Tesla Sending New Wall-Charger Adapters After Garage Fire 195
JoeyRox writes "Tesla is sending its customers new home charging connectors after recent reports of chargers overheating in garages and one instance of a fire inside a wall socket that held one of the chargers. Tesla CEO Elon Musk said the new charging adapter will contain a thermal fuse capable of terminating the charging process if it gets too hot. 'These are very rare events, but occasionally the wiring isn't done right. We want people to have absolute comfort, so we're going to be providing them with an upgraded adapter.' The company also issued a software update in December to address the overheating issue."
Re:Modus Operandi (Score:4, Informative)
Maybe nothing was really wrong. Maybe the wiring sucks, the charger draws too much RMS power due to a dirty wave (Fattened with harmonics), the excess current causes overheating, etc. So rather than putting in a current detector or whatever else to detect faults, he just ... stuck in a thermal fuse. If it gets too hot, it shuts off.
Most hardware doesn't constantly draw that much power. It's really hard to screw up a transformer--the wall charger would just be a transformer and maybe a MOSFET-based rectifier or something else that can pass that much power. Thermal fuse--even a current fuse--is really a "this will never happen, but if anything does happen that creates any kind of bad situation, this will stop it. Whatever it is."
Re:Quality? (Score:5, Informative)
Re:Quality? (Score:5, Informative)
My 20A appliance loop in the kitchen has 15A receptacles because, heyyyyyyy, you're not really going to draw 20A out of these right? Those 2000 watt appliances don't go on a 20A loop that can pass 2200 watts... I use a Breville 1800W toaster oven drawing over 16A through one receptacle. One 15A receptacle on 20A wiring.
Most 15A receptacles are rated for 20A pass-through, so they should be perfectly fine to use on a 20A line. The only time you should need a 20A receptacle is if you have a single device with a 20A T-shape plug.
Re:WTF (Score:4, Informative)
Re:Modus Operandi (Score:5, Informative)
This is one possible scenario which has happened in the past. Maybe it was aluminum wiring, which has a much lower thermal expansion rate than copper. Back in the 70's it was really common for developers to use aluminum wiring in houses because it was cheaper than copper. My house had aluminum wiring. The previous owners of my house were really underhanded. They ran copper off the electrical box up in behind some insulation and connected it to the aluminum from junction hidden junction boxes, and because home inspectors don't do "destructive" inspections, meaning they don't even move insulation, we didn't find out until years after we had bought the house. We had a wall socket stop working and when I opened it up to see what was wrong I found the aluminum wire had completely detached from the terminals. Luckily my father-in-law, who doesn't live near by, is an electrician because we had to have the whole house rewired. It's still not illegal to use aluminum wiring, copper is recommended, but it's not requried. The higher temperature of the adapter could cause the aluminum wire to expand and pop off the plug terminals in the wall box, which can lead to arcing and fires.
It really wouldn't be Tesla's fault if developers were using cheap materials when building the house, but it is nice of them to do something to try and mitigate future issues after it becomes a known possibility. We can't account for every scenario that will ever occur, but we can learn as we go along.
STILL not NEC or NFPA compliant (Score:0, Informative)
According to NEC, a standard 15 amp residential wall socket must be derated to 12 amps for any continuous load that lasts longer than 4 hours.
It is ILLEGAL for Teslas to be plugged into a standard 15 amp wall socket, and it is ILLEGAL for Teslas to be equipped with a NEMA-15 plug.
Re:Modus Operandi (Score:4, Informative)
Sure. But. Calculations are still required for amp draw per circuit (which determines wire size and breaker ampacity), particularly when a specialty appliance has the unique demands of an electric car charger.
Not really any math above addition, and possibly even that if they're running a dedicated circuit for the specialty appliance like they're supposed to. The electrician memorizes some figures/looks at a chart [cerrowire.com]. Heck, I've seen the figures printed on the boxes.
NEMA 5-15(standard outlet): 14 gauge minimum(copper), 15A* max, 12A design
NEMA 5-20(has the notch): 12 gauge minumum, 20A max, 16A design
NEMA 14-30(dryer, 240V): 10 gauge, 30A max, 24A design
NEMA 14-50(range, 240V): 6 gauge, 50A max, 40A design.
The 'formula' for simple installs is easy: Look at the amperage of the product you're using. round UP to the next breaker size. Use specified wire gauge. Manufacturers tend to make this even easier because they tend to not produce appliances that are close enough in amp ratings that you'd need to skip the next largest breaker - IE they don't make appliances that use 'exactly' 30A, they'll produce a <24A model then if you need heavier duty a 32-40A one.
Though I'll note that space heaters and hair dryers today tend to assume that you have a 20A circuit, but there's reasons why the heaters are limited to 1500 watts and dryers to 1875(but they're only this powerful if you feed them 125V, nice advertising guys! In reality they'll be closer to 1.6kw in homes with proper voltage).
*Though to meet code it has to be manufactured to be capable of safe operation at 20A+