Any Comments on this panel?

It’s getting late. Would someone please take a look at this panel and educate me a bit. No disconnect at meter. Cutler Hammer panel with 150 Amp 3-wire SE cable and a 60 AMP breaker labeled in the panel cover as “Main” disconnect. Based on the photo, is this the only disconnect? Is it truly a 60 Amp panel?

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Hi Hank,

This one is a little ticklish, as it appears to be a split bus panel. That is to say that all the 240V circuits are at the top of the panel, but the 240V breaker on the left is in fact controling the 120V circuits.

Inspite of the 150amp conductors I would have to say that the panel is probably rated at either 100amp or 125amp. I would not call it a 150amp.

Regards

Gerry

Thanks for weighing in Gerry. Could the top two or three breakers on the right bus bar be contributing to the number of disconnects in addition to the one and only 60 Amp breaker labeled as “Main”? I think the others may have been 30, 30, & 30. Can’t read those darn Cutler Hammer skin tone breakers from pictures.

Hi Hank,

yes that is the case, the panel still meets the rule of 6 for disconnects.

Update for others: I talked to Hank on the phone as seeing as the home was built in the 1980’s I would feel that the service amperage is in fact 150 amp, but withouit knowing the Panel UL rating it is hard to tell.

Regards

Gerry

The capacity is also limited by the size of the SEC.

I agree with Gerry’s assessment.

“CORRECT” determinations on “Split Buss” panels…while a fuse one can be more complicated…on a breaker one it is important to do what we call BOOKING the combination to determine the actual panel ampacity.

We had this discussion before so I felt it is a good time to explain it…

I will assume the ground work has already been done here and the SEC is rated for 150A…and we will assume the rating of the enclosure is also 150A because of lack of label listing posted ( taking gerry’s word on that…lol …)

So…you see a 60A main breaker…Why not a 60A panel…well it’s capacity is 150A supported by the wire size, more often than NOT the panel will have a rating listed that we will say in this case 150A…so regardless of the breaker labeled 60A main…the true ampcity of this panel is 150A…remember on Split Buss panels you MUST look at the panel rating, then the SEC size…and if no rating is listed…look at the cumulative rating of the main disconnects if it pertains to fuse styles…

These factors will help you list the correct size of a Split Buss…they dont make the old fuse ones anymore…so atleast that saves some confussion.

BTW…if the wires to the panel were rated for 150A but the panel label said the panel is rated for 125A…what is the correct ampacity listing…

Remeber the Weakest Link…In this case the panel is the weakest link…

Bad thing about Split Buss panels like this in the above question…the electrician is PUT on the spot to have corectly calcualted the loads to allow this to take place.

[quote=pabernathyBTW…if the wires to the panel were rated for 150A but the panel label said the panel is rated for 125A…what is the correct ampacity listing…

Remeber the Weakest Link…In this case the panel is the weakest link…/quote]

Thanks Paul. So, the panel rating will effectively de-rate the ampacity listing for the panel despite the SE wires being rated at 150 AMP, correct?

Correct…while the Capacity of the SE is 150A…the panel would only be rated for 125A…thus you can’t exceed the rating of the enclosure.

Wire can be 200A rated if the person chooses to lets say for VD…but that does not change the ACTUAL rating of the enclosure in this example.

But the current (amperage) could potentially exceed the panel rating if the SEC is too large, and therefore, should not be, unless there is an OCPD which would limit the potential of the SEC (sounds good in theory anyway ;-)).

Jeff…that is what my statement said…as it pertains to a SPLIT BUSS ONLY…this was the example…not under the NORM where you simply notice the OCPD in that case.

I was trying to explain HOW to figure out the issue with SPLIT BUSS systems…when you simply cant use the OCPD due to the nature of the setup.

Their is absolutly nothing wrong with using 4/0 to a 150A panel…provided the lugs will accept the size wire…and YES in a normal case the OCPD would have to match ( which it normally would ) the rating of the panel…

But in a Splilt Buss…it just may NOT…due to the nature of it so you have to 1.) Figure the electrician sized it based on the actual calculations and it does not exceed the panels rating…and 2.) does not exceed the SE rating…

HE must account for the WEAKER of the two…split buss layouts can be NASTY if you allow them to confuse you…

Was just attempting to clear some of the MIST on them a bit…:slight_smile:

Remember…Nothing says you can’t oversize the Conductor…BUT the CODE says you SHALL NOT undersize it…

Unless I am mistaken ( Joe I appeal to you fellow Code Man…Correct me if I am wrong…)

Not that I as a contractor would SPEND the money for larger wire than needed…it was just for the example…not practicle in terms of bidding a job…

lol…I had to come back and ADD this…Check out JOE T’s image on his profile…JOE you have JUST been granted the rights to us the " MEMBER OF THE NACHI ELECTRICAL MAFIA " slogan…lol…you frighten me in that image…:slight_smile:

I’m following you Paul. However, I’m looking at something else.

My point was, that you could draw more current than the panel is rated for (in the case of the split bus) if you oversize the SEC.

The capacity of the system and the limiting components of the system are different. If your capacity is 100 amps (based on the panel rating) and your smallest limiting component is the 3/0 copper SEC, there is a potential for exceeding the service capacity, or “over-loading” the panel.

The flip side of that being, the split bus design already allows the potential to draw more current than the (“properly sized”) SEC is rated for.

The single main (service disconnect) eliminates the potential for over-loading the **limiting components **of the system.

BUT the CODE states that in a split buss design it is up to the electrical contractor to ensure the computed load does not exceed BOTH the rating of the panel as well as the SE that supplies it.

I agree with you my friend…BUT thats not how the CODE is written…it simply states the SE MUST be sized for the potential calculation loads…ANYONE can overload a split buss…which is the problem with them.

This is why in a split BUSS you are limited to the 240V circuits and usually one of the SET controls the 120V circuits…to make an effort to eliminate the potential.

The end RESULT is the electrical contractor MUST know how to size it all correctly based on the calculations…but again nothing says you HAVE to size the SE to meet the panel…think of this the OTHER way…YOU just know if you size a split buss EXACTLY as the panel is rated which is allowed…BUT in your theory if their is no MAIN single OCPD…could it be MORE of a problem to potentially EXCEED the SE’s rating…I would worry MORE about that…the oversizing was an example…it aint coming out of THIS electrical contractors pocket…lol…

OH lord…Are we getting far too technical for the everyday inspector here…lol

My point exactly.

I certainly hope not :wink:

Yeppers…I for one am GLAD we just dont mess with them anymore…now some are showing their nasty head in a few commerical jobs I have been messing with…BUT for my bread and butter…WE dont mess with them anymore…Thank Goodness !

BTW…as TIGHT as electrical contractors are…you will NEVER see an oversized SE for the most part…lol…if it is a 150A panel…it gets a SE rated for that…lol…not a DIME more…:slight_smile:

Yep…we are TIGHT

You are still in the “Electrical Mafia” fella…even if you DID change your picture…:wink:

I agree! BTW: Here’s my new profile picture…:slight_smile:

PS: I will be driving to Charlestown, WV from Pittsburgh, PA next Wednesday night and I will be there through Friday

Hey Brother…I wish I could come up…I have a deadline on a new townhouse complex I am bidding…I am just SOOO out of touch lately Joe on my pricing…seems like I am overbidding lately even with the rise in copper…

Lost a HUGE deal over $ 300.00 bucks this week…I will be working on the townhouse bid all week…to ensure we get it…these are gravy townhomes and would like to get them…

Excellent PIC fella…Thats the JOE I remember…lol…not sure WHAT that other one was you had…lol…you looked SHADY in the other one…lol…typical electrician…;)…we all are accused of being shady…lol…and we hardly make a profit on anything we do…

WAIT…let me check my schedule…If you are in charlestown it is only 2 hours and we could visit the Horse Races…:)…I will see what I can do…I just may be able to wrap it up…I will keep ya posted.

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