Grounding

[Darren]

Hey guys (and gals),

Looking for some guidance on panel grounding. 2-family house with additional owner’s panel. 3 separate meters located at ground level. The owner’s panel is located at the first floor and is grounded to a rod and water pipe with jumper across meter. The other 2 panels are side by side at 2nd floor with a ground cable between panels. I can see a bare cable exit 1 of these panels and while I can’t trace the entire length, it does appear to be connected to the rod near the owners panel.

2 part question: are the 2 upper panels now considered grounded to the rod? Do the upper panels have to be tied to the plumbing pipes?

Thanks

Darren

[Richard Moore]

Darren...

Assuming there is only one plumbing system(?), and it's all metallic, then it all sounds OK. The individual water heaters should each be fitted with a hot/cold bonding jumper. Even if the water piping is the main grounding electrode and the rod a "supplemental" the GEC should still be attached within 5 feet of where the water service enters the building. In other words you couldn't just attach a GEC to the water piping on the second floor.

[Darren]

Richard,

Yes, the plumbing is one system and the connection to it from the lower panel is right at the water entrance and I did call out the water heaters. If the 2 upper panels are tied together is that considered a splice in the ground cable?

Thanks for your help

Darren

[a46geo]

Originally posted by Richard Moore

Darren...

Assuming there is only one plumbing system(?), and it's all metallic, then it all sounds OK. The individual water heaters should each be fitted with a hot/cold bonding jumper.

Richard,

I recommend bonding metal water and gas lines but I have never heard of a need to bond hot and cold piping.

Can you give us the rationale behind this or where to find some reference material?

George

[Richard Moore]

George…

Don’t take this as gospel, just my understanding.

A. The water heater may not provide a continuous metallic path between the hot and cold pipes. Teflon tape, plastic dip-tubes, etc, may (emphasis on may) compromise the conductivity. Similar to the jumper around a water meter…probably not really needed, but it is done.

B. The jumper provides continuity should the heater be removed for replacement and, I would imagine, also provides a measure of safety for the installer.

C. Not really a reason…but for the price of two clamps and a length of wire…why not?

Darren…

Code Check states that there be no splices between service and first electrode. However it’s not that simple. First of all the actual NEC section continues…â€

[Darren]

Richard,

Thanks for your help, I will basically say the water heater jumpers are missing and while an electrician is on site, they should confirm all grounding.

George:

Sample of regional differences; Here in New Jersey the jumpers between hot & cold pipes are common while gas pipe bonding does not exist.

Darren

[Richard Moore]

Darren...regarding gas pipe bonding...

part of 250.104(B) reads "The equipment grounding conductor for the circuit that may energize the piping shall be permitted to serve as the bonding means."

In a furnace (or WH) the cabinet should be grounded via the wiring and there is usually direct metallic contact with the piping. I have seen it argued that the gas piping IS effectively bonded. Whether this is sufficient or not may depend on the route the gas piping takes through the home and the likelyhood of it coming in contact with any other wiring. And of course on the ubiquitous local AHJ. Certainly no harm in having a seperate bonding jumper whether it is required or not, but it's a tough call to say you can always "demand" one.

It's amazing just how convoluted the whole section on grounding and bonding gets when you remember that we are dealing with conductors carrying no current under normal circumstances. [:-hspin] [:-hspin] [:-hspin] [:-hspin]

[a46geo]

Richard,

The whole issue has many points that are unclear and or up for debate. As I understand it, the grounding of the gas pipe is not the issue. It is indeed hooked to ground both at the furnace and through the incoming pipe.

The bonding of the gas and water lines together is to prevent a static charge differential from building up between the two systems.

According to Carson & Dunlop, this type of bonding is a code requirement in some parts of the country. I understand how a positive static charge on one pipe system and a negative charge on the other could cause a discharge of voltage between the two ... BUT, I have never heard of it happening in the real world.

I guess if we wait another week, we will hear about some new concern that none of us have ever heard about.

George