water heater circuit ocp
- Thread starter LYLE2231
- Start date
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Jim W in Tampa
Senior Member
- Location
- Tampa Florida
18.75 times 125%. 25 amp breaker
ibew501ed
Senior Member
- Location
- danbury ct/work in white plains ny
i believe 422.10(a) says not less than 125% and422.11(e)(3) limits the max to be 150%
2008
2008
Last edited:
charlie
Senior Member
- Location
- Indianapolis
Common practice here is to use a 30 ampere, two pole circuit breaker on #10 Cu.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Common practice here is to use a 30 ampere, two pole circuit breaker on #10 Cu.
Here also 30 amp is standard. The inspectors use to demand a 25amp breaker years ago. I have seen some new resi water heaters sold at Lowes (I believe) that have a 5000 watt element. 25 amp won't cut it legally.
charlie
Senior Member
- Location
- Indianapolis
The OP's WH element was the standard 4500 watt though. :smile:
Mvillines
Senior Member
- Location
- Western KY on the Ohio River
Prior to the 1990 code cycle a 4.5 kw water heater was restricted to a 25 amp OCPD.
I find it strange that I remember when section 422-27(e) of the 1987 edition changed.
The 1987 and prior NEC stated that an overcurrent device rating shall not exceed 150 % of the rating of the appliance. (4500/240 = 18.75 X 150% = 28.125 amps) At that time there were no provisions to round up to the next standard OCPD.
An exception was added in the 1990 edition stating. Where 150 % of appliance rating does not correspond to a standard overcurrent device ampere rating, the next higher rating shall be permitted. This exception has been changed to positive language and relocated to section 422.11(E) in the 2008 cycle.
4.5 Kw heater, size 10 nm cable with a 30 amp overcurrent device.
I find it strange that I remember when section 422-27(e) of the 1987 edition changed.
The 1987 and prior NEC stated that an overcurrent device rating shall not exceed 150 % of the rating of the appliance. (4500/240 = 18.75 X 150% = 28.125 amps) At that time there were no provisions to round up to the next standard OCPD.
An exception was added in the 1990 edition stating. Where 150 % of appliance rating does not correspond to a standard overcurrent device ampere rating, the next higher rating shall be permitted. This exception has been changed to positive language and relocated to section 422.11(E) in the 2008 cycle.
4.5 Kw heater, size 10 nm cable with a 30 amp overcurrent device.
#10 wire 30 amp breaker no calc needed
thanks for your help! be safe today! lyle
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