25 amp breaker for # 10 wire

[mtfallsmikey]

Musings from the house plumber....

Musings from the house plumber....

So you think a water heater will run for more than 3 hours as a norm? You know it should say the water heater not the water---

Looks like 422.11 does not differentiate between commercial and residential heaters....take a restaurant situation....a 120 gal. HWH could run continuously when used with a commercial dishwasher in a high-volume situation, but in a residential situation, a 50 gal. electric heater has about 20-25 gal. drawdown capacity.....

 

[jetlag]

So you think a water heater will run for more than 3 hours as a norm? You know it should say the water heater not the water---

I probally wouldnt say its the norm but there a lot that do with large family with washer and dishwasher going . I can see where code needs to cover itself. And as mentioned commercial is included in that to. But that wasnt the point I was making , I was saying water doesnt have to run continious for the the load to be continuous

 

[Npstewart]

If it came to it, wouldn't you just have to replace (or) confirm the elements in the heaters have enough Resistance to operate at 4500W?

 

[Dennis Alwon]

I was saying water doesnt have to run continious for the the load to be continuous

I know -- you are getting back at me for being an ass.... I deserve it. I sometimes think way ahead of my typing and didn't type "heater"-- but you knew that....

 

[Dennis Alwon]

As an inspector, I'm not sure it provides adequate basis to turn down an installation of this water heater supplied by a 208 volt, 30 amp circuit using #10 conductors.

So if the OCP is not marked on the heater but the voltage and wattages are then you think that 422.11(E)(3) should be ignored. First you want to use the nameplate then when it is marked with the voltage and wattage for 208 you want to ignore it. I am trying to understand why you think this is not enforceable. It is clear if the unit is marked for 208V then the unit cannot have OCPD more than 25 amps.... What am I missing?

 

[eprice]

So if the OCP is not marked on the heater but the voltage and wattages are then you think that 422.11(E)(3) should be ignored. First you want to use the nameplate then when it is marked with the voltage and wattage for 208 you want to ignore it.

422.11(E)(3) uses the term rated current. The NEC does not have a definition for rated current. I googled that term and came up with this definition from answers.com: "The current that an electrical device can carry, under specified conditions, without resulting in overheating or mechanical overstress." I guess that's not an official definition, but it is best definition I can find.

So, what is the rated current of the water heater? It seems clear from the information on the name plate that it can handle at least 18.75 amps without overheating or mechanical overstress. The fact that it only produces 3380 watts of heating at 208 volts does not change that fact. I believe that 18.75 amps is the rated current that should be used when applying 422.11(E)(3)

I am trying to understand why you think this is not enforceable. It is clear if the unit is marked for 208V then the unit cannot have OCPD more than 25 amps.... What am I missing?

Your conclusion is not clear based on 422.11(3) unless you can show a definition of "rated current" different that the one I found. Or are you saying that if only 208 volts is supplied to the water heater a current of 18.75 amps will now cause the water heater to overheat or experience mechanical overstress?

 

[Dennis Alwon]

Your conclusion is not clear based on 422.11(3) unless you can show a definition of "rated current" different that the one I found.

I simple think if we have a unit at 208V and the wattage at 3380 we can do simple math to get the current. If the unit is rated for 208V and rated for 3380 watts then I gues the rated current is 3380/208 = 16.25.

Again, I don't think it makes a difference but that is the way I read the article. We can argue this all day but it seems clear to me, obviously you need more clarity or something more than is there. I would install a 25 amp breaker and be done with it. And I am done with this thread.... We are both reiterating the same stuff.

Or are you saying that if only 208 volts is supplied to the water heater a current of 18.75 amps will now cause the water heater to overheat or experience mechanical overstress?

No I am not saying that at all.

 

[eprice]

I simple think if we have a unit at 208V and the wattage at 3380 we can do simple math to get the current. If the unit is rated for 208V and rated for 3380 watts then I gues the rated current is 3380/208 = 16.25.

Again, I don't think it makes a difference but that is the way I read the article. We can argue this all day but it seems clear to me, obviously you need more clarity or something more than is there. I would install a 25 amp breaker and be done with it. And I am done with this thread.... We are both reiterating the same stuff.

No I am not saying that at all.

Fine, we can agree to disagree on this one