[hardworkingstiff]

Per the 2011 NEC, ground fault monitoring on the service at marinas is required.

In thinking about this, if the option of monitoring the service conductors before the main is chosen, how would you deal with the parallel path for the neutral (because of grounding at the main service and the earth being a parallel path for current)? I guess you could run all grounding conductors for the service through the CT so any parallel neutral current from the service to the PoCo transformer would not cause tripping of the service (code is 100ma max threshold).

Part of me thinks it would be good to monitor the service so that you can see how much current might be going to ground.

As a side note, what do you think is an acceptable parallel current through the earthing of the neutral at the service? 1/10th of an amp seems a bit low.

 

[robnj772]

Per the 2011 NEC, ground fault monitoring on the service at marinas is required.

Where does it say that? No where in 555 is this even mentioned

 

[hardworkingstiff]

where does it say that? No where in 555 is this even mentioned

555.3

You going to gig me on semantics?

 

[azgard]

Does low mean more amps or less amps? 100 ma is close enough to shock hazard; wet environment here. And I know its been posted on these forums quite a few times how dangerous marina wiring can be.

 

[hardworkingstiff]

Does low mean more amps or less amps? 100 ma is close enough to shock hazard; wet environment here. And I know its been posted on these forums quite a few times how dangerous marina wiring can be.

100 ma is quite a bit above shock hazard, but as a parallel bath for neutral current from the service to the transformer I don't think it is uncommon.

As I was thinking about this, I started thinking it would be nice if the marina operator could know how much current was going from his service through the earth (because like you said, marinas can be dangerous). I would think if you started seeing an increase in earth current from your service, it might be a sign that the neutral (from the transformer to the service) was developing an issue. How nice would that be, to be able to know before equipment got damaged that a problem was developing?

 

[robnj772]

555.3 You going to gig me on semantics?

Where does its say monitoring is required??

 

[hardworkingstiff]

Where does its say monitoring is required??

The main overcurrent protective device that feeds the marina shall have ground fault protection not exceeding 100ma

How would you do it?

If you would put a ground fault main in, the main breaker "monitors" current for ground faults and trips when called for. No warning, no indication of where the problem came from, nothing but slam off.

The product I am looking at will monitor the current and send a warning as fault current rises before it reaches trip level (of course unless it's a quick low resistance fault). Depending on how you route the service grounding conductor you can monitor the current going to ground or not.

Anyway you seem to be arguing that the word "monitor" is not in the code, and I will concede that point with the argument that you cannot comply with the code unless you install something that will monitor ground fault current.

So, now that you got me to admit that I did not quote the code verbatim, would you care to contribute something helpful?

 

[BBQ]

Lou I hate to do this but I don't see a monitoring requirement in 555 anymore than I see a monitoring requirement in 210.8.

You can certainly choose to add monitoring equipment.

 

[ponyboy]

Someone's confused. It's gfp that's required. Monitoring means something different to me

 

[robnj772]

How would you do it? If you would put a ground fault main in, the main breaker "monitors" current for ground faults and trips when called for. No warning, no indication of where the problem came from, nothing but slam off. The product I am looking at will monitor the current and send a warning as fault current rises before it reaches trip level (of course unless it's a quick low resistance fault). Depending on how you route the service grounding conductor you can monitor the current going to ground or not. Anyway you seem to be arguing that the word "monitor" is not in the code, and I will concede that point with the argument that you cannot comply with the code unless you install something that will monitor ground fault current. So, now that you got me to admit that I did not quote the code verbatim, would you care to contribute something helpful?

Well I did just contribute something helpful. I showed that what you said is not true, monitoring is not required by code as you stated it was. I don't know how I would do it because unless the customer specifically asked for it I wouldn't do it. I have done quite a few marinas and never monitored the ground fault and never had an issues. You are giving a new meaning to the old saying" making a mountain out of a mole hill"

If there is a fault, it trips. This monitoring you are wasting your time with is just going to warn you it's going to trip, what , like a minute before it trips.

 

[hardworkingstiff]

Based on others posts, I guess I owe robnj772 an apology.

I apologize rob.

 

[hardworkingstiff]

Now that I've been corrected, anyone care to discuss the problems of having a GFP main set at 100 ma in a marina that might have 40 boats plugged in and the main keeps tripping from someone's intermittent wiring problem on their boat?

I have never installed a GFP main. I assume it monitors the current on each phase inside the breaker, and I would guess it would have to have a neutral CT to input to the breaker if a neutral was used. Do I have a correct assumption?




In discussing this subject with people in this business, GFP mains are not desirable.

 

[hardworkingstiff]

Just a comment to you guys jumping me about equating ground fault protection to monitoring, I offer the following

A GFCI is specifically designed to protect people against electric shock from an electrical system, and it monitors the imbalance of current between the ungrounded (hot) and grounded (neutral) conductor of a given circuit.

http://ecmweb.com/content/how-gfcis-work

Sometimes it gets a bit lawyerly in here.

 

[JRaef]

Just a comment to you guys jumping me about equating ground fault protection to monitoring, I offer the following
http://ecmweb.com/content/how-gfcis-work

Sometimes it gets a bit lawyerly in here.

More lawyerlyishness...

A GFCI is not the same as what is being referred to when discussing GF protection on main breakers. Same basis, similar words, totally different implementation.

But to get off of the lawyerlyishness, GF protection at the 100ma level inside of a CB is mostly done now with Electronic Trip Units (ETUs) that perform what is called the "Residual Current Detection" method. In a nutshell, it just measures the goesouta current from one pole then compares it to the goesinta current from the other(s), and if the difference is more than 100ma, it signals the trip function. So is that "monitoring"? Technically yes, but there is no output value transmission, it's just a another trip function that all takes place INSIDE of the CB and it's all transparent to the user, although some of the nicer ones will let you know WHY it tripped so that you know it was GF as opposed to SC or OC.

You MIGHT be able to add an external GF Monitor (GFM) system to a non-GF main breaker that has a Shunt Trip coil in it, and the GFM can send a trip command to the ST coil. That's the way it was done for years before ETUs existed. But as a rule, the GFMs were UL listed together with the CB so AHJs had no problem accepting it. If you use an off-the-shelf GFM system, like a Bender Systems for example, and tie it to a Main CB that has a ST in it, the AJH will LIKELY accept it, but he may not. I've had it happen. I argued til I was blue in the face, didn't matter. He was the God of his own little world... I had to go buy a new 1000A main breaker (which I was trying to avoid by buying the Bender unit), then Bender refused to let me return their unit. I think I still have it in a dusty back corner somewhere, a reminder of an expensive lesson learned.

As to predictive fault monitoring, that can STILL be done if you like, although in my experience, it will be like robnj772 said, a couple of minutes warning. I don't know if that's worth the expense to me, but you can do what you want.

 

[JRaef]

Funny side note: I read this a few months back when having a similar discussion on GF in ETU main breakers. It was apparently discussing GFCIs, but was misapplied to the Wiki article on Residual Current Detectors, the European version of our GFCIs. I just thought it was worth a chuckle:

These values were set by tests at Underwriters Laboratories during which volunteers holding cups of rice were subjected to shocks of known amperage and voltage. Initially, the GFCI was developed using pigs and hogs in swimming pools, because their skin is like that of humans.

I'm assuming the "cups of rice" were used as a metric on the intensity of the shock. I can just imagine the lab report:

"Subject A was subjected to 3ma for 25 seconds, spilling 14 grams of rice. Subject B was subjected to 8ma for 25 seconds and spilled 220 grams of rice. Clearly 8ma is too much..."

 

[hardworkingstiff]

JRaef

Thank you.

The customers do not want to lose there whole service due to the actions of one boat. So, it looks like the Bender unit with shunt trip breakers for the feeders to the dock pedestals.

The problem I have is this thing fails in the on position as far as power going to the docks. In other words, if the power to the output relays of the Bender unit drops out (for whatever reason) then the Bender unit closing a relay won't send power to the shunt trip breaker. If the Bender unit loses power there is no protection, and no interruption of power.

Do they make a shunt trip breaker that takes continuous power to allow the breaker to close and the loss of power will cause the breaker to open?

I was trying to see if I could just use GFP branches, but it seems that most of them are designed for 3-phase (no neutral) circuits, or don't go to the ampacities I need (100 to 200-amp single-phase).

 

[JRaef]

Thank you.

The customers do not want to lose there whole service due to the actions of one boat. So, it looks like the Bender unit with shunt trip breakers for the feeders to the dock pedestals.

The problem I have is this thing fails in the on position as far as power going to the docks. In other words, if the power to the output relays of the Bender unit drops out (for whatever reason) then the Bender unit closing a relay won't send power to the shunt trip breaker. If the Bender unit loses power there is no protection, and no interruption of power.

Do they make a shunt trip breaker that takes continuous power to allow the breaker to close and the loss of power will cause the breaker to open?

I was trying to see if I could just use GFP branches, but it seems that most of them are designed for 3-phase (no neutral) circuits, or don't go to the ampacities I need (100 to 200-amp single-phase).

There is what's called an Under Voltage Trip as opposed to a Shunt Trip. they trip the mechanism in the breaker when you LOSE power to it's coil. But be forewarned, you have to think through wanting to have to reset the breaker EVERY time you lose power for ANY reason.

 

[JRaef]

Funny side note: I read this a few months back when having a similar discussion on GF in ETU main breakers. It was apparently discussing GFCIs, but was misapplied to the Wiki article on Residual Current Detectors, the European version of our GFCIs. I just thought it was worth a chuckle:

I'm assuming the "cups of rice" were used as a metric on the intensity of the shock. I can just imagine the lab report:

"Subject A was subjected to 3ma for 25 seconds, spilling 14 grams of rice. Subject B was subjected to 8ma for 25 seconds and spilled 220 grams of rice. Clearly 8ma is too much..."

LOL, gotta love Wikipedia and open editing. I think some people make a game of trying to get things into articles as jokes. I revisited that page and the "cups of rice" thing is gone. But now it says this!

A residual-current device (RCD), or residual-current circuit breaker (RCCB) or residual twin-direct current couplet (R2D2), is an electrical wiring device that disconnects a circuit whenever it detects that the electric current is not balanced between the energized conductor and the return neutral conductor.

:laughing:

 

[JRaef]

Here's one possible solution for you.

You have to have the 100ma trip in the main. Do that.

Then you have feeders going to each dock, those must be UL489 listed circuit breakers plugged into the distribution panel, so do that too.

But DOWN STREAM of each of the feeders, you can install some of the IEC style RCD units set for 30ma for example. They are not UL489 listed, so they cannot REPLACE the feeder breakers, but there is nothing saying you can't ADD them to the circuit for your own porpoises as long as the UL489 breaker is ahead of them in the same branch ciruit. So if any single boat starts having a problem, these devices trip at 30ma, well below the threshold that kills everyone by tripping the main CB.

 

[BBQ]

I think some people make a game of trying to get things into articles as jokes.

If you watch Tosh.0 he has challenged people to do just that.


NWSF. http://tosh.comedycentral.com/blog/2010/02/03/your-wikipedia-entries