My new furnace has metal box with an electrical plug and switch on the side. Three-wire conduit (with black, white and green wires) runs from that box up to an overhead light with a metal box. An older piece of two-wire conduit (with black and white wires) runs from the light to the breaker box.

The furnace installer took the green ground wire (that came from the furnace conduit) and attached it to a piece of wire, and wrapped that wire around a copper pipe. I assume this was an attempt to ground?

Later another electrician, came in, said that the ground wire running to the copper pipe was unnecessary as the conduit should be grounded. He removed the wire running to the copper pipe and capped the green wire that came from the furnace conduit.

I'm still nervous because one piece of conduit is 3-wire and one is 2-wire. I read on another site that with 2-wire conduit, the metal sheathing asks as a ground.

Is this correct?

Was the 2nd electrician correct that the ground to the copper pipe was unnecessary?

I just want my house to be safe.

The electrician has taken on the responsibility of being sure the wiring is safe.

A ground wire just wrapped around a copper pipe is not a valid ground. Keep in mind that metal conduit is allowed to act as an equipment grounding conductor, and a green wire, while recommended, is not absolutely necessary.