Water heater wiring

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Old 07-20-06, 08:48 PM
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Water heater wiring

I am replacing a 25-year-old electric watrer heater. When I checked the wiring of the old unit, I found that even though it was a 240-volt unit, only one 20-amp 120-volt circuit was connected to it. The heater has worked fine for 25 years, but how can this be? Am I likely to encounter problems if I connect the new heater the same way? Help!
 
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Old 07-20-06, 09:12 PM
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Bottom line is, you have 2400 watts max available, which in the first place is quite low. You didn't mention how many gallons, but it would take a long time to heat 30 or 40 gallons. A little 30 gallon heater today would probably have minimum 3500 watt elements, and a 40 or 50 gal. would be 4500 or 5500.

Even more important, if you use elements which are rated at 240volts and run them on 120 volts, the power produced will be 1/4 of the rated power. It you have 3400 watt 240 volt elements, running them at 120 volts gives you about 875 watts, which is less than a coffee pot!

So, something is inconsistent with what you have. I think you need to have it checked out
 
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Old 07-21-06, 05:18 AM
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What makes you say that you only have 120 volts connected to the water heater? Did you measure this?
 
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Old 07-21-06, 05:53 AM
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Water hearer wiring

Thanks for the speedy responses--much appreciated.
The heater has a 30-gallon tank. The heater wire is connected to only one breaker at the service panel, and the voltage at the heater checks out to be 120. Could it be that the wiring on the old heater was somehow altered to make it work?? It did produce hot water.
Another question: Could I connect the neutral wire to another breaker at the service panel, thereby running 240 to the heater? The mystery continues.
 
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Old 07-21-06, 06:07 AM
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Assuming that you have proper 12 gage wire (copper, not aluminum) and that there is a ground wire then you can take eliminate the 20 amp 120 volt breaker and instead connect the two current carrying conductors (the existing hot and neutral) to a properly installed 20 amp 240 volt breaker for the new water heater.

Please make doubly certain that you do in fact have the correct breaker. If you make a mistake and put 240 volts on your 120 volt electric items, you will damage them.

I know that there are 120 volt water heaters, but they are usually very small and limited in size. It's possible that someone installed 120 volt elements in this unit.
 
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Old 07-21-06, 07:04 AM
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Water heater wiring

Racraft, That was a speedy reply.
From your reply I understand that there is a 20 amp, 240v breaker, (double pole??). If so, that will solve my problem nicely. Just wanted to confirm what I need to go shopping for. Thanks!
 
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Old 07-21-06, 08:02 AM
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Originally Posted by rusticdon
From your reply I understand that there is a 20 amp, 240v breaker, (double pole??).
Based on this question, I respectfully suggest that you do not have the knowledge to be replacing circuit breakers. Please understand that there are voltages present in many residential circuit breaker panels even with the main breaker turned OFF. This voltage, and the current behind it, is enough to kill you several times over.

Please consider whether you really ought to be doing this job yourself.
 
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Old 08-09-06, 07:54 PM
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Follow-up on water heater wiring

Thanks for all the responses. I appreciate the cautionary words from some of you because my knowledge is rather limited. However, I do try to be careful when working with things that I am not familiar with. Thought you might be interested in a follow-up: rather than experiment with changes, I hooked up the heater as it was before___single 120-volt circuit to 240-volt, 30-gallon water heater. I flipped the circuit breaker on, and, in less than an hour, normal hot water was available. I still don't understand how this works, but the main thing is that I have plenty of hot water. Thanks guys.
 
 

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