6 ms·

Some of us here are actually Engineers (Electrical). I’ve installed 3x 240V 60A EV chargers, was a cakewalk. I didn’t build my own in this case since I was goi

Some of us here are actually Engineers (Electrical). I’ve installed 3x 240V 60A EV chargers, was a cakewalk. I didn’t build my own in this case since I was going for an aesthetic match. Meanwhile you can enjoy paying some alcoholic $1000 for 30 minutes of work to: * pop out a hole on the back * Tap and install 2x screws into studs * pull 3 wires 6” through, wrap around the strain relief, strip/insert/torque * flip a breaker It’s not rocket science, as long as you’re not a complete idiot and turn the breaker off before hand it’s completely safe. 240V isn’t even “high” voltage.

shmoe 3y ago
You're 100% right, but it not being "high voltage" is totally negated by the fact that the two legs together will kill me if it seeks ground via the right (wrong?) path for sure.
- balls187 3y ago
  Don't work with a live panel.
  - repiret 3y ago
    I know a few electricians, and none of them would agree with you. There's some things that can't be done safely on a live panel, but there are some things that can.
    - balls187 3y ago
      It's very hard to imagine any electrician advising a DIY homeowner to install a 240v line on a live panel. It's not difficult to do, which was GP's original point--though you need to take safety precautions (in addition to researching local code requirements).
      - repiret 3y ago
        My point is that electricians work in live panels all the time. (And the voltage of the circuit being installed does t matter. No matter what you install, the panel has 240V with approximately zero output impedance. I don’t know what advice an electrician would give, but the advice I give is that if you don’t feel like you can safely install a new circuit on a live panel, you probably just shouldn’t install new circuits.
balls187 3y ago
First, it’s a bit more complicated than that—unless you went ahead and installed a 60A line without checking if your service(s) can handle the additional load. Advice like this is what gets people to screw up. Second, what’s the material difference between a 40A circuit and a 60A circuit? A few extra hours overnight to charge?
- sib 3y ago
  Well, there are times when you're not charging overnight (e.g., get home with low battery, realize you only have 3 hours before next outing) and you get 50% more charging done in the same time, without having to go out to a Supercharger / DCFC. Or, as in our case, we have two EVs - speed is useful sometimes.
  - balls187 3y ago
    So you installed 2 60A circuits?
    - sib 3y ago
      Actually one 60A and one 40A. We have a 100A subpanel in our garage. Having them asymmetric (vs 2 x 50A) means that if we need one specific car to be charged as fast as possible, we can.
- aaronmdjones 3y ago
  The control pilot PWM signal at maximum duty only gets you 32A (~7kW). It doesn't matter how much the circuit breaker is rated for; the car isn't going to draw appreciably more than 32A. Higher charging currents are instead handled by distributing it across multiple phases. For example, a 3-phase 230V EVSE will give you ~22kW. EDIT: Even-higher-still vehicle charging is handled by having a charger outside of the vehicle and feeding the vehicle with DC, which is what e.g. Tesla Superchargers do.
sowbug 3y ago
I've hired enough licensed, bonded, certified, well-recommended, well-reviewed professionals who completely botched the jobs* to agree wholeheartedly with your sentiment. You can't hire someone without thoroughly understanding what they're doing, and once you reach that level of understanding, you absolutely can make an intelligent decision whether to buy or build. At the point where my house burns down, I really don't care about the credentials of the person who made the mistake. Rather, I personally make sure my house doesn't burn down. * Solar panels installed facing North in the Northern Hemisphere; rapid-shutdown switch installed inside a home; supply side of 240v connection to backyard office has male prongs; fence built with non-pressure-treated wood contacting the soil. The list goes on, and these are only the errors I've discovered in 20+ years of being a homeowner.
- jacquesm 3y ago
  If only it was just the tradespeople. I've had an electrical inspector argue that I should route the ground from my windmilltower into the house and bond it to the distribution panel rather than to ground the windmilltower at the base of the tower. So in case of lightning strike (which is pretty much a given) that would invite that lightning into your home right at the distribution panel. People may be following 'the code' but that doesn't mean they actually understand what they are doing. He wouldn't take responsibility for it, I asked him to put it in writing as an instruction and sign off on it so I could pass it to my insurance company. That never happened...
  - amluto 3y ago
    I don’t know the whole setup, but the inspector is likely right. When you have a feeder to an outbuilding (or external structure or piece of equipment or subpanel or basically anything else), you supply it with the intentionally current-carrying wires and the ground. (Ground may be called “equipment grounding conductor” or “protective earth” or perhaps something else in your jurisdiction. It’s a wire or the metallic conduit you used.) And this is important for lots of reasons. If there is a fault from a hot wire to a grounded object, this (if done correctly) allows the upstream overcurrent protection to trip. And it minimizes the voltage rise of the object that gets energized. And it keeps the line-to-ground voltage within spec. And using a separate ground means that the voltage of “ground” doesn’t get pulled up by resistance in the neutral wire and that current doesn’t normally flow through “ground”. You should, of course, also connect the ground wire to Earth, well, at the base of the structure. And possibly also install something to help conduct lightning currents from the non-ground conductors to ground in the event of a lightning strike.

shmoe 3y ago

You're 100% right, but it not being "high voltage" is totally negated by the fact that the two legs together will kill me if it seeks ground via the right (wrong?) path for sure.

balls187 3y ago
Don't work with a live panel.
- repiret 3y ago
  I know a few electricians, and none of them would agree with you. There's some things that can't be done safely on a live panel, but there are some things that can.
  - balls187 3y ago
    It's very hard to imagine any electrician advising a DIY homeowner to install a 240v line on a live panel. It's not difficult to do, which was GP's original point--though you need to take safety precautions (in addition to researching local code requirements).
    - repiret 3y ago
      My point is that electricians work in live panels all the time. (And the voltage of the circuit being installed does t matter. No matter what you install, the panel has 240V with approximately zero output impedance. I don’t know what advice an electrician would give, but the advice I give is that if you don’t feel like you can safely install a new circuit on a live panel, you probably just shouldn’t install new circuits.

balls187 3y ago

First, it’s a bit more complicated than that—unless you went ahead and installed a 60A line without checking if your service(s) can handle the additional load. Advice like this is what gets people to screw up. Second, what’s the material difference between a 40A circuit and a 60A circuit? A few extra hours overnight to charge?

sib 3y ago
Well, there are times when you're not charging overnight (e.g., get home with low battery, realize you only have 3 hours before next outing) and you get 50% more charging done in the same time, without having to go out to a Supercharger / DCFC. Or, as in our case, we have two EVs - speed is useful sometimes.
- balls187 3y ago
  So you installed 2 60A circuits?
  - sib 3y ago
    Actually one 60A and one 40A. We have a 100A subpanel in our garage. Having them asymmetric (vs 2 x 50A) means that if we need one specific car to be charged as fast as possible, we can.
aaronmdjones 3y ago
The control pilot PWM signal at maximum duty only gets you 32A (~7kW). It doesn't matter how much the circuit breaker is rated for; the car isn't going to draw appreciably more than 32A. Higher charging currents are instead handled by distributing it across multiple phases. For example, a 3-phase 230V EVSE will give you ~22kW. EDIT: Even-higher-still vehicle charging is handled by having a charger outside of the vehicle and feeding the vehicle with DC, which is what e.g. Tesla Superchargers do.

sowbug 3y ago

I've hired enough licensed, bonded, certified, well-recommended, well-reviewed professionals who completely botched the jobs* to agree wholeheartedly with your sentiment. You can't hire someone without thoroughly understanding what they're doing, and once you reach that level of understanding, you absolutely can make an intelligent decision whether to buy or build. At the point where my house burns down, I really don't care about the credentials of the person who made the mistake. Rather, I personally make sure my house doesn't burn down. * Solar panels installed facing North in the Northern Hemisphere; rapid-shutdown switch installed inside a home; supply side of 240v connection to backyard office has male prongs; fence built with non-pressure-treated wood contacting the soil. The list goes on, and these are only the errors I've discovered in 20+ years of being a homeowner.

jacquesm 3y ago
If only it was just the tradespeople. I've had an electrical inspector argue that I should route the ground from my windmilltower into the house and bond it to the distribution panel rather than to ground the windmilltower at the base of the tower. So in case of lightning strike (which is pretty much a given) that would invite that lightning into your home right at the distribution panel. People may be following 'the code' but that doesn't mean they actually understand what they are doing. He wouldn't take responsibility for it, I asked him to put it in writing as an instruction and sign off on it so I could pass it to my insurance company. That never happened...
- amluto 3y ago
  I don’t know the whole setup, but the inspector is likely right. When you have a feeder to an outbuilding (or external structure or piece of equipment or subpanel or basically anything else), you supply it with the intentionally current-carrying wires and the ground. (Ground may be called “equipment grounding conductor” or “protective earth” or perhaps something else in your jurisdiction. It’s a wire or the metallic conduit you used.) And this is important for lots of reasons. If there is a fault from a hot wire to a grounded object, this (if done correctly) allows the upstream overcurrent protection to trip. And it minimizes the voltage rise of the object that gets energized. And it keeps the line-to-ground voltage within spec. And using a separate ground means that the voltage of “ground” doesn’t get pulled up by resistance in the neutral wire and that current doesn’t normally flow through “ground”. You should, of course, also connect the ground wire to Earth, well, at the base of the structure. And possibly also install something to help conduct lightning currents from the non-ground conductors to ground in the event of a lightning strike.