3 ms·

I don’t know the whole setup, but the inspector is likely right. When you have a feeder to an outbuilding (or external structure or piece of equipment or subpan

by amluto 3y ago

I don’t know the whole setup, but the inspector is likely right. When you have a feeder to an outbuilding (or external structure or piece of equipment or subpanel or basically anything else), you supply it with the intentionally current-carrying wires and the ground. (Ground may be called “equipment grounding conductor” or “protective earth” or perhaps something else in your jurisdiction. It’s a wire or the metallic conduit you used.) And this is important for lots of reasons. If there is a fault from a hot wire to a grounded object, this (if done correctly) allows the upstream overcurrent protection to trip. And it minimizes the voltage rise of the object that gets energized. And it keeps the line-to-ground voltage within spec. And using a separate ground means that the voltage of “ground” doesn’t get pulled up by resistance in the neutral wire and that current doesn’t normally flow through “ground”. You should, of course, also connect the ground wire to Earth, well, at the base of the structure. And possibly also install something to help conduct lightning currents from the non-ground conductors to ground in the event of a lightning strike.

jacquesm 3y ago
> I don’t know the whole setup, but the inspector is likely right. That's an interesting start to your comment. So you don't know the whole setup but you do know the inspector is likely right. Well: if he was likely right he would have not shied away from putting it in writing. What happened was that halfway into the conversation he realized he was wrong, hightailed it out of there and simply didn't want to admit that he was wrong. I do know the whole setup. And I have spent enough time installing high stuff made out of metal (mostly: antenna masts) to know that the last thing you want is to give lightning a short path into your dwelling. His whole experience seemed to be based on simple domestic installations, and instead of just admitting that he didn't know exactly what to do and to go look it up or ask someone more experienced to look it over he dug in. Human nature, I get it, but this is safety we're talking about and the amount of flak the OP is getting in this thread from people that likely have more experience with keyboards than with real world engineering is telling. Just like you: they don't know the whole setup but they'll argue that it is unsafe, will void your insurance, will get you investigated for arson(!) and might kill your kids. You last paragraph is exactly the problem: he outright forbade me to ground at the base of the tower because that was in his opinion unsafe. But it wasn't his life and property that was at stake. I've seen up close what lightning will do to various pieces of gear, it isn't pretty, to put it mildly and you make sure you keep it as far away from your house as you can. And have spark gaps to ground at the point of entry for your power cable, just in case. Finally: the proof of the pudding is in the eating. When after a year we pulled the tower down again there was evidence of multiple strikes on the nacelle body at the top of the tower, all of which were dealt with gracefully, to the point that we didn't even realize the machine had been hit. What helped is that for the whole installation we had a massive amount of help from an experienced wind turbine vendor who took an interest in our project.
marcosdumay 3y ago
> you supply it with the intentionally current-carrying wires and the ground Whether you connect both grounds to both themselves and Earth, or just connect both grounds to Earth, or connect them to Earth once and connect them both depends on so many details, it's not funny. What is certain is that you don't want something that doubles as a lightning rod protected on the same internal circuit as your house. So your rationale doesn't apply to the GP. But anyway, every time somebody talks about electrical installations on the internet, somebody says some version of "If there is a fault from a hot wire to a grounded object, this (if done correctly) allows the upstream overcurrent protection to trip." Is it still a recommended practice on the US to rely on overcurrent protection to protect against current leakage? It's an horrible practice, as it requires several amperes of leakage before triggering.
- jacquesm 3y ago
  Indeed. We had proper ground fault protection breaks for that purpose, and it was really hard to get them. That + the use of metal tubing to carry electrical power as well as the incredibly flimsy construction of various sockets and such (as well as the high amperage) translates into lots of preventable fires each year in the USA and Canada. Point a FLIR at your average distribution panel and try not to be amazed at the number of hot spots. My biggest gripe: I don't mind inspectors, I just expect them to be really knowledgeable, not just theoretical. Grounding a structure is inherently different from grounding a circuit. He basically kept on insisting that the windmill is part of the circuit and should be bonded rather than that it had its own ground and that is just patent nonsense, more so because the windmill produced variable frequency AC that first had to be rectified, passed through a battery charger, a bunch of batteries and an inverter. The latter of course was bonded to the house ground.
  - amluto 3y ago
    What’s wrong with metal tubing indoors? Outside is another matter. Those galvanized steel tubes don’t last very long underground, and the results are terrifying. And nothing in the code requires ground fault protection upstream of a 120V circuit running through a corroded steel tube underground.

by amluto 3y ago

jacquesm 3y ago

> I don’t know the whole setup, but the inspector is likely right. That's an interesting start to your comment. So you don't know the whole setup but you do know the inspector is likely right. Well: if he was likely right he would have not shied away from putting it in writing. What happened was that halfway into the conversation he realized he was wrong, hightailed it out of there and simply didn't want to admit that he was wrong. I do know the whole setup. And I have spent enough time installing high stuff made out of metal (mostly: antenna masts) to know that the last thing you want is to give lightning a short path into your dwelling. His whole experience seemed to be based on simple domestic installations, and instead of just admitting that he didn't know exactly what to do and to go look it up or ask someone more experienced to look it over he dug in. Human nature, I get it, but this is safety we're talking about and the amount of flak the OP is getting in this thread from people that likely have more experience with keyboards than with real world engineering is telling. Just like you: they don't know the whole setup but they'll argue that it is unsafe, will void your insurance, will get you investigated for arson(!) and might kill your kids. You last paragraph is exactly the problem: he outright forbade me to ground at the base of the tower because that was in his opinion unsafe. But it wasn't his life and property that was at stake. I've seen up close what lightning will do to various pieces of gear, it isn't pretty, to put it mildly and you make sure you keep it as far away from your house as you can. And have spark gaps to ground at the point of entry for your power cable, just in case. Finally: the proof of the pudding is in the eating. When after a year we pulled the tower down again there was evidence of multiple strikes on the nacelle body at the top of the tower, all of which were dealt with gracefully, to the point that we didn't even realize the machine had been hit. What helped is that for the whole installation we had a massive amount of help from an experienced wind turbine vendor who took an interest in our project.

marcosdumay 3y ago

> you supply it with the intentionally current-carrying wires and the ground Whether you connect both grounds to both themselves and Earth, or just connect both grounds to Earth, or connect them to Earth once and connect them both depends on so many details, it's not funny. What is certain is that you don't want something that doubles as a lightning rod protected on the same internal circuit as your house. So your rationale doesn't apply to the GP. But anyway, every time somebody talks about electrical installations on the internet, somebody says some version of "If there is a fault from a hot wire to a grounded object, this (if done correctly) allows the upstream overcurrent protection to trip." Is it still a recommended practice on the US to rely on overcurrent protection to protect against current leakage? It's an horrible practice, as it requires several amperes of leakage before triggering.

jacquesm 3y ago
Indeed. We had proper ground fault protection breaks for that purpose, and it was really hard to get them. That + the use of metal tubing to carry electrical power as well as the incredibly flimsy construction of various sockets and such (as well as the high amperage) translates into lots of preventable fires each year in the USA and Canada. Point a FLIR at your average distribution panel and try not to be amazed at the number of hot spots. My biggest gripe: I don't mind inspectors, I just expect them to be really knowledgeable, not just theoretical. Grounding a structure is inherently different from grounding a circuit. He basically kept on insisting that the windmill is part of the circuit and should be bonded rather than that it had its own ground and that is just patent nonsense, more so because the windmill produced variable frequency AC that first had to be rectified, passed through a battery charger, a bunch of batteries and an inverter. The latter of course was bonded to the house ground.
- amluto 3y ago
  What’s wrong with metal tubing indoors? Outside is another matter. Those galvanized steel tubes don’t last very long underground, and the results are terrifying. And nothing in the code requires ground fault protection upstream of a 120V circuit running through a corroded steel tube underground.