ECN Forum Forums General Topics of the Trade General Discussion Area Residential Generator Floating Neutral option

Please be patient with me on this one!

I've been out of the trade for 15 years and still miss it! I did pretty much all residential and some light commercial during my career.

Here's my scenario with my question:
This spring I was getting quotes for a backup home generator - way too expensive for a Generac automatic standby (13-14k) and I've also heard of a lot of issues with them.
I finally purchased a Pulsar PGD105TiSCO portable inverter/generator that has a bonded neutral.

I am backfeeding to our home with a 50amp transfer cord and of course a panel interlock kit.

Here's my question: Rather than convert the bonded neutral at the genset to a floating neutral, could I just not feed the ground from the genset to the panel? I would do this at the power inlet box by just not bonding the ground from the 6/3 cable to the inlet box. I'm really not wanting to open the genset and remove the bonding jumper as it may void the warranty. Plus, if I ever want to use the genset as a stand-alone I'd want the bonded neutral.

Again, be kind in destroying me if I'm barking up the crazy tree.

If this is dedicated for use at your house, lift the bonding jumper. I am sure the procedure is in your owner book and that is part of the listing so it should not affect the warranty. Not bonding the generator to the GEC is a worse infraction than paralleling the neutral if you decide not to lift the jumper.
This is an issue of Separately Derived System and whether you are switching the neutral. In a similar situation, I am just living with the parallel neutral since I use this genset stand alone sometime.

If your installing a 50 amp interlock kit on a residential loadcenter I *think* you could use a switched neutral or aux switch breaker, its a 3 pole breaker but only two poles hit the busbar, we use them on fueling stations, but not the 50A variety.
The partnumber for Siemens would be a Q25001
Then your generator inlet would always be switched neutral.
Cheers

I actually never understood the parallel neutral violation in cases like this. Where is the hazard? I think in an emergency situation where connections may be shaky, I would rather have a redundant neutral/ground path than have 2 separate ones. You might argue that the generator frame could be at a slightly higher potential but we did that for decades with 3 wire feeders and 2d buildings and dryer frames. If you are worried set the way back machine to 1995 and drive a rod.

If I may speculate . . . This is not my specialty, and I tend to get all confused when folks start talking about “floating neutrals” and such. Let’s look at my understanding of how things work.
It’s my view that electricity “works” by being able to get back to where it was “born.” That is, back to the transformer at generator where it originated. It seems to me that this is the ONLY place the neutral needs to go; the electricity doesn’t want to go anywhere else.
As for the “grounds,” I see grounding to serve two purposes.

Purpose #1 is to collect any electricity that “leaks” or “gets lost” and return that electricity to its “home.” That is, the generator or transformer where it was made. It is by having a good, solid return path that the fuses and breakers work. So your green wires, etc., need to have a good path back to your generator. I’m not sure that relying on the bonding of enclosures is reliable enough - there ought to be a real wire between your panel and the generator.

Purpose #2 is to give static electricity (read “lightning”) a way to return to Mother Earth without burning up everything in the house. For that you need a good, solid path from your panel into the ground itself. This path has nothing to do with your generator. I see generators with connection points for running a wire to a rod (or other electrode) and I wonder what’s the point? Lightning is going to hit the building, not the generator — and the little ground wire in the generator cord isn’t going to help much!

This leaves the question: When we use the generator, what do we do about the neutral connection to the utility? I suppose it’s better to separate your system completely from the PoCo grid, if for no other reason that you’ve lost power because something has gone wrong on the PoCo side, and you don’t want anything to do with them until they get their stuff fixed. Do transfer switches typically also switch the neutral?

Just what, I ask, is a “floating neutral?” If by that you mean that any voltage applies to the ground wires and conduit has no place to go, no path back to the neutral terminal on the generator . . . I say that’s a very bad idea. Without such a path there’s no way for the breakers to clear faults.

Am I missing something?

The utility connection is interesting but usually in a hurricane, they cut the power before the storm so the poles are dead. The issue is with a legal breaker interlock as your only "transfer equipment" so you are stuck with that utility connection.

You have a good grasp of everything you spoke of but the open question is can you have 2 MBJs?

Inspectors I know knee jerk "parallel neutral" but in this particular case, I don't see the hazard. There are twice as many paths to trip that breaker. The ones that are on are 15 or 20a so either path is plenty big enough in a 30a generator cord.

I bet way more than half of the 30a or lower class generators get plugged into a dryer receptacle.

Oh,, I certainly agree with you there!

Apart from the reflexive reaction to condemn ignorant handymen, I blame the industry for this situation, at least in part.

Code language is surprisingly silent regarding manual transfer switches, focusing instead on elaborate automatic switches with load-shedding, exercise cycles, and so on. Even generator suppliers are pretty silent about transfer mechanisms. Manual switches are hard to find, and often wildly overpriced.

What Joe Homeowner probably wants is a simple manual switch, one that mounts next to the panel and has switches for perhaps six circuits. And, of course, a proper “inlet” for connecting the generator power cord. These things exist; even at today’s prices I suspect you’d spend about $800. Are, simple, and you can keep the lights, microwave, and furnace running.

But you can’t buy something if you don’t know it exists, or where to buy it. Just try to buy a power inlet device or even a 240V/30A cord cap at the supply house! Small wonder “suicide cords” are so common.

I am amazed at the price they get for the interlock device. It is a stamped out piece of sheet metal and some mounting hardware that costs over $100 when I bought mine. All it really does is make sure you can't have the main breaker on when you turn on the back feed breaker from the generator. No other switching is involved. I assume the price reflects what it costs to get it listed and the lawyer tax for potential liability.
The 30a (L14-30x) devices are at Home Depot and Lowes along with pre made cords so that part is easy and they do sell the 6 breaker transfer switch but I doubt many homeowners will screw with that.
The reality is my 5.5kw Briggs generator will run my general lighting load if I turn off the central air, water heater and don't use the range. I don't have a separate generator panel. In the 20 years I have had this generator, I used it 3 times. Our power is generally very good here and it is only after a storm like Ian or Irma that it is out long enough to worry about a generator. I also had one PoCo maintenance related outage that lasted several hours.
I do know most of my neighbors do the dryer plug thing. They find out pretty fast that if they forget to trip the main, the generator trips out when it hits the locked rotor of their neighbor's HVAC.
The smart ones have all the breakers they need to trip marked with nail polish or something. I cringe a little when I see it but I ain't a cop.

Just the usual parallel path neutral issues like if you had a meter/main service out at a pole then a 4-wire feed to a house panel that had the transfer interlock and the generator was always plugged in.
Then say the neutral went bad in that feeder. Possibly elevated voltage on the generator frame or neutral current flowing thru the generator, to the equipment ground back to the intact neutral in the meter /main.