In mobile homes, connect the fourth green ground wire to the dryer frame, esp. in states like Alabama during hot dry weather where dry clay soil does not make a good electrical conductor to the house ground stake which is driven into the earth.
Otherwise, during dry spells, I have measured up to 90 volts between the electrical ground and the metal housing of househole appliances.
Hot wires- Phase A (black) is 120VAC to common (white). Phase B is 120VAC to common (white).
Get 240 across Phase A and Phase B.
Common (white) – Connects directly to the second lower mounted wire on the utility pole.
Ground -(green) – connects to the common (white) at the electrical junction box.
Ground (utility) – Metal mobile home frames are grounded with a metal stake driven in the earth. When the earth is dry and rain begins to fall, standing on the metal steps to open the front door can draw a spark. Thusly, the purpose of the fourth ground strap.
