Grounding a metal chimney
When I remodeled my house seven years ago, I added a woodstove with an exterior metal chimney, which is now the highest part of the house. Should I ground the chimney? Would a lightning rod on the house help?
Bernard Veuthey, Washington, DC
Rex Cauldwell, a master plumber and electrician from Copper Hill, Virginia, replies: I once had a customer who was washing dishes during a heavy thunderstorm. A ball of lightning came out of an outlet and flew across the room, heading straight for his head. At the last instant, it veered off and hit a metal chimney near the sink. His chimney was grounded, and I recommend that yours be grounded as well.
Ground the chimney by attaching #4 copper wire to both the top and the bottom of the chimney, and run both wires to the ground-rod system of the house. Attach the wires to the chimney with three or four metal-band clamps.
The top wire will take most of the lightning strike to ground. The bottom wire grounds any leftover charge that has followed the chimney and would have nowhere to go except to arc to you. The lower ground wire also provides the path to ground for any ball lightning that might be floating around the house looking for someone to zap. Forget attaching a lightning rod to your house unless you can get it higher than the chimney.