GFCI protection for electric water heaters
- Thread starter Protek
- Start date
- Status
- Location
- Illinois
- Occupation
- retired electrician
Because you don't put your body or parts of your body in the water heater.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
You
You are a "Junior Member" and you act that way?
In a pool, the water is not necessarily bonded and you are immersed in the water and may provide a lower resistance path to grounded metal or even just across a voltage gradient in the water.
In a shower, the water has to get to you through at least a short length of grounded (bonded) metal pipe.
The electrocution hazard in a typical shower installation is far more likely to come from direct leakage contact to the pipe from other wiring which may not be GFCI protected or from an energized drain coupling rather than from a problem at the water heater.
growler
Senior Member
- Location
- Atlanta,GA
I think the key word here is "need".
Need is determined by the number of incidents where people or injured or killed.
If a number ( even a small number ) of people were injured by faulty water heater elements then I think GFCI protection would be required. Or if the electrical manufacturers thought that the public could be suficiently scared into believing this was necessary.
His answer was ridiculous, sorry. I've been working with electrical systems and power for 36 years, I'm not a 'junior' anything.
The water itself is a conductor and being in the shower water your body resistance is reduced to 300 ohms and you can be killed. Look here for more info: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763825/
luckylerado
Senior Member
- Location
- Lake of the Ozarks
Tap water is a terrible conductor and in a spray or stream is not cohesive enough to create a gradient that is hazardous. Difference of potential is a whole different ballgame when talking about gradient.
JR., I do not agree with the responses that I get on this forum 100% of the time either but you come across like a total dick.
JR., I do not agree with the responses that I get on this forum 100% of the time either but you come across like a total dick.
- Location
- Illinois
- Occupation
- retired electrician
You can call my answer ridiculous, but it is fact. The main reason that the code does not require GFCi protection for electric water heaters is as I stated. If you think that is a real world issue, you have until the first Friday in November 2017 to work up a "public input" and substantiation for a 2020 code change.
Another reason is the fact that the metal tank of the heater is connected to the EGC. Water heaters are hard wired devices, and it is much more unlikely for a hard wired EGC to fail than the one that is part of cord and plug connected current.
Also water is really not very conductive. The very fact that it is not very conductive, is the main issue when a person is in energized water.
In the shower, because of the fact that the water stream is not a solid stream, it is very unlikely that even if you had energized water, that it would be able to conduct electricity to the person.
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winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
One could as easily ask 'why don't use high impedance grounded services with every device from the main breaker to the least receptacle being an auto-coordinating gfci device'?
All protective measures have to be considered in the context of both cost and benefit. The NEC is about 'practical' safeguarding, not 'perfect' safeguarding.
With a hot tub, you have people immersed in the 'appliance' itself, in close proximity to the heating elements, pump(s), controls, and wiring. The water usually has lots of added chemicals which will change its conductivity. In the event of a failure there is some chance that a person will intercept a current flowing through the water.
With a water heater, people are not immersed in the appliance itself, and are usually separated from the heating elements by grounded and bonded piping. The water heater itself is metallic and is grounded and bonded. In the event of a failure, it is very unlikely that a person will intercept the path of current flowing through the water.
However: if the water heater tank is not properly bonded, and the plumbing is plastic, then the water could be energized. Another situation that can leave the water 'energized' is if the water from the hot water heater is grounded/bonded but the shower _drain_ becomes energized because of incidental contact to a wire. But this requires 2 failures: the heating element and the lack of proper bonding, and the use of plastic pipe for the hot water with a grounded (eg metallic) drain.
If you feel that the risk presented by electric water heaters justifies the cost of a GFCI breaker, then by all means submit a proposal to the NEC. But please justify this in terms of both the cost and the benefit. For example, is the amount of current carried through water in plastic pipe likely to cause injury, how often does this sort of failure occur, have there been emergency room visits, etc.
As a side not, and totally a monetary rather than a safety issue, a heating element failure can easily cause current leakage through the water to the tank. This leakage can continue even when the thermostat is not calling for heat, and this can waste lots of money. A GFCI breaker would prevent this economic loss.
Finally, regarding luckylerado's comment. He used an inappropriate, argumentative and impolitic expression to explain that you are being argumentative and impolitic. I disagree with the way he said things, but you do come across and argumentative and impolitic.
-Jon
All protective measures have to be considered in the context of both cost and benefit. The NEC is about 'practical' safeguarding, not 'perfect' safeguarding.
With a hot tub, you have people immersed in the 'appliance' itself, in close proximity to the heating elements, pump(s), controls, and wiring. The water usually has lots of added chemicals which will change its conductivity. In the event of a failure there is some chance that a person will intercept a current flowing through the water.
With a water heater, people are not immersed in the appliance itself, and are usually separated from the heating elements by grounded and bonded piping. The water heater itself is metallic and is grounded and bonded. In the event of a failure, it is very unlikely that a person will intercept the path of current flowing through the water.
However: if the water heater tank is not properly bonded, and the plumbing is plastic, then the water could be energized. Another situation that can leave the water 'energized' is if the water from the hot water heater is grounded/bonded but the shower _drain_ becomes energized because of incidental contact to a wire. But this requires 2 failures: the heating element and the lack of proper bonding, and the use of plastic pipe for the hot water with a grounded (eg metallic) drain.
If you feel that the risk presented by electric water heaters justifies the cost of a GFCI breaker, then by all means submit a proposal to the NEC. But please justify this in terms of both the cost and the benefit. For example, is the amount of current carried through water in plastic pipe likely to cause injury, how often does this sort of failure occur, have there been emergency room visits, etc.
As a side not, and totally a monetary rather than a safety issue, a heating element failure can easily cause current leakage through the water to the tank. This leakage can continue even when the thermostat is not calling for heat, and this can waste lots of money. A GFCI breaker would prevent this economic loss.
Finally, regarding luckylerado's comment. He used an inappropriate, argumentative and impolitic expression to explain that you are being argumentative and impolitic. I disagree with the way he said things, but you do come across and argumentative and impolitic.
-Jon
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Let's be clear here. AS moderator moderates. This does not necessarily mean we know more than anyone else around here. Truth in fact is that Don is one of the more knowledgeable members of this forum.
Water in general is a terrible conductor. Have you ever read stories about basements in New Orleans being underwater from Katrina and the service panel was still energized? Well it happened. If water was a good conductor I doubt those breakers would have held.
AdrianWint
Senior Member
- Location
- Midlands, UK
Agreed. It is the dissolved salts in water which make it (semi) conductive.
In the entrance foyer to the electrical engineering building at my old University was a working CRT based TV. Nothing special about that.. except that it was fully immersed in a tank of (very pure) water! Pure water is a better insulator than air.
- Location
- Illinois
- Occupation
- retired electrician
I live in an area with hard water and the piping in my house is all copper. If I take a hot wire from the bathroom GFCI and put the bare end in running water the GFCI does not trip. I am not sure if that is because the water is not conductive enough or because the the aerator breaks up the stream enough so that it is not continuous. Probably a combination of both.
mbrooke
Batteries Included
- Location
- United States
- Occupation
- Technician
I agree with what is said here:
1. Water is not to conductive
2. A hard wired EGC is not likely to fail compared to other wiring methods.
My old home was all electric and I had a heating element leaking current into the water and never felt anything. What got my attention was hot water rain out faster, and sure enough the lower element had its sheath corded off in some places with the element shorting against the water.
1. Water is not to conductive
2. A hard wired EGC is not likely to fail compared to other wiring methods.
My old home was all electric and I had a heating element leaking current into the water and never felt anything. What got my attention was hot water rain out faster, and sure enough the lower element had its sheath corded off in some places with the element shorting against the water.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Depending on the shower head and or it's setting the steam may or may not be a continuous stream.
Difference as mentioned is you are not immersed in the water heater tank like you are in a hot tub, and if the water is energized - in the shower it is still more likely at same potential as water piping, with a whirlpool tub you have other metal items bonded to the supply pump so those items are at same potential as the pump.
With a hot tub, you often have grounded objects or just the ground surface itself around the tub at "earth potential" therefore even a raise of just a couple volts of the water in the tub will be able to be felt. Raise the voltage on the water in a water heater tank and it generally becomes equalized by the equipment grounding conductor bonded to the tank, grounded metal piping or other components before that voltage gets to the user in a tub/shower. Should it get to the tub/shower, there may still be either places to shunt that voltage away from the user or there just is enough isolation there is no potential within reach of the user.
Not saying there is no way a hazard can be present, but statistics do not show this is a very big risk or we would have requirements for enhanced protection in this area.
I have had service calls for shock incidents in a tub, so far every one of them was a water pipe bonding issue, whether it be the water supply piping or metallic drain piping. Old metal drain pipes seemed to be most common - and are easily forgotten about but if they are metallic all the way to "earth" then you are bringing true earth potential to the bathtub which may have voltage present just because of voltage drop on the service neutral which is bonded to the metal supply piping.
Difference as mentioned is you are not immersed in the water heater tank like you are in a hot tub, and if the water is energized - in the shower it is still more likely at same potential as water piping, with a whirlpool tub you have other metal items bonded to the supply pump so those items are at same potential as the pump.
With a hot tub, you often have grounded objects or just the ground surface itself around the tub at "earth potential" therefore even a raise of just a couple volts of the water in the tub will be able to be felt. Raise the voltage on the water in a water heater tank and it generally becomes equalized by the equipment grounding conductor bonded to the tank, grounded metal piping or other components before that voltage gets to the user in a tub/shower. Should it get to the tub/shower, there may still be either places to shunt that voltage away from the user or there just is enough isolation there is no potential within reach of the user.
Not saying there is no way a hazard can be present, but statistics do not show this is a very big risk or we would have requirements for enhanced protection in this area.
I have had service calls for shock incidents in a tub, so far every one of them was a water pipe bonding issue, whether it be the water supply piping or metallic drain piping. Old metal drain pipes seemed to be most common - and are easily forgotten about but if they are metallic all the way to "earth" then you are bringing true earth potential to the bathtub which may have voltage present just because of voltage drop on the service neutral which is bonded to the metal supply piping.
mbrooke
Batteries Included
- Location
- United States
- Occupation
- Technician
I vote the above for post of the month 
The water heater may have metallic piping to plumbing fixtures, but the plumbing is bonded to the same place as the EGC including the UFER and all other metal paths creating equal potential when the heating element is leaking current.
The water heater may have metallic piping to plumbing fixtures, but the plumbing is bonded to the same place as the EGC including the UFER and all other metal paths creating equal potential when the heating element is leaking current.
- Location
- Massachusetts
Not possible, just like it is not possible to bond something to earth and expect it to remain the same potential as the dirt.
mbrooke
Batteries Included
- Location
- United States
- Occupation
- Technician
Explain. Earth is a high resistance. The equal potential system in a home is very low on the other hand. Think ORs.
Why is it that is that during an open neutral the voltage between a stove and bonded plumbing is near zero but say 40 volts spigot to remote earth?
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