GFCI trip weirdness - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: December 19, 2021, 11:51:49 pm
content: Hi,We have a switchboard GFCI protecting our house AC sockets.Our dishwasher packed in months ago, we turned the DW off at the socket until the repairer came out.The repairer came out a few weeks ago, we switched the DW on the day before, the GFCI tripped early in the day before the repairer came. The repairer found a fault on the DW control board and checked the heater was OK, he left and ordered a new board. The GFCI tripped again early the next day. I put two-and-two together and switched the DW off at the socket.The repairer came back, replaced the control board (image of old board attached) the dishwasher is now working but the GFCI tripped the next day, I switched the DW off at the socket.The repairer came back to try and find this fault, nothing found, fingers crossed that he actually fixed it inadvertently.But if he didn't fix it, I've ordered an Arlec Single Outlet RCD and I'm going to put that on the socket.The thing thats really confusing me is why would it take 12 hours+ to trip the GFCI, the GFCI trips when the DW isn't running?I'm a beginner, what is the next step, get an electrician out? (the appliance repair guy hasn't been much help, I think he just runs a few basic checks and replaces anything thats bad).I have an EEVBlog DMM if that helps.Thanks.Richard

author: jmelson
author_rank: Super Contributor
timestamp: December 20, 2021, 01:25:27 am
content: Quote from: rthorntn on December 19, 2021, 11:51:49 pmUgh! These can be beastly to diagnose. It is possible that the (whole house?) GFCI has become faulty. Do you have any outdoor sockets? These could be getting condensation in them during the night and causing the trip. Otherwise, if it really is the dishwasher, it could be difficult to find the defective component.Good luck, you will need it!Jon

author: rthorntn
author_rank: Frequent Contributor
timestamp: December 20, 2021, 01:31:14 am
content: Thanks, it only trips if the dishwasher AC socket switch is on.

author: SmallCog
author_rank: Frequent Contributor
timestamp: December 20, 2021, 01:42:13 am
content: Given it's apparently not tripping as soon as it's turned on, or as soon as a cycle starts, is there any other pattern to when it trips? Is it in the middle of the night or x hours after a cycle has finished?Could the machine possibly be doing some sort of caretaking task and there's a fault to do with this?If it trips and you immediately turn the RCD back on does it trip again?

author: Tomorokoshi
author_rank: Super Contributor
timestamp: December 20, 2021, 02:32:53 am
content: The circuit board has some interesting damage:1. Burning in the PCB at the device in the lower middle.2. Burning just above the ST D2PAK device on the right.3. Corrosion around the cluster of 0402 or something parts in the lower right.4. Corrosion indication in the edge contacts.Is there water leakage onto the board? Was that fixed? Random water exposure, flow, and drying could explain some of the randomness and timing issues.

author: KaneTW
author_rank: Frequent Contributor
timestamp: December 20, 2021, 03:05:39 am
content: Isolate the subcircuit and run an isolation test between L/N and PE. You can do a binary search to speed things up, and there's no need to disconnect appliances if you keep the testing voltage sufficiently low (below peak AC; it might now show all faults as a result though).If you find too low isolation resistance, you'll at least have some probable cause.