Water heater

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Jpflex

Jpflex

Electrician big leagues
Location
Victorville
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Electrician commercial and residential
This Rheem water heater has no listing for size of an OCPD nor branch circuit wiring

Without reviewing checking the NEC code book, I believe it’s no more than a 20 ampere breaker for such a water heater 120 gallons or less using 13.33 amperes or less or

150% of rating (current calculated?) if the same conditions but with over 13.33 amperes rating?

I also don’t get why the name plate for 240 volt 1 phase which we’ll be supplying this with is rated 4500 watts for the top heating element and 4500 watts for the second bottom heating element, with total watts listed at 4500 watts. 4500 + 4500?

So if I take 4,500 watts / 240 volts = 18.75 i amperes

Then 18.75 x 1.50% = 28.125 i

Conductor size
= #10 AWG THHN @ 75 degree termination

OCPD
= 28.125 i, next standard size 30 i breaker

Does this sound correct?
 

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I don't know where you are getting 150%. A storage tank WH is considered a continuous load and those are to be factored at 125%.
You are correct on the 18.75A
18.75A x 125% =23.4A
next size up 25A
Most go ahead and use a 30A breaker, and I can only guess because the 30A is more common than the 25A.
 
Jpflex said:
I also don’t get why the name plate for 240 volt 1 phase which we’ll be supplying this with is rated 4500 watts for the top heating element and 4500 watts for the second bottom heating element, with total watts listed at 4500 watts. 4500 + 4500?
Click to expand...
Because they're never both on at the same time.

Does this sound correct?
Click to expand...
Yep. The only decision is a 25a or a 30a breaker.
 
the water heater is only requiring 125% not 150%
2023 NEC 422.13 Storage-Type Water Heaters.
The branch-circuit overcurrent device and conductors for fixed storage-type water heaters that have a capacity of 450 L (120 gal) or less shall have an ampere rating of not less than 125 percent of the ampere rating of the water heater.

(4500W/240)*125%
 
augie47 said:
You are good to go. The 150% is from 422.11(E) and 30 amp would be correct.
Click to expand...
After looking up the book it gets cinfusing if allowed to go 120% max per 422.13 specific to water heaters for 25 OCPD max or

Use 422.11 E for 150% OCPD max for general non motor appliances but NOT specific to water heaters for 30 amp max
 
Jpflex said:
I also don’t get why the name plate for 240 volt 1 phase which we’ll be supplying this with is rated 4500 watts for the top heating element and 4500 watts for the second bottom heating element, with total watts listed at 4500 watts. 4500 + 4500?
Click to expand...
Taken from a Bradford White spec sheet.

"These heaters are wired inter-locking (Non-Simultaneous, Single Phase) 240V with two 4500W elements, unless otherwise specified."

Unless special order, they are interlocked.

 
Jpflex said:
After looking up the book it gets cinfusing if allowed to go 120% max per 422.13 specific to water heaters for 25 OCPD max or

Use 422.11 E for 150% OCPD max for general non motor appliances but NOT specific to water heaters for 30 amp max
Click to expand...
422,13 does not set a maximum OCPD, it sets a minimum. The 2017 does not address the OCPD rating, but requires 125% sizing for the branch circuit.
2017 code
422.13 Storage-Type Water Heaters.
A fixed storage-type water heater that has a capacity of 450 L (120 gal) or less shall be considered a continuous load for the purposes of sizing branch circuits.

2020 code
422.13 Storage-Type Water Heaters.
The branch-circuit overcurrent device and conductors for fixed storage-type water heaters that have a capacity of 450 L (120 gal) or less shall be sized not smaller than 125 percent of the rating of the water heater.

2023 code
422.13 Storage-Type Water Heaters.
The branch-circuit overcurrent device and conductors for fixed storage-type water heaters that have a capacity of 450 L (120 gal) or less shall have an ampere rating of not less than 125 percent of the ampere rating of the water heater.
Click to expand...
Correct, 422.11(E) is a general rule and applies to all appliances not covered by specific rules.
 
don_resqcapt19 said:
422,13 does not set a maximum OCPD, it sets a minimum. The 2017 does not address the OCPD rating, but requires 125% sizing for the branch circuit.

Correct, 422.11(E) is a general rule and applies to all appliances not covered by specific rules.
Click to expand...
Okey dokey
 
4x4dually said:
Taken from a Bradford White spec sheet.

"These heaters are wired inter-locking (Non-Simultaneous, Single Phase) 240V with two 4500W elements, unless otherwise specified."

Unless special order, they are interlocked.

Click to expand...
So non simultaneous meaning the heating elements cannot come on at the same time so this explains why two heaters at 4500 watts = 4500 watts
 
Appears you have pex piping... no bonding necessary.. just connect your EGC to the screw provided at the connection point.
 
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