LED Bulbs On a GFCI Breaker Circuit... A Tricky Problem? - Page 1
Forum section: electronics / repair

author: t1d
author_rank: Super Contributor
timestamp: November 29, 2020, 10:19:13 pm
content: The GFCI breaker (fuse box type) in my bathroom is kicking out more often, now. The light and fan are on this circuit.The problems could be...The breaker is bad...The switches (light and/or fan) are bad...The wiring is bad, or a loose wire connection....The fan is bad...The bulbs are bad... And that is what might be interesting. I would never have thought of a bulb problem, back in the days of incandescent bulbs. But, these are LEDs and they have circuitry in their bases.So, let's think about the LEDs... They certainly will have capacitors. Capacitors appear as instantaneous dead shorts, when the circuit is first powered. (This is called "in-rush current".) The GFCI protects against shorts. That makes the bulbs a likely culprit, to me.A little more in depth... The capacitors could be small, in-circuit caps. But, LEDs are known to be built on the cheap. Meaning, that they are likely to employ large dropping caps, to regulate the voltage, instead of a more expensive transformer. (An in-series dropping cap works like a resistor, in an AC circuit... Give it a google...) Such caps are of large value, making the in-rush current higher and the likelihood of them being the problem more probable.An in-series NTC Thermistor would solve the problem. I rather think it unlikely to have been included in the circuit, if the manufacturer cheaped out with a dropping cap, or, if included, it could have failed.So, I think I will try using incandescent bulbs and see if that is the cure... Thoughts? EOT

author: coppice
author_rank: Super Contributor
timestamp: November 29, 2020, 10:25:19 pm
content: A GFCI should not trip on an inrush current. It trips on a current imbalance between the 2 power wires, not the level of that current. Either you have a faulty GFCI, or a current leak to ground.

author: shakalnokturn
author_rank: Super Contributor
timestamp: November 29, 2020, 10:53:34 pm
content: Nah, I don't get the question here either...Isn't a GFCI there to trip on live/neutral current differences only?All your suspects must have an earth wiring or a sufficiently low resistance path somewhere between live or neutral and masonry, metal work or just about anything that would be damp enough.My first suspect would be the fan, even more if it is a through-window type where having a warm and cool side may encourage condensation.I've seen some (far east) E27 bulb holders with cardboard insulation between screw thread and outer metal body, not exactly the ideal design for a bathroom.

author: themadhippy
author_rank: Super Contributor
timestamp: November 30, 2020, 12:33:45 am
content: Is it a stand alone GFCI or is it a combined gfci/mcb,commonly known as rcbo's on this side of the pond.

author: fordem
author_rank: Regular Contributor
timestamp: December 03, 2020, 01:47:49 am
content: Quote from: t1d on November 29, 2020, 10:19:13 pmYour problem is not the LEDs - either the fan or the breaker - as has been mentioned, the GFCI function won't trip the breaker unless there is a path to earth, which there isn't with LED lamps in an E27 screw type socket, that leaves over current or a defective breaker as the cause of the trip - the increasing frequency of occurrence suggests the breaker.Open up any one of your LED bulbs and examine the internal electronics - the traces are so thin they will "fuse" long before there is enough current flow to trip the breaker - whether the cause be capacitor inrush or a dead short.Starting in 2016, I've switched pretty much all the lighting in three family homes to either CFL or LED, in one of the three, everything is LED - no tripped breakers on a lighting circuit in any of the three.