Bidirectional Breaker

You don't want a generator setup where grid voltage can be active when the generator is operating, you need a failsafe switch, a 3 way type switch that is either or....You might know how it works but somebody else might not...as such the power comes in from the same direction...

So why don't you use a 200A contactor with a changeover set of contacts stacked such that when the supply is present the contactor is energised and the mains are connected to the switchboard and on deenergisation the aux supply contacts are closed allowing the generator to feed the switchboard.

Breakers sense overcurrent and do not depend on the direction of the current flow.

Contacts can stick, the points tend to weld themselves together over time....It's best to have a manual switch for safety...

Yes, this would be the configuration. To avoid any improvisations, I will take the Square D kit.

1) In your diagram Main switch disconect is the existing 200A general circuit breaker, that will be locked on the generator time.

2) Transfer switch would be my choice but it is not simple to connect the generator to the panel busses. A 50A breaker would do the job, is a plug in on bus at one end and has screw connection for generator wires, at the other. This is why I need a two way 50A breaker.

It looks that Square D can provide a breaker, too.

Thank you

What you describe will work, but is potentially dangerous and illegal in most countries.

There may be an issue with this scheme.

If I recall correctly (somebody please confirm or correct this), a very common welder receptacle NEMA type 6 50 amp (6-50R) is two phase lines and a ground, from which 120 VAC cannot be derived if backfed.

A NEMA type 14 (14-50R), which has 2 phase lines, neutral, and ground is appropriate if properly wired to the respective breaker.

My recollection on this is sort of fuzzy; can a member better versed in this review and comment before someone burns their house down?

Good point but in my case (and I don't remember if I had line/line/neutral or line/line/ground the neutral and ground were bonded together in the main panel so either way I was good.

I know it works as I have run the house on the genny.

The generator that I have in mind, Westinghouse 12500W, has the neutral bonded to the generator frame. In the manual they show you how to disconnect the neutral wire from the generator frame. This is the recommended configuration to connect the generator (floating neutral) to the house electrical panel.

More on the subject is here

https://generatorbible.com/blog/bonded-neutral-vs-floating-neutral/

It depends on whether the system is a separately derived system or not; If the transfer switch breaks the neutral as well as the feeders it is considered a separately derived system,and it must be bonded only at the generator.

If the neutral is not broken by the transfer switch,it is not considered a separately derived system and the generator must not be bonded.

As per NEC article 100 and 250.30 note1

Also refer to article 445.13

Based on NEC(c) 2011 Rule 220.87 Articles 445, 700, 701, and 702.

I am unable to reply with a drawing, unfortunately. In most generator installations I've seen, there is a breaker on the generator that goes to the transfer switch which then goes to the panel box's main line (input). Your generator should have a breaker on it. If it doesn't, put one in. It's simpler and safer because if you have to work on the generator, you'd want to ensure that no one will switch the breaker ON while you're working on the thing.

One last thing, there is no such thing as a bidirectional breaker. I think you're referring to the transfer switch, you're just using a different name for it.

regards,

Vulcan

Important to remember:Transformers work both ways.The transformer on the pole converts approximately 19,200 volts to 240volts,center tapped for 120vac.If you accidentally connect the generator to the mains,and the power company has the high voltage source turned off,a lineman could be killed by the 19,200 volts that he thought was turned off,and you could be charged with homicide.Most linemen always check before handling high voltages ,but if the voltage appears after he tests it..well... you see what I mean.Be very careful of "sneak paths" for the voltage.Redundant disconnects are always better.

You need to have a twist lock in-feed connector for your genset so you aren't using a "dido-of-death" male-male cable.

Second, you should have the genset breaker right next to the mains breaker with an interlock kit to prevent both being in the on position at the same time.

Third, you must use a 4 wire cable and you must disconnect the neutral tie to ground in the generator.

Here you go...just what you need.

Not cheap,but what price a life?

https://www.amazon.com/TC10323R-Outdoor-Generator-Emergency-Transfer/dp/B07J9RGC8D

TC10323R 100 AMP Single Phase 240 Volt Outdoor NEMA 3R Generator Emergency Manual Transfer Switch ON Off ON

Here is a link to everything you ever wanted to know about back up generators but were afraid to ask.Too long for me to explain here so follow the link,take your time and understand the requirements.

https://windsorlocksct.org/wp-content/uploads/2020/09/generator_requirements.pdf

Like many in the Houston area I am going to upgrade my e-service with a standby generator, in particular the Westinghouse TriFuel 12,500. I plan to use a 50amp 240 10 breaker Transfer switch. My question is there a self activating on sensing line voltage the to isolate the generator from the returning grid power. Yes I can do the manual, but given our utility is Centerpoint who reputable electric power utility analysts rate as the worst in America that requires my presence to change back to grid power at a moments notice and no warning at all.

That is a feature of many automatic transfer switches (ATS) but...

your genny will continue to run.

I’m uncertain that you really gain very much for a big expense.

Some home generator systems have an automatic transfer switch as part of their system.

A 14000W tri-fuel can be bought for around $4000.That may be your best cheapest way to go .

If you are going to be away from home for extended periods,an Automatic Transfer Switch is the way to go.

I've run my house on my 4-wire generator through a welding plug a couple of times. Always check that the main breaker is off two or three times, but I'm still uncomfortable with it.

I like the idea of a manual transfer switch, $210 from Amazon doesn't sound all that bad.

I'm not familiar with the American domestic power system, but just checking with some of the proposals re. plugging it in: will your earth leakage/residual current device (RCCB/GFCI) still operate? If not, you'll get power to the house, but still kill someone in the rare case that something goes wrong. Over here it is plain illegal - must get it installed and certified by a red-seal installation or master electrician, with some form of transfer switch. We've had people killed here from these sort of connections when insulation failed on a device or similar issues that otherwise would have tripped the RCCD. 12kW (50x240?) is not a small genny - this is one of the cases where I'd pay for the electrician to do it to code.

I looked in the problem of floating neutral. For a portable generator, like Wgen10500, if it is connected to the house panel, and if the cable from gen to transfer switch has two wires only (carrying L1 and L2 from the gen), than it must be a separate wire (dimensioned for the current) from the neutral of the gen (it is enough to be the neutral wire in the 50A connector) to the neutral bus of the house (which is grounded). Initially, I thought that two wires would be sufficient but this leads to imbalance between the two legs of the house network. So floating neutral for the generator (disconnecting from the chassis) means, in the gen manual, that the neutral of the gen is floating with respect to the gen chassis and that the grounding of the chassis is optional.