Heating elements in hot water tank

lazzalazza Solar Expert Posts: 330 ✭✭✭
HI

I've been trying to recover an old immersion electric water heater (220V supply). It's rated 1400W and has two 700W elements. The idea I have is to use only one of the elements (or both in series), to reduce power and heat water when the PV battery system has excess production.

However, the heater keeps tripping the RCD differencial breaker. I've tried both elements separately and they do the same. They work for a few minutes, and then trip the breaker.

Can anyone explain what may be happening and what the solution would be?

Thanks alot
Larry

Comments

  • Joe_BJoe_B Solar Expert Posts: 318 ✭✭✭✭✭✭
    Re: Heating elements in hot water tank

    The RCD will trip if there is an imbalance between the hot and neutral indicating a leakage path to ground. It might be that the element has leakage to the tank thereby current is flowing to ground through the water pipes. Most water heaters have dielectric couplings to isolate that current. It is also possible that one end of your element is shorted to the tank. The element should not have any connection to ground.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Heating elements in hot water tank
    lazza wrote: »
    However, the heater keeps tripping the RCD differencial breaker. I've tried both elements separately and they do the same. They work for a few minutes, and then trip the breaker.
    How low a current does your RCD actuate on? In some cases an older immersion heater element will have high capacitive current leakage to the water or tank itself. As long as the tank is grounded, it is not a safety problem but may be enough to trip an RCD.
    SMA SB 3000, old BP panels.
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Heating elements in hot water tank

    COULD be that the outer sleeve on the elements have corroded or burned (powered on when not covered with water) through, allowing current to leak out into the water. It is after all "old". Unusual to have this happen to both elements at once, but anything is possible. Good ohm meter, disconnect all wires from elements and check element connections to ground.
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