Service entrance ground

[Gary Bottomley]

I ran into a 35 year old house with the main panel ground only connected to the Service Entrance conduit. (See attached photos: the ground wire is connected to the collar connector via what appears to be a factory applied screw connector clamp. Sorry it doesn't show up well on the photo.)
Was that an acceptable method for grounding at that time?
If so, how should this be covered in my report?

[Robert Meier]

A metallic service raceway is required to be bonded by a means other than a standard locknuts. What you have in photo #2 is a bonding bushing. This is one of the permitted ways to bond that service raceway. It should terminate at the neutral bar. Is there a metallic water pipe in the building? There should be a grounding electrode conductor (GEC) run to that pipe if it's in contact with the earth for 10' of more.

[Gary Bottomley]

Originally Posted by Robert Meier

A metallic service raceway is required to be bonded by a means other than a standard locknuts. What you have in photo #2 is a bonding bushing. This is one of the permitted ways to bond that service raceway. It should terminate at the neutral bar. Is there a metallic water pipe in the building? There should be a grounding electrode conductor (GEC) run to that pipe if it's in contact with the earth for 10' of more.

Robert:
Am I hearing that the bonding bushing, connected to the metallic service raceway which, as shown in photo #1, does continue into the ground, would be considered as one acceptable means of grounding as the GEC does terminate at the neutral bar? And, was this possibly acceptable by code at the time of installation?
I understand that the current code requirements are two forms of grounding as you suggest via the metallic water pipe method.
This house is on a private well system which was not part of my scope of inspection and therefore, unfortunately, I failed to look at the pipe coming into the building from the well as it was covered with insulation. So, I can't say the 10' long pipe would exist.
Would a seperate GEC run to a ground rod if, more than 10' from the service entrance conduit, comply with current code?

[Robert Meier]

OK since you mentioned current code, from the 2008 NEC, you would need to use all grounding electrodes that are present. This would include 10' of buried metallic water pipe. If there is no metallic water pipe then you would need to install a so called made electrode. This could be a ground rod, ground plate or a ground ring. The rod is the most common and must have a resistance of 25 ohms or less. If it does not then it must be augmented with another electrode. Typically a second rod.

Around here we just install two rods otherwise an inspector may ask for the single rod to be tested to prove it has the 25 ohms or less. Testing is expensive, ground rods are cheap.

The part you've mentioned about two forms of grounding is somewhat inaccurate. The NEC says that a metallic water pipe electrode must be supplemented by one additional electrode. If you do not have a metallic water pipe electrode then only one electrode is required. Take for example a new building with a Concrete Encased Electrode (CEE) in the building footing and a plastic water pipe. That building would only require one electrode, the CEE.

The grounding bushing and jumper are required to bond the metallic service raceway since such a raceway is not permitted to be bonded by a standard locknut.

So if we go down a sort of check list:
-The metallic service raceway is properly bonded, OK.
-Is there a main bonding jumper which bonds the neutral bus to the enclosure?
-Is there a GEC run to an electrode such as a ground rod or a water pipe from the neutral bus?

[Gary Bottomley]

Thanks Robert;
Very informative and from this, I believe I can cover the response.

[Robert Meier]

Originally Posted by gbottomley

Thanks Robert;
Very informative and from this, I believe I can cover the response.

Anytime, glad that I could help.