Friday, July 25, 2014

Electricity for homeowners

Just a few bits of wisdom picked up over the years.  Understand, electricity can be dangerous, can burn your house down, so if you have any doubts about a do it yourself project, you ought to call a pro. 
   Juice comes into the house from the street with three wires.  Two hot wires, color code black, and a neutral wire, color code white.  The two hot wires are 120 volts, alternating current (AC) which means the voltage goes up and down, current goes back, and forth 60 times a second.  The two hot wires are 180 degrees out of phase with each other, which means when one wire is plus, the other is negative, and vice versa.  Which means you have 220 volts measured from one hot wire to the other.  Things like electric stoves, electric car chargers, big power tools , central air, and the like  get 220 volt power.  It is customary to run a special branch circuit for each 220 volt appliance.  The familiar branch circuits are all 120 volts, which is obtained by using one hot (black) wire and one neutral wire.  The hot wires each measure 120 volts to the neutral wire. 
  Black to brass, white to chrome.  Old electricians proverb.  The screws on the sockets and light fixtures are alternately brass and chrome.  Wire black to brass and white to chrome and you won't get hot and neutral switched around. 
   Fuses, or circuit breakers are there to protect the wires, not the appliances plugged into the branch circuit.  Should a short circuit occur, massive amounts of current will flow in the wires, which are buried in your walls, and heat them red hot, setting the house on fire.  The fuse or circuit breaker will open the circuit and cut off the current before anything bad happens.  New houses use #12 wire for branch circuits which can handle 20 amps.  Older houses had lighter #14 branch circuits which called for a 15 amp fuse. 
  Never fuse the neutral.  Another old electricians proverb.  It's complicated, and I cannot explain it without several diagrams.  So just take it from me.  Don't fuse the neutral.
  Treat neutral as if it were hot, i.e. don't think it's safe to touch.  A whole bunch of common faults can make neutral become hot and shock the bejesus out of you. 
  Run a safety ground color code green on all new work.  Safety ground protects against shock should the appliance insulation fail and allow a hot wire to touch the case, making the case hot.  If the case is connected to safety ground, all sorts of current will flow, and the fuse will blow, removing power and making the case safe to touch.  Back at the fuse box, the green safety grounds want to be connected to a good earth ground, say a 4 foot iron pipe driven into moist dirt, or the cold water pipe coming in from the street, before the water meter. 
   Most electric codes call for the neutral to also go to earth ground.  This is worth checking out.  One of the houses I owned over the years came to me with the neutral ground clamp rusted clean off and dangling in midair. 

No comments: