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-   -   Water heater, receptacle, and panel questions (https://www.askmehelpdesk.com/showthread.php?t=297485)

  • Dec 31, 2008, 10:50 AM
    Labor
    Water heater, receptacle, and panel questions
    I have a 4500/4500 watt standard water heater. The upper and lower heating elements fire in sequence. THEY DO NOT FIRE SIMULTANEOUSLY. I ran 10/2 and hooked it up to a double pole 30 amp breaker (which is plugged into an UNpowered panel) as the heater requires 240 volts. I have not powered up the water heater yet because I still need to finish the plumbing. I just want to confirm that this wiring is OK. If not, please let me know what is wrong.

    Also, I have 6 can lights and one ceiling fan on a 20 amp circuit (12/2), each light draws 65 watts and the fan draws 75 watts. I would also like to power a number of 15 amp plug receptacles on the same circuit. I cannot find any limitations in the code regarding the number of receptacles I can hook up to the circuit. Can anyone tell me what, if anything, the code says on this? If the Code says nothing on this, can anyone tell me what a good rule of thumb would be for keeping things safe?

    Lastly, I have 200 amp service. This may be a very stupid question, but I've got to ask it before I have the inspection done. When added up, must the amp ratings on all of the breakers total 200 or less?

    Thanks for any help you can offer.
  • Dec 31, 2008, 11:18 AM
    stanfortyman
    Quote:
    Originally Posted by Labor View Post
    I have a 4500/4500 watt standard water heater. The upper and lower heating elements fire in sequence. THEY DO NOT FIRE SIMULTANEOUSLY. I ran 10/2 and hooked it up to a double pole 30 amp breaker (which is plugged into an UNpowered panel) as the heater requires 240 volts. I have not powered up the water heater yet because I still need to finish the plumbing. I just want to confirm that this wiring is OK. If not, please let me know what is wrong.
    10/2 is completely typical to use for a residential electric water heater.



    Quote:
    Originally Posted by Labor View Post
    Also, I have 6 can lights and one ceiling fan on a 20 amp circuit (12/2), each light draws 65 watts and the fan draws 75 watts. I would also like to power a number of 15 amp plug receptacles on the same circuit. I cannot find any limitations in the code regarding the number of receptacles I can hook up to the circuit. Can anyone tell me what, if anything, the code says on this? If the Code says nothing on this, can anyone tell me what a good rule of thumb would be for keeping things safe?
    There is no limit on the number of these items you are describing. We simply use common sense. Typically I will keep it to 8-12 items on a circuit. If I am doing just recessed lighting that number goes way up.
    Combined lighting and receptacles I'd keep it to 5-6 receptacles depending on their expected use.




    Quote:
    Originally Posted by Labor View Post
    Lastly, I have 200 amp service. This may be a very stupid question, but I've got to ask it before I have the inspection done. When added up, must the amp ratings on all of the breakers total 200 or less?
    The sum of the breaker is a totally meaningless number.
  • Dec 31, 2008, 11:28 AM
    Labor
    Quote:
    Originally Posted by stanfortyman View Post
    10/2 is completely typical to use for a residential electric water heater.

    Stanfortyman, thank you for your help. Is the 30 amp double pole breaker appropriate?


    There is no limit on the number of these items you are describing. We simply use common sense. Typically I will keep it to 8-12 items on a circuit. If I am doing just recessed lighting that number goes way up.
    Combined lighting and receptacles I'd keep it to 5-6 receptacles depending on thier expected use.




    The sum of the breaker is a totally meaningless number.
    So I do not have to worry about matching the sum of all the breakers to the total number of amps supplied to the house?
  • Dec 31, 2008, 11:32 AM
    stanfortyman
    Quote:
    Originally Posted by Labor View Post
    So I do not have to worry about matching the sum of all the breakers to the total number of amps supplied to the house?
    No, not even close.
    It is not at all uncommon to have 600-800 amps (or more) worth of breakers in a 200 amp panel.
  • Dec 31, 2008, 11:52 AM
    Tev

    Did the water heater instructions tell you to use a 30 amp breaker? I ask because for that wattage 25 amp would seem the right choice. If it does specify 30 then you are fine but if not you should use a 25.

    As for receptacles, Stan is pretty close to what I would do so go by that.

    The breakers in a panel will add up to more than the main breaker size in many installations. It's not something to worry about.
  • Dec 31, 2008, 11:59 AM
    stanfortyman
    Quote:
    Originally Posted by Tev View Post
    Did the water heater instructions tell you to use a 30 amp breaker? I ask because for that wattage 25 amp would seem the right choice. If it does specify 30 then you are fine but if not you should use a 25.
    May I ask why? The ONLY time I have ever seen a 25 used was in a modular home. EVERY other 4500 watt water heater I have seen or wired has been on a 30A circuit.
    The breaker is not protecting the unit, it is protecting the wire.
  • Dec 31, 2008, 12:46 PM
    Labor
    Quote:
    Originally Posted by stanfortyman View Post
    No, not even close.
    It is not at all uncommon to have 600-800 amps (or more) worth of breakers in a 200 amp panel.
    Thanks for all your help stan.
  • Jan 1, 2009, 11:07 PM
    Tev
    Stan, I am guilty of letting my own opinion on this influence my advice.

    A 30 amp breaker on a 4500 Watt water heater is fine and within code as long as the manufacturer instructions don't call for a different size. However, I prefer 25 amp for this wattage.

    My reasoning is that although the breaker in this case can be 150% of the rated current and then up-sized to the next available breaker size if it doesn't correspond to a standard size, it is unnecessary to go over 150% in this case. A 25 amp breaker is big enough, so why go bigger if you don't have to?

    It may very well be that every 4500 watt water heater you've worked on has had a 30 amp, but some (including the one in my home) require a 25 amp per the manufacturer. Which is where my question about the instruction manual comes in. If it says 30 then I use 30, if it doesn't specify a size I use the smallest breaker I can for the load, which is 25 amp in this case.
  • Jan 2, 2009, 04:42 AM
    stanfortyman
    Quote:
    Originally Posted by Tev View Post
    My reasoning is that although the breaker in this case can be 150% of the rated current and then up-sized to the next available breaker size if it doesn't correspond to a standard size, it is unnecessary to go over 150% in this case. A 25 amp breaker is big enough, so why go bigger if you don't have to?
    Because a 25 is an odd size. This and A/C are about the only times I would use one, and in every case a 30 works just the same. Like I said, the breaker is protecting the wire, not the unit, so there is absolutely no safety issue at all.
    A manufacturer requirement? That is another story.



    Quote:
    Originally Posted by Tev View Post
    It may very well be that every 4500 watt water heater you've worked on has had a 30 amp, but some (including the one in my home) require a 25 amp per the manufacturer.
    I have to say again, it's not just that that's all I install, I have never in all my years seen this from a typical 4500 watt unit.
    If you say yours required it I don't doubt you though.

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