# Hot water heater Breaker????



## Bigbobdallas

What is the recommended breaker size for the hot water heater


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## Gary_602z

If electric normally 30 amp. Do you have your instructions? It may say on the side of it also.

Gary


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## InPhase277

Bigbobdallas said:


> What is the recommended breaker size for the hot water heater


How many watts? Your average residential 30 or 40 gallon water heater is 4500 watts and usually goes on a 30 A breaker.


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## Gigs

The wire size of the circuit feeding it determines the breaker amps, not the water heater itself. Come on guys.


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## Bigbobdallas

*Wire size*

Ok if it is the wire size then. What wire size should I have cominy to the heater?


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## Bigbobdallas

*Wire size*

Ok if it is the wire size then. What wire size should I have coming to the heater?:thumbsup:


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## jerryh3

Depends on the heater. We need a little more info. Nameplate rating, model number, ... A "standard" water heater would be a 30A breaker on 10/2 wire.


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## Termite

Gigs said:


> The wire size of the circuit feeding it determines the breaker amps, not the water heater itself. Come on guys.


Huh? The appliance manufacturer specifies the circuit ampacity, the appropriate breaker is installed, and the necessary wire size is installed based on the circuit ampacity. By your statement, he could theoretically use #14 wire and a 15 amp breaker on his water heater...And although I know that's not what you meant, it illustrates the point. 

Bigbobdallas, check your water heater's manual or download the model's information from the manufacaturer's website. #10 wire and a 30 amp breaker is pretty common for residential water heaters, but not in every case. If you can't find that, provide the wattage information and as Inphase277 suggested, we can get you right in the ballpark.


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## Bigbobdallas

*Breaker gets hot and flips*

Thanks for all the info. When I get home tonight I will check this out.

I am not sure what it is but here in the last three or four days it has been flipping off ever so often and wife says it is hot.


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## Wethead

What brand of water heater is it?


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## Termite

Then it is doing its job! :thumbsup: Sounds to me like your breaker is undersized, which leads me to believe that there's possibly a wire size issue as well. Is it a new water heater???


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## Bigbobdallas

*At Work*

At the present time I can't remember. It is about 1 yr old and can't remember sorry.


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## Gigs

thekctermite said:


> Huh? The appliance manufacturer specifies the circuit ampacity, the appropriate breaker is installed, and the necessary wire size is installed based on the circuit ampacity.


Yes, yes, but for all we knew he was eyeballing a 12/3 wire that ran near his water heater. I think it's an important distinction to make sure people understand the wire gauge determines the maximum overcurrent protection you can use. It may seem basic to us but maybe not to everyone asking questions here.


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## Termite

I just don't want it to be convoluted into making the OP think that any wire is fine as long as the breaker is sized to for it. That's a backwards approach that could easily lead to dangerous mistakes. Start with the appliance and work toward the panel and you can't go wrong.


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## micromind

Is this water heater a replacement for an older one? If so, the breaker and wire might be too small. 

Years ago, it was not uncommon to have a 3000 or 4000 watt water heater fed with #12's and a 20 amp breaker. This was fine for these heaters, but most modern heaters are 4500 watts. They will trip a 20 amp breaker, and if a 30 is installed using existing wire, it'll eventually burn up the wire and likely start a fire. 

A 4500 watt heater needs #10's and either a 25 or 30 amp breaker.

Rob


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## Stubbie

Gigs said:


> The wire size of the circuit feeding it determines the breaker amps, not the water heater itself. Come on guys.


Nope not for a 240 volt water heater.... by your analysis a 4500 watt hot water heater less than 120 gallons would be serviced by 12 awg copper conductors and a 20 amp breaker. Not all equipment is subject to a breaker equaling the wire size ampacity. So you cannot make a blanket statement of that nature. In this case you need to know the characteristics of the load and the appliance type. If he was looking a 12 AWG romax and a 20 amp breaker he would think everything is fine, when it is not. 

4500 watts at 240 volts is 18.75 amps so if he had 12 awg copper on an individual circuit under your analysis he would be fine but the appliance requires 25 amp conductors minimum and either 25 amp breaker or a 30 on 10 awg copper.


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## handyman78

thekctermite said:


> Then it is doing its job! :thumbsup:


Hey KC, better watch out- You might recall the last time (in Nov) I made a statement like that the post went on forever! :whistling2:


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## Termite

handyman78 said:


> Hey KC, better watch out- You might recall the last time (in Nov) I made a statement like that the post went on forever! :whistling2:


Nah, no need for me to step lightly around that statement. If the breaker is tripping, it is reasonably safe to say it is doing its job. :yes:


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## jbfan

thekctermite said:


> Nah, no need for me to step lightly around that statement. If the breaker is tripping, it is reasonably safe to say it is doing its job. :yes:


Agreed! This info might have helped if it was stated in the opening post!


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## Yoyizit

Bigbobdallas said:


> says it is hot


Loose connection at breaker?

How hot?
"Burned in 30 seconds by 54°C, 5 sec. @ 60°C, 1 second @ 71°C."
No burn in 8 hrs. at 43°C. 
Less than 40°C probably feels cool to the touch.

Anyone know the rise-above-ambient for a breaker carrying rated current? I doubt it is 24°C.


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## InPhase277

Yoyizit said:


> Loose connection at breaker?
> 
> How hot?
> "Burned in 30 seconds by 54°C, 5 sec. @ 60°C, 1 second @ 71°C."
> No burn in 8 hrs. at 43°C.
> Less than 40°C probably feels cool to the touch.
> 
> Anyone know the rise-above-ambient for a breaker carrying rated current? I doubt it is 24°C.


Don't know right off hand. But I do know that any breaker carrying at or near its rated current will heat up significantly. Most breakers are 40 C, meaning they will maintain their thermal trip characteristics til that point, I think...

I have seen breakers in outdoor enclosures go way over their rated capacity because it was below freezing outside. There was a 20 A breaker with 32 A continuous, without tripping. I changed it for a new one, and almost the same thing. At any rate we had to reduce the load.


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## Yoyizit

InPhase277 said:


> any breaker carrying at or near its rated current will heat up significantly. Most breakers are 40 C, meaning they will maintain their thermal trip characteristics til that point, I think...
> 
> I have seen breakers in outdoor enclosures go way over their rated capacity because it was below freezing outside. There was a 20 A breaker with 32 A continuous, without tripping. I changed it for a new one, and almost the same thing. At any rate we had to reduce the load.


I'll have to e-mail Square D or Cutler Hammer and ask, if they'll talk to me at all.

20 A squared = 400, 32 A squared ~1000, so this breaker had 2.5x the normal temp-rise-above-ambient for the thermal part, without tripping.
The NEC must know about this (?) and probably takes it into account. I guess they figure the wire is also colder, so the insulation is still below max temp.

Maybe the local codes for Alaska tweak these numbers a little.

Another way to figure this is max 30mV across closed, good contacts at rated current. At 30A this would be about 1w, and that won't heat something as large as a breaker. 
For the thermal trip part they may have a 10w resistor in there. I'll have to take one apart sometime.

_And so I did take one apart and found a mysterious component in it, which measured "zero" ohms on my meter. _
_10w at 20A is 25 mΩ, so I'll have to find some other way to measure this supposed resistor._

Rev A
Below 36°C probably feels cool to the touch
no burn @42°C
burned in: 
30 seconds @ 54°C, 
5 sec. @ 60°C, 
1 second @ 71°C.

With the aid of some rum & coke, the internal resistor of a Square D Q0 breaker comes in at 4.4 mΩ. 20A through this gives ~2w to heat up their bimetallic mechanism. 2w dissipated in a plastic case with a surface area as big as a breaker can't get very warm.

I don't know why the breaker you mentioned was hot at rated current, based on what I measured.


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## Gigs

Stubbie said:


> 4500 watts at 240 volts is 18.75 amps so if he had 12 awg copper on an individual circuit under your analysis he would be fine


That was not what I was saying. 

I just said the wire size determines the maximum breaker size. If you disagree with this then we have bigger problems.


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## Stubbie

Gigs said:


> That was not what I was saying.
> 
> I just said the wire size determines the maximum breaker size. If you disagree with this then we have bigger problems.


I certainly disagree if your saying this is always the case.


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## Termite

Gigs said:


> I just said the wire size determines the maximum breaker size. If you disagree with this then we have bigger problems.


Your methodology is 100% backwards and in conflict with basic electrical system design practices. Wire size is determined by the breaker ampacity. The ampacity of the specific circuit is determined for you by code or by the appliance manufacturer's requirements, and you pull the correct size of wire accordingly.


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## Gigs

thekctermite said:


> Wire size is determined by the breaker ampacity.


If you were pulling a new run then it might seem backward to say that the wire dictates the maximum breaker ampacity, but we are talking about an existing run in this thread.

It's just two different ways to say the same thing:


Breaker ampacity determines minimum wire size
(Smallest) wire size determines maximum breaker ampacity.


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## Stubbie

I realize we are all bored here but wire size does not dictate breaker size in all cases. In this case we are serving a hot water tank...storage type.... so if the existing branch circuit breaker conductors are 12 awg copper then the maximum breaker is 20 amps. So I would agree that looking at an existing run of lets say 12/2 awg romax serving a hot water tank then 12 awg copper would dictate a maximum 20 amp circuit breaker.
What I am saying is that this is not always the case for maximum circuit breaker depending on what equipment or appliance the branch circuit serves exiting run or not. A 20 amp breaker on 12 awg copper romax is not necessarrily the maximum breaker size. I could put it on a 30 amp breaker.


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## kbsparky

> ... A 20 amp breaker on 12 awg copper romax is not necessarrily the maximum breaker size. I could put it on a 30 amp breaker....


In some cases, yes. Like with an A/C unit or other motor load.

In the case of a water heater (which is the topic of this thread), then no you are not allowed to use a 30 Amp breaker on a #12 wire.

For those who are lurking here, let's point out that a 4500 watts for a water heater circuit is considered to be a _continuous load _and as such has to be figured with a 125% multiplier. 18.75Amps x 125% = 23.43 Amps. 

This translates to:

Minimum Circuit Ampacity = 25 Amps.​-- and --

Maximum overcurrent protection = 30 Amps.

Many new manufactured homes come equipped with a #10 wire connected to a 25 Amp breaker for a 4500 watt water heater.




​


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## Stubbie

kbsparky said:


> In some cases, yes. Like with an A/C unit or other motor load.
> 
> In the case of a water heater (which is the topic of this thread), then no you are not allowed to use a 30 Amp breaker on a #12 wire.
> 
> For those who are lurking here, let's point out that a 4500 watts for a water heater circuit is considered to be a _continuous load _and as such has to be figured with a 125% multiplier. 18.75Amps x 125% = 23.43 Amps.
> 
> This translates to:
> 
> Minimum Circuit Ampacity = 25 Amps.​-- and --
> 
> Maximum overcurrent protection = 30 Amps.
> 
> Many new manufactured homes come equipped with a #10 wire connected to a 25 Amp breaker for a 4500 watt water heater.
> ​



Thanks for saving me the typing....that is exactly where I was going.


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## Bigbobdallas

*Thanks All*

Went and got me a new breaker and it is working great. Thanks for all the info. By the way it had a gas hot water heater and I ran a 220 from the main and put into a small breaker box and then put a 30 amp to the new Hot Water heater. But any how it is working OK now after two days.


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## Yoyizit

Bigbobdallas said:


> Went and got me a new breaker and it is working great.


So the hot breaker was actually bad,
or during installing the new breaker bad connections were tightened up in which case reinstalling the old breaker would have worked, also.

All's well that ends well.


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## Gigs

Bigbobdallas said:


> Went and got me a new breaker and it is working great. Thanks for all the info. By the way it had a gas hot water heater and I ran a 220 from the main and put into a small breaker box and then put a 30 amp to the new Hot Water heater. But any how it is working OK now after two days.


What size wire did you use?


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## old dutchman

*Breaker trips*



Bigbobdallas said:


> Went and got me a new breaker and it is working great. Thanks for all the info. By the way it had a gas hot water heater and I ran a 220 from the main and put into a small breaker box and then put a 30 amp to the new Hot Water heater. But any how it is working OK now after two days.


Did you check if the lower Heat tube is good. Do you have soft water,or could you have a deposit on the lower unite grounding out?


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