Water heater

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hhsting

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277V 4.5kw single phase water heater has branch breaker of 30 amps. Full load is 16.2x1.25=20.3A or 16.2x1.5=24.3. Next highest both cases is 25A.

Is 30A big?

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You are correct, I didn't do the math and saw your 24,3
25 amp would be the acceptable overcurrent device
 
Another one of those things. I'm no engineer; just an electrician that's worked on houses of every age in southern NV for 25 years. EVERY tank electric water heater is on a 30A breaker. And 4500W is the normal element size.
 
MAC702 said:
Another one of those things. I'm no engineer; just an electrician that's worked on houses of every age in southern NV for 25 years. EVERY tank electric water heater is on a 30A breaker. And 4500W is the normal element size.
Click to expand...
4500 w on 30A but what voltage and phase you see this on?

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hhsting said:
4500 w on 30A but what voltage and phase you see this on?
Click to expand...

I do residential service work mostly, 240V single-phase. EVERY such water heater and dryer is a 30A ckt. I guess it's another of those things where the entire state does it wrongly again.

Maybe we have state amendments that are allowing cord-and-plug furnaces and 30A ckts for water heaters. I must admit I've never tried to engineer either, and just use my 25 years of experience to wire them the same. This thread has been another very interesting one for me.

No, I'm not going to start stocking 25A breakers. And I doubt I will even buy one for a specific job. Maybe I'm a rebel.

I'm NOT telling the OP what to do, to be clear. Just musing.

I once looked into water heating issues at a commercial facility. Had been in place quite some time, but the 3-phase water heater was operating on single-phase. The unused phase was brought to the heater and capped off. All I had to do was hook it up. Worked a lot better. After that, we looked at their other one where they hadn't NOTICED an issue. Same thing. I do a lot of barter work. That one paid me with a single-action revolver.
 
MAC702 said:
I do residential service work mostly, 240V single-phase. EVERY such water heater and dryer is a 30A ckt. I guess it's another of those things where the entire state does it wrongly again.

Maybe we have state amendments that are allowing cord-and-plug furnaces and 30A ckts for water heaters. I must admit I've never tried to engineer either, and just use my 25 years of experience to wire them the same. This thread has been another very interesting one for me.

No, I'm not going to start stocking 25A breakers. And I doubt I will even buy one for a specific job. Maybe I'm a rebel.

I'm NOT telling the OP what to do, to be clear. Just musing.

I once looked into water heating issues at a commercial facility. Had been in place quite some time, but the 3-phase water heater was operating on single-phase. The unused phase was brought to the heater and capped off. All I had to do was hook it up. Worked a lot better. After that, we looked at their other one where they hadn't NOTICED an issue. Same thing. I do a lot of barter work. That one paid me with a single-action revolver.
Click to expand...


The common water heater here is 4500 watt/ 240 volt which would be 18.75 amps and a 30 amp breaker would be allowed by 422.11
 
MAC702 said:
I do residential service work mostly, 240V single-phase. EVERY such water heater and dryer is a 30A ckt. I guess it's another of those things where the entire state does it wrongly again.

Maybe we have state amendments that are allowing cord-and-plug furnaces and 30A ckts for water heaters. I must admit I've never tried to engineer either, and just use my 25 years of experience to wire them the same. This thread has been another very interesting one for me.

No, I'm not going to start stocking 25A breakers. And I doubt I will even buy one for a specific job. Maybe I'm a rebel.

I'm NOT telling the OP what to do, to be clear. Just musing.

I once looked into water heating issues at a commercial facility. Had been in place quite some time, but the 3-phase water heater was operating on single-phase. The unused phase was brought to the heater and capped off. All I had to do was hook it up. Worked a lot better. After that, we looked at their other one where they hadn't NOTICED an issue. Same thing. I do a lot of barter work. That one paid me with a single-action revolver.
Click to expand...
No no your situation is different:

Your FLA is 18.75A.

18.75Ax1.25= 23.43A next high is 25A
18.75Ax1.5=28.12A next high is 30A

So yours 25A or 30A works.

Mine FLA is 16.24A

16.24x1.25= 20.30A next high is 25A
16.24x1.5= 24.36 next high is 25A

So its 25A no matter what in my situation



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Thank you. I totally missed the 277V.

67634255.jpg
 
Conductor ampacity

Conductor ampacity

I don't understand this thread. There is no mention of conductor ampacity. I thought the breaker was there to protect the conductors?
 
augie47 said:
The common water heater here is 4500 watt/ 240 volt which would be 18.75 amps and a 30 amp breaker would be allowed by 422.11
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Are you referring to (2017 NEC) 422.11(E)(3)? We always have put 4500 watt/ 240 volt on a 25 as per 422.11(A) and 110.3(B) as the manufacturers instructions, typically in a pocket on the unit, usually marks them for a 25.
Our supply house stocks a 2 pole 25 in many brands. I just with they had a lockout built in to them as we dont set a disco at the unit.
 

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tortuga said:
Are you referring to (2017 NEC) 422.11(E)(3)? We always have put 4500 watt/ 240 volt on a 25 as per 422.11(A) and 110.3(B) as the manufacturers instructions, typically in a pocket on the unit, usually marks them for a 25.
Our supply house stocks a 2 pole 25 in many brands. I just with they had a lockout built in to them as we dont set a disco at the unit.
Click to expand...

If you have manufacturer documentation, I agree (I've not seen those instructions on water heaters sold locally..part of the chart was cut-off..does it say "maximum" ?
As far as a disconnect, most of the guys here use 422.31(B) and a breaker lock.
 
augie47 said:
If you have manufacturer documentation, I agree (I've not seen those instructions on water heaters sold locally..part of the chart was cut-off..does it say "maximum" ?
As far as a disconnect, most of the guys here use 422.31(B) and a breaker lock.
Click to expand...

Honestly its a photo I took years ago, the 25A two pole breakers cost the same as the 30 so I just spec the 25's for the 50 Gal 4.5kW water-heaters. It would be surprising to find any manufacturers instructions that indicated a 30A breaker should go on a 4500 element.

Same here as far as disconnects, they all use breaker lockouts, I hate it when I open a panel and all the breaker-lockouts fall all over the place. Here in the NW we have allot of older buildings with electric resistance heating, so a typical 200A panel will have several breaker lockouts. I wish they made a breaker with the lockout molded into the breaker.
Cheers
 
tortuga said:
Honestly its a photo I took years ago,
Many years ago a 25 was required due to Code. I don't recall but I imagine the OCP rule was 125%.. we did have a lot of 25s then and the habit is still around........... I wish they made a breaker with the lockout molded into the breaker.
Amen! . I hate them!
Cheers
Click to expand...
:)
 
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