Three Questions About 10-2

Discussion in 'Electrical Forum discussion & Blog' started by molo, Aug 11, 2007.

  1. molo

    molo Member

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    1. There is 25 extra feet of it in the attic. IT supplys power to the water tank. Is this costing us more money in electriciity ($10, $50, $100 per year)?

    2. Can I the same single pole switch you use for 12/2 lighting switch to provide a disconnect for the water heater at the heater? IT WILL be 10-2 going into the switch.

    3. Does a 240 volt heater have to be tied in to a 30 amp double pole breaker or can you use a 20 amp breaker?

    TIA<
    MoLo
  2. Cass

    Cass Plumber

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    The extra wire in the attic is not causing your heater to consume more energy.

    No you can't use a SP switch to kill power to the water heater.

    Use a non fused, 2 pole, quick disconnect, if you want something to kill power to the water heater without shutting the breaker. It can be located near the heater.

    The wire size determines the amperage of the breaker. 12/2 WG would use a 20A breaker 10/2 WG would take a 30A breaker 120V would use a SP breaker and 240V would use a DP breaker.

    The watt draw of the heater, which is based on the wattage of the elements, would determine the wire size needed.
    Last edited: Aug 11, 2007
  3. molo

    molo Member

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    Can the non-fused, 2-pole, quick disconnect be rated for 12 and 10 gauge wires?
  4. Bob NH

    Bob NH In the Trades

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    A 4500 Watt water heater requires 4500 Watts /240 Volts = 18.75 Amps.

    However, the National Electrical Code requires that continuous loads (A household water heater is defined as a continuous load.) may not exceed 80 percent of the capacity of the circuit. Therefore, you must have a circuit that has a capacity of at least 23.44 Amps.

    Standard circuits in common use are 20 Amp and 30 Amp. Therefore, it should have a 30 Amp breaker and #10 wire.

    That is not to say that it won't work with #12 wire and a 20 Amp breaker (It is drawing only 18.75 Amps.), but it will be in violation of the code.

    It would be very dangerous to use a standard light switch with a 240 Volt circuit because someone might think the circuit is turned off by the switch and get zapped when working on it because the other side of the circuit is hot.

    There are unfused 2-pole disconnects used with Air Conditioners that would work with a water heater.
  5. Cass

    Cass Plumber

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    I don't remember their amp rating but I believe it is over 30A
  6. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

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    Disconnected are not rated in wire size, they are rated in amperage. The lugs will have a conductor size range, but this is not the rating of the disconnect.

    Most small disconnected are either 30A or 60A.


    Also, yes, a single pole switch can be used to turn off a water heater. It CANNOT however be used as the required service disconnect.
  7. molo

    molo Member

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    Location:
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    is this the dconnect?

    is this it? this is for my well pump

    TIA,
    molo

    Attached Files:

  8. Bob NH

    Bob NH In the Trades

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    Yes........... .
  9. hj

    hj Moderator & Master Plumber Staff Member

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    disconnect

    Only you can tell, because only you can see where the wires are connected.
  10. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

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    Is what it? What is the question?
  11. molo

    molo Member

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    Location:
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    THIS DCONNECT IS FOR MY WELL PUMP, i"m wONDERING IF THIS IS THE KIND i nEED FOR MY WATER TANK

    tia,
    MOLO
  12. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

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    Yes?

    I don't think you'll find one like that but that one will work. A simple little 60A "pull-out" disconnect would be the easiest.
  13. Cass

    Cass Plumber

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    A single pole switch can not be used to turn off a 240v water heater.

    If the heater was 120v a quick disconnect should still be used in place of a sp switch, in my NSHO.
  14. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

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    Location:
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    Cass, please re-read my post. I think I clearly stated it cannot be used as a disconnect.
    For control purposes a SP switch most certainly can shut off a straight 240v load.
    Have you ever looked at the way the thermostats inside a water heater work??? They are SP.
  15. Cass

    Cass Plumber

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    Location:
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    Were talking about installing a sp switch outside of a W/H to cut 240v service to a W/H.

    You tell me how a SP switch shuts off both sides of a 240v circuit.
  16. jimbo

    jimbo Plumber

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    The point about a "switch" meaning a toggle switch mounted in a single gang box....is that you probably wont find one rated for the amps.

    I have seen some old 30 gallon heaters with 3500 watt elements, on 20 amp circuits. You could find a double pole switch rated at 20 amps, but I just wouldn't go there on a WH. Today, most 30's and all larger tanks are on at least 4500 watts, meaning 30 amp required. I don't think you will find a 30 amp rated toggle. This becomes a disconnect.

    The picture you posted is a disconnect, rated at 30 amps, cant tell if it is fused or not, but fused disconnect not required for a WH, as long as it is coming from a breaker.
  17. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

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    Location:
    NY State, USA
    Cass, I don't know how I can be any clearer. I am talking about TWO different things.

    First off, Molo is being quite ambiguous about this whole thing. Is he trying to shut off the water heater like a weekender would? Or does he want a service disconnect to work on the unit?

    A switch that cuts one leg of a 240v circuit will shut off that circuit. This is a CONTROL, NOT a disconnect.

    A two pole DISCONNECT will cut both legs and is required as a service disconnect. Many times the circuit breaker serves this purpose.

    A disconnect is not necessarily a switch, and a switch is not necessarily a disconnect.

    YES, there certainly are 30A single and double pole toggle switches that fit in standard device boxes, provided the box has enough room for the wiring.
  18. If you install a HD water heater which always has 4500 watt upper/lower elements on a 12/2 20 amp breaker, it will blow the breaker every single time.

    I always tell the customer that if you are supplying me with a HD electric water heater, better have 30 amp breaker in the panel.

    3 weeks ago,

    "Yeah home depot said that you all would come out and fix the water heater, they pay you for the call but I just installed it a few days ago and the breaker keeps tripping."

    "What size breaker?"

    "20"

    "Whelp, I'll tell you that you have too small of a wire running to your heater, you have to run 10-2 and 30 amp breaker and we collect from you the charges for our time....you take it up with home depot for reimbursement."

    "I've put a few of these in with no problems, just this one."

    "If you've been ignoring the fact you need a larger wire and circuit to operate these heaters, expect to have to go back to all of them and upsize the wire unless they catch on fire first. GOOD LUCK!!!"
  19. jimbo

    jimbo Plumber

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  20. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
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    Location:
    NY State, USA
    That switch is a welder starter switch. Very specialty.
    A Leviton 3031-2 is a 30A single pole toggle. A 3031-2 is a double pole toggle.
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