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If you run a separate earth wire that is hard grounded at the sub and hard grounded at your house and nowhere in between. In this situation if you get a lightning strike at or near your house then the ground potential rises. This flows through the earth wire to the sub ground and can be a massive current, enough to make the network fail dramatically. This rise in ground potential can also be caused by other things such as a faulty insulator on an MV or HV tower (pylon) or pole. Even if insulators are good then you can still get this ground potential rise. You can easily measure it with a length of wire and two earth spikes, put one near a tower and the other a distance away and you can see a significant voltage. If you also have a separate wire called neutral running form the sub then the potential between that wire and the earth wire is unknown so you have a risk of lethal voltage between neutral and earth, a situation that is not expected and potentially extremely dangerous.

I know this goes against what many of you have been told and understood your entire career, but take a deep breath and read on.

A decent quality electrician’s screwdriver will have its insulation voltage rating stamped on its handle, though the absence of a rating is not necessarily a reason not to use it. A lot of screwdrivers have first-rate insulated handles, but without a voltage rating because they are sold for general-purpose use rather than specifically electronic. When you choose a screwdriver or other tool, consider the amount of plastic it puts between you and the metal, and pick accordingly. Wooden handles may not provide adequate protection, and metal handles should be avoided at all costs.

So a 20 amp breaker is designed to take the load shift on startup. A 15 amp breaker will carry the nominal load, but that surge on startup will kick it every time. In the days before switching supplies the input voltage would vary from 108 to 115VAC where I did work. This occasionally caused breaker trips on the unprepared circuit. I learned to spec high enough to minimize that issue and keep a safety factor in play.

1. 25A for 22A? Too close for my comfort. 2. A thin sheet of aluminum is not much of a heat sink. 3. Sitting on top of the hot water heater means ambient temp is going to be a bit higher. 4. Summer in a garage is likely to get hot.

All of the wire in the high current path is 10 gauge wire that was cut from SOOW cable, so it is, indeed, rated for 600V. In addition, it has 105 degree insulation, which means that it’s actually good for more than 30A. But it’s largely moot since the NEMA 5-15 plugs would only ever be found on 20A circuits (and even then, they likely wouldn’t be dedicated).

It would work, you could try just one winding on its own to start with but beware the voltage surge you get when disconnecting the current, as a minimum it should make a nice spark, even with a small battery driving it, at its worst it is shocking(!) I think the reason for winding your own coils is to get the optimum ampere turns for a chosen voltage, if you use what the transformer comes with you will have to work out what voltage gets you the highest magnetic strength without burning out the winding.

GFCI breakers aren’t usually used because they aren’t accessible to normal operators like a outlet mounted one would be.

All of these ratings can be found in NEC (NFPA 70) Table 310.15(B)(16) in detail, but as an example, according to this NEC chart, a 6-gauge copper circuit rated at 90°C (194°F) has an ampacity of 75 amps while a 6-gauge aluminum conductor rated at 60°C (140°F) has an ampacity of 40 amps. Of course, there are other considerations in addition to this, but it is clear the rules of thumb we often use can get us in trouble if we aren’t aware that exceptions exist and what those exceptions are.

• Find some space: Although you can store a portable generator in a garage or shed, it must be at least 20 feet away from your home when running because it produces carbon monoxide. You may be glad it’s 20 feet away, because portable generators can be obnoxiously noisy. (This may not please your neighbors, however.)

I prefer polycarbonate chassis with see-through lids. That facilitates continuous inspection while the device is in operation. I do agree that an output circuit breaker is not a bad idea. I’m comfortable with relying on the individual breakers on the input circuits combined with the two primary relays, which rather indirectly achieve the same purpose as the trip bar.

The key is to reference NEC NFPA 70 Table 310.15(B)(16) to find the ampacity of a conductor and size that conductor according to the MCA listed on the unit label. When this is done, the conductor will be properly sized according to the NEC.