Electric baseboard causing 30 amp breaker to hum

Discussion in 'Electrical Forum discussion & Blog' started by artmg, May 10, 2020.

  1. artmg

    artmg New Member

    Jan 30, 2007
    New York
    I have a room with (4) six foot electric baseboard heaters that I have never used. Today I looked at the thermostat and found that it had two low voltage wires like a normal thermostat. I turned the heat on and heat was coming out of the heaters but I heard a humming sound coming from the 30 amp breaker in the next room. I shut it down and turned off the breaker Any ideas of what is causing this humming sound?
  2. Reach4

    Reach4 Well-Known Member

    Sep 25, 2013
    I would get a clamp-around ammeter, and measure the current through one hot. If the current is less than 30 amps during the humming, I would replace the breaker.
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  4. WorthFlorida

    WorthFlorida The wife is still training me.

    Oct 28, 2009
    Orlando, Florida
    It's needed to know if these are wired for 240 volts (most likely) and are all 4 units on one breaker?
    What gauge wire is used to the heaters?
    Is is one thermostat per two units?
    Do you get the buzzing with just one thermostat turned up?

    An electric heater of this size should be 240 volt. Each one is probably rated at 1500 watts. 6000 watts @ 240 volts is 25 amps and it should be 10 gauge wire at the breaker.

    The low voltage wiring? If in fact it is low voltage, there has to be a set of 24 volt relays that would switch the power to the electric heaters. Did you hear any kind of click noise when turning up the thermostats? It is possible the relays are inside the breaker panel and they can be the source of the noise. A very common fault with 24 v AC relays. Either they fail completely or buzz away. Do you know who installed these units? A previous DIYer home owner?

    Pictures would help and any model number for the heaters? Do as Reach suggest and use a clamp meter to get a read on the current draw?
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    FWIW, on something like a heater that could be on extended time, I think you'll find that requires use of the 80% rule, or on a 30A circuit, a maximum load of 24A.

    Relays (more likely a contactor) can be noisy. So can a circuit breaker. ANything with a coil in it if it's not built well can vibrate at the powerline frequency.
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