50-55gal. Water Heater 240v

[donnie]

After doing all the code rules and calculations for a 4500 watt 240 volt 50 - 55 gal. water heater, I come up with a breaker size of a maxium of 25amps, but I'm wondering if there is something I am missing that would allow a 30amp, I realize that a 30amp would be going two sizes up.


Thanks for any replies.

 

[hillbilly]

Re: 50-55gal. Water Heater 240v

422-13.,422-10. (99 NEC)

 

[donnie]

Re: 50-55gal. Water Heater 240v

Thanks , Hillbilly

That's the articles I used to get my answer , except I used the 2002 NEC.

 

[hillbilly]

Re: 50-55gal. Water Heater 240v

Donnie, are you familiar with Article 240? Specifically 240-3.(d).
steve

 

[hbiss]

Re: 50-55gal. Water Heater 240v

I realize that a 30amp would be going two sizes up.

Two sizes up from what? 25 sits smack in the middle of 20 and 30 last I looked. You go to the next available which is 30 and use 10ga wire.

 

[donnie]

Re: 50-55gal. Water Heater 240v

hbiss, This is the way I do my math.

4500w/240v=18.75a then I apply Art. 422.13
18.75 X 125% = 23.43a , Art. 240.4(b) allows me to go to the next size breaker.
Answer is 25a.
Therefore going to a 30a would then be two sizes up.

Thanks: Donnie

 

[charlie b]

Re: 50-55gal. Water Heater 240v

The breaker protects the cable, not the water heater. If the cable is at least a #10, you can protect it with a 30 amp breaker. But I'm curious as to why you would want to use a 30.

 

[pierre]

Re: 50-55gal. Water Heater 240v

Donnie
In the installation instructions, do the instructions specify what the maximum fuse/breaker size is?

Pierre

 

[hbiss]

Re: 50-55gal. Water Heater 240v

Ok, they do make 2 pole 25's but when was the last time you saw one?

 

[donnie]

Re: 50-55gal. Water Heater 240v

Pierre,
I haven't never seen an installation instructions for a water heater.
But I have seen the Name Plate that usually states the wattage and the voltage.
By which I used in my previous reply.

Thanks Donnie

Charlie b,

I guess what I'm asking is, if you use a #10 copper conductor can it be on a 30a breaker,and if so would it violate art.422.13 and 240.4(b) and if not what is the code references.

Thanks Donnie

 

[tonyi]

Re: 50-55gal. Water Heater 240v

Originally posted by hbiss:
Ok, they do make 2 pole 25's but when was the last time you saw one?

Fairly common for A/C compressors.

 

[donnie]

Re: 50-55gal. Water Heater 240v

Thanks for all the replies.

And Charlie b,

Disregard my last reply, I must of have read Art.240.4(b) to fast and not paid attention to the words.
I can use the next size breaker above the (ampacity of the conductor being protected) If it doesn't correspond to a standard breaker, I was for some reason or another thinking of above the load.

Please Forgive,
Thanks. Donnie

 

[bonding jumper]

Re: 50-55gal. Water Heater 240v

You know what threw me the other day, I had the same problem, installing a 4500W 240 water heater and home depot put this description under their 20 double pole breaker.

Cutler Hammer
20 amp Double Pole Circuit Breaker
Model CH220B

Using wire size #12-2 copper with ground, this 20 amp, 120/240 Volt, two pole replacement breaker is used in a Cutler Hammer load center. Typical applications, up to 8800 watts, include electric baseboard heat, fan forced heat and air conditioners (240 Volt, up to 23,000 BTU). These are only suggested applications and cannot assure your compliance with all local codes. Please check local electrical codes before starting any electrical project.

Internet/Catalog # 359995
Store SKU# 578416

Now that number 8800 watts is very misleading. Where do they get that number? 8800 / 240 = 36.6A You can't load that circuit up that high. Where do they get off suggesting that? I didn't trust their 8800 rating and used a 30 double pole which according to them, can take 13,200 watts, or 55 amps 240.

[ November 03, 2003, 04:11 PM: Message edited by: bonding jumper ]

 

[pierre]

Re: 50-55gal. Water Heater 240v

When removing the water heater from the packaging, there will be installation instructions for the plumbing, electrical and other assorted info. The electrical part will usually state the maximum fuse/breaker size. The last one I installed had instructions stating, maximum rating for 30 amps.

Pierre

 

[hbiss]

Re: 50-55gal. Water Heater 240v

Where do they get that number?

Consider the source. Somebody is going to get hurt someday and I hope they sue Home Despots you know what off for encouraging and enabling the unknowledgeable to do their own work.

 

[sockie1924]

Re: 50-55gal. Water Heater 240v

"4500w/240v=18.75a then I apply Art. 422.13
18.75 X 125% = 23.43a , Art. 240.4(b) allows me to go to the next size breaker.
Answer is 25a." This I agree with but I was always told that a breaker cannot be loaded more than 80% if this is the case than a 30A breaker would be required because 80% of a 25A breaker is 20A therefore a 30A breaker would be required. Am I right in this or have I been mislead?

 

[roger]

Re: 50-55gal. Water Heater 240v

Sockie, the load is 18.75, so the 25 amp breaker is fine. The 125% is the inverse of 80%.

Take 100

100 / .80 =125

100 x 1.25 =125

100 /1.25 =80

100 x.80 =80

I have never had to wait for a standard frame and AIC 25 amp two pole breaker from my suppliers whether it be SQD, CH, or Seimens, just go pick one up.

Roger

[ November 03, 2003, 07:49 PM: Message edited by: roger ]

 

[sockie1924]

Re: 50-55gal. Water Heater 240v

I get it roger thanks.

 

[steve66]

Re: 50-55gal. Water Heater 240v

I get a 30A breaker and #10 wire.

Minimum breaker per 422.10 is 4500/240 * 1.25 = 23 amps. This is a minimum, so a 25 amp breaker is the minimum size.

Maximum breaker per 422.11(E)(3) is 4500/240 * 1.5 = 28 amps. This can be rounded up to a 30 amp breaker.

Finally, a 30 amp branch circuit requires #10 wire.

All this assumes the Hot water heater doesn't have a maximum OCP marked on it.

Steve