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"Giant" hot water tank stoped working

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  • "Giant" hot water tank stoped working

    Good day everyone,

    Im stuck and do not know what els to do. Friday night my hot water tank, made by Giant 40gal 1999 stoped working.

    We drained the tank, shut off the braker.
    We replaced the 2 elements with 2 brand new giant elements the thermostats were replaced with new ones. We tested the wires and 120 is going to both so 240 in total. Hooked back up everything with the giant specifications. We still have no hot water. A hot water tank is just 2 elements +thermostats and a tank so if I replace everything it should work right ? the only thing i didnt replace was the tank.

    I wish there was a led or a small lcd screen telling me whats not working. any help would be great

  • #2
    check out the illustrations there is a wiring diagram for most domestic hot water heaters in there. make darn sure you got everything wired correctly. your power input should be 240 NOT 120 as you stated.


    • #3
      Hi thanks for your reply,we bought a tester and each element is receiving 120 so that mean 240 in total or should 240 be going to each element?. I will be going back and checking up on the wirering.

      The funny thing is that i just bought a house and im moving out of this one in 1 week, so now my plan is to buy a new hot water tank, set it up at the new house and bring the old one over here.


      • #4
        the power input to the heater should be 240 volts. check the top two screws at the upper thermostat, it should read 240. if it isn't go back to your panelbox and look at the breaker(s) feeding the tank. the breaker should be a two pole breaker. sometimes two single pole units are installed with a plastic tie-bar across the two breaker's handles so if one trips it takes the other with it. if this is not the case then put in a tie-bar. across each operating element you should read 240 volts NOT the 120 you state. True, from each leg to earth ground you'll read 120 volts but the elements are meant to operate at 240 volts.


        • #5
          I would be curious to know where you touched your meter probes when you measured 120v?

          As Hayzee has already explained in a 240 circuit both "Line1" & "Line2" of your incoming power line are powered at 120v. The bare or green earth ground wire of your incoming power cable should be connected to a green grounding screw at the point where the power cable attaches to the water heater. That grounding screw is connected to the body of the water heater to the tank will always be at ground potential.

          In a water heater the top thermostat is a SPDT (single pole double throw) switch, which performs an either/or function between the top and bottom heating elements.

          During cold start the upper thermostat sends the power to the bottom thermostat, which is a normally closed-open on rise thermostat. During cold start the bottom thermostat would be closed sending the power to the heating element. If you touch one probe of your meter to one terminal on the lower heating element and the other probe to the opposite terminal you should read 240v.

          With 240v the heating element is on and it should be heating the water. When the water temperature reaches the preset temp on the thermostat the thermostat opens, turning the heating element off. At that point you should read zero volts on the heating element terminals, however, if you touch the red probe of your meter to either pole on the heating element and the black probe to the water heater steel tank you will read 120v. The reason here is simple. The thermostats switch "Line1" but "line2" is wired direct to the heating elements therefore if you measure from the heating element terminals to the steel tank you are measuring "line2" to earth ground, which will always be 240v.

          The bottom line, if you measure the voltage across the two heating element terminals and you get zero, that element is in the off position. If you measure 240v it is in the on position.

          If you are measuring across the heating element terminals and getting 120v your water heater is not wired correctly and you have both elements in series.
          Last edited by LazyPup; 05-01-2008, 07:58 AM.


          • #6
            Hi Everyone,

            Thank you for all your help. Just to update you I finally called in a ellectrician and the problem was at the main braker box. He replaced cables in there and now the hot water tank is working great. it seems that only 120 was going from the braker box to the tank. No more going to my parents for a shower lol