Power Management, Chapter 8: Power Management ICs | Lrd12 Overload Relay

Haha the big experts get all positive votes, but yours truly with a Master Electrician’s License gets all negatives. Hey, Believe what you want.

Heater might be pulling 22 A when hot, but on power up … likely much more. Think about incandescent lightbulb or electric motor, for example.

I use a contactor with my sonoff, 1kw pool pump. The sonoff is seriously under specced for switching a pool motor.

This is a heater that’s going to be near fingers, or elbows, and is completely accessible to them, completely easy to touch. One day, when he’s distracted thinking about something else (not rare), he’ll end up touching the heater and getting a shock.

You’ll notice that I didn’t explain exactly how to correct this. I do this intentionally because I’m not going to do the work. This situation could be easily fixed by replacing the dimmer switch with a simple toggle switch, by installing a dimmer rated for a higher wattage, or by installing bulbs with a lower wattage. Any of those would be fine, but as the home inspector, I don’t design the repairs.

Most systems now do not distribute ground (earth) from the MV / LV substation. At the sub the neutral is connected to ground through a low value resistor (<1 ohm) to a nest of earth spikes. Live and neutral are then distributed. At the house Neutral will be connected to a suitable ground point and at that point the earth connection is split off from the neutral. This means that any difference in ground potential is slowly leaked through the big resistor at the substation and it is a big resistor, looks like an oil tank maybe 2 metres high and 1.5 metres across. It is also normal that if there is any equipment at a pole it will also have an earth nest for the neutral wire.

The place to start when talking about mains-voltage equipment is your bench. We realise you’ll probably be working at your kitchen table or wherever you happen to be, but it’s best to start an article like this with a baseline, of what you really should have when doing this stuff. There are three things we’d consider essential in the mains power system on a mains-voltage bench. An isolation transformer to power the item you are working on if it needs a mains supply, a residual current circuit breaker for the rest of your mains supplies, and an emergency isolation switch for all bench power.

Sorry.. gotta disagree here. I’m sure L1 charging can work for some people who don’t drive very much. But people who buy an EV thinking they are going to be able to do everything using the 120V EVSE are going to wind up ver dissatisfied with their EV owning experience. When you get buy a 240V unit from clipper creek for $300 these days, plus maybe a few hundred for electrical work, there is really no excuse not to get this done in most cases.

The real problem with mains voltages is that somewhere, some day, some bonehead will manage to fry himself – and the media will blame the maker movement for it. I’ve already seen far too many absolute beginners planning to wire up their home appliances to an Arduino as their first project…

Step 4:  Use the V-I curve (Fig. 3) in the MOV’s datasheet to verify that leak voltage will be less than the 300-V ceiling.

A 40G HWH uses 3000W elements. Constant draw is 12.5A@240V and requires a 20A breaker (max draw / 80% safety margin = 15.6A so round up to 20A). 60G uses 4500W or 18.75A@240V and requires a 30A breaker (23.4A @ 80% safety margin so round up).

Toasters kindof have to use mains voltage, there’s a kilowatt or so of power in there. They do their best to keep the mains voltage away from hands, you’d have to deliberately put your fingers in to get shocked. Always remember to switch off at the wall before you stick the knife in to dig out your crumpets!