Water Heater Elements Burning Out Quickly

[ozark01]

Hello....I have been reading your web site and found it very interesting and informative. I hope you will be able to answer a question I have about water heater elements.

Per the manufactures information an element rated at 4500 watts at 240 volts has a resistance of 12.8 ohms. Also per the manufactures information a 6000 watt element at 277 volts also has a resistance of 12.8 ohms. This leads me to believe that these two elements are the exact same element with different ratings stamped on the plastic. Is this true or do the two elements have different electrical and mechanical characteristics even though they have the same resistance?

The reason I ask this is because I have a water heater that has 250 volts going to it and it is burning out the 4500 watt, 240 volt elements at the rate of about one a week. By my calculations the 250 volts has changed the rated 4500 watts to 4882 watts and I think this is what is burning out the elements. I have contacted the power company and they said the area we are in has 250 volts and there is nothing they can do to lower the voltage.
My possible solution is to install 277 volt, 6000 watt elements in the heater. At 250 volts this 6000 watt element will be rated at 4882 watts and should not burn out like the 240 elements are doing.

Am I correct in this thinking or am I going off in the wrong direction? Any help you can provide will be appreciated!

 

[Jadnashua]

As long as the element is covered with water when on, I don't think it's your inlet voltage that's causing the problem. If the connector and wire has some corrosion on it, that can increase the heating right at that connection, and give you problems. Higher voltage will produce higher wattage verses the listed values - the formula is Power = voltage *current and Voltage = current *resistance, and by substitution, Power = volts^2 * resistance. Raising the voltage by 10, doesn't raise the power all that much, and the resistance changes as things heat up.

 

[Sponsor]

 

[Master Plumber Mark]

Is your water heater full of LIME?? Are you throwing the element into a bed of
sediment and mud and expecting it to work properly??
You need to clean the LIME out of the heater or it will burn out elements fast....

You ought to install the heavy duty Stainless steel elements in your heater
you can buy them at Lowes for 20 bucks each....

They will last a lifetime ....... BUT if you are expecting them to work in a heater
that is full of junk, it will surely fail too....

 

[ozark01]

Thanks for the replies. The heater is new and I have tried several different types of elements with the same results. They last about a week then get a hole burnt in them normally at the bends.

 

[Bill Johnson]

You are exceeding the design rating on the 240V element. That 277 volt element is heavier duty and should solve your problem.

 

[Stuff]

Lots of places deliver over 250v at low usage times of the day without complaint. Power company does that so when everyone turns on their a/c at the same time you don't get a brown-out.

Are you on well water? Maybe something strange going on there. What are your neighbors seeing with their water heaters?

 

[Jadnashua]

I thought the 'normal' min/max was +/- 10% of nominal. Am I wrong? Wouldn't be the first time...

 

[ozark01]

I've secured a 277 volt 6k element. I will post back if it solves my problem....

 

[ozark01]

You are exceeding the design rating on the 240V element. That 277 volt element is heavier duty and should solve your problem.

I hope you are correct!

 

[Reach4]

ozark01, do you lose water pressure on occasion? There is the possibility that if you do, and you don't have a vacuum breaker, the water could siphon out of your WH via the dip tube. Then one or both elements could be out of the water.

I know it sounds unlikely. The other possiblity would be whoever you buy your elements from got mixed up and is providing 120 volt elements. That seems unlikely also.

 

[ozark01]

ozark01, do you lose water pressure on occasion? There is the possibility that if you do, and you don't have a vacuum breaker, the water could siphon out of your WH via the dip tube. Then one or both elements could be out of the water.

I know it sounds unlikely. The other possiblity would be whoever you buy your elements from got mixed up and is providing 120 volt elements. That seems unlikely also.

The problem is mainly with the top element but the bottom one has burned out about 1/3 of the time the top one has. (Six for top element vs 2 for the bottom element). Also it is my understanding that most dip tubes have a small hole at the top of them to help prevent siphoning but at this point I am open to any and all possibilities. Thanks for the ideas!

 

[Jadnashua]

Power = volts*amps...so back to your original post, just the act of raising the voltage on exactly the same heating element will cause it to draw more power. So, those two heating elements may be identical except for the labeling. It would be fairly easy to have the 240vac one be able to support 270 volts, and if you did, it would create more heat. If you assume the incoming voltage is supposed to be regulated to within +/- 10%, that's 24 volts up/down...really close to that 270vs in the scheme of things.

Exactly where are the failed elements 'burning out'? Is it visible? Typically, as long as they are immersed, they won't burn out. Now, a 120vac element used in a 240vac system, probably doesn't have the capacity to handle twice the power going through it, but a 240vac element would still work at 120vac, but produce half of the heat.

 

[ozark01]

Normally there is a 1-2" spot on the element where the outer covering on the element is missing. The elements are 240 volt elements based on the numbers stamped on the plastic on the element.

 

[hj]

I replace DOZENS of lower elements for every top one that fails, because the top one VERY SELDOM operates unless you use a lot of hot water all at once. I would be interested in seeing one ot the elements that burned out. Were they "single loop" or "double/fold back" ones.

 

[ozark01]

They were both. The single loop were high density and the fold backs were low or ultra low density. I'll post a picture later as I don't have the elements nearby at the moment.

 

[ozark01]

If anybody still cares....the 6k 277 volt element has lasted three weeks. This is two weeks more than any other of the 240 volt 4.5k elements have lasted. The amp draw on the element is about the same as a 4.5k element so the wattage is about the same...

 

[Stuff]

Good to know that Ohm's law still helps people out of a jamb!

Did you ever find out how your neighbors deal with this?

 

[ozark01]

No problems anywhere else nearby....still think it is a power company problem but they said no.... I posted this followup just to keep the group informed...

 

[ozark01]

Good to know that Ohm's law still helps people out of a jamb!

Did you ever find out how your neighbors deal with this?

What do you mean by ohms law fixing this? Did you know this all along and did not share?

 

[Stuff]

I was on a tangent. Just a different way of saying what you figured out on your own. As long as the resistance is the same then you'll get the same current (and wattage) with the same voltage. Ohm's law showing that the higher voltage element had the same resistance: voltage=amps x resistance (v=ir) and then power=amps x voltage (p=iv) so p=v*v/r 6000=277*277/12.8 and 4500=240*240/12.8