Split Bus Electrical Panels—No Main Breaker.

Doesn’t the Electrical Service Panel HAVE to have a Main Disconnect Breaker?”

Main Breaker in Service Panel

Main Breaker

The simple answer to this question is, “No—Probably not.”

Because most electrical service panels are NOT installed by homeowners or “Uncle Harry,” it is actually pretty rare to find a main panel without a main disconnect.  There are a couple of ways where it might “appear” to be missing—but is in fact there after all.  My goal is to keep this post simple enough that most readers can understand what I am talking about.

Real estate agents and home owners need to understand the basic principles so that when the inspector calls for replacement of what appears to be a perfectly good panel, they can understand why.

The first point I will make is that ALL electrical services to the home MUST have a means of shutting off all the power.

Being able to shut off all of the power is usually achieved by a Main Disconnect Breaker in the electrical service panel—and should be labeled as such. (I am not going to talk about fuses in this post). Where it gets a little confusing is when that main disconnect breaker is in a different location from the panel in the home—like outside the home at the electric meter (as in mobile homes, townhouses, condos and other instances).  In these instances the panel in the home is not the electrical service equipment but is instead called a sub-panel.  This type of panel doesn’t “require” a main breaker unless it is in a detached structure.  Of course it does no harm to have one and one is often installed for convenience.

The following picture is of a pretty close to correctly wired sub-panel.  As a Seattle Home Inspector I love finding panels this nicely wired.  This type of panel will not usually have a main disconnect—it will be located at the electrical service equipment—-typically where the meters are located.

Nicely Wired Sub-Panel

Nicely Wired Sub-Panel

There is another type of panel that looks, at first glance, like it might be missing a main breaker.  This type of panel is configured such that it takes a maximum of 6 throws to shut all the power off.

This type of Service Panel is called a Split-Bus Panel.

The following picture is of a typical split bus panel with its dead-front cover in place.  Notice it says, “SERVICE DISCONNECTS” in the center between the upper breakers?

Split Bus Electrical Panel

Split Bus Electrical Panel

This means that when all those top breakers are turned off—all power to the breakers in the panel will be off—including the lower breakers.

The next picture is of a split bus panel with the cover off—notice how much it looks like the sub-panel picture above (well except for neatness)?

Split Bus Electrical Service Panel

Split Bus Electrical Service Panel

What is different about the panels can be visualized by by the following picture with descriptive overlays.

Split Bus Electrical Service Panel

Split Bus Electrical Service Panel

The blue dotted lines are where the power coming into the panel attach to the bus bars.  Note that the top six double pole breaker spaces are outlined with blue dotted lines and are numbered 1 through 6.  Note how the wires from breaker #2 travel down behind the six spaces and attach (trust me) to the bars for the bottom breakers highlighted in red.  Notice also that some of the double pole breakers in the area labeled “Service Disconnects” have been changed to single pole breakers—violating the 6 throw rule.  Violations of this type are common with these panels as more circuits are desired and there just isn’t room in the panel for any more.

Here is another panel with only three double pole breakers in the top six spaces but one of them has blue wires that run to the bus bars for the lower circuits.

Split Bus Electrical Service Panel

Split Bus Electrical Service Panel

In this case it only takes three throws to shut off all the power in the panel—still well under the 6 throw rule.

These panels were common into the early 70’s and I still find them very often.  Most panel manufacturers made such panels—-and in many different versions.  The code allows for this type of panel as long as all the power can be shut-off in 6 throws or less—known as the “6-Throw Rule.”  Inspectors and homeowners sometimes mistake these split-bus panels for sub-panels and incorrectly call for repairs to the way they are wired—or wonder where the main breaker is.  I don’t want to go into the differences between how service panels are wired differently from sub-panels, but just understand that they are wired VERY differently and it important for the home inspector to know these differences.

To recap:

In a typical split bus panel found in a residence there will be provision for “6” double pole breakers (or less)—one of which is the disconnect for all the breakers located below the 6 double pole breaker locations.  Wires will run from that one breaker and be connected directly to the bus bars for the other section of breakers.  (Bus bars are the energized metal bars that the circuit breakers connect to.)

These panels are often crowded and no longer have ample space to accommodate modern wiring requirements.  Most of the time I find myself recommending to my buyers that they upgrade these panels.  Often the service size itself is adequate for the home—the panel simply lacks the space to add new circuits.  Replacing just the panel is almost always going to be cheaper than a whole new service to the home.


Charles Buell, Seattle Home Inspector

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  1. Very helpful post. I’m curious, is it easier to add a sub panel underneath a split bus panel and rewire the house to that or just replace the old panel entirely? I am updating a house from the 40’s that appears to have had a few piecemeal updates here and there but nothing seems to have been done “right”. Lots of electrical tape, few proper junctions and willy-nilly outlets piggybacked to odd lines throughout the house.

    I am a student and cannot afford to hire an electrician. Updating this old house will be my part-time job over the next few years, and I hope to make a small profit from its sell.

    • Charles Buell says:

      Well of course one could add a sub-panel but in the end you will still have the old main panel with no main disconnect. Even with a new panel for the same size service you can generally get a panel with a main breaker that has more available spaces for circuits than the current split-bus has. I am assuming all work is being done under permits, so having to pull the meter to replace the whole panel should not be an issue.

      • Charles,

        I don’t see a main equipment grounding conductor coming in the sub panel to the lug on the grounding bar? There should be 4 conductors (2 hots,1 neutral,and 1 equipment grounding conductor) Correct?

        • Charles Buell says:

          Duncan, in this installation the metal conduit to the panel is the acting as the grounding conductor.

          • Charles,

            In response to my to previous reply,you said the metel conduit is acting as
            the grounding conductor in the subpanel. I don’t see a metal bonding bushing on the conduit to ground the subpanel enclosure? All I see is a gray fiber bushing which just screws on the threads of the conduit to protect the conductors. I still think you need a grounding conductor run back to the main panel which feeds the subpanel. If your using the metal conduit solely as a ground, what would happen if one or more of the fittings (couplings etc.)would come loose or disconnected being used as the ground path back to the service? Could cause a fire. I know for this reason,good practice tells me to run a grounding CONDUCTOR back to the source.



          • Charles Buell says:

            Yes, and that is exactly why they do not allow it any more. The metal lock nut under the plastic bushing was considered adequate to connect the conduit to the box itself—continuity of the conduit was “usual” but difficult to “guarantee.” I have found them disconnected—but that is considered rare but due to the possibility we now want to see a ground wire inside the conduit.

  2. i have an old house that has no service disconnects just a meter base and a split bus pannel inside. theere is no main disconnect anywhere. the distribution pannel is inside. i want to upgtrade the dis pannel. do i have to add a pannel with disconnects or will the individual circuit breakers suffice

    • Charles Buell says:

      Carlos, I am not sure why you would want a nice new panel and not want a main disconnect? Am I reading you correctly? As far as I know, you have to have a single main disconnect in modern installations.

  3. Great Blog! My father and I were both convinced that my service panel was missing the main breaker, but I see that I have a Split Buss panel thanks to your blog. I purchased a home in MI without an inspection or seeing it in person. I inherited a box that is overlystuffed and even had wires connected directly into the front with the cover off! In the state of MI they require an electrical safety inspection on any home that has the electricity off for more than a year (mine has been off for 3 now). So I am preparing myself to clean up some of the obvious no, no’s and have the inspection. Hopefully, my nothern Mi inspector will be as knowledgeable and helpful as you seem to be. Keep up the good work! Wish you were in MI!

  4. Louis Mallet-Paret says:

    Great post! I was convinced my daughter’s “new” (1950’s) old house was missing the main breaker but now understand much better what’s going on with the split bus panel. One question though. What overcurrent device protects the incoming wiring from the meter to the panel? Our 1950’s house has 120/240 volt #4 AWG copper TW which I think is good for only 60 Amps. When I add up the breakers on the first half of the split it comes out to more than 60. I have not found any main breaker upstream of the panel but am wondering if there are fuses or something hidden in the sealed meter enclosure. Any comments would be greatly appreciated. Thanks!

    • Charles Buell says:

      Louis, regardless of whether there is a main breaker in the panel or a split-bus means of disconnecting the power there is no protection of the wire between the meter and the panel and why it has to be in conduit and a very short distance between the two. Also adding up the amperage of breakers is not really indicative of anything except as indicated by the data plate. #4AWG copper is good for 100amps typically. Have the panel evaluated by an electrician if you have concerns about it.

  5. Dear Louis,
    I’m rewiring a house to make it more EMF friendly
    ie no EMF’s.
    It was suggested to use split bus to separate the loads. Emf high loads and resistive loads.
    A few details please!
    I’m suffering from emf sensitivity.

    • Charles Buell says:

      Ann, I know of no scientific evidence to support that EMF’s are a problem related to residential wiring. A Split Bus panel is a type of panel and would likely not make a difference in any electrical conditions related to EMF’s that I am aware of. “Anecdotal” information can sometimes seem convincing but generally just confuses the issue.

  6. I live in a townhouse and the circuit breaker panel appears having no main breaker, where a square hole above the two columns of circuit breakers is labelled “Main” but it is really an empty hole covered by two plastic pieces. I guess the circuit breaker panel in my unit is of the type you described in this article, a sub-panel.

    The circuit breaker dedicated to the kitchen’s under-sink waste disposal seems out of service, no power is available on this line when this breaker is flicked on, and it won’t trip either. So I’d like to replace this circuit breaker with a new one. However, all I read on how to replace a circuit breaker recommend to “turn off the power at the main breaker”

    You mentioned in this article about sub-panel, ” This type of panel doesn’t “require” a main breaker”, should I interpret this as I can replace the faulty circuit breaker without bothering to find out where the main breaker outside my unit is? Or, I have to turn off the main breaker outside my unit, which I assume is inside a box at the end of the building and locked up, so I really have no direct access to unless through the power company.

    In the whole last paragraph I am only guessing the possibilities. I hope you’d give me some advice on what I could do in this situation. Thank you for your help in advance.

    • Charles Buell says:

      Tom, based on the questions you ask I must suggest that you contact an electrician to make these repairs for you.

  7. Joel Neff says:

    I have a split bus panel from pushmatic. Home was built here in Michigan in 1965. The main lines from the meter go into the top of the panel in side my one family home. The first two breakers are 30amp and then a 60 amp panel starts for home lighting. I’d like a 100 main put inline but, the electricians here say it’s just better to upgrade the panel. There is nothing wrong with this panel other then not having a main 100 amp breaker. I can’t see spending $1500. to $2500. on a new panel install. Any ideas on what I should do??

    Thanks Joe

    • Charles Buell says:

      Joel, besides the lack of a main breaker there are other reasons why you should be looking to upgrade the panel. If there is nothing wrong with the panel, as you say, other than missing a main breaker why not just leave it alone? There is nothing inherently wrong with a split-bus panel. The problems arise when you need more spaces for modern circuit requirements when remodeling. If the six throw rule cannot be maintained it is time to upgrade. There is often insufficient space in these older panels and often breakers have been double lugged. I think you are probably getting good advise to upgrade the panel. If you don’t have to upgrade the entire service you should be able to get just the panel changed out for under $1500.00—it certainly would not cost more than that in my market. It will cost you something to have a main breaker installed—just put that money toward a whole panel is my advice.

      • Joel Neff says:

        Thanks for that fast reply. I don’t need to add a breaker to the panel. To me, having a main breaker coming into the panel seemed smart. Maybe in the years to come i’ll think about a upgrade. Thanks again for your comment on this.


  8. Kevin Murray says:

    Hi Charles,

    This article is the closest thing I could find that addresses our sub-panel problem.

    We just bought a 1941 house that seems to have had the electrical panel updated by the seller (or maybe his Uncle Harry!). There is no main shut-off, only a sub-panel installed with 4 circuits for the whole house. We’re looking to have a 200-amp main panel installed professionally and run some new circuits to key appliance outlets as we can afford to do so.

    We got a local recommendation from a trusted source here in L.A. and the electrician just gave us a quote. His plan is to leave the sub-panel as-is (cloth wiring and all) and only run any new circuits we’ve requested from the new main panel. I understand that this, in theory, should be fine but we had an earlier quote from our real estate agent’s contractor which included rewiring all of the circuits to the new panel (and for a good deal less).

    Is this just a matter of preference or is there a right way to do it?


    • Charles Buell says:

      Kevin, it can be done either way most likely if I read you correctly. If you would like to email me privately so that you could show me some pictures I might be able to advise you more appropriately.

  9. Charles: I was supposed to get a new service panel installed today,but my electrician found that there’s a sewer drain line directly under the box. The old box is 13″ x 24″,& he says they’re no longer made.The panel is a split buss type. Any suggestions? There just isn’t any room for abigger one.We’re not looking to add anymore circuits-just a problem with the buss.

    • Charles Buell says:

      Roger, I am not sure I fully understand what you want to know. I don’t know why the electrician can’t install a new panel in place of the split-bus panel. Modern panels that size will typically accommodate a main disconnect and still have room for all the circuits. Feel free to call me if you want.

  10. I realize this is an older post but I hope you can help me figure something out.
    We recently had an electrician (a very young one) out to do some other work and after looking at our system he recommended upgrading our system to 200 amps to the tune of $6000. Doesn’t make sense as we haven’t had symptoms of a lack of ampage – no frequently tripped breakers, flickering lights or the like. Reported that we currently have 150 amp service. He also expressed concern that we had no main shutoff.
    I looked back at our home inspection report to see if this issue was mentioned. The inspection report states that we do have 200 amp service. So I’m looking at the service panel trying to figure out what is going on and I’m confused.
    We have a large panel with 42 receptacles – several of which are not used. At the top left of the panel (which I understand to be where the main shutoff should be) is a double breaker with 100 printed on it, however it is labeled “Heat”. There are 4 breakers below it in place 5,7,9,11- 2 single switches and one double switch with 60 printed on it – all labeled “Sub-Main”. On the right side there are also 3 other double switches with 50-range, 30 – water heater and 30 – dryer. The breakers on the bottom half are all single and mostly printed with 20 and 30.
    So could this possibly be one of these split bus systems and that’s why there is no main shutoff? And do I have 100, 150 or 200 amp service?
    Home built in 1978, all electric, a little over 1600 sqf.
    Thanks for any enlightenment you can give.

    • Charles Buell says:

      Jessica, this sounds very much consistent with a split bus panel. There are many factors that would come into play to determine whether it should be replaced or not. The needs of the home. The manufacturer. Is there space for more circuits, etc. If you send me a picture privately I will try to be of further assistance. On the panel legend it should tell you the panel rating (size). If that is missing it may also be on a legend inside the panel but I would not recommend you remove the dead front.

  11. I have a dual split bus or whatever panel… I am going to have a throw switch installed with a lock assembly between the meter and the panel so I can kill power in one throw. This will also prevent back feed of my generator. Any thoughts on this?

  12. Raymond Carbone says:


    According to your description, I seem to have a split bus panel in my 1959-built home. Since we have many trees in the area, I am sorry to say that loss of power is becoming more common and I would like to be able to plug in a portable 7KW run-rated generator to power the in-house well jet pump, gas fired hot water furnace, and 2 refrigerator/freezers. Can an interlock be installed on a split bus panel to guaranty that only one source of power is connected?

    If a panel interlock switch can not be installed, I can use extensions from the portable generator to power the refrigerators and furnace (a 110 plug is built into the control unit and the emergency switch can be thrown to off), however how can I provide emergency power to my 220V jet pump? There is a small power box installed next to the pump that contains (2) 15A glass fuses used to cut power to the pump.

    I would appreciate your thoughts and suggestions.


    • Charles Buell says:

      Ray, I just inspected a 1959 house with a split bus panel 🙂 I am pretty certain that you cannot put an interlock type generator interface on it. Consult with a licensed electrician however. Given the age of the panel you might want to consider upgrading than the work it would take to making the old one work.

  13. Raymond Carbone says:

    Thank you for your quick reply. I appreciate that an upgrade would be best but not an option at this time. If an interlock can not be installed on the split-bus panel, how can I apply generator power to my in-home 220v jet pump servicing my water well? As mentioned above, along with the circuit breaker on my split-bus panel, there is a small power box installed next to the pump that contains (2) 15A glass fuses. Would it be a good idea to install a 220v twist receptacle between the small power box and pump to apply emergency power? Although I would be eliminating the short cut-off of the local fuse box, I am depending on the generator’s circuit breaker for any short encountered on any of the other connections.

    Again, thank you for your article and response. It has been very helpful.

    • Charles Buell says:

      Ray, I am afraid you have gone beyond my pay grade 🙂 These interfaces can be incredibly dangerous to workers down line of the service, so making sure these installations are done properly is critical. Consult with an electrician at this point. I will say though, that making an interface work (if it can be done) with this old system may be more expensive than simply upgrading the panel.

  14. From your description it seems I have a split bus electrical panel. One of my double pole breakers has been tripping frequently ( to my range) and makes a buzzing sound from time to time. I’m thinking it may need to be replaced. As there is no main shut off, would I need the power company to turn off my power first? Does it sound like a problem that replacing the breaker will resolve?

    • Charles Buell says:

      Shari, too many possibilities to diagnose from the information you give. Time to have an electrician check it out for you. The power company will not likely be necessary to change the breaker—just an electrician.

  15. Tom DeCamp says:

    Just looked at a home that my niece was thinking of buying to render an opinion on its condition. (I’ve been a residential carpenter for 30 years.) I couldn’t figure out why there was no main shut off breaker in the circuit breaker box. The box was rated at 125 amps but only had a 60 and 30 amp double pole breakers in the top 2 spots. It must have been a split bus panel as you so clearly explained on this webpage. Thanks for the very informative description of this type of panel that I never new existed.

  16. James Critcher says:

    I have a split- bus panel which is located under meter and sub-panel is in the house. One of the 100 amp breakers is tripping and I need to replace it. There is no main labeled, so if I cut all breakers off in panel under meter, will power to house and this box be off.

    • Charles Buell says:

      I can’t tell you anything based on the information given. Pictures might help, but an electrician might be your safest bet.

  17. Tom Rodgers says:

    This article is excellent, thank you. My client just had a home inspection done on a 1972 home. The inspector noted that there was no main breaker and that code required it since 1937. This made sense to me at the time. I started reading on, came across yoru article, and realized this must be a split bus panel. SO…if I am understanding this peroperly, this set-up is fine unless of course the new homeowner wants to add more circuits.
    To cut power off entirely- all the upper breakers must be flipped, correct?

    I shared the link to this article with the inspector and asked him to read it as well. I don’t want to be askign the seller for work to be done on something that is not necessarily defective.

    Thanks, Tom

    • Charles Buell says:

      Hi Tom, the “code” certainly has allowed split bus panels for a long time—in fact the 6 throw rule still applies although I doubt any manufacturers are still making a split bus panel. They pretty much went out of favor sometime in the 80’s—at least in my area. As long as you can shut off all the power in six throws or less you should be good to go in that respect but there may be other issues typical of any older installation. Lots of these panels are fine—some are very crowded and need upgrading.

  18. I have what appears to be a split bus 100 Amp panel mounted directly below the meter. This would have been added to the 1950 house when “most” of the wiring was updated. Immediate plans are to add a 16 kW generator with 200 Amp auto transfer switch panel. Long term (2 to 3 year) plans are to add on to the house including removing the entire rear wall of the house where the panel is located. That would result in a relocated, entirely new 200 Amp service and total rewire of entire gutted house.
    Advice from electricians vary. One says I must upgrade to a 200 Amp panel now before adding the generator, even though the new panel will have to be moved in the future ($3000 for new panel and wiring generator.) Other advice is to connect wires from meter and wires from generator appropriately to the 200 Amp auto switch panel which will adequately and safely control power fed to existing 100 Amp split bus panel. Optional 100 Amp breaker box could be added between auto switch panel if local inspectors don’t like 200 Amp feeding 100 Amp panel. Third advice was to add a new 200 Amp panel nearby to be fed from auto switch panel (meter or generator). This 200 Amp panel would then have only one 100 Amp breaker that feed the existing 100 Amp panel which effectively becomes a sub panel (less wiring and easier to move panel during remodel).
    Which makes more sense?
    Even though the trend has been to upgrade to higher Amperage panels in recent years, I am confident that my 1800 sq ft remodeled home will draw less Amps/Wattage than in its current 1200 Sq Ft state due to deep energy upgrades (tight/insulated envelope, more efficient lighting and appliances) and a smaller furnace/AC combo (2 ton 16 SEER/ 96% eff 36,000 BTU furnace vs current leaky duct 3 ton 12 SEER / 60,000 BTU single stage furnace). So I really wonder if we are looking at electric service upgrades in the wrong way anyway?

    • Charles Buell says:

      I assume you are putting in the 200 amp generator disconnect in anticipation of the new 200 amp service? Why not do that but simply change out the disconnect breaker to a 100 amp breaker so that it fits with the existing service and then change the breaker back to 200 amps when and if the service gets upgraded? This may or may not be an option—discuss with the electrician. Also I would consider an “in-panel” type of generator disconnect as opposed to an isolated type. This could all be done by simply replacing the existing split bus panel with a new 100 amp panel and a $50.00 transfer kit.

      • You are correct about the anticipation of the 200 Amp service. While I have no plans to do so, 12 of the nearest 15 homes have been recently torn down or doubled/tripled/quadrupled and McMansionized. For the low cost to upgrade transfer switch now, I figure it will make it a positive for resale in the future, or at least not a negative.
        I like the idea of changing the disconnect breaker from 200Amp to 100 Amp. I will investigate the brand I am looking at to see if that is possible.
        I could live with the manual disconnect inside the panel, but MSOWMABO (my significant other who must always be obeyed) insists on it being automatic, and she is willing to foot the extra bill. I have, however, shown at least one neighbor how a simple transfer kit would allow them to use their portable generator without extension cords. It’s purely coincidental that that neighbor is the most likely to annoy me on any given day and even more likely to crash at out house during a power outage.
        Thanks for your advice!

  19. BTW, excellent explanation of split-bus panels!!!

  20. I am in a large apt building circa 1960 construction. I was removing a light fixture to replace it and the black power line shorted out against the jbox as I moved it. (I neglected to at least turn off the light at its switch) Now, in my new split bus bar panel, half the breakers are not working. I have two 120v supply lines and a 200A rated panel.

    I moved them all to one side but am very worried this is a load imbalance (although it’s mostly for modest lights and no AC this time of year.)

    Is the main breaker bad? Could there be a fuse box in the basement to check?

    In short, excuse the pun, I know I need an electrician in but any advice would be of interest.

    Thanks in advance,


    • Charles Buell says:

      Scott, I wish I could help but you have not given me the kind of information that I would hazard a guess about. Like you already know, call a sparky and get it sorted out. I can tell you, that it probably won’t be too difficult.

  21. Hi Charles great article. I just bought a home and the home inspection states that i have a 200amp main disconnect and a 100amp entry. Does this mean I have a 200amp underground service from the power company to the house? Then a 100 amp panel entering the home? I’m unclear why there would be a 200amp main disconnect?

    • Charles Buell says:

      Brent, can you send me some pictures?

      • I take the possession of the home in 2 weeks. I can send them at that point. Wow really appreciate the quick response. That’s GREAT.

        • Charles Buell says:

          Did the inspector put any pictures of the panel interior in the report?

          • No just and outside breaker shot. No pictures of the main disconnect. It won’t let me paste the pics i have from the report here.

          • Charles Buell says:

            Brent, email me privately when you have some pics.

  22. Dean Miller says:

    I really liked the article but now I have a bunch of questions, to post here now. One that I can post is that I have a home built in 1999 that has the 150 amp main breaker located by the power meter.

    The panel in the garage does not have enough room to add the needed breakers for me to add power outlets in the gearage where I am making it my work shop. I will need at least two 220v @ 20amp and six 110v @ 20amp breakers.

    I forgot to mention it is a Cutler-Hammer panel. Would I upgrade the panel or run a subpanel off of it to accommodate the workshop breakers/outlets?


  23. I have ran out of breakers. This house was built in 1965 and has the split bus. I notice some of the circuits are just for lights and some have several outlets for example, microwave, toaster, items like this. Can I, using a pigtail in the panel change a couple of the outlets to a different breaker? After testing the circuits I have found what wires run what things.

    • Charles Buell says:

      Sorry, Joe, I don’t have enough information to help you. I recommend you call an electrician that can actually look at your situation.

  24. I have to tie a solar photovoltaic (PV) system (1.5 kWac) into the residential electrical service panel of a customer. The service panel is a “Pushmatic Electric Center” with two vacant slots. I plan to insert a 2-pole 20 A Pushmatic circuit breaker into one of the slots and tie the PV system (240 V, single phase) to it so that PV electricity can flow to residential loads and/or back to utility for credit (net metering). After reading your explanation of split bus service panels, I believe that is what I have here. My question is: “How do I insert the Pushmatic breaker and wire to it safely, as the two vertical buses are always energized?” Do I need to pull the meter to break the connection between utility lines and service panel, or is there a more convenient way to do this? Thanks very much for considering my question.

    • Charles Buell says:

      I am afraid you are going to have to consult with a licensed electrical contractor that is experienced in the installation of PV systems. I strongly urge upgrading the ancient pushmatic in the context of any new installation.

  25. Thanks for the excellent explanation. I’ve been in the RE and home remodeling business for over 50 years and have seen these and other odd layouts of electrical – many of which are perfectly legal and allowed as long as no changes are made to them. Even now however, I see odd wiring schemes in older buildings that can still mystify me and have recently run into another.

    Discovered a new “mystery” panel lately and cannot figure out what the heck is going on in this building. I hope you can comment/help/offer some guidance. The panels are old “stab-lock type panels and are at least 50 if not 60 years old. The building was originally built as in city apartments c. 1959, and later converted to condos sometime in the late 60’s/early 70’s. There are two floors in each building. With 12 units per floor. The AC is central water-cooled and there are individual air handlers that utilize the cold or hot water from the chillers. The Water-based air handlers have 220 v motors in all of them. Also, each apartment has an electric stove – full sized. Minimum of 40 – 50 amps required for each of them. The breakers for the lights, outlets are in two centralized panels in the hallway on each floor (2 per floor) but these panels have NO 220v breakers in them what-so-ever. Nor is there any mention made of stove or air handler/AC shut offs!

    An older-than-I-am electrical engineer friend proffered the thought that perhaps there were central 220v panels running the stove and AC in each apartment. However we cannot find any such animal! There is a “mystery panel” outside of the building that seems to have six or eight 100 amp breakers in it. Could this be set up to power the AC Blower motors and/or stoves across multiple apartments? It isn’t labeled. And I can find no place else that has a large number of 220v breakers. However even with 8 of them @ 100 amps each – could those be used to meet the power draw of 3 stoves @ 40-50 amps each? And then you’ve got no way to power off the individual stoves (or air handlers if that’s what it’s connected to.)

    I’m lost. Any ideas of what may have been legal back then in a multi-unit building. BTW: these were built as modern, but high end “luxury” apartments in Phoenix and are very near the Phoenix Country Club and the Art Museums, Opera, etc. Even in their days as apartments they were ‘pricey’ and marketed to upscale renters. As condos they’re very much in demand because of 50 year old landscaping and the spaciousness of the layouts. However this strange electrical set-up is discouraging me from buying a couple of these units. I sense a potential for a big rewiring job or a fire hazard or both. And rewiring these to current codes would probably run in excess of $5000 per unit for the 1br/1ba and more for the larger units. Possibly much more!

    Any thoughts or ideas about what I am seeing and how this thing may have been wired to accommodate 12 stoves and 12 air handlers per floor and yet only have 8 100 amp 220 breakers visible anywhere in the building that we can find – so far???

    • Charles Buell says:

      MI, if you could send me some pictures privately I might be of some assistance. That said it is not practical or advisable to attempt to maintain these Stab-loc panels. They should be replaced in my opinion and at that time any wiring deficiencies would/could be resolved—likely. It is unlikely that the several 100 amp disconnects have anything to do with the ranges etc and are more likely the main disconnects for the panels on each floor, or in units, or HVAC units or something else. If you have pictures of the interiors of the panels or even the face of the breakers with the dead-front still on, something may jump out at me.

  26. Jake Werner says:

    I am installing a 100 amp subpanel in a detached garage. Obviously the neutral and ground need to be separated, but what about the main breaker (I had to buy a 100 amp main panel.)
    Can I leave the main 100 amp breaker in the subpanel, or do I need to remove it? If so, how?

    • Charles Buell says:

      Jake, anything I say should not be a substitute for proper evaluation by a licensed electrical contractor, but any sub-panel in a detached building is, among other things, required to have a main disconnect.

  27. Joe Jackson says:

    Just wanted to say thanks for the excellent description/explanation of split bus panels. I have one in my house, and I couldn’t figure out why I didn’t have a main disconnect.

  28. Charles
    Great Blog and very helpful.
    I do have a few questions regarding my situation. I have a split bus service panel. In the top 6 there are only have 4 double breakers, one which shuts off the lower panel. One is a 50 amp and feeds my range. I am changing over to gas and only need a single pole 20 amp breaker. I want to change it to a single pole breaker so I can use the same wires for my gas stove. In the breaker box I will take one wire to the neutral bar and the other to the single pole breaker. On the range side I will replace the 240 volt receptacle with a 20 amp receptacle using 12 gauge wire to pigtail off the existing larger gauge wire to install the new receptacle. Do you see any concerns with this and if I shutoff the top 4 breakers is it safe to work in breaker box to change out breaker? Thank you for your feedback

    • Charles Buell says:

      Larry, I was just about to reply to your comment on the blog post when I got a long winded phone call. Obviously I cannot tell you to just go ahead and make repairs yourself for liability reasons. I can say it is common to see single pole breakers installed in the top section of split bus panels typically reserved for 240 volt breakers. You would have to look at the panel data plate to see if the panel is rated for such installation. The key is that there can never be more breakers than would result in 6 throws. As to using the old wire to the range, that might be possible if it is three wire feed where the former ground can be utilized as the ground and one of the hots can be re-identified as a neutral. It does not matter if the wire you are attaching to it is a smaller size as long as the breaker is appropriately sized. With no main breaker a split bus panel is always going to be more dangerous to work on than a regular panel with a single disconnect and why you should have a licensed electrician do the work for you.
      I do not know what code cycle you are under but current regulations would require that receptacle for the range to now be AFCI protected and that old split bus panel might not accept them.

  29. The picture in split-buss2 shows a sub panel that I believe is wired incorrectly. Sub panels are supposed to be supplied with power from the main panel by using an SER cable that has 4 separate conductors. This permits for 2 hot , 1 neutral & 1 ground conductor. The reason for this is that in the sub panel the ground & neutral conductors are to be isolated from one another. From what I can make out in the photograph, there are only 3 leads coming from the main panel to the sub panel & the neutral buss and the ground buss are connected to each other. I believe this is a code violation. I am writing this so that no one makes the mistake of using this picture to install & wire a sub panel.

    • Charles Buell says:

      Dave, you are sort of correct. It was only relatively recently (2008 NEC code cycle) that a 4th wire became required between panelboards. For a long time the metal conduit between panels was allowed to act as the ground path (fourth wire).

  30. James O. Stone says:

    Hello Charles,
    My question has to do with copper clips(shoes) placed on the bus blades in Position 1 of a Seimens 250A split-bus entrance panel. These clips appear crimped on to the bus blade preventing insertion of a breaker. Generator transfer is accomplished by throwing two breakers positioned at the “split. The main breaker is a 1/4 mile down the road which, of course, has to be thrown to off first before the split bus breakers are thrown for generator transfer. Can these clips be removed to utilize the breaker position?


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