enter image description hereI added 2 separate circuits to a small space on the first floor.

Both circuits were AFCI/GFI protected in the breaker panel.

Both circuit home runs ran to one junction box before splitting.

1st circuit was 20A single gang outlet, nothing else.

2nd circuit was 15A for direct wired radiant heater (line thermostat controlled) that would draw max 6A.

All grounds were connected in the junction box.

After consultation with the heater/thermostat company I learned that AFCI/GFI breaker cannot be used with the thermostat. It requires a conventional breaker. Conventional 15A breaker installed for the 2nd circuit.


circuit 1 trips immediately when circuit 2 breaker is switched on.

Circuit 1 does not trip with circuit 2 breaker off and vice versa. (Btw before switching from AFCI to conventional style 2nd breaker only worked if 1st breaker off and vice versa)

Heater (2nd circuit) works fine as long as other breaker is off.

Outlet (1st circuit) works fine as long as other breaker is off.

Eaton breaker panel and Eaton br115 and Eaton All-in-one 20A breakers.

I’m open to all suggestions to resolve.

Thanks very much

  • 2
    Can you take a picture of the wiring in the junction box where they split?
    – Moshe Katz
    Nov 17, 2020 at 23:50
  • 6
    Smells like crossed neutrals or a neutral to ground short, but more like crossed neutrals.
    – Ecnerwal
    Nov 18, 2020 at 0:45
  • 2
    > All grounds are connected in the junction box You didn't mention neutrals. What about those? Nov 18, 2020 at 1:42
  • 4
    Does this answer your question? Upgrading 2 breakers to AFCI, always trips Nov 18, 2020 at 3:53
  • 3
    You guys are the frickin greatest..... No crossed neutrals in the Jxn box but...... what about in the Breaker panel. Aha 😤 Problem solved. I feel shame and sadness. Try to be sooooo careful and still muck things up.
    – Handydoc
    Nov 18, 2020 at 16:53

1 Answer 1


Neutrals were crossed in the breaker panel. AFCI is happy now.

Many many thanks 🙏 to everyone who took a few seconds from their busy day to help me.

  • Glad you were able to lick it! Nov 19, 2020 at 0:23

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