariably of higher rating than those of POCO with the result that the POCO's protective devices operate faster than those in any of the buildings whenever there is a fault inside and this may cause considerable inconvenience.
But that happened at a failed connection. Have you ever seen the insulation melted away from connections purely from heat from overloaded conductor?
NO.
Well once. On a welder temp. I hooked up some 60' from it's original location. I came in on a Monday morning and I don't know who did what.......but the insulation on the entire
length of the insulated ground was gone.
I have very seldom run into this problem. ...................................
Putting in a fuse with 1 amp higher rating on a 7.2kV line makes a big difference in how much current can flow on a 120/240 secondary without opening the fuse.
I think the protective devices co-ordination problem arises in indoor HV installations of consumers at connection points with POCO'S or upstream.
It is more a case of NEC and NESC to work together.............Many of those cases could be solved by having site engineers and POCO engineers work together instead of just thinking they know more than the other guy.
The POCO can't get away with overloading their transformers:those transformers will fail prematurely..............Still, damage was limited by the impedence of the transformers.
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The POCO can't get away with overloading their transformers:those transformers will fail prematurely.
It is more a case of NEC and NESC to work together.............
Not in this case but yes, I have seen a triplex burn up. I occasionally do work at a day camp that runs hot (electrically speaking) in the summer. I've been there on at least 2 occasions where the triplex they had running to a kitchen facility building burnt. Something in the kitchen probably started the issue. When I got there I pulled the meter and one of the lugs in the meter enclosure was blue it was so hot. We suspected it was a feed to another building where they had a kiln that was used for ceramics. Checked all connections inside the breaker panel. All were good. Put the meter back and a week later the triplex burnt. Was it one of the crimps ? Maybe but not sure. POCO came and replaced it with the same size triplex but the issue never resurfaced because they moved the kiln and the ceramics activities to another building.But that happened at a failed connection. Have you ever seen the insulation melted away from connections purely from heat from overloaded conductor?
Ever wonder why POCO's can do things like this
And we have to size wire for services in accordance with the size of the main breaker installed and then de-rate and down-size wiring in accordance with 310.16 when we install sub-panels ?
And yes, they're feeding 6 services of various amperages (all 120/208 3 phase but probably not larger than 100 amps each) off the same feeder and transformers:
I don't know what size the feeder quad-plex is but it seems small by the standards we have to comply with. It's been working a long, long time so I guess it's sized correctly by POCO standards