I recently installed a GFCI outlet in an aluminum sunroom in the interior wall of the sunroom. It worked fine in the summer but now in the winter months when it gets real cold at night the GFCI trips.

The walls are just over two inch thick, and the insulation used is some cheap styrofoam condensed pebbles. Since the wall is just over two inches, the back of the metal box touches that outside facing wall. Not sure if that is affecting it.

If you’ve experienced this or have any idea why it’s happening and how to solve it that would be great.

  • Probably moisture from the air hitting the cold surface. Not sure if just moving the GFCI protection to inside of the house and a regular outlet or need a surface mounted box with insulation behind it.
    – crip659
    Nov 30, 2023 at 17:46
  • The gfci is on the inside of the sunroom. I’ll update the question for clarification.
    – Zach Smith
    Nov 30, 2023 at 17:54
  • 1
    It might be inside, but the warm moister air inside hits the cold back plate of the box and condenses.
    – crip659
    Nov 30, 2023 at 18:07
  • When you installed it, did you remove the warning tape and connect anything to the screws under the warning tape? If so, did you apply labels to the affected outlets? Nov 30, 2023 at 22:12
  • 1
    To test if my comment and the answer is correct, in the early morning turn off the breaker for that outlet and pull out the outlet. Should find drops of water in the box. Make sure you turn off the right breaker or the main breaker, there is still power to the outlet, just none past it.
    – crip659
    Nov 30, 2023 at 23:08

1 Answer 1


Condensation --> Ground Fault

That's all. You probably can't prevent all condensation on an outer wall in cold weather, especially in a thin wall.

There are a few ways to mitigate the problem:

  • Inside the Box

Remove the GFCI/receptacle. Tape (electrical tape only) over all connections/exposed metal parts. Install it again. If the problem is due to condensation dripping down from the top and shorting out just enough to cause a ground fault, that may be enough to fix it because the condensation won't touch the hot or neutral lines.

  • Before the Box

If the problem is water getting into the GFCI mechanism itself, a simpler (not GFCI) receptacle, preferably weather resistant (to have a better chance to stand up to water, though in this case from the wall rather than from the weather outside) may solve the problem. But you can't get rid of the GFCI protection, so you need to move the GFCI protection to either a previous receptacle in the chain (in a different room or in this room but on a different wall) or to the breaker.

  • Move the Box

As suggested in a comment, move the GFCI/receptacle from an inside-the-wall box (which is normally best but not here because of condensation due to the thin outside wall) to a surface-mounted box. That will make the entire receptacle be inside the conditioned space (even if you are not running HVAC all the time, it will still be better than the outer wall) and have the entire usual wall thickness as insulation.

  • 2
    For the Move the box point, just in case it's not obvious, fill the hole where the box was with insulation.
    – FreeMan
    Nov 30, 2023 at 18:20
  • 2
    Might also add a gasket to the box to reduce the airflow from the room into it, thus reducing the moisture available rom the air. Can also pack duct seal around cable entries.
    – Ecnerwal
    Nov 30, 2023 at 20:33

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