Question about installing a regular dimmer switch.
I remove the old regular on/off switch. It had only 2 black wires, coming out of the box screwed to it, no ground.
The new dimmer switch had 2 black wires and 1 green/ground wire coming out of it. I attached the 2 blacks to the 2 blacks from the box.
In the back of the metal box it had 2 bare ground wires twisted together. They were looped around a screw that was screwed into the back of the box. They were too short to pull out to be able to work with. So i took the green/ground wire from the dimmer and wrapped it around that screw also that was screwed into the box, along with the other 2 bare wires.
So 2 black wires from dimmer switch to 2 black wires from box and 1 green wire from dimmer switch to screw in back of box along with bare ground wire.
If you have more than one wire under a screw, and there are no grooves or ridges or retaining washers to hold the wires in place, then there is danger that the wires might slip off.
The correct way to deal with the ground wires is to remove them all from the screw. Get an extra piece of bare wire perhaps 7 inches long, wire nut this and the other three ground wires, and attach the free end of the extra piece to the screw.
The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.