EV Charger Plug fire - be careful! (Input requested. Link to pics below).

Dodged a full house fire last night. Outlet completely melted. Fire burned casing and wall, but went out on its own.

Equipment:

  • Siemens versicharge 240/30A plugged into a NEMA 6-50 in a drive under garage.
  • Dedicated line with 40A fuse
  • Professionally installed during home construction.

Events:

  • Charged friends MS 100D for 8 hrs during the day
  • Charger rested for 1.5 hrs
  • Plugged in a MS 75 to top off for the evening
  • MS charged for a few hours then breaker tripped

Next morning I go out to find this near catastrophe.

Very scary. Melted box, all wood is charred.

Curious if I need to replace the entire wire (which is run through about 50 feet of walls in my house).

I read that EV chargers should be hardwired to avoid fault points like a plug.

Also read that most NEMA plugs aren’t intended to handle current for long periods of time (designed for a few hours running a dryer).

Electricians coming tomorrow.

Welcome any comments about how to protect myself in the repair/ reinstallation.

I’m likely going to hardwire the charger (no plug) and look into adding a temperature sensor or something - and definitely a fire sensor.

Link to pictures of failed plug: https://imgur.com/gallery/2joUiOp

  • flyfreeflylow@alien.topBEnglish
    1·
    1 year ago

    A few things going on here, potentially…

    1. Plugs wear out from use (plugging/unplugging). This can reduce the contact surface area and increase heat for long-running loads. If using a plug-in type charger, it’s best to plug it in and leave it plugged in. Don’t plug/unplug repeatedly.
    2. Some plugs just aren’t built to handle long-duration loads. They have smaller, thinner, contacts that heat up over time. This is fairly well documented for some Leviton NEMA 14-50, but wouldn’t be surprising to see in other plug types too.
    3. Improperly torqued wire connections can cause a failure like this on any plug, whether it’s in good shape and quality built or not. If the wire connection wasn’t torqued tightly enough, then the contact surface area between the wire and the lug on the plug can be smaller, leading to heat over time. Also, if not torqued properly, the connection can loosen up over time due to heat/cool cycles.

    Hard to say which of these factors is relevant here, although from all that charring and burnt electrical box behind the plug I’m betting on proper torquing, but yes, you need new wire. It’s (literally) toast - wire is a good conductor, not just of electricity but also heat. The issue that caused the fire could also have melted the wire’s insulation in the walls. Think about that for a minute, and then be REALLY happy nothing else caught…