Changing hot water heater, 3800 to 4500

Discussion in 'Electrical Forum discussion & Blog' started by Danny Brown, Jan 1, 2019.

  1. Danny Brown

    Danny Brown New Member

    Jan 1, 2019
    San saba tx
    Im haveing to change from a 50 gal 3800 watt to a 40 gal 4500 watt do i need to change the breaker from 20 amp
  2. LLigetfa

    LLigetfa DIYer, not in the trades

    Feb 6, 2011
    NW Ontario, Canada
    Using basic math, 4500W at 240V is less than 20A but what is the code req in your area? Code may req 125% of the heater's rated ampacity. What does the water heater manufacturer say? What is the wire size? The breaker cannot be increased if the wire size is inadequate.
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  4. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    Wire size is the limiting factor. If you have #12, you CANNOT use a larger breaker, even though 4500 elements usually have a 30 amp breaker. WHY are you going to a 40 gallon heater in the first place, regardless of the element sizes?
  5. WorthFlorida

    WorthFlorida The wife is still training me.

    Oct 28, 2009
    Orlando, Florida
    You can buy 3800 watt elements to replace the 4500 watt units. This is commonly done when the electric is NOT 10 gauge wire with 30 amp breaker. If it is 12 gauge and 20 amp you are limited to 3800 watt elements.

    When I worked at Sears during the 1990’s, Sears probably sold more replacement water heaters than anyone. Since they had to cover the entire market, millions of homes were built with 20 amp, 12 gauge wire. For liability protection and not telling customers they needed to upgrade the electric, the 3800 watt unit was almost standard for them. Nowadays with Home Depot and Lowe’s, there is no product training so a lot of 4500 watt units get installed by the DIYer that should not be.

    A 4500 watt element uses 18-19 amps. A 20 amp breaker may or may not trip but continuous use the breaker will degrade and the wires may run warm at the connections. The insulation may slowly degrade and get false tripping at the breaker because breakers trip on heat. For a friend who had a problem with the water heater, it turned out the pervious owner rewired the water heater so both elements were on at the same time ( a big no no). Amazing the house didn’t burn down with 12 gauge wire and the breaker internally had fused where it could not trip. It started to trip after a home inspector switched off and on all breakers, then the water heater was tripping all the time. A very short distance from the circuit breaker to the water heater is what might have saved the day.
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