# Sub Panel



## Kristofor Pinkerton (Aug 20, 2018)

I am purchasing a new house with only 1 open breaker. I believe it is a 100 amp main. Can I run 2 100 amp sub panels feeding them with 60 amp breakers? One will be due to needing the open space for the 60 amp breakers since it currently only has one spot and a few spares. The other sub panel will go in the detached garage as it currently doesn't have any power. the sub panels would not be in line but both fed off the main itself.


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## Snoonyb (Aug 20, 2018)

Welcome.
How big is the house?


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## Kristofor Pinkerton (Aug 20, 2018)

1886 sq ft 3 bed 2 bath.


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## Snoonyb (Aug 20, 2018)

Thanks.

I'd be inclined to upgrade to a 200Amp service, because a 60Amp sub off a 100Amp main will be at best marginal.


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## Kristofor Pinkerton (Aug 20, 2018)

ok i don't really have the money in a budget for the 200 amp upgrade that's why i was wanting to do the 60 amp sub panels, since i don't need a lot in the garage or for the sub in the house. i've budgeted 10k for other things.


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## Kristofor Pinkerton (Aug 21, 2018)

would you recommend a different way to do the sub panels? Larger breakers on the main?


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## Snoonyb (Aug 21, 2018)

The service panel will dictate the max. main breaker allowed for that service, and if it is 100Amp, then that is the max for the existing buss's.

The use in the house will be determined by the number of elec. appliances serviced, as well as a general use calc., or an "every light in the house is on" method.

If your proposed load for the garage is 60Amp, then you'll need to sub for that, which may eliminate any spare breaker space you have, as you have indicated.

There's no magic bullet, just math, and your sig. other.


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## hornetd (Aug 21, 2018)

Snoonyb said:


> The service panel will dictate the max. main breaker allowed for that service, and if it is 100Amp, then that is the max for the existing buss's.
> 
> The use in the house will be determined by the number of elec. appliances serviced, as well as a general use calc., or an "every light in the house is on" method.
> 
> ...


There is a difference between a Lighting and Appliance Panel Board and a Service Disconnecting Means.  Even when both of those are housed in the same cabinet they are 2 distinctly different things.  What the OP asked was could he install 2 breakers using one for each of the 100 ampere Lighting and Appliance Panel Boards.  The answer is yes.  A new Service Disconnecting Means  would be installed which would have 2 main breakers in it.  Each of those would supply 1 Lighting and Appliance Panel Board.  The National Electric Code (NEC) specifically allows up to 6 separate Breakers, Fused Pull Outs, switches, or some combination of them to serve as the Service Disconnecting Means.  The entire service bust be arranged so as to be able to be disconnected by 6 throws of the hand.  This doesn't have some scientific or engineering basis.  It is just the number at which the Code Making Panel; which is responsible for the section of the NEC which covers services; decided to call a stop to the number of operations that would be needed to deenergize the entire Service.  He will have to do the Service load calculation to make sure that it is within the ampacity of the Service Entry Conductors. 

Were I doing the upgrade under tight budget constraints I might install a 200 Ampere, Main Lug Only (MLO) panel with only 12 slots.  I could then install up to 6 double pole breakers in that panel to Serve as the Service Disconnecting Means.  Then I might install 2 100 Ampere breakers to supply those 2 panels.  That would give the OP the flexibility to add up to 4 additional double pole breakers to serve loads which might be added later.  One thing to remember is that Service Entry Conductor size is determined by the calculated load and not by adding up the ampacity of the separate Service Disconnecting Means. 

I rewired a youth summer camp that had several small panels placed in a variety of buildings.  I installed a 400 Ampere MLO panel board to which the Electric Utility terminated their Service Entry Lateral.  I then installed Feeders based on the size of the calculated load in each building,  The feeders were protected at the Service Disconnecting Means by a breaker which was sized to the ampacity of the conductors after the conductor size had been raised to compensate for voltage drop.  The Building Disconnecting Means at each building's panel was sized to the buildings calculated load.  That resulted in the Lighting and Appliance Panelboards' main breakers being a lower ampacity than the Service Disconnecting Means breaker which protected the feeder which supplied that panel.  This was done so that if an overload occurred it was much more likely that the Building Disconnecting Means breaker would open prior to the Service Disconnecting Means breaker opening.  The total of the 6 Service Disconnecting Means breakers certainly exceeded 400 Amperes but the calculated load did not.  

-- 
Tom Horne


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## Snoonyb (Aug 21, 2018)

I read it as the OP having a 100Amp service with a couple of breaker slots vacant, from which the OP wants to sub feed a panel with several breaker slots, from which he wants to run a subfeed to the garage.


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## hornetd (Aug 21, 2018)

Snoonyb said:


> I read it as the OP having a 100Amp service with a couple of breaker slots vacant, from which the OP wants to sub feed a panel with several breaker slots, from which he wants to run a subfeed to the garage.


Then perhaps you missed his last line.  "the sub panels would not be in line but both fed off the main itself."  If you read all of his posts I think you will find that he is being fairly clear.  For instance he asked "would you recommend a different way to do the sub panels? Larger breakers on the main?"

I think he needs a least costs solution for right now and if that is true putting in a 12 slot MLO panel "which is Listed for use as Service Equipment" is probably the answer.

Let me just say that I do not like the term "Sub Panel."  It is not defined in the Code and and the lack of a common definition seems to lead to quite a bit of confusion.  There are 2 types of panels defined in the Code.  they are a "Lighting and Appliance Panelboard" and a "Power Panelboard."  The definition depends on whether 10% or more of the circuits "are 30 amperes or less and have a connection to the Neutral of the panel board."

Even when the Service Disconnecting Means is located in the same cabinet that does not change the nature of the panelboard.  All panels that are supplied by Service Conductors must be "Listed for use as Service Equipment."  Panels which are supplied by Feeder Conductors do not have to be "Listed for use as Service Equipment."  In this case both the panel in the house and the panel in the detached garage would be supplied by Feeders protected by breakers that are mounted in a Panelboard that is MAIN LUG ONLY and Listed as Service Equipment.  Panels which meet both conditions will only have room for 6 Double Pole Breakers or less.

The panelboard in the house will have to be converted to have separate Neutral and Equipment Grounding Conductor busses.  Once the Service Disconnecting Means and the main bonding jumper are not in that panel no connection between Neutral Conductors and Equipment Grounding Conductors is permissible.

--
Tom Horne


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## Snoonyb (Aug 21, 2018)

Did you miss that this is a single family residential service?
How many single family dwelling have a separate mains and distribution panels for lighting and appliances?


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## hornetd (Aug 21, 2018)

Snoonyb said:


> Did you miss that this is a single family residential service?
> How many single family dwelling have a separate mains and distribution panels for lighting and appliances?


No I did not "miss that this is a single family residential service."  I have worked in the electrical craft for 50 years old son.  I have done electrical work on French Frigate Shoal, Alaska, Tierra del Fuego, Uganda, and several other places I no longer recall the names of.  I have been inspected by inspectors from the US Army Corps of Engineers to the Alexandria Virginia Inspector who chaired the Code Making Panel Coordinating Committee.  I have never failed an inspection.  Not Once!

Installing a Main Lug Only panel which is Listed as Suitable for use as Service Equipment is a very common way of economically upgrading older homes that have multiple panels or were the existing equipment is maxed out.  It is one of the methods which MUST be considered when working under the Federally Assisted Code Enforcement (FACE) program which brings housing owned by the elderly up to minimum safety standards under the nationally recognized building codes.  I can show you several homes within 20 miles of my home were it has been done.  It is often used as a way of dealing with Split Buss panelboards when additional breaker spaces are needed in a home's electrical system.  It is also a very good way to hold down costs for cash strapped customers that need to add capacity to their home without the cost of fully replacing the existing electrical panel.  The idea that because you have never seen it that it has never been done is the hallmark of those who have worked in only a few jurisdictions in their time in the craft.  

-- 
Tom Horne


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## Snoonyb (Aug 21, 2018)

That's good.

The OP is in OHIO, so you mite stop by and show him exactly how he can accomplish what he wants to do, since you've done so many.


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## Kristofor Pinkerton (Aug 21, 2018)

I want to keep the main service at 100 amps. Take out 3 breakers and move them to a sub panel, since there is only one open slot. taking out the 3 breakers will give me 4 slots to run 2 60amp breakers to run 2 sub panels. One sub panel next to the main and one sub  in the detached garage. I want to run 60 amps to the garage because i will be putting a 20 amp welder in there which will rarely be used along with miter saw table saw and so on. All the lighting will be LED on a 15 amp breaker and roughly 4 15 amp outlets excluding the 20 amp outlet. I know that only adds up to 50 amps so I would have space to add another 15 amp if need be. The sub in the house would have 1 extra space as well. this would put me in the same boat as now with only having one open breaker slot, but i would have everything else done this way. Since breaker panels are only $20 a piece and breakers aren't much this would be the most cost effective way for me except for the expensive 4 gauge wire to the garage, but it is what it is there. I seem to see this is what people do, but if this is a recipe for disaster then I wont do it this way. I dont care about extra breaker slots at the moment.


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## Snoonyb (Aug 21, 2018)

That's what I thought you meant all along.

Maybe TOM could supply you with a line drawing and an equipment list so you could first find out if it can be permitted in your area, I know the sub panels can, and determine the cost so you will know if your budget will fit.


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## Kristofor Pinkerton (Aug 21, 2018)

Snoonyb said:


> That's what I thought you meant all along.
> 
> Maybe TOM could supply you with a line drawing and an equipment list so you could first find out if it can be permitted in your area, I know the sub panels can, and determine the cost so you will know if your budget will fit.




the panels and breakers are less than $100. the wire different story. conduit is cheap and ground rod is cheap. I'm sure I cant do it for under 500, but i know any other option would be expensive.


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## Snoonyb (Aug 21, 2018)

The trench can be a challenge, as well.

Solid conductors are the least expensive. I prefer stranded because they go around corners better and there is greater ampasity.


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## Kristofor Pinkerton (Aug 21, 2018)

Snoonyb said:


> The trench can be a challenge, as well.
> 
> Solid conductors are the least expensive. I prefer stranded because they go around corners better and there is greater ampasity.



Trench will be easy the way the house is and things. I plan on running a second conduit as well just empty. Does what i'm saying make sense and will it be ok to do that way?


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## Snoonyb (Aug 21, 2018)

Just curious, what's the plan for the 2nd conduit?


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## Kristofor Pinkerton (Aug 21, 2018)

Snoonyb said:


> Just curious, what's the plan for the 2nd conduit?



No plan as of now, but everyone says to run an extra or run larger with a pull string.


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## Snoonyb (Aug 21, 2018)

You can, just don't terminate them in the same panel. The better plan is the run a larger conduit and conductors to a single sub panel where you have the ability to increase the breaker, as the demand changes, and you have far less chance for an explosion if someone who doesn't understand makes an erroneous assumption.


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## Kristofor Pinkerton (Aug 21, 2018)

Snoonyb said:


> You can, just don't terminate them in the same panel. The better plan is the run a larger conduit and conductors to a single sub panel where you have the ability to increase the breaker, as the demand changes, and you have far less chance for an explosion if someone who doesn't understand makes an erroneous assumption.



So all in all running the 2 sub panels off 60 amp breakers will be just fine and if i ever need to change something i can cross that road when I get there.


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## WyrTwister (Aug 22, 2018)

Sorry to be getting in on this late .  Do you have a main in your existing panel ?  ( In the Garage ? )  What brand is it ?

     Or is the main outside ?

     Photos would help old guys like me .   

Best of luck ,   
Wyr
God bless


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## Kristofor Pinkerton (Aug 22, 2018)

WyrTwister said:


> Sorry to be getting in on this late .  Do you have a main in your existing panel ?  ( In the Garage ? )  What brand is it ?
> 
> Or is the main outside ?
> 
> ...



The main is the in the house in the basement. There is a single overhead line to the garage to run a couple lights currently. I don’t know the brand as of right now but I will know Friday as I’ll be there.


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## WyrTwister (Aug 22, 2018)

If the existing panel is Federal Pacific Electric , parts / circuit breakers are expensive & not very desirable .  they often do not trip when they should .  In that case , I recommend you replace it with something like Sq D Homeline .  A large enough loadcenter ( panel ) to take care of all of your future needs .  ( Or , maybe *Cutler Hammer* / Eaton  . )

     Not that expensive to DIY , but you may not be up to it , or not ?


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## Kristofor Pinkerton (Aug 22, 2018)

WyrTwister said:


> If the existing panel is Federal Pacific Electric , parts / circuit breakers are expensive & not very desirable .  they often do not trip when they should .  In that case , I recommend you replace it with something like Sq D Homeline .  A large enough loadcenter ( panel ) to take care of all of your future needs .  ( Or , maybe *Cutler Hammer* / Eaton  . )
> 
> Not that expensive to DIY , but you may not be up to it , or not ?



I’ll do the work. Im hoping it’s sq D. The new panels will be sq D for sure. I just want to make sure the way I planned it out will be ok to do that way.


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## hornetd (Aug 22, 2018)

Kristofor Pinkerton said:


> I want to keep the main service at 100 amps. Take out 3 breakers and move them to a sub panel, since there is only one open slot. taking out the 3 breakers will give me 4 slots to run 2 60amp breakers to run 2 sub panels. One sub panel next to the main and one sub  in the detached garage. I want to run 60 amps to the garage because i will be putting a 20 amp welder in there which will rarely be used along with miter saw table saw and so on. All the lighting will be LED on a 15 amp breaker and roughly 4 15 amp outlets excluding the 20 amp outlet. I know that only adds up to 50 amps so I would have space to add another 15 amp if need be. The sub in the house would have 1 extra space as well. this would put me in the same boat as now with only having one open breaker slot, but i would have everything else done this way. Since breaker panels are only $20 a piece and breakers aren't much this would be the most cost effective way for me except for the expensive 4 gauge wire to the garage, but it is what it is there. I seem to see this is what people do, but if this is a recipe for disaster then I wont do it this way. I don't care about extra breaker slots at the moment.


Kristofor

Allow me to suggest an alternative approach.  Instead of filling up your existing panel with those 2 double pole 60 ampere breakers you may want to consider installing a Main Lug Only (MLO) panel which is rated for 200 Amperes and Listed as suitable for use as Service Equipment.  The MLO Service Equipment will have not more than 12 slots in it so that it will never have more than 6 double pole breakers installed.  The MLO Service panel would contain the breakers that would be your new Service Disconnecting Means.  That panel would go between your present panel and your meter.  You would then install the breakers that feed the existing house's panel and the panel in the detached garage in the new Service Disconnecting Means enclosure.  Not having any  pictures of your home to go by I am going to have to do a little guessing here.  When this type of arrangement gets installed the new Service Disconnecting Means often gets mounted on the Outside of the building that already has electrical service.  That is because it makes it easier to run the Feeder/s that will supply the other building or buildings.  If that is the approach that is taken then the new MLO Service panel will have to be Rain-tight.  The type most often used for that is a National Electrical Manufactures Association (NEMA) Type 3R.  Do not plan on using the other slots in the Service panel for other individual loads unless they are 240 volt only with no neutral in the circuit or they are greater than 30 amperes.  If you do not put those 2 60 ampere feeder breakers in your existing house panelboard you may not need an additional panel in the house.  If you do need an additional panel in the house you can supply it from an additional double pole breaker in the new MLO Service panel.

Adding up the ampacity of the breakers in a panel is not how you determine what size of supply it needs.  You will have to do a residential service calculation.  There are several work sheets on line that will help you to do that.  Calculating the service load for the premises will tell you whether you can use 100 Ampere Service Conductors to supply the total load.  If the calculated load is greater than 100 Amperes then you will have to upgrade the size of the Service Entry Conductors to the size derived from the calculation.  Not doing the calculation will put you at risk of nuisance tripping of your present panels main breaker or of overloading your Service Entry Conductors. 

If you need help just ask. 

--
Tom Horne


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## WyrTwister (Aug 23, 2018)

That is more or less what I did when I upgraded my service to a 200 amp meter base and installed a 200 amp 12 space N3R loadcenter .  

2p - 30 - dryer

2p - 50 - range

2p - 30 water heater

2p - 100 - kitchen loadcenter on opposite side of the wall 

2p - 40 - " charging station " for the Nissan Leaf we had in the past 

2p - 30 spare

     However , I am uncertain if the OP is up for that extensive of a project , at this time ?

     That is why I suggested changing out the existing loadcenter that only has 1 space left .  With a 30 or 40 space MLO loadcenter .


Best of luck to you ,  
Wyr
God bless


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## WyrTwister (Aug 23, 2018)

Kristofor Pinkerton said:


> I’ll do the work. Im hoping it’s sq D. The new panels will be sq D for sure. I just want to make sure the way I planned it out will be ok to do that way.


     If you buy the same brand / style loadcenter that you have now , you likely can re-purpose the existing circuit breakers and save a little $$$ .

Best of luck ,   :-0
Wyr
God bless


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## Kristofor Pinkerton (Aug 23, 2018)

WyrTwister said:


> That is more or less what I did when I upgraded my service to a 200 amp meter base and installed a 200 amp 12 space N3R loadcenter .
> 
> 2p - 30 - dryer
> 
> ...


I’m looking to do the quickest and cheapest but yet safe and effective due to being on a time constraint and budget.


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## hornetd (Aug 23, 2018)

Kristofor Pinkerton said:


> So all in all running the 2 sub panels off 60 amp breakers will be just fine and if i ever need to change something i can cross that road when I get there.


Please use one of the on line "electrical service load calculators" to verify that the entire load is within the capacity of the 100 ampere breaker.  

-- 
Tom Horne


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## Kristofor Pinkerton (Aug 23, 2018)

hornetd said:


> Kristofor
> 
> Allow me to suggest an alternative approach.  Instead of filling up your existing panel with those 2 double pole 60 ampere breakers you may want to consider installing a Main Lug Only (MLO) panel which is rated for 200 Amperes and Listed as suitable for use as Service Equipment.  The MLO Service Equipment will have not more than 12 slots in it so that it will never have more than 6 double pole breakers installed.  The MLO Service panel would contain the breakers that would be your new Service Disconnecting Means.  That panel would go between your present panel and your meter.  You would then install the breakers that feed the existing house's panel and the panel in the detached garage in the new Service Disconnecting Means enclosure.  Not having any  pictures of your home to go by I am going to have to do a little guessing here.  When this type of arrangement gets installed the new Service Disconnecting Means often gets mounted on the Outside of the building that already has electrical service.  That is because it makes it easier to run the Feeder/s that will supply the other building or buildings.  If that is the approach that is taken then the new MLO Service panel will have to be Rain-tight.  The type most often used for that is a National Electrical Manufactures Association (NEMA) Type 3R.  Do not plan on using the other slots in the Service panel for other individual loads unless they are 240 volt only with no neutral in the circuit or they are greater than 30 amperes.  If you do not put those 2 60 ampere feeder breakers in your existing house panelboard you may not need an additional panel in the house.  If you do need an additional panel in the house you can supply it from an additional double pole breaker in the new MLO Service panel.
> 
> ...





Kristofor Pinkerton said:


> The garage does not have a panel right now. Then I will have open slots to run a 60 amp to the garage in the mlo. I could also switch any breaker larger than 30 amps to the MLO which would open up more slots in the main. Now wouldn’t that be the same as putting 60 amp breakers in the main for electricity draw if the main service isn’t enough? I would run the mlo in the house then trench the yard to the garage for new service there. Put a 100 amp box in the garage but fed with a 60amp breaker cuz the 100 amp box is way cheaper to buy. The MLO sounds easy to install as I could just kill the main use the feed through on the main to supply the MLO. Is that correct? Next question yis if the house is 100 amps would I would want to keep the MLO low on amps to make sure the MLO has enough supply? Is that correct? I see you say to install it between the meter and the main that is currently there though. Is that the better option then running after the main using the feed through on the main? I’m sure I confused you a little there sorry.


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## WyrTwister (Aug 23, 2018)

Can you post some photos of your existing installation .

     Sounds like you may have to do this in phases .

Best of luck ,   
Wyr
God bless


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## Kristofor Pinkerton (Aug 23, 2018)

WyrTwister said:


> Can you post some photos of your existing installation .
> 
> Sounds like you may have to do this in phases .
> 
> ...


I will take some tomorrow!


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## Kristofor Pinkerton (Aug 23, 2018)

.


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## WyrTwister (Aug 23, 2018)

If everything will not run off the existing 100 amp main , then the whole ball game changes .  And the OP will have to either change plans or change expectations ( what can be done with the existing service ) .

     And the probable budget gets larger , quickly .

Best of luck to you ,   
Wyr
God bless


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## hornetd (Aug 23, 2018)

Kristofor Pinkerton said:


> The garage does not have a panel right now. So if I put the MLO in then I supply the existing house panel with a 100 amp breaker off the mlo.  Then I will have open slots to run a 60 amp to the garage in the mlo. I could also switch any breaker larger than 30 amps to the MLO which would open up more slots in the main. Now wouldn’t that be the same as putting 60 amp breakers in the main for electricity draw if the main service isn’t enough? I would run the mlo in the house then trench the yard to the garage for new service there. Put a 100 amp box in the garage but fed with a 60amp breaker cuz the 100 amp box is way cheaper to buy. The MLO sounds easy to install as I could just pull the meter to kill the power to the house run the lines from the meter box to the MLO then from a 100 amp breaker in the MLO to the main with the existing wire that fed the main from the MLO to the main. Next question is if the house is 100 amps I would want to keep the MLO low on amps to make sure the main has enough supply? Is that correct? I’m sure I confused you a little there sorry.


You will have to replace the cable between the MLO and the panel with a 4 wire cable.  The cable must be 4 wire because the Equipment Grounding Conductor (EGC) must be kept separate from the neutral everywhere except at the service equipment which would now be the NLO panel.  Buy the 4/0 cable even though you plan to use a 60 ampere breaker.  That way if you end up needing to increase the capacity of the whole service you won't have to replace that wire when that time comes.  You would then buy a couple of the add on Equipment Grounding Busses and put them in the house panel.  Take all of the EGCs off of the neutral buss and move them to the new add on equipment grounding busses.  You then remove the main bonding jumper from the house panel so that there is no longer a connection between the neutral and the cabinet which encloses the house panel board.  The MLO Service equipment will come with a new bonding jumper that you will install in it.  

Crucial in all of this is to do the Service Load Calculation to determine that your present Service Entry Conductors can carry the actual load.

-- 
Tom Horne


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