Possible ground loop

[redwire]

Re: Possible ground loop

I'm not sure about picking off ground from the panel neutral bus. It would have to have the current rating including all the neutral currents. Square-D might have made a mistake there- does it make sense, the feeder bus bar and neutral (return) buss bar carry the same currents for 120VAC loads. Example: take two 40A loads on one side (120VAC), you have 80A flowing on the little neutral buss bar. It's much smaller than the feeder buss bar.

What I've done (for sub-panels) is use a split-bolt to bond the ground-rod wire to the ground wire running out to the sub-panel.

I would not worry about PDU ground loops. It can be an issue between some crappy RS-232 serial systems or audio gear where a few V is a problem, so I've used orange duplex receptacles which have an isolated ground to prevent ground loops.
Your PDU's are grounded together in the rack, and back at the junction box. So there is a loop but not a prob.

[petehall347]

Re: Possible ground loop

way i understand ground loops is with audio equipment .. only one unit should have an earth wire connected to the outlet .

[Spork Schivago]

Re: Possible ground loop

ground and neutrals bonded at same place says you should be fine so far as i understand it .

Yes, that's the way I understand the ground loops. I believe I misunderstood the electrician when he said he was running a seperate grounding wire throughout the basement. I saw the two bare copper lines and thought there were two rods in the ground. I am not sure if there's any benefit to the way he ran those wires, but I guess it looks a little nicer.

I have 4 gauge lugs or whatever they're called. I crimped one on the bare wire for the rack, that bonds to the ground wire above it. I want to replace that with the (insulated?) green with yellow stripe wire and run it directly to the panel. Just need to find a place that sells it in 4 gauge.

[petehall347]

Re: Possible ground loop

ground and neutrals bonded at same place says you should be fine so far as i understand it .

[Spork Schivago]

Re: Possible ground loop

can you explain the incoming supply ? or draw a diagram . trying to get a handle on this .
for example we have high voltage transformer up a pole that supplies single phase 240v . terra terra system .. dead easy if working from same main panel . only ground loops caused from more than one unit unit connected to supply earth .

Yes sir, to the best of my ability. I believe we have a transformer at that pole that receives 240VAC and supplies two 120VAC lines plus a neutral to the house breaker. I believe it's called centre tapped.

On the panel, every other breaker is on one of the 120VAC lines. So we install a dual pole breaker, we're getting 120VAC from one incoming line, another 120VAC from the other incoming line, 180 degrees apart, giving us 240VAC.

On the panel is two bare copper lines, 4 gauge, stranded. One them runs throughout the basement and the various utilities get bonded to this line. It ties in right next to where the neutral from the pole ties into. One the GND buss bar is where the other 4 gauge stranded wire hooks up. It's a shorter run and goes out to my side yard, where it's buried and attached to a rod (I believe).

This is now why I don't think I have a ground loop at all. Even though both receptacles are ran seperately to the breaker panel, they're still sharing the same earth connection.

Originally, I thought the electrician ran two earth connections to the panel, because of the two bare copper 4 gauge stranded wires coming out of the panel.

Does this help you at all?

[delaware74b]

Re: Possible ground loop

It's different than the stuff at the auto parts stores. Here is a link to it at Big Orange:

https://www.homedepot.com/p/Ideal-NO...-202276208-_-N

[petehall347]

Re: Possible ground loop

can you explain the incoming supply ? or draw a diagram . trying to get a handle on this .
for example we have high voltage transformer up a pole that supplies single phase 240v . terra terra system .. dead easy if working from same main panel . only ground loops caused from more than one unit unit connected to supply earth .

[Spork Schivago]

Re: Possible ground loop

I might not have a ground loop here at all. I have two dual pole breakers, one on each side of the panel. Each breaker is using both incoming lines. The two buss bars, GND and Neutral, are connected together. I measure voltage on both receptacle metal boxes and don't see any voltage, at least as fine as my meter can measure.

I'm now grounding the various equipment. The splitter doesn't have a spot for me to hook up a ground wire. I believe the case just grounds directly to the rack through the case nuts. However, the local cable company is insisting it be bonded per their requirements, which includes running a cable from the splitter to that bare cable running throughout the basement's ceiling, or directly to the panel, if it's 20 feet or closer away.

I think I'll take a screw out and just put a D-ring terminal on 10-gauge THHN stranded green wire, bond it the way they want, call them to come verify it's to their satisfaction, have them hook the new hard line up at the pole, and then start running the coax and ethernet lines to the new system.

I still need to ground the router and install the wireless APs. Then I can start working on making money. I was sick for a long time and it really put me behind schedule, but I'm starting to feel a lot better and it's good to get back to work!!!!!!

[Spork Schivago]

Re: Possible ground loop

The two hot feeds do contain it as well. Is that the same stuff they give you at auto supply stores when you buy a new car battery? Looks the same.

For the ground wire for the rack... What's the reason for running a dedicated wire from the rack to the ground buss bar in the panel? Is it in case the water, gas, or cable accidently get struck by lightning or something, there's no chance of it going to the rack on its way to earth?

I used 4 gauge bare stranded wire. I will use insulated for this new wire but should I use 4 gauge? Can someone suggest a link to a good source? I noticed the stuff in the house vs the stuff I bought at Corning Building has different twists and probably different number of individual strands...

[delaware74b]

Re: Possible ground loop

The gray paste on the neutral is Noalox and is required on outdoor aluminum connections. It is optional for indoor connections. Personally, I use it on all stranded connections, regardless of location. The 2 hot feeds under those yellow safety covers should also have the Noalox like the service neutral.

[stj]

Re: Possible ground loop

wrong, sleeving is mandated by the 17th edition of the codes.
it's strict on the colours too.

[petehall347]

Re: Possible ground loop

some electricians here use bare earth wire . i follow them round and add sleeving . not really necessary unless close to live wires to cause arcs or dead short like we had here . the earth rod was smoking

[Spork Schivago]

Re: Possible ground loop

can you not get earth wire sleeving ?

example

In this area, I've only ever seen the bare copper wire being used. Various companies all carry these blocks that attach directly to the bare wire, so it might be a local code or something?

[Spork Schivago]

Re: Possible ground loop

unshiethed earth wires - yuk.
what's the gray paste-shit on the incoming N wire?

That N wire looks like aluminum. It's on the other two hot legs as well. My guess is some sort of conductive material that might prevent oxidation, especially being in a basement. We run a dehumidifier down there 24x7, that drains directly into the city sewage. Perhaps the electrician thought it was necessary?

[petehall347]

Re: Possible ground loop

can you not get earth wire sleeving ?

example

[Spork Schivago]

Re: Possible ground loop

yes, i was wondering why there is a wire-twist instead of putting the incoming and box earths into the socket terminal.

Do you mean wrap the incoming gnd or earth around the screw on the receptacle, leaving a long enough end to also screw it to the box? If so, I thought about doing that, but personally felt the way I did it looked a little nicer.

I wanted to buy some of those splicer box things you showed me that one time. I just haven't gotten around to ordering them. They looked interesting.

[Spork Schivago]

Re: Possible ground loop

Yep, this why it is better to ground the box instead of relying on the contact between the outlet GND and the face plate to the metal box. I always GND my outlet box with GND wire just in case.

That's what I did. It wasn't too long ago that we found a light switch that failed. It literally was broken in half.

I do not mind spending the extra couple mins to run a pig tail for extra safety. I don't know if it's required by code, but it always feels like it's the right way to do it...

[stj]

Re: Possible ground loop

yes, i was wondering why there is a wire-twist instead of putting the incoming and box earths into the socket terminal.

[budm]

Re: Possible ground loop

as long as the screws are all good, but if the center ones fail the assembly will be floating inside.

Yep, this why it is better to ground the box instead of relying on the contact between the outlet GND and the face plate to the metal box. I always GND my outlet box with GND wire just in case.

[stj]

Re: Possible ground loop

as long as the screws are all good, but if the center ones fail the assembly will be floating inside.