confused with what's going on, ground/neutral issues, tripping GFCI etc. 1

[michaelwoodcoc]

I'm not an electrical engineer but I thought I'd get better responses here than if I posted in the hobby section.

I'm having a strange issue and I'm a little tired to get my head weapped around it for the night so I figured I'd ask before I jump on it tomorrow.

My shed has a sub panel coming off a sub panel for the hot tub which is run off a GFCI breaker in the main panel. When the ground rod is connected in the shed, the GFCI trips. No ground rod, it doesn't trip.

I can measure .1 volts from either leg to the ground rod at the shed. I figured something wierd might be happening like my shed was conducting ground current from the house to the rod.

I pulled on the wire from the meter box to the ground rod and the wire just came out of the ground.

Also the main panel is not grounded like I'd prefer to see, but if it's supposed to be grounded at the meter that's fine I guess but it was not grounded at the meter, and the wire they used seems inadequate compared to the wire (#8 I think) that I used for the shed.

I had one ground rod left from the shed that has not been finished and I pounded it in near the meter box and grounded that wire for the night. GFCI still tripped but the ground rod by the shed is in much more moist soil so it's more conductive.

Much of the glaring problems I've already fixed. The wires from the spa panel to the shed are now THWN run in water right conduit, no rommex in conduit. Some I have yet to fix.

I'm just curious, is there something I'm totally overlooking here? It seems like I should not have the GFCI tripping, but I also need two ground rods for the main panel, can I just do that at the meter or do I need to have the panel attached directly to the ground rods?

Engineering student. Electrical or mechanical, I can't decide!
Minoring in psychology

 

[itsmoked]

Have you attempted resetting the tripped GFI after the ground at the shed has been connected?
GFI's are instantaneous and sensitive. Hooking up the ground could cause a trip that wouldn't normally occur.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[IRstuff]

Alternately, you have a leakage path that is completed when the ground rod in engaged.

The ground wires aren't supposed to be carrying current, so whatever gauge they are, they're probably adequate for any exigent circumstances, like a solid ground short. Nevertheless, bad insulation, etc., could allow some line current to leak into the grounds, which would trip the GFCI, since it wants all the current coming in to go back out the way it came.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

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[RRaghunath]

Apparently, the leakage through the bad (or aged) insulation of wiring to ground is causing the trip of GFCI.
Have you checked all the panels, junction Boxes / terminal boxes for sign of moisture or dirt?
How old is the installation?
Splitting the wiring of the installation to go through two separate GFCIs (instead of the present one GFCI taking all the leakage) could help.
Other option is choosing GFCI that can be stable at higher leakage current. 100mA rated GFCI should provide human protection in addition to being more stable, though 30mA rating is the best for human protection.

 

[waross]

Take another look at the hot tub sub panel Keith.
It looks as if the ground wires are landed on the neutral bus.
End of story.
The GFCI feeding the sub panel compares the current on the hot conductors and the current on the neutral conductor.
If the currents do not sum to zero, the GFCI trips.
If you connect the neutral to the ground downstream of the GFCI, the ground conductor shares the neutral current and the GFCI trips.
Install a ground bus in the Hot tub sub panel similar to the ground bus in the shed sub panel and connect ALL the ground conductors to the ground bus.
Check the neutral bus in both the hot tub sub panel and the shed sub panel for a grounding screw.
It is common for one screw in a neutral bar to go through to the panel to connect the neutral to the grounding system.
Some panels use a jumper instead of a screw.
If the panel is NOT a main panel, this screw should be removed.
This is a code issue. Sub panels in a separate building may be an exception.
BUT
If you have the neutral connected to ground downstream of a GFCI the GFCI will not work properly.
The GFCI is not connected to ground and does not care if the system is grounded.
The GFCI looks at the current balance between the hot(s) and neutral and if it sees an unbalance it assumes that some current is going where it should not and trips.
I hope that you know that if you are completely isolated from ground (insulated boots, dry wooded floor, not touching any grounded surface, and you make contact between a hot and neutral or between two hots, the GFCI WILL NOT SAVE you.
YOUR PROBLEM IS THE CONNECTION BETWEEN THE NEUTRAL AND GROUND IN THE HOT TUB SUB PANEL.
Did you know that the first GFCIs were constructed of discrete components mounted in a 6"x 6" x 4" junction box?
Not my first rodeo and not my first GFCI by almost 50 years.
And don't forget: Once you have corrected the wiring, you may still have ground current leakage somewhere else.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

By the way, best practice is to install a GFCI on each circuit that is to be protected.
If a GFCI is mandated by the code, as for a hot tub and possibly lights and receptacles near the hot tub, then the GFCIs must be the lower rated GFCI.
The GFCI should be in the hot tub sub panel and you may need more than one depending on what is connected to the panel.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

Engineering student. Electrical or mechanical, I can't decide!

How's mechanical looking today? grin

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Ahh, you nailed it Bill! Good eye.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[stevenal]

This is a mess. For one thing, white wires on breakers are not allowed. Suggest you get a licensed electrician to look thinks over.

 

[thebard3]

I think white wire for a power conductors is okay, if you indicate so with a piece of colored tape at each end (Red, for example).

Brad Waybright

The more you know, the more you know you don't know.

 

[michaelwoodcoc]

yeah I agree this is a total mess. The spa was redone by a spa guy many years ago, not an electricion.

I was thinking of doing the following:
SPA panel no longer on GFCI from main panel

SPA equipment each receives it's own GFCI in the respective panel

Shed stays wired as is, with the neutral and ground both landing on the neutral bar from the spa, assuming this does not in anyway create a hazardous condition.

We're looking at getting an electrician out here, some of the things I found are alarming, like the house not being grounded properly. That must've been done by an electrician who just didn't care, and although I don't know everything I need to, I care enough to try.

Engineering student. Electrical or mechanical, I can't decide!
Minoring in psychology

 

[waross]

There is probably a grounding electrode buried somewhere below where the wire ended.

Shed stays wired as is, with the neutral and ground both landing on the neutral bar from the spa, assuming this does not in anyway create a hazardous condition.

Any neutral current will be divided between the neutral conductor and the Grounding conductor.
This is a code violation in Canada.
In the US it depends.
If the hot tub sub panel is in the same building as the main panel it may be a code violation.
Someone who is current on the NESC help me out here please.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[badservo]

There is no neutral conductor going to the hot tub panel so it is not able to supply 120V circuits. You are connecting the hot tub panel ground through the neutral conductor of the GFCI which is also wrong. The combination of poor grounding at the meter, the ground rod at the shed, and the improper grounding / neutral connections are causing the breaker to trip. You need a neutral conductor and a ground conductor going to the hot tub panel and they must not be connected together at the hot tub panel. You should seek professional help for this.

 

[MacGyverS2000]

Ugh... white wire of a 240V run not taped in black to indicate it's a hot line, subpanels that appear to be grounded locally rather than run back to main panel <shudder>. Well, at least the wire runs are relatively clean rather than jammed in there all willy nilly.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[waross]

Under the latest rule change in the Canadian code, the only connection between the neutral and ground shall be in the main panel.
This was always the way inside a building, but in some circumstances a second connection between the neutral and ground was allowed in separate buildings fed from the main building.
This exception has been removed from the Canadian code.
It may still be a rule in the NEC, for separate buildings.
Your hot tub panel appears to be fed by USEI90 Cable: Underground Service Entrance, 90 degree rated.
This cable was two hot conductors and a bare concentric neutral.
The concentric neutral was allowed to be used as both neutral conductor and as an equipment bonding conductor.
This is no longer allowed under the Canadian code for new work but is still allowed for repairs to existing installations.
The replacement cable for underground services and sub services is ACWU90: Armoured Cable Wet Underground.
ACWU90 is available with copper conductors.
This cable is most commonly supplied with aluminum conductors and is often erroneously called Aluminum Cable Wet Underground.
Not so.
AC90 cable, similar to the old BX cable is commonly supplied with copper conductors and AC indicates Armoured cable.
ACWU90 is an extension of AC90.
Think, BX with a plastic jacket.
Three conductor ACWU90 has three insulated conductors and a bare equipment grounding conductor.
The good news is that you don't have to replace the USEI90 cable but you do have to move the GFCI breakers as you have indicated that you intend to do.
GFCIs in the hot tub sub panel should work as expected as long as there is no connection between the neutrals if there is more than one neutral conductor going to the hot tub and as long as there is no connection between the neutrals and the ground or grounding conductor.
You can not use a common neutral for GFCI circuits.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[EdStainless]

At the end of the day don't overlook a faulty GFCI. I have spent hours chasing an issue that was a bad breaker.
These can age and develop wonky response, especially outdoors.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[waross]

Good call, Ed.
In this case however, the cause is obviously bad wiring. If the wiring is corrected and the GFCI still trips, come back and re-read Ed's post.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[michaelwoodcoc]

I'm slightly confused on some of the wiring specifics, for example the grounding. The hot tub panel is technically the same structure or part of the house.

The shed is a different structure and panel and thus I added a ground rod.

Before I grounded the house with one rod I was able to measure .6 volts in the shed between the neutral and ground rod. After grounding the house I only measured .1 volts if I remember correctly.

One thing that I need to ensure is I think a difference in ground potentials or ground loops if either of these is the correct terminology.

I'm running cat6 to the shed for two or three security cameras. I've heard there can be issues with different, or maybe it was the same ground, for network connections. If that's the case I'll do whatever is best for the network.

We're having an electrician come take a look but I'm not the most confident in others' work. I already fixed some work done by an "electrician", romex run in questionable conduit under ground.

There was 240 running to the shed on 10/2 with no sub panel on a 30 amp breaker in the hot tub panel. It was split in a junction box in the shed to a 240 outlet for solar panels that I installed and a 120 outlet. I questioned whether any of that was up to code, and if the 240 breaker would provide adequate protection for the 120 circuit. No way to call the electrician back, he passed from covid.

Engineering student. Electrical or mechanical, I can't decide!
Minoring in psychology

 

[waross]

No way to call the electrician back, he passed from covid.

That reminds me of a problem with a generator in a lobster fishing boat.
Boat owner;
"We had an electrician go over the generator last summer but we can't ask him what he did."
"Why can't we ask him?"
"He was working under the local church ans something went wrong with his electric drill."
"I see what you mean."
The church in question was built on pilings over a coral reef.
Working under the church he would have been up to his waist in sea water.
COVID is probably a lot less painful.
I wouldn't worry about those low voltage levels.
Quite possibly you are seeing battery action due to dissimilar metals in your measurement circuit. Some multi meters will respond to DC on the AC scale.
And, when the neutral is connected to the ground downstream of the main panel connection, the ground passes some of the neutral current.
Most of the outbuildings in North America have lived with that issue since day one.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[wde0665]

eh, residential wiring isn't in my sandbox, but was advised when adding a sub-panel to a remote shed, that a ground conductor had to be run back to the main panel ground, making for a 4/C cable for 240V service, that a separate, independent, isolated ground rod at the shed was not allowed, at least around here... Right or wrong, no problems with the GFCI in the remote building...