Last weekend a neighbor and old customer asked a question.  Is it better to replace a lower element again or the whole heater?  He told me he wasn't getting 220/240 volts to the heater. Was this a 120 volt unit?

1) Where was he checking the voltage?  I went over and he had disconnected the wires from the input terminal box on top of the heater.
2)  He was only getting 120 volts instead of 240 as shown on the electrical plate on the heater. 
3) All water heaters must have a Plate, Sticker, or some manufacturer's information showing wattage, voltage, and capacity of tank.
4) This eliminated a problem with the heater without further checks.
5) A shorted element could have tripped a breaker but a reading of ½ the rated voltage of 240 was impossible if the proper breaker was installed and working properly.  The proper breaker would have been a 30 Amp/two pole/common trip breaker.  A common trip breaker should have passed either 240 volts or 0 volts.  Common trip means that both 120 volt legs necessary to produce 240 are disconnected at the same time for the same reason.
6) At the load center it was determined that instead of a 30 amp breaker; someone had installed a 50 amp breaker. The conductors feeding the heater were only #10 with an ampacity of 30 amps.  A shorted element, bad connection, could have produced enough heat through this #10 wire to create a fire when it was protected for 50 amps. The breaker fell within the parameter of the ampacity of the #10 conductors and the new breaker.  All was well.
7) The old breaker did not completely trip as designed. This breaker would not reset both the common trip halves. We replaced the breaker and terminated the conductors on both ends.
8) When the heater was working an ammeter check was taken and the current (amps) as determined.
9) Both elements heating at same time would crowd the 30 amp breaker.  Normally the current check will only show the amperage of one element.(approximately 15 amps).

A few simple checks determined the water heater was not at fault and eliminated a dangerous situation.  An oversized breaker could have overheated the conductors and been the cause of a house fire in the attic.  3 Children Sleep in the House.

Check out my website for tools and meters. http://www.baldeagletraders.com

Eddie Ellison