Strange grounding

[slybry]

I just moved into a house that was built in 1951 but has been totally renovated and rewired.

I have been replacing light switches with timers and dimmers. I did not see any ground wires to attach to new switches. I did see copper ground wires attached along flush with the back of each box. I called the electricain who did the job. He said the boxes are grounded in such a way that any switch installed wil be grounded. He said there is no need to attach the ground wire from the switch. I think he said they become ground just by virtue of the screws holding switch into the box (I think he said that).

I had been putting switches in and just capping the ground wires from the switch.

Is anyone aware of what grounding method he used? Do you think I am ok with just capping my grounds.

[HayZee518]

IF the replacement switches have provisions by means of a spring wire acting against the mounting screw to bond the yoke to ground and the box, it should not be considered GROUNDED. New as well as some old installations, the electrician grounds the box and brings the ground wire forward to connect to the grounding green screw of the device yoke. Where this is impractical and the box is grounded then a grounding pigtail is installed withion the box with a 10-32 green grounding screw. The pigtail is then attached to the device yoke.

[slybry]

I appreciate the answer but I am afraid you lost me a bit. Or should I say you have lost me completely. Sorry no where near an expert here.

[HayZee518]

I made up a diagram of a new work wall case. At the top and bottom are metal clamps that hold the romex in place within the box. You'll notice two - tapped holes, the smaller ones that are meant for grounding of the bare copper that comes in a cable set [wire] A 10-32 screw is screwed into the hole and the bare ground is wrapped and tightened around this screw. ALL bare grounds are wirenuted together with one screwed around this ground screw. where it is impractical to bring out a ground for devices, a grounding pigtail like the one I drew is installed. the device ground green screw is connected to this pigtail.