Square D Q0 200A Panel - how to convert to sub panel (separate neutral / ground bars)

[pclausen]

So I got this 1980's Square D panel (there are 2 actually, but I'm putting this one behind a transfer switch).

Here's the label:

And here's another part of the label, showing the bonding screen between the neutral bar and box. I know I need to remove this.

View of the entire panel. Note that I have already removed the original feeder wires, which entered in the top left corner. I have installed a 2" metal plug there. I have also marked the 4GA ground wire with a green arrow that goes to the ground rod. This will be pulled and connected to the Asco transfer switch instead.

Closeup of the neutral bars. Note how the original installer randomly used both the inner and outer bars for neutral and ground connections. The green arrows are the bars I intend to dedicate to ground. The yellow arrow points to the screw that is bonding the neutral bar to the box. As stated above, I'll be removing it.

Another angle of the neutral/ground bars. I don't see a way to isolate the inner bars from the main neutral bar.

So my plan is to move all neutral connections to the outer bars, unscrew the 2 inner "ground" bars, and drill holes and bolt then directly to the box as seen in the very crude illustration below:

Unless I'm missing something, it would seem that unlike Cutler Hammer, these Square D Q0 panels, do not offer an easy way to separate ground from neutral, thereby not making them an ideal choice for a sub panel in the first place?

Can you suggest an easier method to turn this panel into a sub panel?

PS In case you're wondering what that thick neutral wire still in the panel is, that feeds a 100A subpanel where my 3 outdoor units reside.

Thanks

 

[check]

What the heck? I have several Square D panels, and I have never seen the neutral and ground connected to each other.

 

[GLyford]

Would it be easier to leave all the neutrals on those 4 bars, and just buy 2 new bars to mount as you want? You'd have half as many wires to move, unless they put a bunch of grounds and neutrals in the same connection. Last time I checked (it's been a while) ground bars were cheap.

 

[Ed L]

Would it be easier to leave all the neutrals on those 4 bars, and just buy 2 new bars to mount as you want? You'd have half as many wires to move, unless they put a bunch of grounds and neutrals in the same connection. Last time I checked (it's been a while) ground bars were cheap.

This.

One has to buy the ground bars separate.

Ed

 

[pclausen]

Appreciate the feedback. I ended up removing the 2 inner bars and installing a new ground bar. It was less than $5 so no big deal.

Here's the final result:

Since most of the circuits in this panel are 240V, most of the "ground wires" were actually neutral wires. So I only wired the 120V circuits to the ground bar, using wire nuts and #12 green wire (had a 500' spool laying around). I did double up some of the #14 grounds into a single #12 green wire. I think that's ok? There were no 4 wire 240V circuits in the panel.

A view of both panels. Getting that copper 3/0 wire through that 2" conduit was a total pain.

And a view of the Asco 200A transfer switch once I got power back on.

I'll be installing a 36KW diesel generator. Even at that size, it would not have been able to pull both panels, so I decided to have it just power the panel with all the HVAC units and well pump, and a few other amenities. I might install a 1.5" conduit between the panels, and extend some other essential circuits, like the kitchen, fridge, and TV and office circuits over into panel 2.

Here's a diagram of the circuits in each panel. There are some heavy hitters in panel 2 (which is on the transfer switch).

 

[quicksandfarmer]

Since most of the circuits in this panel are 240V, most of the "ground wires" were actually neutral wires. So I only wired the 120V circuits to the ground bar, using wire nuts and #12 green wire (had a 500' spool laying around). I did double up some of the #14 grounds into a single #12 green wire. I think that's ok? There were no 4 wire 240V circuits in the panel.

Not an electrician, but I don't think that's right. Every circuit has to have a ground, neutral is optional. Decades ago it used to be OK to use ground as neutral in a 220v circuit, but nowadays if you want neutral you have to run a wire for it. So every circuit should have a wire going to the ground bus, only circuits with a neutral wire should have a wire going to the neutral bus.

 

[schmism]

What the heck? I have several Square D panels, and I have never seen the neutral and ground connected to each other.

check again.

per code, the main box has to have the grounds tied to the neutrals. in subpanels they want them separate with a ground rod at each sup panel.

 

[pclausen]

Not an electrician, but I don't think that's right. Every circuit has to have a ground, neutral is optional. Decades ago it used to be OK to use ground as neutral in a 220v circuit, but nowadays if you want neutral you have to run a wire for it. So every circuit should have a wire going to the ground bus, only circuits with a neutral wire should have a wire going to the neutral bus.

I was wondering about that. The fact that the original wiring was all randomly wired between the neutral and ground bars threw me off on the 220v circuits.

Easy enough to change. I'll do that tomorrow (house in unoccupied at the moment).

Thanks!

 

[quicksandfarmer]

I'm also trying to figure out the thick aluminum ground conductor. It looks like it's going to neutral on both panels. Are either of the two panels we see the main service entrance, or are they subpanels? Ground and neutral have to be bonded at the main entrance and then separate everywhere else in the system. If these are subpanels that thick ground conductor has to go to ground, not neutral.

Again, not an electrician, although I did study electrical engineering in school.

 

[quicksandfarmer]

You can buy ground bars that have one big lug, I think that's what you want here.

 

[quicksandfarmer]

I did double up some of the #14 grounds into a single #12 green wire. I think that's ok? There were no 4 wire 240V circuits in the panel.

The ground is a safety feature. On 120v circuits it has to be able to carry the full breaker current of the circuit. A #14 wire can carry up to 15 amps, a #12 up to 20 amps. One #12 can't carry the current of two #14.

 

[pclausen]

I'm also trying to figure out the thick aluminum ground conductor. It looks like it's going to neutral on both panels. Are either of the two panels we see the main service entrance, or are they subpanels? Ground and neutral have to be bonded at the main entrance and then separate everywhere else in the system. If these are subpanels that thick ground conductor has to go to ground, not neutral.

Originally both were main service entrance panels with a 400A meter base connected directly to both panels. I converted the one on the right to be a subpanel since it now has a Service Entrance rated transfer switch in front of it. The panel on the left is still a main service entrance panel. I'll pick up a large ground lug that will allow me to transfer that thick aluminum ground conductor to ground in the right side panel.

 

[pclausen]

The ground is a safety feature. On 120v circuits it has to be able to carry the full breaker current of the circuit. A #14 wire can carry up to 15 amps, a #12 up to 20 amps. One #12 can't carry the current of two #14.

Thanks. I'll pick up both some #12 and #14 bare copper wire and wire every ground separately to the ground bar. I'll pick up another ground bar as it looks like I'll need to install another one to make everything fit.

If/when I transfer some circuits from the left service entrance panel to the right sub-panel, it looks like I'll have to extend all 3 wires from the service panel to the sub-panel. Just moving the breaker over and extending the hot won't cut it I don't think since the ground would then be connected to the combined neutral/ground in the left panel.

 

[Cord]

On the newer panels, there is a green bonding screw that connects the neutral to ground. I'm not seeing that screw in your older panel. That said, for my QO subpanels, I had to install a ground bar just like you did. Looks like you have a dedicated ground (maybe a bit light on the gauge? I believe this wire should be a #6) and have the wire polarities taped, so the install is looking good to me. Do you have nolox on the aluminum ground wire?

 

[JPRambo]

Most QO panels I have worked in have a spot for the ground bar to go in the panel. Look behind the wires near the top of the panel. If not why not just put the ground bars there? Panels are panels not junction boxes to make splices in. (It would fail inspection here with wire nuts used to continue the grounds).
Also if the right panel is now a SUB-PANEL it should not have a MAIN BREAKER it should be MAIN LUGS since the transfer switch has the main breaker.

 

[pclausen]

I added another ground bar at the bottom and moved all the bare ground wires from the neutral bars to the ground bars. I also extended each one separately instead of having 2 #14's share a single #12.

I also added a small ground bar at the top side of the cabinet, where I terminated the 2 large aluminum ground wires.

Here's a view from the outside showing the meter base and transfer switch.

 

[pclausen]

Looks like you have a dedicated ground (maybe a bit light on the gauge? I believe this wire should be a #6) and have the wire polarities taped, so the install is looking good to me. Do you have nolox on the aluminum ground wire?

That is a #6 ground wire going to the grounding rod. #6 is what was there before. So I extended the original #6 from the grounding rod into the transfer switch and then run a new #6 from the transfer switch to the 200A sub-panel.

Not sure what you mean by wire polarities. I do have neutral taped white and the 2nd 220v feeder taped red. Do you mean that I should tape the 1st feeder blue like it is in the meter base coming from the power company as shown here? (you have to look close, but there is blue tape on that one wire running along the bottom up to the left most lug)

By nolox, do you mean anti oxidation paste? If so no, I only used that on all the 3/0 copper wire. There was none used before on anything.

 

[pclausen]

If not why not just put the ground bars there? Panels are panels not junction boxes to make splices in. (It would fail inspection here with wire nuts used to continue the grounds).

I thought about that, but space is pretty tight at the top of the panel. If I fail inspection, I suppose I'll go back to do it that way after all. I would just to with one large horizontal bar in that case.

Also if the right panel is now a SUB-PANEL it should not have a MAIN BREAKER it should be MAIN LUGS since the transfer switch has the main breaker.

I agree that would be ideal, but I can't image the current setup failing inspection due to having one extra 200A main breaker. If I have to remove that 2nd main breaker, I'd probably need to custom fabricate some bars to carry the current from the main lugs to the bars.

 

[hr3]

How did you delete the old feeder that you took out of the meter enclose ???

 

[pclausen]

It was a huge pain. My original plan was to route the 3/0 copper through the opening between the meter base the the right panel. But once I got the old feeder removed from the meter base, I realized there was no conduit in the wall between the meter base and panel on the inside. So I then had to unbolt the inside panel as was the bared able to get to the set screws on the 2" clamp on the back. Once I got that loose, I was able to pull the old feeder through from the inside. I was lucky that the clamp on the meter base was not tight and I was able to pull the feeder through, although I had to pull on it hard to get it to go. Once I got it out, I mounted the panel to the wall again and installed a 2" plug in the hole.

I thought about installing a 2" conduit pipe in the wall between the meter base and panel, but after pulling out the old feeder, I realized that the existing hole was not 2" diameter but rather 3 smaller holes drilled next to each other, just large enough for that original feeder wire. So I had to get rent a core bit and drill and drilled a 2 5/8" hole in a new location, and then installed my 2" conduit for the new feeder wires to run through.