Mike Lamb Posted October 15, 2013 Report Share Posted October 15, 2013 Would a 90' triplex service drop of #3 CU be adequate for 200 amp service? Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted October 15, 2013 Report Share Posted October 15, 2013 Just a quick WAG, but probably yes. Especially since most 200-amp residential services rarely, if ever, see 200 amps. Plus, any losses aren't paid by the customer. Quote Link to comment Share on other sites More sharing options...
Mike Lamb Posted October 15, 2013 Author Report Share Posted October 15, 2013 Then I guess it would be worth mentioning it is a 7 unit apt. bldg. Quote Link to comment Share on other sites More sharing options...
Tom Raymond Posted October 15, 2013 Report Share Posted October 15, 2013 Here is an ampacity chart for future reference. Download Attachment: ampacity2010.pdf 114.53 KB Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted October 15, 2013 Report Share Posted October 15, 2013 Then I guess it would be worth mentioning it is a 7 unit apt. bldg. Presumably with 60-amps to each unit and all gas appliances? Quote Link to comment Share on other sites More sharing options...
John Kogel Posted October 15, 2013 Report Share Posted October 15, 2013 Then I guess it would be worth mentioning it is a 7 unit apt. bldg. I would report on the service size in the building but I rarely mention the service drop unless there is a visible problem with the installation. Does the building have a common laundry room and gas heat? Then maybe 200 amps is adequate. And if it wasn't the breaker would be tripping, but that's never been a good excuse. It is common here for the service cable to appear to be undersized, but it is in free air and not limited by the sizing requiremnets for residential wiring, or so Ive read. Quote Link to comment Share on other sites More sharing options...
Marc Posted October 15, 2013 Report Share Posted October 15, 2013 I seriously doubt that any utility would ever knowingly install #3 service drop conductors on a 7 unit all-electric apartment building. If there's no AC's and all major appliances are gas then maybe, but just maybe. Marc Quote Link to comment Share on other sites More sharing options...
Mike Lamb Posted October 15, 2013 Author Report Share Posted October 15, 2013 Very old building. All gas appliances. 200 amp main fuse serving 8 subpanels. 2 outlet receptacles per room. I am just guessing on the service drop size from a distance. Looked #3-ish. Click to Enlarge 68.58 KB Click to Enlarge 63.58 KB Click to Enlarge 74.62 KB Click to Enlarge 55.46 KB Quote Link to comment Share on other sites More sharing options...
Mike Lamb Posted October 15, 2013 Author Report Share Posted October 15, 2013 Here is an ampacity chart for future reference. Download Attachment: ampacity2010.pdf 114.53?KB It might be my computer but I could not view that PDF. Quote Link to comment Share on other sites More sharing options...
Chad Fabry Posted October 15, 2013 Report Share Posted October 15, 2013 I hope you charged enough for that inspection. Quote Link to comment Share on other sites More sharing options...
Marc Posted October 15, 2013 Report Share Posted October 15, 2013 With no 240 volt breakers, I believe I'd not make a ruckus over it...unless...I see portable microwaves, window units, portable electric heaters or hot plates in the apartments, then I'd write up the electrical installation as needing a fresh load calculation by an electrician and suggest the utility be updated on the results of that new calculation as well as following any upgrade recommendations the electrician makes. Could turn out to be a big finding. Marc Quote Link to comment Share on other sites More sharing options...
Jim Baird Posted October 15, 2013 Report Share Posted October 15, 2013 here service drop is not anybody's bidnis but utility... Quote Link to comment Share on other sites More sharing options...
Jim Port Posted October 16, 2013 Report Share Posted October 16, 2013 here service drop is not anybody's bidnis but utility... Agreed, the POCO can do what they want. They use different criteria to size their conductors. Quote Link to comment Share on other sites More sharing options...
Tom Raymond Posted October 16, 2013 Report Share Posted October 16, 2013 Here is an ampacity chart for future reference. Download Attachment: ampacity2010.pdf 114.53?KB It might be my computer but I could not view that PDF. Here's the link: http://cerrowire.com/files/file/ampacity2010.pdf Quote Link to comment Share on other sites More sharing options...
Mike Lamb Posted October 16, 2013 Author Report Share Posted October 16, 2013 Here is an ampacity chart for future reference. Download Attachment: ampacity2010.pdf 114.53?KB Thanks. But I don't think this chart applies to open air conductors such as a service drop. It might be my computer but I could not view that PDF. Here's the link: http://cerrowire.com/files/file/ampacity2010.pdf Quote Link to comment Share on other sites More sharing options...
SNations Posted October 17, 2013 Report Share Posted October 17, 2013 With no 240 volt breakers, I believe I'd not make a ruckus over it...unless...I see portable microwaves, window units, portable electric heaters or hot plates in the apartments, then I'd write up the electrical installation as needing a fresh load calculation by an electrician and suggest the utility be updated on the results of that new calculation as well as following any upgrade recommendations the electrician makes. Could turn out to be a big finding. Marc Marc, what bad thing do you see happening from the service drop being smaller than the SEC needs to be? Quote Link to comment Share on other sites More sharing options...
Marc Posted October 17, 2013 Report Share Posted October 17, 2013 I've made no connection to the SECs. Someone else on this thread may have. SEC's and utility drops answer to different standards, different authorities. The utility drops are basically out of my scope during an inspection but that won't stop me from speaking up if I see something that can affect the property in a significant way. It has to do with the heat developed in air suspended conductors and what the limits are. Too much heat and they could fail, denying the customer service until repair crews can arrive, perhaps even damaging customer property. Marc Quote Link to comment Share on other sites More sharing options...
SNations Posted October 17, 2013 Report Share Posted October 17, 2013 It has to do with the heat developed in air suspended conductors and what the limits are. Too much heat and they could fail, denying the customer service until repair crews can arrive, perhaps even damaging customer property. Marc OK, that's a bad thing. Now I'm curious: has anyone ever heard of a service drop failing because it overheated? How much heat would it take for it to fail? Personally, I can't believe that in a million years that would happen for 90 feet of #3 Cu to a 200 amp service. Quote Link to comment Share on other sites More sharing options...
Tom Raymond Posted October 17, 2013 Report Share Posted October 17, 2013 I doubt it would fail due to heat. It might work harden making it more susceptible to failure from strain, but then again... Click to Enlarge 81.69 KB Quote Link to comment Share on other sites More sharing options...
SNations Posted October 17, 2013 Report Share Posted October 17, 2013 I would think that excessive voltage drop would be a problem long before any kind of excessive heat or mechanical failure. Maybe the solution is to measure the voltage at or near the main panelboard. Of course that's just a snapshot based on current load conditions. Quote Link to comment Share on other sites More sharing options...
Marc Posted October 17, 2013 Report Share Posted October 17, 2013 It has to do with the heat developed in air suspended conductors and what the limits are. Too much heat and they could fail, denying the customer service until repair crews can arrive, perhaps even damaging customer property. Marc OK, that's a bad thing. Now I'm curious: has anyone ever heard of a service drop failing because it overheated? How much heat would it take for it to fail? Personally, I can't believe that in a million years that would happen for 90 feet of #3 Cu to a 200 amp service. I took a look at an EE pocket book I have. The resistance of #3 copper wire is 0.1970 ohms/1000 feet. A 90' foot long service translates into 180' of wire. The power developed in that wire at 200 amps is 1,420 watts, a little higher than common 120 Volt portable heaters. So it's not as bad as I thought, but all that's needed is for the insulation to burn or melt then a short does the rest. The voltage loss would be just under 8 volts out of 240, about 3% voltage drop. Aluminum wire would generate more heat than that. Decide for yourself if you're going to write it up. Marc Quote Link to comment Share on other sites More sharing options...
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