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Comment by rootusrootus | Hacker News Reader

To be fair, some of these features are available on the recently released hybrid, as well.

What I would like to figure out is if it can actually backfeed the home with 240V split phase power. That would be a seriously big deal if it could, it's not a common generator feature as it is. I'm skeptical, but they did claim it could transition from charging to supplying the house and back to charging when the power returned. Probably some fine print there where they say "only with the 120V charger". Otherwise, that would just be killer. An automatic whole-house UPS that can easily support all your needs for hours or even a couple days in a pinch.

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Backfeeding houses with generators is indeed a killer feature... but not in the way you mean. It can be done safety, but when done incorrectly (if the house isn't removed from the grid first) it can kill linemen. It's a good thing most generators a homeowner might causally buy at the hardware store don't have this feature. Unfortunately I've seen male-to-male extension cords sold online for this purpose. I think these are actually illegal, at least in some places.

https://www.cdc.gov/disasters/elecgenerators.html

> Backfeeding houses with generators is indeed a killer feature...

oh, you mean like solar PV on-grid setups ...

Those are generally fine because they are generally installed and configured by licensed electricians. Generators with suicide-cables installed by homeowner Joe Blow are the problem.

Close. It's not the electricians qualifications that make it safe, it's a feature in generating home inverters called 'anti-islanding'.

A correct install is of course also required as it's possible to screw up and unintentionally cripple this important safety feature.

Your basic solar inverter monitors the grid voltage, and if the grid goes down it stops generating.

Needless to say, if you're looking for a backup power source this isn't a property you want.

d'oh. i'm an idiot.

(an idiot who the state of NM certified last year to install his own on-grid solar PV system, so doubly an idiot!)

People with generators and suicide cables know to shut off the main breaker. Per my buddy who is a lineman in a rural area, DIY solar systems in cabins and such are much more of an issue.

Yeah, our local utility won't let you feed the house from panels without grid power unless you also install a battery.

All of the grid tied solar systems are able to conform to the IEEE 1547 standard. Amongst the particulars are a 300 second reconnection time if there's an interrupted grid to protect utility workers. Most (all?) USA utilities mandate this standard.

Some battery systems, like the Tesla Powerwall include a contactor that allow their microgrid battery systems to conform to the standard without a loss of power to the site they power.

https://standards.ieee.org/standard/1547-2018.html

Yes you definitely have to get it installed by a licensed electrician (and possibly approved then by the local utility) if you are going to backfeed your own house.

It is good that people are aware of the risk, but in reality the risk is quite low. It is standard procedure for a lineman to ground a line he's about to work on, to mitigate the risk of any power source feeding it. But I'd never advocate a DIY setup. But damn near everyone I know with a portable generator has a suicide cord and just flips the mains. Ah well.

I do hear this kill a lineman a lot as soon as any talk goes into backup power.

How many linemen are killed a year in the US due to backup generators or similar? Are there no procedures they can do to work on lines safer?

Are GP mentioned, the safety procedure to protect you from a line you're working on becoming inadvertently energized is temporary protective grounding. A grounding jumper is connected to each phase of the power line near the work location so that the worker touching the line works in a zone of equipotential. Because everything the worker is touching bonded together, if the line becomes energized the worker's hands and feet are elevated to the same voltage simultaneously, so there is no potential difference across the body and no current flows through the worker.

But since lives are at stake here, we prefer to have layers of protection rather than just one thing. Grounding jumpers can fail if not properly connected (a large mechanical force will be applied to the jumper when the phase-to-ground fault current flows through it).

Bottom line, respect the electrical code and connect generators through a transfer switch. These rules are in place for a reason.

Could an isolating transformer be an alternative to connecting generators through a transfer switch?

Transformers only block DC. Unless your house is wired for that (pretty rare in almost every country) You'll backfeed AC which will go through transformers.

In fact it's likely the transformer on the street between your house and the network that's responsible for the death of the linemen. IIRC that's a step down transformer (so step up when run backwards like this.)

Shouldn't this be called a "homicide cord"? It's the unsuspecting lineman that'll be harmed, not the homeowner, right?

I assume Ford’s lawyers are all over this, as the liability is immense, and Ford has deep pockets.

The language on the site talks about requiring a whole house manual or automatic transfer switch. Plus the thing has a 240v outlet. (presumably split phase, 240v single phase is not common in US residential settings).

I wonder if the wiring is basically plug the 240v split phase into a special outlet in the house that feeds the transfer switch. The 80amp charger is then just a charger.

Could be completely wrong though. We'll know more at launch.

That is basically how generators work.

Right. The backup function will require the house be set up with a transfer switch and the appropriate inlet setup, just like a whole house generator. The interesting bit is just the fact that the truck has a 240v split phase inverter built-in and ready to go.

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