I have a Square D Q030 MW 200 load center with an QON30MW200-1 panel board interior (installed in 1983 when house was built). I want to add a 30 amp QO breaker and position it for a generator interlock kit. Panel is full and I need to add two tandem breakers in order to free up space for the 30 amp generator breaker. I have two bus bars mounted to the same bare metal "box" (or bridge?) where the heavy bare neutral (from meter) is also connected via the large lug. This box or bridge is located in the upper right center of the load center immediately to the right of the 200 amp main breaker switch.

My bus bars are full with several grounds double and triple-tapped. Even some of the 14ga neutrals are double and tripled tapped. I guess this was allowed back then????? In any event, I have never had a problem and the connections seem quite secure. The work was done by one of the major, more popular local, licensed(?) electrical outfits that had been in business for years.

The first bus bar is mounted to the face of the metal box/bridge and has 11 slots. The second bus bar has 18 slots and is mounted on the side of the box/bridge and therefore sits at a different (lower) level than the first bar, to it's right, otherwise they are essentially next to each other. This second, rightmost bar has the bare grounds attached to it, each in its own slot alone. There is only one wire leading to the ground bar outside so I presume the second wire is attached to plumbing piping. I see no green bonding screw anywhere but I assume these two bars are considered bonded since they attached to the same bridge with what look like the standard bus bar attachment screws?

My first question is can I replace the smaller bus bar with a 15 or 18 slot bus bar just to get additional slots for the additional 30 amp generator breaker?

Secondly, there are designated slots for the QOT tandem breakers. Can I simply shift breakers down as I add the two tandem breakers or do I need concern myself with the load on each of the phases A & B.

I believe I have attached pics of the bus bars showing the ground wires and connections. I have others of all the labeling and overviews of the load center if needed.

Incidentally the large bar has what looks like a strap/collar at the top for attaching a large ground wire to it? It occupies two terminals and is unused. I was considering removing this to free up the two slots I need for the generator breaker.


Thanks
Mike

 

That is a 30 space 30 circuit panel, it doesn't accept tandems. I am pretty sure there are some tandems that might fit it, but it would be a code violation to install them since that panel was designed and U.L. Listed for a maximum of 30 poles.

 

Hi CJ.

The diagram on the inside of the panel cover shows the last six slots with dotted lines so that would indicate (if it is the right cover: QOC30MW225 series L7) that 12 tandems can be used bringing it to the max of 42.

When I finished the basement later, the electrician added 5 tandem breakers. I don't know if he cut the QOT tabs to get them to fit.

What do you think?

 

You must have a lot of tandems in that panel to have so many neutral with 30 spaces.
Usually panels have bars on both sides. How many tandems spaces are shown on the panel cover or ID plate ?

You can have two grounds under one screw. Only one neutral per screw. Never three of anything under one screw.

It might be easiest to add an additional ground bar. Move the grounds out of the neutral/ground bar to the ground bar. Since that is the main panel you should verify that the neutral to ground screw is in place.

 

I think you are right but labeling and instructions are confusing. Both the labels on the panel board interior and the load center box state to use CTL types QO, QOA, Q1, Q1C AND Q1A BREAKERS. No mention of QOT unless any of those designations indicate a tandem breaker. Yet The installation instructions paperwork provide instructions for QOT breakers and indicates the square D CTL system is UL listed and has the safety features in it to prevent too many branch circuits. Unless this simply translates to no provision for tandems on this box.

 

I address that that in my previous post. currently 6 tandems installed total.

I was trying to avoid adding another ground bar just to free up two terminals. Wouldn't you consider the current set up bonded or does it have to be the green screw to provide the magic that makes this bonded? Where would the green screw go and how would it perform differently than the current configuration where the ground wire from the ground rod outside is connected directly to the bus bar. Or is that where the green screw would go?

What if I free up two terminals by removing the unused collar on the bus bar?

 

Add an auxillary ground bar and move the grounds to it. This will give you enough space for the neutrals.

 

I have 5 tandem breakers (not six) and 5 double pole breakers. So in total I am at the max of 30 circuits. The two bus bars together, after considering the slots occupied by 4 mounting screws and two grounds from the plumbing and exterior ground bar would have only 23 slots for grounds and neutrals so you can see quickly how 30 circuits or 60 grounds/neutrals end up double/tripled tapped in the slots. BTW, I saw where the electrician twisted several grounds together in a pseudo pig tailing so that only one ground needed to be connected to the bar.

Be that said, if I install the generator breaker, I come to 31 circuits but in reality will almost always operate only 30 circuits since the gen breaker is virtually always off. In an emergency, my portable 7000 watt generator cannot support 30 circuits, so I will only operate a handful of circuits with the others off.

So until I add a separate ground bar and separate neutrals and ground, if I just upgrade my 11 slot bus bar to a 15 or 18 slot bar or take the unused collar off of the bus bar just to add a dormant generator breaker, wouldn't that essentially leave me in the condition I am currently in? As well I can move some of the triple tapped conductors to the open slots.

So is there any additional harm to swapping out the smaller bus bar for a slightly larger one or utilizing the slots occupied by the unused collar?

In the mean time I would love to understand how the green bonding screw would work (fit) under my current config.

 

Adding the ground bar would make more sense than adding a longer bar until you can add the ground bar. You only have to deal with them once, not twice.

The panel label should show where the bond screw goes.

Can you post a picture of the whole panel? Is there another breaker or disconnect ahead of this panel?

 

Logically, your right. But from a practical standpoint, and from my perspective swapping out the shorter bus bar for a longer one is the easiest task since it requires no rerouting of wires or pig tailing, etc. The short bar has easy access and I don't have to touch anything except the conductors on it.

Hers a close up of the buss bars. having trouble loading the whole panel pic but will keep trying. No other disconnects ahead of this panel.

 

panel overview pic - hopefully it worked

 

The longer bar may not fit if you install the bond screw that should be installed.

 

You have an older Square D QO series panel, I recognized the catalog number. You cannot exceed 30 poles and you have at least 35 poles now because you stated you had 5 tandems. This is a CTL (Circuit Total Limiting) panel that allows up to 30 poles. The electrician obviously didn't have his work inspected or he simply doesn't understand the codes. Some inspectors also fall in this category. If this panel accepted the QOT tandem breakers, there would be small rectangular slots in the pan mounting rail to allow the metal rejection clips on the QOT breakers to be installed.

No mention of QOT tandem breakers is made because they aren't allowed in this panel. Back when this panel was being manufactured, the cover/door assembly was sold separately and it may have fit several different catalog number panels, some of which may have allowed tandem breakers. On this vintage Square D panel, you cannot go by the label inside the door and must go by the label inside the panel box.

The installation instructions are not panel specific and apply to probably all QO series panels of that vintage. Yes, the CTL system is U.L. Listed and this is a CTL panel. That is why QOT tandem breakers are not listed on the label, they cannot be used in this panel. There is such a thing as a non-CTL tandem breaker that has no rejection clip feature that is approved ONLY for use in pre-1968 panels and this is probably what the electrician installed in your panel. Most non-CTL tandem breakers have a paper label on them stating this.

 

Here are the label Pics with references to the ground bar kit (18!) and the bond screw location. If I am reading this correctly, my panel has a screw in the bond screw location and I could use the larger 18 bus bar than the short one that is shown. Seems the one I have has been cut because its an odd length at 11 slots.

Sorry about the sideways/upside down orientation of the pics

 

These are ground bar kits and are installed separately from the neutral bus like PCboss has already mentioned.

Using the separate ground bar to free up holes for neutral conductors is what I would do to solve that problem, but it doesn't address that you still have a code violation with having too many poles installed in the panel.

 

CJ,

I think you are pretty much right-on on all points in your post #13. If I recall, the same electrician who originally wired the house also installed the tandems later when I finished half the basement. I don't believe they were inspected. I can check if the bars are designed for tandems or if the electrician cheated, but between your memory and the labeling, seems tandems are out.

I see two choices:

1) short-term: Increase the size of the smaller bus bar since the bonding screw is present (be it a 12, 15 or 18 bar) since I'm only going to add a dormant generator breaker which in practically isn't going to increase the load beyond what the box is carrying now. In practically, the loads on the 5 tandems are quite light and in almost 35 years I've never popped a breaker because of too much load on a circuit; only when I accidently short something. I see this as low or no risk.

2) mid-term: Upgrade to a larger panel to solve the code violation, because the time and labor spent separating the grounds and neutrals for a new ground bar kit would be better applied towards the installation of a new (40 circuit?) panel. Any restrictions to moving to a larger panel?

 

PCBoss

I'm not sure why you say this. Based on my photo and the panel labeling (it's upside down), isn't the bonding screw already not a factor in terms of clearance?

Does an auxiliary ground bar need to be grounded only to the case via the self-tapping metal screws that attached the bar to the case, as I have read in instructions provided in other posts? I don't see supplemental threaded screw holes for auxillary bars in my case, though I haven't quite looked that hard for them.

From what I understand, you don't bond this ground bar to the neutral else you energize the case. I will try to see if the box recommends the locations for the aux. ground bar.

 

The bars will mount in several places in the panel. Look for raised dimples with holes in line with them. The ground bar needs to be bonded to the neutral so the breaker will trip. I do not see the bond screw in your panel which also needs to be addressed.

The ground bar will be less than $10. A larger panel will be $150-200 along with a solid day of labor to change to a larger panel. Add in the permit costs and inspection times.

 

Haven't read all the posts but is there a reason you haven't considered a subpanel. That would solve your problem for a reasonable price and only a little work. Just move all the non CTL breakers and a couple of lightly loaded 120 over to it and you should have room for the generator and the subpanel breaker in the main panel.

 

Agreed on the subpanel idea. You already have a 200A main in good condition -- no reason to replace it just for more space. Throw a 30 space 100A sub adjacent to the main with a steel nipple between them and move a few circuits over there to alleviate the space problem in the main box.

Alternatively you could consider making this subpanel a generator transfer panel instead of the interlock kit and kill two birds with one stone.

 

PCBoss:

There is a large screw in the large neutral plate (or bus/bridge - whatever it is technically called) It is toward the bottom of the plate and centered. It sits at the approximate position that is depicted in the diagram/label pic I provided with an arrow pointing to it and a description that says: "BOX BONDING WHEN REQ'D." Did you not see this screw or do you just not consider it as the bonding screw?

I will take a harder look for these.

Ok on the ground bar but as CJ said I would technically still have the code violation on the 35 circuits in a 30 circuit panel. As suggested in recent posts a subpanel is also an alternative.

 

Gents

Thanks for the feedback and input so far. I certainly have a better grasp at my overall panel situation besides figuring out how to accommodate the additional generator breaker.

One thing still confounds me as to why such a reluctance to just swap the shorter bus bar for a larger one, assuming the bond screw I have indicated is indeed the bond screw. To me it doesn't change the current situation but just gives me a few more screw slots for the generator breaker and would take only about 20-30 minutes to swap out the bars. Much easier than the ground bar kit and I can save that effort for a subpanel later since the ground bar kit doesn't solve for fact that I have 5 more circuits than the current box allows for?

 

Also a good idea on the subpanel. I just preferred the interlock kit over a transfer switch because I would have total flexibility on the circuits I want to feed and not be limited to only the circuits of the transfer switch.

 

My suggestion would do that. But Ben's idea is good also.

 

H Ray

Yes yours would accommodate the interlock.

The electrician at Home Depot provided another option. His own setup is a quasi subpanel/transfer switch config using an emergency double throw power transfer switch connected to some kind of a small subpanel to which he had moved those circuits from the main panel for emergency use and to be powered by the generator. He wasn't a fan of interlock kits and said his setup would free up my main panel unlike the glorified generator transfer switches that are expensive and add even more wiring to the main panel. This double throw transfer switch then would allow the subpanel to be powered by either the generator or the main panel depending on which way you throw the switch. So not possible to back feed the utility pole and if power is restored it doesn't matter which position the double throw switch is in. It sounds better than the big generator transfer switches but I still lean towards the flexibility of the interlock kit. Thanks.

 

I don't think you'll find a larger neutral bus for your panel which I am guessing is from the early to mid '80s by the location of the bonding screw. The longer bus bars you have mentioned in an earlier post are not a larger neutral bus, but are auxilliary ground bars. Here is a 15 terminal ground bar.

Square D 15 Terminal Ground Bar Kit-PK15GTACP - The Home Depot

I like the subpanel idea as well, but you cannot transfer the non-CTL breakers to it. You should replace each non-CTL tandem breaker with either two normal sized single pole breakers or with CTL tandem breakers if the new subpanel will accept them.

 

So what your saying is the ground bar you just suggested is not interchangeable with my short neutral bar (installed in 1983) and won't fit on the neutral bus? The auxiliary ground bar is attached to the side of the neutral bus but it won't fit on the face like my shorter bar does? They seem identical other than length.

When I study the two bars on the neutral bus they both look like one end was cut. One has 18 slots and one has 11 slots. Is it possible they were one bar of 30 slots and cut into two pieces, destroying one slot by the cut? Course I don't see how a bar that long could work in this panel. If the original bar was a ground and was cut to fit the face of the neutral bus then maybe grounds can fit as neutrals. Or I guess the ground bar kits are designed to fit the auxiliary positions provided on the panel other than the neutral bus.

The longer bus bar in my panel does have the ground to earth bare wire connected to it. The electrician connected the 2 bare ground wires to two of the screw terminals rather than the provided ground strap/collar. Not sure why he did it this way.

Roger that on the non CTL breakers.

 

The auxilliary ground bar isn't mounted on the neutral bus, but mounted directly to the panel box. The label inside the box probably has a diagram showing where pre-drilled hole are located for it. If not, check the instructions that come packed with the auxilliary ground bar. If there are no pre-drilled holes, you can locate the ground bar anywhere inside the box on the back of the box and drill your own holes. The holes have to be slightly smaller than the self tapping mounting screws provided with the ground bar. Here is a list of steps to install a ground bar; all appear to be correct except #6.

How to Install a Ground Bar | eHow

That is correct. The GECs from both ground rod and water service terminate on the neutral bus since this is the service panel with the first OCPD (main breaker).

 

okay so both bars on my neutral bus are considered neutral bars and technically my neutral bars are grounded to earth via the GEC wires. Neutral and ground conductors can land on either bar.

Neutral is bonded to the panel via bonding screw. When I add the ground bar kit then neutral and ground bars are also then bonded via the panel. I can land grounds on both the neutral and ground bars since they are bonded.

But I can't replace the short neutral with a bar taken from a ground kit as it will not align or physically fit to the neutral bus.

If Install a subpanel , neutral and ground bars cannot be bonded there (remove bonding screw in subpanel)

#6 of the aux ground bar install. is not necessary because the Ground Bar will be bonded to neutral via the panel and Neutral bar is grounded to rod via the GEC wire?

Hope I got this right.

 

It sounds like you have all of your bases covered.

 

ok thanks!

shall we discuss how to install a subpanel now ;-)...just kidding. I'll go do my home work first.

 

It's really not too bad of a job. Ray has made up these very helpful diagrams:

 

Perfect. I thought it would be relatively simple and that already answers a half dozen questions I have.

How big a breaker to feed the subpanel? 100 Amps? I have to move at least 5 circuits from main panel to get it back down to the main panels limit of 30 circuits. So I thought I would move like 8 to the subpanel. I could move just the light circuits? the breaker that feeds the sub is a double pole so it will draw from both A & B phases of the main?

Or should we not go here in this thread?

 

Only ground wires can land on the ground bus. If you landed a neutral there you would put neutral current on the enclosure.

Ground wires are bonded to the neutral with a bond screw or strap in the service panel.

 

100A is a typical size for which you can use #3 copper THHN wire through a conduit nipple between panels. You could move whichever circuits you want or that are most convenient to move. The subpanel is powered by a double-pole breaker which draws from both legs of the service.

 

perfect, thanks ----------------

 

okay, glad you mentioned because I've read (I think) conflicting things. I've read exactly what you've said above and then read that moving just the grounds to the ground bar is cosmetic only. maybe I'm mixing up situations. An auxiliary bar with 15 posts should handle all the grounds so I should be able to follow your advice.

 

One more just to confirm:

For those circuits I plan to move from the main to subpanel, all of the NM wire for those circuits coming down from the ceiling need to come out of the main panel and fed to the sub panel via the knockouts of the subpanel. Then I can connect those wire to the appropriate breakers, neutral and ground bars of the subpanel?

And I can just staple the wires to the wall ( Plywood) for the span between ceiling and subpanel. No conduits needed? Just like the main panel.

 

All correct............................

 

There are many websites where you can get information, but you have to be careful because many "How To" websites also give incorrect information. That is why I specifically said that #6 in those instructions to install a ground bar was incorrect. That is most likely why you are getting conflicting information.