# water heater question



## BuzzKill (Oct 27, 2008)

Got a 3 phase water heater name plated at 50 amps and run with #8 wire, however the wires are pretty darn hot; considering a WH is a continuous load as per 422.13, does it say anywhere in the code that I can safely upsize the breaker and wire to a 60amp and #6?


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## jwjrw (Jan 14, 2010)

BuzzKill said:


> Got a 3 phase water heater name plated at 50 amps and run with #8 wire, however the wires are pretty darn hot; considering a WH is a continuous load as per 422.13, does it say anywhere in the code that I can safely upsize the breaker and wire to a 60amp and #6?



I don't think so. Why not just upsize conductor? You can always pigtail "8 on to the #6.


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## BuzzKill (Oct 27, 2008)

jwjrw said:


> I don't think so. Why not just upsize conductor? You can always pigtail "8 on to the #6.


the load is pulling 48 amps as it is...upsizing the conductors sounds like an idea.


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## jwjrw (Jan 14, 2010)

BuzzKill said:


> the load is pulling 48 amps as it is...upsizing the conductors sounds like an idea.




Was the 50A on nameplate already at 125%?


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## BuzzKill (Oct 27, 2008)

jwjrw said:


> Was the 50A on nameplate already at 125%?


no but after doing the math I can go up to #6 and a 60amp breaker, it looks like..wait a minute, according to 422.11(a) (1), I can't go over the nameplate rating of 50amps.


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## MDShunk (Jan 7, 2007)

If your only reason for throwing money at that water heater installation would be that the wires are hot, stop right there. Conductors can compliantly be pretty hot. That said, what is the conductor type? How hot is hot?


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## BuzzKill (Oct 27, 2008)

MDShunk said:


> If your only reason for throwing money at that water heater installation would be that the wires are hot, stop right there. Conductors can compliantly be pretty hot. That said, what is the conductor type? How hot is hot?


actually I don't know how hot, I am TSing for a friend in the field!...if they are 90C thhn, that's pretty f'n hot. He can keep his hand on them only for so long...?


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## MDShunk (Jan 7, 2007)

Probably something he ought to measure. 90c is something like 190f

If it's romex, by the way, you can't really use #8 for 50 amp, but you probably already knew that.


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## pacificlp (Oct 23, 2010)

#8 is good for only 40 amps


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## jwjrw (Jan 14, 2010)

pacificlp said:


> #8 is good for only 40 amps




No #8 Romex is only good for 40amps. Thhn is good for 50amps.:thumbsup:


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## electricalperson (Jan 11, 2008)

when wire reaches its max ampacity it does get very warm. id just upsize the conductor. did you measure the amps with a amprobe?


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## electricalperson (Jan 11, 2008)

dont forget to derate for the terminals on the breaker and if there is terminals on the water heater. either 70c or 60c


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## nitro71 (Sep 17, 2009)

Is the 50 amps the min circuit ampacity or just the water heater rating?


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## pacificlp (Oct 23, 2010)

number 8 wire is only good for 40 amp no matter what, romex or thhn because it's under 100 amp. the rating of the wire is based on the terminals of the breaker, under 100 amp circuit you always use the tw scale but you can use the thhn scale when derating for voltage drop.
it's a common mistake most electricians make. any breaker under 100 amps will have a rating of 60C, which is the tw scale, above 100 is 90C. it wasn't until i worker for an electrical engineer for 4 years i learned this.


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## Southeast Power (Jan 18, 2009)

BuzzKill said:


> no but after doing the math I can go up to #6 and a 60amp breaker, it looks like..wait a minute, according to 422.11(a) (1), I can't go over the nameplate rating of 50amps.


 I really dont see why you couldn't put #4 on a 50 amp breaker if you wanted.
Did I misread your post??


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## McClary’s Electrical (Feb 21, 2009)

pacificlp said:


> number 8 wire is only good for 40 amp no matter what, romex or thhn because it's under 100 amp. the rating of the wire is based on the terminals of the breaker, under 100 amp circuit you always use the tw scale but you can use the thhn scale when derating for voltage drop.
> it's a common mistake most electricians make. any breaker under 100 amps will have a rating of 60C, which is the tw scale, above 100 is 90C. it wasn't until i worker for an electrical engineer for 4 years i learned this.


 

You're full of it. I've got all kinds of 60/75 rated breakers that are under 100


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## Bob Badger (Apr 19, 2009)

pacificlp said:


> number 8 wire is only good for 40 amp no matter what, romex or thhn because it's under 100 amp. the rating of the wire is based on the terminals of the breaker, under 100 amp circuit you always use the tw scale


That is false.




> any breaker under 100 amps will have a rating of 60C,


No, most modern breakers will be marked 60/75.



> above 100 is 90C.


False, you will not find any breakers under 600 volts that have a 90 C rating, they will be marked 75C.



> it wasn't until i worker for an electrical engineer for 4 years i learned this.


That engineer needs to hit the books.


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## Dennis Alwon (May 9, 2009)

pacificlp said:


> it's a common mistake most electricians make. any breaker under 100 amps will have a rating of 60C, which is the tw scale, above 100 is 90C. it wasn't until i worker for an electrical engineer for 4 years i learned this.


I am afraid this is a mistake many electrician can make but also an incorrect assessment by the engineer you worked for.

Look at 110.14(C) in the NEC and you will see exceptions which allow circuits 100 amps or less to be used at 75C. Since almost all equipment today have terminals rated 75C then we can use the 75C column. 

We cannot use the 90C except for derating as there really isn't any (many) pieces of equipment that are rated 90C. Thus 75C is the common column used unless we are limited by NM cable and other factors.


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## Dennis Alwon (May 9, 2009)

Buzz if the nameplate is 50 amps then you annot use an OCPD more than the nameplate as I read 422.11(E) however you can upsize the wire which probably should be done if there is any long distance involved in the run. 

It is okay for wires to get hot as long as it isn't hotter than the temp. they are rated for.


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## pacificlp (Oct 23, 2010)

Bob Badger said:


> That is false.
> 
> *"read what is written on the breaker itself. all breakers at marked 60/75C. look next to the strip guide (the amount of insulation to remove) on the side of the breaker, all square d breakers, old zinscos and other are molded with "40C" written on the breaker, not on the paper label. since the terminal screw is only rated for 40C the wire size must match.
> 
> ...


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## jwjrw (Jan 14, 2010)

pacificlp said:


> Bob Badger said:
> 
> 
> > That is false.
> ...


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## Bob Badger (Apr 19, 2009)

40C is the maximum ambient temperature that breaker is listed for.


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## Bob Badger (Apr 19, 2009)

From the UL marking guide



> 60/75°C Wire — All circuit breakers rated 125 A or less are marked for use with 60° C,
> 60/75°C or 75°C only wire. This marking indicates the proper wire size for termination in
> accordance with Table 310.16 of the NEC . It is acceptable to use wire with a higher
> insulation rating if the ampacity is based on the wire temperature rating marked on the
> ...





> 40°C — A thermal-magnetic circuit breaker that is suitable for use in ambients up to 40°C is
> marked “40°C.” Circuit breakers with electronic type trip units are not affected by the ambient
> temperature and are not required to be marked to indicate the suitability. These devices may
> be used in 40°C ambients unless marked 25°C.


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## McClary’s Electrical (Feb 21, 2009)

pacificlp said:


> Bob Badger said:
> 
> 
> > That is false.
> ...


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## nitro71 (Sep 17, 2009)

pacificlp said:


> Maybe i'm wrong, maybe the engineer i worked for is wrong, maybe all the inspectors i've worked with are wrong, maybe...


Problem is that you're basing your knowledge on the monkey see, monkey do method. If you think you're correct crack open the code book and prove it.


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## pacificlp (Oct 23, 2010)

nitro71 said:


> Problem is that you're basing your knowledge on the monkey see, monkey do method. If you think you're correct crack open the code book and prove it.



Art 210-24 summary


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## pacificlp (Oct 23, 2010)

Bob Badger said:


> From the UL marking guide


thanks for that. please read art210-24 summary and let me know how you interrupt that.


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## nitro71 (Sep 17, 2009)

I had some time to dig back into this one.. I'm not so sure that the 50 amps that is on the device is a protective device rating. After reading 422.11(A) to me it has to be labeled like an AC with min/max numbers for it to apply. Same for 422.11(E)(1). So given the tidbits of info we have I'd size the conductors for 125% of the load. #6 THHN and you could put a 70 amp breaker on it.


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## Dennis Alwon (May 9, 2009)

pacificlp said:


> thanks for that. please read art210-24 summary and let me know how you interrupt that.


I am not following what this section has to do with temp rating of the wire or are you on to something else?


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## Dennis Alwon (May 9, 2009)

nitro71 said:


> After reading 422.11(A) to me it has to be labeled like an AC with min/max numbers for it to apply. Same for 422.11(E)(1). So given the tidbits of info we have I'd size the conductors for 125% of the load. #6 THHN and you could put a 70 amp breaker on it.


Where are you getting this info from. 422.11(E) says nothing about needing min/max numbers. It simply states in (1) that the OCPD does not exceed that marked on the appliance.


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## nitro71 (Sep 17, 2009)

What would 422.11(E)(3) mean if (1) says that you just take any amperage value on the nameplate and don't exceed it? To me (3) says that if I just have an amperage rating on the appliance I can size my overcurrent protection to 150%. Why do you need (3) if you never exceed whatever is marked on the appliance per (1)?


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## Dennis Alwon (May 9, 2009)

nitro71 said:


> What would 422.11(E)(3) mean if (1) says that you just take any amperage value on the nameplate and don't exceed it? To me (3) says that if I just have an amperage rating on the appliance I can size my overcurrent protection to 150%. Why do you need (3) if you never exceed whatever is marked on the appliance per (1)?


That's a good question and the answer is when the appliance doesn't have a nameplate then (3) may be needed. It even states *"if the OCP rating is not marked and the appliance is rated over 13.3 amps"* However if the appliance has a nameplate you are good to go.


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## nitro71 (Sep 17, 2009)

I agree that if the OCP rating is on the appliance there aren't any questions about sizing for it. Of course I would size off that if it was available. So will every appliance have a OCP rating on it? Or is it posbible that the hot water tank just came stamped with 50 amps load? Seems suspect as it is pulling 48 amps. I would expect a hot water tank that pulls 48 amps to have a min conductor size rated for 60 amps as it's considered a continous load. I enjoy picking this stuff apart, never know when I might be connecting one.


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## Dennis Alwon (May 9, 2009)

nitro71 said:


> So will every appliance have a OCP rating on it? Or is it posbible that the hot water tank just came stamped with 50 amps load?


Most water heaters that I have wired have wattage & voltage not the OCP on the nameplate


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## Dennis Alwon (May 9, 2009)

(3) is why you can put a 30 amp breaker on a standard resi water heater.

4500/240=18.75
18.75 x 1.25 = 23.4

Now one could think that a 25 amp breaker is required but (3) allows us to use 150% of the rated current

18.75*1.5= 28.125 (3) also states we can go to the next higher breaker.

So, in fact we can have either a 25 or 30 amp breaker on this circuit with #10 wire.


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## nitro71 (Sep 17, 2009)

Wouldn't the same logic apply to Buzz's problem? 125% of 50amps...


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## Dennis Alwon (May 9, 2009)

nitro71 said:


> Wouldn't the same logic apply to Buzz's problem? 125% of 50amps...


Buzz said the nameplate was 50 amps thus 50 amps is as big a OCPD as you can install. Now you can use a larger wire without any issues except for perhaps 250.122(B)


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## JohnR (Apr 12, 2010)

To the OP, you may also want to check that someone has not replaced the elements with ones larger than original values. 
I suppose however, that if the breaker is not tripping, this would not be the case. But then there are those guaranteed nevertrips we find around.


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## Bob Badger (Apr 19, 2009)

Dennis Alwon said:


> Buzz said the nameplate was 50 amps thus 50 amps is as big a OCPD as you can install. Now you can use a larger wire without any issues except for perhaps 250.122(B)



Dennis, Buzz never said the label stated 50 amp OCP.

Without having seen the label I think we are all guessing.


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## MDShunk (Jan 7, 2007)

In my mind, the whole exercise is moot until we figure out exactly how hot "hot" is. Seems like some times has passed, so it's probably already sorted out.


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## Dennis Alwon (May 9, 2009)

Bob Badger said:


> Dennis, Buzz never said the label stated 50 amp OCP.
> 
> Without having seen the label I think we are all guessing.


You may be right but 422.11(C)(E) states


> (E) Single Non–motor-Operated Appliance. If the branch circuit supplies a single non–motor-operated appliance, the rating of overcurrent protection shall comply with the following:
> (1) *Not exceed that marked on the appliance.*


Does that mean the OCPD that is marked on the unit or the amps marked on the unit? I took it to be the marking on the unit. Buzzkill said 50 amps.


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## Dennis Alwon (May 9, 2009)

I have been thinking about this section again and it seems to me that if the appliance is rated max. ocpd then there is no need for 422.11(E)(1). So the question is if the unit is marked min. cir. ampacity we would assume the 125% is involved but then why would we be limited to 125% on the breaker size. I guess I have never seen a water heater marked with max OCPD. I don't know what to say on this. :icon_confused:


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## frenchelectrican (Mar 15, 2007)

This part will not be excatally off topic but simauir track but I did recalled in the NEC codé book about the heating element circuits limitation it did stated 42 or 48 amp max before it can subpair it.

I know it was in Mid 300's in the NEC but were there couple more spot which I did miss it ??

Merci,
Marc


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## HARRY304E (Sep 15, 2010)

frenchelectrican said:


> This part will not be excatally off topic but simauir track but I did recalled in the NEC codé book about the heating element circuits limitation it did stated 42 or 48 amp max before it can subpair it.
> 
> I know it was in Mid 300's in the NEC but were there couple more spot which I did miss it ??
> 
> ...


Its in the mid 400's


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## frenchelectrican (Mar 15, 2007)

HARRY304E said:


> Its in the mid 400's


 
Crap., I miss 100 cents so I have to own ya 100 cents 

Merci,
Marc


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## HARRY304E (Sep 15, 2010)

frenchelectrican said:


> Crap., I miss 100 cents so I have to own ya 100 cents
> 
> Merci,
> Marc


 :laughing::laughing:


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