Bonding hot to cold

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genesparky

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Kingman Az.
A plummer in my work crew tells me that he has seen the hot and cold water pipes bonded together (ground clamps and wiring, he's not sure what size) at water heaters he has been called on to service (all electric). I personaly have not seen this and I don't see where it is required but I do see a FPN that says it provides additional safety. I maybe overthinking this but 250.52 A,1 says interior water piping located more than 5 feet from the point of entrance to the building shall not be used as part of the grounding electrode system. Any thoughts from the experts?
 
Re: Bonding hot to cold

gene, we normally bond the hot and cold water lines (jumper across) above the water heater due to the dielectric unions the plumber uses to connect waterlines to water heater the continuity between is broken. This is in conjunction with the main water pipe entrance. With the common use now with PEX poly water lines this is starting to fade away.
 
Re: Bonding hot to cold

Remember, using the pipe as an electrode is what requires the "witin five feet of entrance". The pipes should be bonded to each other, and the panel's ground, even if the pipe is not being used as an electrode.

By "electrode", I mean the earth connection, as in at least ten feet of continuous pipe in contact with earth.
 
Re: Bonding hot to cold

Here locally we also have to bond across the pressure reduction valve, to keep a good mechanical bond. Is this common in other areas of the country. Also some plumbers use a type of compression coupling or tee that is make of plastic on copper pipe and this also has to be bonded.
 
Re: Bonding hot to cold

growler, yes we bond across pressure reducing valves, backflow preventers and any thing that is removable or non metallic interruptions in continuity of water piping here in Indiana. As I mentioned above the dielectric unions are used per plumbing code. Also, Black and CSST gas piping.
 
Re: Bonding hot to cold

Originally posted by richwaskowitz:
Hold on there.... If one bonds the hot outlet pipe to the cold inlet pipe, doesn't that kind of negate the purpose of the dielectric union for corosion prevention?
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Isn't the dielectric union for corrosion inside of the tank?
 
Re: Bonding hot to cold

The dielectric coupling is to used to stop corrosion of the galvanized nipple to the copper that is in the house.
 
Re: Bonding hot to cold

lucky1974 is correct. It is only to stop corrosion at the nipple (copper vs galvinized pipe), no where else.

On service change overs and new construction I place a bonding jumper between Hot, Cold and gas line. That way there is no issues with the AHJ regarding whether it requires or not a bonding jumper.
 
Re: Bonding hot to cold

On service change overs and new construction I place a bonding jumper between Hot, Cold and gas line. That way there is no issues with the AHJ regarding whether it requires or not a bonding jumper.
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At one time we did the same thing around here, but some inspectors wouldn't allow the jumper to the gas pipe. Even had one take out a screw driver and remove the jumper. Seems that the interpretation here in NJ is that the jumper to the gas pipe is not required since the EGC to the gas appliance will provide the bonding. Still don't know why the guy removed the jumper though. :confused:
 
Re: Bonding hot to cold

Seems that the interpretation here in NJ is that the jumper to the gas pipe is not required since the EGC to the gas appliance will provide the bonding
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Infinity, this was changed several years ago when Ashok Mheta (head of the Code Interpretations Dept. down at the DCA) made an interpretation stating that the bonding of gas pipe was not required. We started bonding the gas lines and the gas companies would come in and remove it when they came to do any service. Mike Holt also had an article several years ago about gas lines corroding (somewhere in Austin, TX I believe) because the gas lines were bonded to the electrical systems of the buildings and residences. If I can find the article I'll post it.

Now, getting back to the question at hand if you look at 250.104(B)Metal piping it states that bonding jumpers shall be sized in accordance with 250.122 using the rating of the circuit that may energize the piping system(s). Thus, if you have a 200 amp service you are not required to use larger than #6 to bond across the hot and cold water lines. Having said that, there is a growing number of inspectors up here in northern NJ that are requiring this bonding jumper to be the same size as the bonding wire to the cold water main. So, for a 200 amp service I would have to use #4 (according to whomever the AHJ is). It really doesn't matter to me one way or another because there's always enough scraps on the job to use either size. I just wish the DCA would make a greater effort to get all these guys on the same page.

I believe the reasoning for bonding these together was the same reasoning as bonding across the water meter. Years ago the wiring methods (especially K & T) for many dwellings were such that the power feeds were run from room to room across the ceilings to each lighting fixture outlet and switch legs were dropped down to turn on lights. When you got to the bathrooms, homeowners wanted convenience receptacles for hair dryers, etc but had no neutral at the switch box. So what did they do ? They tapped the hot leg off the switch and ran a jumper wire from the water pipes under the sink to the other side of the receptacle. This worked fine until the plumber came to change out the hot water heater. If he removed the heater and grabbed both the hot and cold lines he became a fuse. Same reasoning for bonding across the water meter.

Phil,
Gold Star Electric

[ January 27, 2006, 06:32 AM: Message edited by: goldstar ]
 
Re: Bonding hot to cold

The dielectric union separates the copper from the steel. I don't see how bonding the hot and cold waterlines would effect that.ie.(causing corrosion) Before these unions entered the picture the piping had continuity. Also, The way I interperate 250.104(B) 05' NEC is for multiple occupancy buildings and then (A) size Metal Water piping table 250.66 and all other size ie. gas table 250.122 Is this correct? Bond sizing that is.
 
Re: Bonding hot to cold

Originally posted by goldstar:
if you look at 250.104(B)Metal piping it states that bonding jumpers shall be sized in accordance with 250.122 using the rating of the circuit that may energize the piping system(s). Thus, if you have a 200 amp service you are not required to use larger than #6 to bond across the hot and cold water lines. Having said that, there is a growing number of inspectors up here in northern NJ that are requiring this bonding jumper to be the same size as the bonding wire to the cold water main. So, for a 200 amp service I would have to use #4 (according to whomever the AHJ is).
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250.104(B) is not the right section. That is for "Other Metal Piping". The correct section for bonding metal water piping is 250.104(A). 250.104(A)(1) references Table 250.66. Assuming the 200 amp service uses 2/0 cu or 4/0 al service entrance conductors, Table 250.66 requires a #4 bonding jumper.
 
Re: Bonding hot to cold

Don't forget to bond around whole house water filters and water softeners too if you feel the need. I did a service change in October in which I billed out for 8 water pipe bonding clamps. Seven of them were for bonding around stuff, and one was for the GEC connection. It ain't like the old days...
 
Re: Bonding hot to cold

250.104(B) is not the right section. That is for "Other Metal Piping". The correct section for bonding metal water piping is 250.104(A). 250.104(A)(1) references Table 250.66. Assuming the 200 amp service uses 2/0 cu or 4/0 al service entrance conductors, Table 250.66 requires a #4 bonding jumper.
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Eprice,

Section 250.104(A) is for the main bonding wire (bonded to the cold water main and across the water meter) that is attached to the service equipment enclosure. In that case a #4 copper wire is the correct size. We're talking about the bonding(or jumper or shunt wire) across the hot and cold water pipes that emerge from the hot water heater. This falls under "Other Metal Piping." I believe that my reference to 250.104(B) is correct.
 
Re: Bonding hot to cold

The hot and cold water pipe at the water heater is still water pipe. 250.104(B) is for "Other Metal Piping" (pipe that is not water pipe), such as gas piping. The language in 250.104(A) does not limit itself to the main bonding wire, but covers "The metal water piping system". The second sentence of 250.104(B) mentions "bonding jumper(s)", indicating that there may be more than one required. The bonding jumper across the water meter and the bonding jumper from hot to cold both serve the same function, to make sections of the metal water piping system electricaly continuous.

[ January 30, 2006, 07:00 PM: Message edited by: eprice ]
 
Re: Bonding hot to cold

eprice,

The more I read through this section the more confused I become. I will agree that your interpretation makes more sense, however, I can't seem to find a section that deals with the bonding across the water meter or from hot to cold on the water heater. While it makes sense to do this I fail to see where you're instructed or directed to do so. Like I originally said, it makes no difference to me whether I use #6 or #4 because there's always enough #4 scraps available to make the jumper. My gripe is that all the inspectors aren't on the same page with this and it's a bit picayune to fail what is in all other respects a quality installation just because an electrician used a #6 water heater jumper instead of #4 for a 200 amp service. If you stop and think about this, is there any point within a residence (except at the service panel which is already bonded to the cold water main) where 200 amps is likely to energize a water piping system ?

[ January 31, 2006, 06:00 AM: Message edited by: goldstar ]
 
Re: Bonding hot to cold

I believe the requirement for bonding across the meter and at the water heater comes from the general requirement in 250.90 that the fault current path be made electrically continuous. If a fault to the water piping occurs any where along the system, we need to make sure that the fault current has a continuous path back to the source of the current. Section 250.104(A) is the place where we find the specific requirements for doing that bonding when it comes to the water piping system. Note that, unlike 250.104(B), 250.104(A) does not limit the bonding requirement to piping systems that are "likely to become energized".

I have to agree with you, in that I'm not entirely sure why the bonding for the water piping system follows different rules with respect to sizing and the need for a likelihood to become energized than for other metal piping systems. Maybe it is because the metal water piping system will be in such close proximity to people where they are using water, and gfci protection can't be used to reduce the risk of shock from this source like it can from cord connected appliances. Maybe it is just because it seemed like a good idea at some point in time in the history of the code making process, and no one has submitted sufficient justification to support a code change.

[ January 31, 2006, 03:55 PM: Message edited by: eprice ]
 
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