International Association of Certified Home Inspectors
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| Plumbing Inspections Contains discussions about plumbing. |
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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,CPI,CME National Electrical Code Expert Electrical & Fire Protection Systems Code Supervisor- Alexandria,VA Weekly Live Radio Show :http://en.1000mikes.com/show/the_electrical_guru Weekly Chat on Wednesdays -7:30 PM E.S.T * Get my 13 hour commentary audio CD for the book "How to Perform Electrical Inspections" 2007 InterNACHI Member of the Year |
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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,CPI,CME National Electrical Code Expert Electrical & Fire Protection Systems Code Supervisor- Alexandria,VA Weekly Live Radio Show :http://en.1000mikes.com/show/the_electrical_guru Weekly Chat on Wednesdays -7:30 PM E.S.T * Get my 13 hour commentary audio CD for the book "How to Perform Electrical Inspections" 2007 InterNACHI Member of the Year 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,CPI,CME National Electrical Code Expert Electrical & Fire Protection Systems Code Supervisor- Alexandria,VA Weekly Live Radio Show :http://en.1000mikes.com/show/the_electrical_guru Weekly Chat on Wednesdays -7:30 PM E.S.T * Get my 13 hour commentary audio CD for the book "How to Perform Electrical Inspections" 2007 InterNACHI Member of the Year |
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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,CPI,CME National Electrical Code Expert Electrical & Fire Protection Systems Code Supervisor- Alexandria,VA Weekly Live Radio Show :http://en.1000mikes.com/show/the_electrical_guru Weekly Chat on Wednesdays -7:30 PM E.S.T * Get my 13 hour commentary audio CD for the book "How to Perform Electrical Inspections" 2007 InterNACHI Member of the Year 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,CPI,CME National Electrical Code Expert Electrical & Fire Protection Systems Code Supervisor- Alexandria,VA Weekly Live Radio Show :http://en.1000mikes.com/show/the_electrical_guru Weekly Chat on Wednesdays -7:30 PM E.S.T * Get my 13 hour commentary audio CD for the book "How to Perform Electrical Inspections" 2007 InterNACHI Member of the Year |
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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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#10
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Does anyone have good verbage in laymen terms, that I could use to explain this issue to clients?
Thanks "I have not failed, I have just found a 1000's way's that didn't work" Thomas Edison www.newbeginningshomeinspection.com |
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#11
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Most clients will understand this about electric water heaters:
Your water heater is wired to a 30 amp circuit and should give good service for about 10 years. The most common problems are burned out elements. A bad top element will cause the tank to have no hot water and a bad lower element will cause it to have reduced hot water capability. The top thermostat must be hot before it lets the lower one come on. The water is drawn from the top and the cold water comes in at the lower part of the tank interior. B.A. King Home Inspections, LLC www.BAKingHomeInspections.com Serving Charlotte NC area and Rock Hill SC areas. CMI Certified Master Inspector and Independent 704 301-3207 "Discovery consists in seeing what everyone else has seen and thinking what no one else has thought." - Albert Szent-Gyvrgyi, Nobel Prize for Medicine 1937 |
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#12
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Please Note:
Brian A. MacNeish is a non-member guest and is in no way affiliated with InterNACHI or its members.
Quote:
Our 40 Imperial (Canadian) gallon electric hot water heaters (roughly equivalent to the US 50 gal units) have 3000 watt elements only and are breakered at 20 amps while using #12/2 wire. Why the 4500 watt elements in a similarly sized unit....faster recovery times?? Our 60 Imp gal tanks have 4500 watt elements with #10/2 breakered at 30 amps. |
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#13
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It is true that with residential water heaters both elements are never allowed "on" at the same time. However, I have seen numerous comercial heaters that do allow both elements (4500 to 5000 watt) "on" at the same time. Personally I do not know if they "within code" or not. Of course, these heaters are wired for the increase amperage (#6-wire) and are breakered accordingly (60 amp) as well. Are we sure that this residential heater was not "salvaged" from a defunct restaurant. If it was, I am not saying it would be a correct usage.... just explaining why it might be there.
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