The reason an ungrounded GFCI trips when you press the test button on the device itself is because instead of applying current through a resistor between the hot and ground prong, it's does so between the line hot and load neutral, or load hot and line neutral depending on the manufacturer, therefore placing an imbalance current to verify the device will provide personal protection when you need it most. For this reason, let's pretend I hit the jackpot in this challenging housing market and score a house that suits my needs, location and budget, great. There's only one problem. It was built in 1950 and still has the original 60 amp fuse panel, cloth sheath two wire no ground NM and a couple two prong receptacles, all the rest test open ground. Let's also assume money is tight and I don't have the funds to replace the fuse panel and run new NM wiring right away, but I want to protect myself and loved ones from the dangers of outdated wiring in the meantime. The most cost effective way (and code compliant) to handle this situation is to place a GFCI/CAFCI type receptacle as the first receptacle of every circuit, and protect everything downstream with the LOAD terminals, and apply the GFCI PROTECTED and NO EQUIPMENT GROUND labels to the receptacles.
What is the value of the resistor in the tester? It should trip at 6mA. So by applying ohms law, R=E/I, R=120/.006, then R=20K ohms. That's my theory anyway.
Thanks. great explanation. This happened to me today and I was very confused.
I appreciate you watching. I’m glad it was helpful.
The reason an ungrounded GFCI trips when you press the test button on the device itself is because instead of applying current through a resistor between the hot and ground prong, it's does so between the line hot and load neutral, or load hot and line neutral depending on the manufacturer, therefore placing an imbalance current to verify the device will provide personal protection when you need it most.
For this reason, let's pretend I hit the jackpot in this challenging housing market and score a house that suits my needs, location and budget, great. There's only one problem. It was built in 1950 and still has the original 60 amp fuse panel, cloth sheath two wire no ground NM and a couple two prong receptacles, all the rest test open ground. Let's also assume money is tight and I don't have the funds to replace the fuse panel and run new NM wiring right away, but I want to protect myself and loved ones from the dangers of outdated wiring in the meantime. The most cost effective way (and code compliant) to handle this situation is to place a GFCI/CAFCI type receptacle as the first receptacle of every circuit, and protect everything downstream with the LOAD terminals, and apply the GFCI PROTECTED and NO EQUIPMENT GROUND labels to the receptacles.
As always, great information and advice. Thanks so much.
What is the value of the resistor in the tester? It should trip at 6mA. So by applying ohms law, R=E/I,
R=120/.006, then R=20K ohms. That's my theory anyway.