3 wire sub panel

[RonRock]

I built my pole barn before the house so that I would have a shop to work out of. That was about 20 years ago. Time moves on.

When I built the shop I bought a Siemens 125 amp Load Center. Screwed it to the wall and even bought the 4 gage wire to run from the main panel to the sub for a 60 amp sub panel. It was intended to be a place to wire in a 50 amp for my welder, and a couple other recepticals for whatever came along. The sub is across the shop near the OHD so that if needed I can plug in a welder and work outside or the far side of the shop.

So one thing leads to another and time flies. Now I am finally at a point where I want to actually run some non metallic tubing from the main to the sub. So the reason for the post is based on the time the project actually began and the materials purchased and installed then, and what is needed now.

My load center is dated 1998, was screwed to the wall at the time. But never wired. It only has 3 lugs for line in. Two hot, and a ground / neutral. The ground / neutral is isolated from the box.

So as I understand, a sub panel now needs a 4 wire in. Two hots, ground and neutral. No bond between the ground and neutral until the main panel. I plan to wire a 50 amp receptical for my welder, and like mentioned a couple other recepticals. Maybe 240v for future use and a couple 120v recepticals. My welder has a 50 amp 3 wire plug and the 120v recepticals would only use 3 wires. So do I need to replace the load center with a new one that has a 4 wire in? Or can I simply use the one that is already installed? I know that the existing box will work, but am I limiting myself by using it or should I just start over. After all I been on this for a while already.

Or can I simply buy a lug bar and screw it to the box and use it as the ground?

 

[wyliesdiesels]

Yes, it needs to be a 4-wire feed. No u dont have to replace the panel. Buy a ground bar kit, same brand as your panel.

And BTW, the original neutral/ground bar SHOULDVE been bonded to the enclosure. But that doesnt matter now...

Make sure the EMT is sized large enough for the wire...

 

[RonRock]

Thanks. I will check to be sure on the bond. You are probably right now that I think about it. Back then with a 3 wire sub it would make sense that the box would be bonded with the neutral/ground. I just looked at it and saw that it is mounted on plastic before the post.

Like I said it has never been wired. I actually screwed it to the wall where I figured I'd want it, then placed my welder below it. Then plugged the welder in with an extension cord. As luck would have it, the cord was actually pretty useful so it just stayed that way. Time to "clean" things up a bit.

 

[Dagny]

A sub panel has always needed 4 wires. I think my oldest code book is 1978. so at least that long. It doesn't say you need 4 wires it says something like you can't have grounded neutrals anyplace but the main.

 

[RonRock]

I went out and took some pictures and did a continuity test on the ground bar. It is not bonded. Don't know why the pictures went sideways, not how I loaded them.

 

[alfredeneuman]

4 wires per se aren't required, even today.

3 wires plus a ground is.

Rigid Metal Conduit, Intermediate Metal Conduit, and EMT can all be used without a ground wire for grounding purposes.

In the past flex conduit also was suitable for grounding purposes, but the rules were changed to require a ground wire in flex

 

[CNGsaves]

I went out and took some pictures and did a continuity test on the ground bar. It is not bonded. Don't know why the pictures went sideways, not how I loaded them.

Orientation of Pic's fixed with free software IrFanView.

 

[Charles (in GA)]

To this very day, almost all smaller subpanels are made like yours, with no ground bar. It is an extra cost option hanging on a peg in the electrical section at HD or Lowes. Larger panels come with the ground bar, but not the smaller ones.

Charles

 

[RonRock]

Cool. Thank you all. I will add a ground bar and run 4 wires.

So what if it takes a little time. Been on this for around 20 years already.


Appreciate the help.

 

[sberry]

You don't need to add a ground bar to the shop panel but at the sub, to be clear, a 3 wire service o a building must have the N and G bonded with the exception that it was piped from building to building with metallic pipe.
Another thing to consider here,,, are there other metallic connections from each premis, phone lines, copper gas or metal water lines? They are the reason they went to 4 wire. With bonded N in the secondary the currents may be carried by these usually thru grounded equipment, furnace, phone etc.

 

[Zeke]

You don't need to add a ground bar to the shop panel but at the sub, to be clear, a 3 wire service o a building must have the N and G bonded with the exception that it was piped from building to building with metallic pipe.
Another thing to consider here,,, are there other metallic connections from each premis, phone lines, copper gas or metal water lines? They are the reason they went to 4 wire. With bonded N in the secondary the currents may be carried by these usually thru grounded equipment, furnace, phone etc.

Interesting. That isn't brought up here much.

 

[sberry]

The fact that 4 wire is needed is talked about endless,,, why not so much, once a guy understands why it becomes a reflex.

 

[RonRock]

Now you bring up a whole new can-o-worms. A quick layout of my situation.

400 amp service with 1 power meter and ground rod in ground. 2- 200 amp disconnects. 1 to house, 1 to shop. In house and shop 200 amp main breaker in breaker box. From mains to subs.

House mains and subs 4 wire un bonded. All ground goes to meter or service drop I don't remember for sure where the ground terminates then to ground rod.

Sound right?

 

[sberry]

Because there are disconnects at the main modern installation would require 4 wires. If it was done before 4 wires and has only 3 from the primary disconnect to each building they must be bonded at the building. (They still need rods but the only purpose they have here is to confuse,,, ha) There is a problem with this second bond. While it may have been legal at one time the addition of new utilities threw the electric out of compliance and allows for a second pathway for electric currents, both in the case of faults but also any neutrals and they would carry all of it in the event of a N interruption.
Might even actually work without notice with the N removed?

 

[sberry]

Some old equipment has hidden bonds, some furnace controls I think. But I try to get rid of it. Run 4 wire to appliances. I ran a sheetload of UG 3 wire here, I actually dug it back up and fed another wire with it along with some other pipe. Taped it right to the other 3 current conductors and put the dirt back.

 

[sberry]

The wiring config is treated as a sub when there is a disconnect ahead of it but its really a service to a detached structure fed from another service. I am not sure in the code where the term sub is used? It has the ground stake and uffer requirements of a service as well as main breaker or disconnect rules.

 

[sberry]

House mains and subs 4 wire un bonded. All ground goes to meter or service drop I don't remember for sure where the ground terminates then to ground rod

The 4th wire as ALWAYS must terminate at a bonded neutral, ideally at service main. If this is not possible as there are only 3 wires due to an obsolete feed then that connection must be made at the 3rd wire at the point of disconnect entering that building.
You can add a hundred ground rods if you want but none of them replace an electric pathway thru wire to service main for short circuit protection.

 

[sberry]

If we understand this right Ron will have a building feed 3 wire and another sub within that building must be 4 wire. This insulates neutral currents (for lack of better term,,, should really be currents on grounded conductors,, but,,,) on everything within this building and the 4th wire will return a short to the frame as well as keep the potential between all this connected equipment the same. (the ground rod does a little of this with the floor and earth) (not enough for a fault to trip breaker though,,, hence the gfci.)

 

[sberry]

The best earth would only return a few amps at this voltage and not enough for a surge to open a breaker. A wire does this. A gfci protects in the case of 2 wire equipment or faulty ground with 3 wire but trips at 6MA vs letting 120 stand with potential to ground up to several amps actually flowing without trips.

 

[sberry]

Stupid nhandyman cuts the ground wires out of appliances, cut the ground off and routed thru several old obsolete boxes instead of wiring to a panel even closer,,, so stupid but could leave a huge potential on an ungrounded water heater with a faulty element. In the case I found it was typical of his work and lucky the shower drains were plastic.

 

[RonRock]

To this very day, almost all smaller subpanels are made like yours, with no ground bar. It is an extra cost option hanging on a peg in the electrical section at HD or Lowes. Larger panels come with the ground bar, but not the smaller ones.

Charles

Seems to be true. I picked one up yesterday. Hanging there right where you said they would be. Actually I knew they were there, I just never gave them much thought. Also looked at the small panels while there. Right on that point as well. They all seem to be 3 wire. That sure seems jacked up. But oh well.

 

[sberry]

They go both ways as they are suitable for use as service entrance equipment. Its why they come with bond screw and without bar.

 

[wyliesdiesels]

A sub panel has always needed 4 wires. I think my oldest code book is 1978. so at least that long. It doesn't say you need 4 wires it says something like you can't have grounded neutrals anyplace but the main.

U have the code reference for that? A 3-wire feeder was allowed in detached buildings up until 2008....

Now you bring up a whole new can-o-worms. A quick layout of my situation.

400 amp service with 1 power meter and ground rod in ground. 2- 200 amp disconnects. 1 to house, 1 to shop. In house and shop 200 amp main breaker in breaker box. From mains to subs.

House mains and subs 4 wire un bonded. All ground goes to meter or service drop I don't remember for sure where the ground terminates then to ground rod.

Sound right?

PoCos do not use grounds in service drops. Your grounding electrodes and service neutral should be bonded in your main service panel or the meter pan if your PoCo allows that...

 

[RonRock]

I looked after posting. Mine is run up from the ground rod to the meter.

So all of the grounds in my house and shop go directly to the ground rod at the pole. All isolated from the other three lines.

 

[wyliesdiesels]

I looked after posting. Mine is run up from the ground rod to the meter.

So all of the grounds in my house and shop go directly to the ground rod at the pole. All isolated from the other three lines.

Your service neutral/bar should be bonded to rods, grounds and panel...