International Association of Certified Home Inspectors
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#1
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I was looking at my brother in laws 50 gallon AO Smith electric water heater last night and noticed that the unit was on a 60 amp breaker. Is that correct or is it over amped? I could not find a max amp on the unit similar to the AC compressor nameplate.
Richard W. Washington, owner RW Home Inspections, Inc. www.RWHOMEINSPECTIONS.com Texas Real Estate Commission (TREC) Professional Inspector License #7238 Texas Professional Real Estate Inspectors Member (TPREIA)-Greater Houston Chapter InterNACHI member since 2004 Based in Katy, serving Houston and all surrounding communities |
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#2
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Sounds like it is overfused. What gauge wire was used?
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#3
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Yes, it is over sized.........I have never seen a 60A water heater and most certainly not any made by A O Smith.
Paul W. Abernathy,CMI,CEI,CEPE NEC® Consultant/Columnist www.twitter.com/ElectricalGuru - ICC & IAEI Certified Electrical Inspector - ICC & IAEI Certified Electrical Plans Examiner - Look for my article in the Nov/Dec 2009 IAEI Magazine - 2007 "Top Gun" Winner - Mike Holt Enterprises " visit www.TheElectricalGuru.com Today !" |
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#4
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Hint....always take a picture of the nameplate for future reference. Now I know the one you had did not have a nameplate..this is just a general reminder as it is nice for reference later and do it on all appliance nameplates.
Chances are the 50 Gallon water heater is a 4,500W unit, so figuring this for your friend 4,500W/240V = 18.75 x 1.5 = 28A ( next size up rule per 422.11(E) ) 30A breaker is the proper size Here is the section if you would like to see it...: (E) Single Non–motor-Operated Appliance. If the branch circuit supplies a single non–motor-operated appliance, the rating of overcurrent protection shall: (1) Not exceed that marked on the appliance. (2) Not exceed 20 amperes if the overcurrent protection rating is not marked and the appliance is rated 13.3 amperes or less; or (3) Not exceed 150 percent of the appliance rated current if the overcurrent protection rating is not marked and the appliance is rated over 13.3 amperes. Where 150 percent of the appliance rating does not correspond to a standard overcurrent device ampere rating, the next higher standard rating shall be permitted. Paul W. Abernathy,CMI,CEI,CEPE NEC® Consultant/Columnist www.twitter.com/ElectricalGuru - ICC & IAEI Certified Electrical Inspector - ICC & IAEI Certified Electrical Plans Examiner - Look for my article in the Nov/Dec 2009 IAEI Magazine - 2007 "Top Gun" Winner - Mike Holt Enterprises " visit www.TheElectricalGuru.com Today !" Last edited by pabernathy; 2/4/07 at 3:22 PM.. |
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#5
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Another point along this line is; both heating elements are NEVER on simultaneously, hence no need for a huge breaker to handle the load. I found that many people were unaware of this little tidbit of info.
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#6
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Yeppers......thats why you only use 4,500W in the equation...not the sum of BOTH elements...
Paul W. Abernathy,CMI,CEI,CEPE NEC® Consultant/Columnist www.twitter.com/ElectricalGuru - ICC & IAEI Certified Electrical Inspector - ICC & IAEI Certified Electrical Plans Examiner - Look for my article in the Nov/Dec 2009 IAEI Magazine - 2007 "Top Gun" Winner - Mike Holt Enterprises " visit www.TheElectricalGuru.com Today !" |
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#7
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Another good point is the NEC defines this as a Cont. load so the conductors have to also be sized at 125% of the non- continuous load.
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. Ironically enough...422.11(E) says it needs to be 150% on the OCPD and in all Mr. Holts books it desribes it as such....yet 422.13 says it is considered continuous and we know that means 125%.... *Note- if the unit is rated for 100% contin. then that is fine also but I dont see that in standard water heaters....just threw that in. Part II. Branch-Circuit Requirements Text was revised to specify that a fixed storage water heater of 120 gallons or less is to be considered a continuous load. This simple change causes feeder/service conductors and overcurrent protection devices to be increased in size. An electric water heater having a capacity of no more than 120 gallons is considered a continuous load.Question: What is the calculated load for a 4,500W, 230V water heater? (a) 15A (b) 20A (c) 25A (d) 30A Answer: (c) 25A I = P/E P = 4,500W E = 230V I = 4,500W/230V I = 20A Calculated continuous load for conductor sizing and protection = 20A x 1.25 = 25A The revision to 422.13 ( in 2005 NEC ) specifically identifies an electric water heater with a storage capacity of 120 gal or less as a continuous load. This revision requires the branch circuit overcurrent device and conductors to be sized based on 125 percent of the water heater nameplate rating unless the overcurrent device and the assembly it is installed in are listed to be used at 100 percent of its continuous current rating. In addition, feeders and services that supply water heater branch circuits are also impacted by the fact that this type of equipment is considered to be a continuous load. Paul W. Abernathy,CMI,CEI,CEPE NEC® Consultant/Columnist www.twitter.com/ElectricalGuru - ICC & IAEI Certified Electrical Inspector - ICC & IAEI Certified Electrical Plans Examiner - Look for my article in the Nov/Dec 2009 IAEI Magazine - 2007 "Top Gun" Winner - Mike Holt Enterprises " visit www.TheElectricalGuru.com Today !" Last edited by pabernathy; 2/4/07 at 4:42 PM.. |
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#8
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lol....The point is I think mike needed to make the change in his newest book and he probably did already...
Paul W. Abernathy,CMI,CEI,CEPE NEC® Consultant/Columnist www.twitter.com/ElectricalGuru - ICC & IAEI Certified Electrical Inspector - ICC & IAEI Certified Electrical Plans Examiner - Look for my article in the Nov/Dec 2009 IAEI Magazine - 2007 "Top Gun" Winner - Mike Holt Enterprises " visit www.TheElectricalGuru.com Today !" |
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#9
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Wow. I need to reread this thread again. Holy cow! 30amps max.
Richard W. Washington, owner RW Home Inspections, Inc. www.RWHOMEINSPECTIONS.com Texas Real Estate Commission (TREC) Professional Inspector License #7238 Texas Professional Real Estate Inspectors Member (TPREIA)-Greater Houston Chapter InterNACHI member since 2004 Based in Katy, serving Houston and all surrounding communities |
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