The Tank › Bradford White electric water heater – melted wires
- November 17, 2010 at 11:50 pm #14491Tom_in_KYParticipant
I have a Bradford White 80 gal electric water heater that is about 4 years old. This morning I awoke to a cold shower – checked the breaker box, and the 40 amp breaker had tripped. Checked the wiring on the unit, and one leg had a wire nut that had got hot enough to melt the insulation off. Could this have been caused by a bad T-stat or element? I disconnected the wiring to the elements and ran a continuity and resistance check using a DVM, and they seemed to check out. I am tempted to just replace both elements and T-stats, but this is a 4 year old unit inn a house with a water softener, and the anode has never been replaced. I have no idea what the inside of that tank will look like at this point, but I am sure the anode has to be gone by now. Am I throwing good money after bad? Obviously, it concerns me greatly that the wires were able to get that hot before tripping the breaker. Has anyone ever experienced this? Bad breaker?
Going back to the anode, after reading this site it is clear to me that an electric anode would be the way to go. Problem is, this 80-gal heater uses the anode that is incorporated into the hot side outlet. Is there any solution for these type units? If I end up replacing the whole thing, can you make any recommendations on a good 80-gal electric heater that uses the separate anode that is easily changed? If I end up replacing this thing, I’ll be darned if I’m painting myself back into the same corner.
Thanks in advance for any help you can provide! Awesome and informative site!
TomNovember 18, 2010 at 11:39 pm #14499
Hello: Normally heaters are on a 30 amp breaker, not 40. That is part of the problem. Unless your heater is supplied with large gauge wire and has really big elements, you don’t want it on big breakers. The most likely fault is in elements. Have a look in tanklets and “electric water heater problems”. You’ll find instructions on how to test elements with an ohm meter for both continuity and leakage to ground.
Four years old is pretty young for a heater. I would check the anode and plan on replacing it if anything is left of it. Randy is far more up to date on what can and can’t be done with powered anodes, so I’ll defer to him on that part of your question 😉
Yours, LarryNovember 18, 2010 at 11:39 pm #14500November 19, 2010 at 12:16 pm #14505Randy SchuylerKeymaster
SKU25 is the powered anode for heaters like yours. It includes a tee and a couple of nipples so that there are is a place for the anode, but still a place for the hot water to flow out.
Randy SchuylerNovember 19, 2010 at 7:22 pm #14510energyexpertParticipant
A 12.8 ohm WH element draws 18.75 amps at 240 volts and produces 4500 watts. The National Electric Code (NEC) section 422.13 defines WHs as a continuous load. NEC 422.10(A) requires branch circuit ratings of continuous loads to be sized at not less than 125% of nameplate. 18.75 x 125% = 23.44 amps. This moves you to #10AWG wire and a 25 amp breaker. #10AWG can be protected up to a 30 amp breaker. Electricians out of habit would install 30 amp breakers when 25s should have been installed. Finally the NEC was changed rather than inspectors enforcing the use of 25 amp breakers on 4500 watt WHs.
NEC 422.11(E) permits breakers to be sized for WHs at 150% (28.125 amps) or the next standard size above 150% (30 amps).
Now about the melted wire nut. The breaker only senses current, not temperature. If you drain your WH and then turn on the breaker the top element will get hot enough (in usually less than one minute) to burn in two. The breaker will not trip. My guess is you had a poor mechanical joint inside the wire nut. A poor joint will get hot. A hot joint will tend to create oxidation. This increases the joint resistance further. So over time (4 years) the joint gets hot enough to melt the wire nut and result in an open circuit. Total current will go down due to increased resistance in the circuit. I doubt there is anything wrong with the tstats or elements.
Even if you had 5500 watt elements you should have #8AWG wire if you have a 40 amp breaker. The only other explanation is that on 40 amp breaker if the top tstat malfunctioned so as to permit simultaneous operation then both 4500 watt elements operating together would draw 37.5 amps which would not trip the 40 amp breaker but could heat up a poor joint.
DavidNovember 19, 2010 at 7:52 pm #14511Tom_in_KYParticipant
Thanks for the replies, guys. I was wrong about the breaker size – it is a 30. I guess I’m getting senile in my old age. 🙂
I agree that a bad connection in the wire nut was probably the root of my problem. I cut the lead back a few inches to make sure I had fresh copper and retwisted the joint, and also made sure I had the appropriate sized wire nut on there. I also tested the elements and T-stats, and flushed and drained the tank, pulled out the elements and cleaned them, and replaced the anode. The anode was shot – nothing there but rusty wire! I guess that wire nut did me a favor by prompting me to give some long overdue attention to the water heater. I replaced the hard line on the hot side with a flexible connector to make future maintenance easier. I will not check that anode on a semi-annual basis.
Randy, how much do the electric anodes that you mentioned sell for? I will definitely consider getting one when this new anode is ready for replacement, especially if it gets eaten up within the next year. I had to go ahead an get a regular anode in there and get the tank back up and running. I was catching some “heat” from the boss for all the cold showers she had to endure! 😯
Thanks for the replies, and special thanks to Randy for maintaining this excellent and extremely informative site!November 19, 2010 at 10:11 pm #14512Randy SchuylerKeymaster
The powered anode costs $239 — as opposed to $41 for a .84-inch-diameter magnesium anode. Quite a difference. Check the replacement anode in six months and then contact me and send a picture, and I’ll give you my take on this.
The powered anode is capable of throwing a lot more protective current than a sacrificial anode. Considering the shape of the old one, that might be important. But my inclination right now is that you put a combo magnesium anode in the tank and see if it lasts six months. If it does, you might change to powered. If it doesn’t, then you’ll be replacing the tank and know the next time not to let things go so long!
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