Gen on backfeed breaker won't power GCFIs

Question

I've been doing research online to try to help me narrow down things. Here's what I've got:

1. I bought a small (3500W) generator with a floating neutral. It has a 120v 3wire TT30 receptacle. No special GCFI protection built in. My intent is to power some circuits in the house when the power goes out occasionally. Refrigerator, few lights, TV, etc.
2. I installed a new breaker in my home's main breaker panel to be used as a backfeed breaker. I installed the proper interlock kit that matches up with Square D make/model of my panel and breaker.
3. I installed a L5-30 receptacle near the home panel and wired white to the neutral bar, black to the backfeed breaker, and green to the ground bar. This is the generator power inlet.
4. I made a TT30/L5-30 plug to plug cable so I can connect power from the generator to the inlet mentioned above.
5. Double checked all my wiring and everything is lined up as it should.

The result: I switch off the city power and bring up my generator system. Lots of stuff in the house works...except the circuits with GCFI outlets OR those on the few GFCI breakers that are installed.

From my reading, I believe my problem is that in my home, the neutral and ground are bonded (per code) inside the home breaker panel. Some of the current is bleeding into the home's ground system, being detected, and the GCFI's are doing what they're designed to do which is turn off.

I've read about installing a whole second transfer switch, instead of using the backfeed breaker. Cost and these are limited in circuits you can power.

I've read about setting up a sub panel to switch the neutrals. This sounds a lot like a home-made transfer switch. I might not understand this option well.

I don't want to take GCFI's out of the home circuits, so that's off the table.

Is there some smart/safe/easy way to debond the home's ground+neutral lines when I'm using the generator? One extra big bonding switch I can add in the panel?

What are all these other people with backfeed breakers doing? Seems like I'm missing something. Thanks for your help in advance.

Update - Found a clue, or maybe the whole issue! While looking at the wiring again I realized that I only powered one side of my backfeed breaker. My generator is 1ph 120v. The hot wire I put to the upper terminal so I realize now I'm only powering one side of the load center. Let's call it A since it's in the upper most position. All my unresponsive circuits are on the B side. I feel a little dumb now but I spotted that. Photo for clarity:

So here's the question now...move my important breakers to the A side so they're all powered OR gang/bond the two terminals on the backfeed breaker. I think moving the breakers is probably safer long term.

Found this related discussion HERE.

Answer 1

I installed a L5-30 receptacle near the home panel and wired white to the neutral bar, black to the backfeed breaker, and green to the ground bar. This is the generator power inlet.

An inlet has prongs sticking out of it, not socket slots. This is what you should be installing:

I made a TT30/L5-30 plug to plug cable so I can connect power from the generator to the inlet mentioned above.

You mean a plug to socket cable, i.e. that can plug into itself, like any normal extension cord.

Only a "suicide cord" has prongs on both ends.

I've read about installing a whole second transfer switch, instead of using the backfeed breaker. Cost and these are limited in circuits you can power.

Those things are hokey and play very badly with AFCIs, GFCIs and MWBCs. They won't fix a thing.

While looking at the wiring again I realized that I only powered one side of my backfeed breaker. So here's the question now...move my important breakers to the A side so they're all powered OR gang/bond the two terminals on the backfeed breaker.

Depends. As the article you found stated, you must search the system for Multi-Wire Branch Circuits (MWBCs) aka shared neutral. If the wiring is done in cables, the red flag will be red wires on breakers. Investigate every red wire. If it goes to a 120/240V appliance like a range or dryer, that is not a MWBC.

If any MWBCs are present, you cannot split the 120V supply to feed both legs of the breaker. You can rearrange, but you must be careful not to mis-position any MWBCs. All of them need to have handle-ties anyway, and those will ensure correct phasing. (one hot on each phase).

If your panel has no MWBCs, feel free to split and power both hot legs.