Jay, Agreed that LOTO is the industry practice: https://en.wikipedia.org/wiki/Lockout-tagout I have heard enough stories of divers who refuse to dive for ship maintenance *unless* they are physically carrying *all* keys that can start the engines. Ideally, there is tagged lock they can place so they carry their own padlock keys, but if not, the ship owner has the choice of either surrendering the keys or no work gets done, since the diver is surrendering his life into the hands of the person with the keys.
From Bobs telling of this story, I gather this info (I expect he will correct me if I am wrong): - He tagged (not locked) the breaker he was back-feeding. This is pretty obvious, because he said he was prepared to lose his inverter if someone accidentally would flip the breaker back on. NOTE that a breaker lockout is not expensive: https://www.ebay.com/itm/Lockout/221562247214 - He moved the circuit of the outlet to the tagged breaker. Sometimes there is a single outlet on a circuit, typically a bathroom outlet intended for a hair dryer, but most wall outlets are daisy-chained and so a string of outlets (and possibly lights and other devices) are on one circuit, represented by a single wire in the service panel. So, a typical way of moving an outlet to a different breaker involves moving the entire circuit that this outlet is on, to join it with the circuit that was tagged out. This may be not a problem for power draw if none of the other outlets/lights/devices is actually in use. But as you indicate, joining two wires at one breaker is questionable – if properly spliced into a single wire and that attached to the breaker, it is acceptable. I have seen this done in service panels when one circuit consists of two runs to different areas in a building. Attaching two wires under one screw at the breaker is exceedingly difficult to guarantee a good contact and therefor it is usually not allowed under code. - Suicide cord: Bob was silent on this one, so I presume that yes, he used a “suicide cord” to plug powered prongs into the outlet to back-feed it, instead of opening the outlet and splicing a cord onto the installation wiring, which would be a safer way to back-feed, but more work. This will still not avoid the “surprise” factor that if someone needed to work on the moved circuit and flipped the breaker off for that circuit, not knowing the circuit was being backfed, he would still get a nasty surprise when assuming it was dead after flipping the breaker. I understand that the chance of such a coincidence is small, on the other hand – electrocution is serious enough to avoid even small chances of surprising someone. In safety related matters, surprise is the synonym of danger. I have seen installations of service and sub-panels to allow local (genset) feeding of a building in a safe way. The least intrusive ones did not look anything different than a regular service panel, other than two features: - Having *two pairs* of main breakers opposite or adjacent each other with a metal interlock plate between them, so that only one pair can be turned on at the same time. This instituted the code-compliant lock-out for either grid- or generator-feeding of the service (sub-) panel. - An inlet with prongs attached to the second pair of breakers for feeding 240V from a genset into the panel when the grid breakers were off and the genset inlet breakers could be turned on. An alternative to the double pair of breakers is a separate lockout switch that chooses between two inputs to feed the panel, but the ones I have seen are both more expensive and take more space (an extra enclosure) than the solution with two pairs of breakers and interlock plate. It is relatively easy to make an interlock plate yourself, in case you can’t find one for your (sub-) panel. Generally it consists of 2 or 3 screws with locking nuts or with bushing to allow a small plate to slide when both breaker pairs are off. Only in each extreme position is one breaker pair able to be turned on. You can find a host of illustrations for various styles of panels on Ebay, search for “Panel interlock”: https://www.ebay.com/sch/i.html?_nkw=panel+interlock Cor. Sent from Mail for Windows 10 From: Jay Summet via EV Sent: Monday, January 21, 2019 11:23 AM To: ev@lists.evdl.org Cc: Jay Summet Subject: Re: [EVDL] Using EV to demo emergency power > Just to be clear, you were doing only 120vac? That is, half the outlets > in the building were dead? > He turned off and tagged out the circuit breaker, not the panel breaker, so ONLY the lights and outlets on that particular circuit were energized by the inverter. (All other circuits were powered by the grid.) I agree that a simple "tag out" without some type of physical lock/interlock isn't something you want to do long term, but as he was on-site and presumably monitoring the circuit/system/panel it doesn't seem too dangerous. (Unless he used a suicide cable that somebody could unplug from the outlet and touch the ends while it was still powered by the inverter....I was also concerned when he said he had moved the outlet circuit to the same breaker as the light circuit, which made me suspect he had a double-tap off of that breaker, which is also a No-No.) Jay _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20190122/6f639e00/attachment.html> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
