Elec. Hot water heater circuit breaker

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  #1  
Old 10-20-13, 10:39 AM
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Elec. Hot water heater circuit breaker

Hi, I have no hot water. It's a Rheem 240v, 4500 watt with upper and lower elements. I Replaced both elements and both thermostats, still no hot water. I tested every screw on the thermostats and elements and have 110v on each. Could it be the breaker? It's a 25 amp double breaker.

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  #2  
Old 10-20-13, 10:58 AM
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It's a 25 amp double breaker.
First of all it should be a 30 amp breaker so it needs to be changed, but that isn't your issue. Check the voltage across both hot leads at the water heater, you should get 240 volts. If not, start working back upstream till you get to the panel and check across the lugs at the circuit breaker, you should get 240 volts. At any accessible point along the circuit, such as a junction box, you should get 240 volts across the two hot leads.
 
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Old 10-20-13, 11:13 AM
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4500watt / 240v = 18.75 a

Water Heaters under 125 gallons shall be considered continuous duty

18.75X 1.25= 23.43a.

Round up to next standard size 240.6 = 25a over current protection


Still think it needs 30a?
 
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Old 10-20-13, 11:16 AM
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First of all it should be a 30 amp breaker...
A 25 ampere circuit breaker is acceptable. The code states that electric storage tank water heater branch circuits be designed for 125% of the full load amperage; 4500 watts at 240 volts is 18.75 amperes. Multiply that by 125% and you get 23.44 minimum circuit Ampacity.
 
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Old 10-20-13, 11:49 AM
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A 25 amp breaker is acceptable but may be hard to find. 30A is the next commonly stocked breaker size.
 
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Old 10-20-13, 12:39 PM
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Water Heater Circuit

NEC 422.11 covers Overcurrent Protection for Nonmotor Appliances. A water heater circuit for a 4500VA would allow you to figure 150 percent as long as the heater rating is over 13.3 amperes. 4500/240= 18.75 x1.50 = 28amps. Next standard breaker is 30amps. 422.13 covers the conductors that would be rated at 125% so 18.75 x 1.25=23.40 which would be #10AWG CU per table 310.16.

As mentioned you need to read 240V at the supply to the water heater. Reading from each element screw to ground will give you 120V even if you have lost one phase from your supply breaker because you are reading through the element. I would start by checking the breaker, then at the water heater disconnect (if your water heater is out of site of the panel and breaker cannot be locked open) and finally at the heater itself.
 
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Old 10-20-13, 01:51 PM
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A 25 amp breaker is acceptable but may be hard to find. 30A is the next commonly stocked breaker size.
Square D style QO is the only commonly available 25 ampere circuit breaker that I am aware of.
 
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Old 10-20-13, 02:40 PM
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Thanks for the help. After reading the replies, it's pointing toward the breaker. I've had some other issues with power. One circuit under the 25 amp went out for a few days. It all seems to be on the left side of the breaker box. The double 25 amp is at the top of the box on the left. Could that affect the lower circuits?
 
  #9  
Old 10-20-13, 02:57 PM
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Water heater Breaker and Panel

Your description makes me think you may have a problem with one phase. Not knowing what your panel looks like or if supplied by the utility overhead or underground Ill just give you some general advice. If you can check the supply conductors at the main breaker for 240V. If you cannot check the main then check between both phases by removing two single-pole breakers to expose both buss bars. If you do not have 240V then you need to contact the utility as the problem could be in the meter base if you have an all-in-one panel or at the utility connections at the pole and/or weather head. If you have one bad phase it may turn on and off as the bad connection is failing, so there will be other circuits effected such as lights etc even if for a short time. You may only notice a flickering of lights for example, they do not need to go totally off for there to be a problem indicated.
 
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Old 10-20-13, 03:40 PM
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Still think it needs 30a?
You are right, a 25 amp breaker is acceptable, I sopke too quickly without thinking. That being said, either a 25 or 30 amp breaker is acceptable.

Square D style QO is the only commonly available 25 ampere circuit breaker that I am aware of.
I think it depends on the distributor whether they stock 25 amp breakers. I know of one distributor who handles both GE and Cutler-Hammer products and they stock the 25 amp 2 pole breakers in the C-H BR series, but not the CH series nor do they stock a 25A 2P in the GE line.
 
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Old 10-20-13, 03:50 PM
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Thanks for the help. After reading the replies, it's pointing toward the breaker. I've had some other issues with power. One circuit under the 25 amp went out for a few days. It all seems to be on the left side of the breaker box. The double 25 amp is at the top of the box on the left. Could that affect the lower circuits?
The location of the 25A breaker shouldn't affect the other positions, but you may have a bad connection on one leg at the main lugs, in the meter socket, at the service connection or even at the pole/transformer feeding your house. If you can verify that one leg may be out intermittently, call your power company and tell them you suspect you have a bad connection to your service because you are intermittently losing one leg.

After reading the replies, it's pointing toward the breaker.
Not necessarily. If you have 240 volts across the panel's two main lugs, but don't have 240 volts across the lugs on the breaker then you have a bad breaker, but if you fail to see 240 volts across the main lugs, refer above and call power company.
 
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Old 10-20-13, 06:31 PM
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On second thought, measuring 120 volts from a terminal screw to ground for all the screws really means nothing.

A heating elemnt could be "switched off" and you would measure 120 volts from either end to ground if the other end is still connected to one side (the "negative" or -120v side) while the switch (say in a thermostat)controls the "positive" or +120v side.

Using "positive" and "negative" when discussing alternating current is not meaningful but a "dumb" 240 volt all electric water heater (which has no electronics) will work equally well on 240 volts direct current including a system with +120 and -120 for the two legs if such a power source existed.

A home water heater never has both elements on at the same time. So you would measure 240 volts across the element terminals for only one element (or neither if the tankful of water is fully heated). If the water heater had been "off" for a long time and all the hot water used up, the upper element should give you the 240 volt reading across its terminals (not to ground) and the lower element should give 0 volts across its terminals.

Are you having issues with selected circuits all over the house? If not then chances are the power company lines and the service drop are not the problem.
 

Last edited by AllanJ; 10-20-13 at 07:06 PM.
  #13  
Old 10-20-13, 07:51 PM
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I've had some other issues with power. One circuit under the 25 amp went out for a few days. It all seems to be on the left side of the breaker box. The double 25 amp is at the top of the box on the left. Could that affect the lower circuits?
Almost all residential distribution panels are built so that each leg of the 120/240V single-phase service supplies alternating rows of breakers.

Since you have a 2-pole 240V breaker that occupies two vertically adjacent spaces, that's how your panel is made. And no, the condition of one branch circuit breaker won't affect the performance of any other branch circuit breaker.

The breakers in the left-hand column could be loosely connected to the tabs on the bus bars. You can take the cover off the panel and push on the connecting end of each of those breakers to see if any of them will click into a more solid position and make better contact.

The end of the breaker that makes contact with the feed bus is usually the end toward the center of the panel.
 

Last edited by ray2047; 10-20-13 at 07:55 PM. Reason: 129>120
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