Thread: Double panel box

Today's work was a large old house that has had many renovations over the years.
Being that there are 6 bedrooms, 5 baths, 2 garages, a swimming pool, landscaping lights, a large kitchen, two family rooms and a living room, I expected there to be sub panels.
When I worked my way thru the maze of basement walls I found the panel boxes.
The service was upgraded maybe 10 years ago to an underground service. Conduit into the basement where two panels are feed thru conduit. So I can't tell if one is the main and the other is a sub. The panel on the right is so badly rusted I could not remove the cover. The one on the left is also rusted but got the cover off. Left panel had a 200A main and 29 breakers.Right panel had a 200A main and 12 breakers all were 30A, 40A and 60A. Unlabeled.
Neutral and ground were not separated on the left and had a bonding screw.
There was a hot wire dangling in the basement, two dead outlets in one family room, several mystery switches and none of the landscape lights worked. One breaker in the left panel was tripped and would not reset.
I recommended an electrician replace rusted panels and verify all circuits.

So, is the panel on the right a sub or could it be two main panels.
Thank you for any insight and criticism.

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Originally Posted by Chuck Miller

I expected there to be sub panels.

You only find sub panels in submarines.

You find "service equipment" (AKA "service equipment panels") and "panels".

So I can't tell if one is the main and the other is a sub.

They are both simply panels, and one, or maybe both, will be the service equipment too.

From your description you have TWO SERVICE EQUIPMENT PANELS, neither one is a "main" and neither one is in a submarine either (unless there is something you did not tell us).

I would agree with Jerry that you likely have a 400 amp service with a couple 200 amp service equipment panels with three wire service entrance being fed from a class 320 meter base enclosure with double lugs.

Just so you know ... everyone understands what you mean by 'sub panel' but it is a term not technically correct. Frankly I do not understand why it seems to be a point of concern.

The reason I think you have two service equipment panels is you say they are both 200 amp and have individual conduit runs to each panel and the one you were able to get the cover off has the main bonding screw installed. You didn't say if the panels had main breakers or not.

I have at times run across situations where there were 2 service equipment disconnect enclosures between the meter and the panels. The 2 panels in the dwelling are main lug. And I have also seen them fed with 3 wires from the service equipment in pvc and neutral and ground bonded. Isn't correct but I have seen it done more than once.

As you know these are panelboards (not sub-panels) load side of the service equipment in this situation I just described.

What I think you have is two 3 wire parallel runs from the meter base of 2/0 copper or 4/0 aluminum in conduit to a couple 200 amp main breaker panelboards. These panels are service equipment because the first means of disconnect for all power to the dwelling is located in these panels. They are side by side because the electrical code requires the service disconnects to be grouped together with no more than 6 disconnects for a service entrance to a single family dwelling.

Originally Posted by Roger Frazee

Just so you know ... everyone understands what you mean by 'sub panel' but it is a term not technically correct. Frankly I do not understand why it seems to be a point of concern.

Roger,

You do not understand why it is a point of concern because you have not been around here long enough to see that people STILL do not know how they are wired and where the neutral is isolated from ground (at the service equipment only).

I have found that by simplifying it to the correct terms: "service equipment" and "panels" that the confusion goes away and they understand and learn. Which also means that NOT "everyone understands" what is meant by those two incorrect terms anyway.

That is why my avatar shows a submarine and a sub panel ... if you are not in a submarine you are not looking at a sub panel, and if you were, it would like like that panel in my avatar.

Well I'm going to agree with you .....reluctantly..... I like the avatar for what you are trying to teach others about the confusion of using the term sub-panel.

The laymen term sub-panel is derived from 'sub-distribution panel.
There is also; flex, greenfield, used for FMC
thin wall, used for EMT
neutral, used for a grounded conductor and an actual neutral. The list is endless.
As an AHJ, I've learned to live with it as long as I know what the person means. Otherwise I would be interrupting every conversation every few words. uggg
It's typical to see two (2) service panels in a dwelling these days.
Seeing allot more of this the past year as 'metered rate' services are being used for GEO Therm heating, PV systems (separately derived), and more wind generators.

Don't forget to look for the service conduit to be sealed in some fashion when it originates from outside to an inside panel. The Art# escapes me at the moment.....We have three code books in MI now, and in the endeavor to memorize the new residential code #'s I've seem to have forgotten all the NEC #'s, just gone blank.
An old mind is a terrible thing to waste.
Bob Smit, County Electrical Inspector

Originally Posted by bob smit

The laymen term sub-panel is derived from 'sub-distribution panel.

I believe it was shortened from "sub-fed panel" in that it was "sub-fed" from a breaker in another panel upstream.

As an AHJ, I've learned to live with it as long as I know what the person means.

It's not that *I* know what they are talking about, I want to make sure *they* know what they are talking about.

Don't forget to look for the service conduit to be sealed in some fashion when it originates from outside to an inside panel. The Art# escapes me at the moment.....We have three code books in MI now, and in the endeavor to memorize the new residential code #'s I've seem to have forgotten all the NEC #'s, just gone blank.

Bob, be careful on that one, see my bold and underling ...
- 300.7 Raceways Exposed to Different Temperatures.
- - (A) Sealing. Where portions of a cable raceway or sleeve are known to be subjected to different temperatures and where condensation is known to be a problem, as in cold storage areas of buildings or where passing from the interior to the exterior of a building, the raceway or sleeve shall be filled with an approved material to prevent the circulation of warm air to a colder section of the raceway or sleeve. An explosionproof seal shall not be required for this purpose.

There are many locations where that "and" part does not fit as condensation "is not known to be" a problem. It then gives two examples of that "and", but they are still part of that "and" "known to be".

I think it should be worded like this to eliminate reading problems :
- Where portions of a cable raceway or sleeve are known to be subjected to different temperatures or where condensation may be a problem, as in cold storage areas of buildings or where passing from the interior to the exterior of a building, the raceway or sleeve shall be filled with an approved material to prevent the circulation of warm air to a colder section of the raceway or sleeve.

With that wording, there is no "well, maybe" to it.

Agreed.
I was making an assumption here relative to the locale of the panels...basement I presume.
A few decades ago I had to make a service call on a new panel I installed using this very situation. A few Square D breakers had failed. There was condensation in the panel and obviously the breakers.
Have come across this when the conduit was run directly into a panel board located in a basement on a few occasions.
Conversely, no problems encountered when run into a main floor panel or a heated area panel, or from outside to inside a garage.
Bob Smit, County Electrical Inspector

I do think Bob may be thinking of article:
230.8 Raceway Seal
Where a service raceway enters a building or structure from an underground distibution system, it shall be sealed in accordance with 300.5(G). Spare or unused raceways shall also be sealed. Sealants shall be identified for use with the cable insulation,shield, or other components.

300.5(G) Raceway seals
Conduits or raceways through which moisture may contact live parts shall be sealed or plugged at either or both ends.

Thanks, guys, I knew that I could get straightened out here.
I should know the correct terms but I got lazy. Sometimes I succumb to information overload.
I suspected that they are two Service Equipment Panels because of the size of the house. But since I could not verify the service entrance conductors to the one panel I thought I should get other opinions.
By the way both panels have a 200 amp main breaker. Which is why I figured both to be Service Equipment Panels.

Originally Posted by Chuck Miller

By the way both panels have a 200 amp main breaker. Which is why I figured both to be Service Equipment Panels.

Chuck,

Without further information or photos, that is the same thing I was basing my statements on.

I still call them sub-panels. The term has been widely used for decades and every electrician knows exactly what that term means. We used the word neutral long enough it made its way into the 2008 NEC. Makes life easier when you are talking about sub-feeds off the load side of a main disco.

I understand Jerry's point but I will still call them sub-panels unless the NFPA decides to give them a name and a definition. I was getting sick of calling the neutral a grounded conductor too.

I was told many years ago the term sub-panel came from the fact that the panel is subordinate to the service disconnect.

Now that I have thought about this situation more, my question is: if both panels are 200A, the total 400A. That is over the max for 4/0 alum. cable, right?

Originally Posted by Chuck Miller

Now that I have thought about this situation more, my question is: if both panels are 200A, the total 400A. That is over the max for 4/0 alum. cable, right?

Chuck

Nope it is a matter of the meter base and utility service entrance being 400 Amps. Each panel has service entrance conductors ran to them from the 320 class meter enclosure that are rated 200 amps using 310.15(B6). The main breakers in the service panelboards protect the set of conductors ran to them. The total non continuous and continuous load is then carried by the meter class and service from the utility. Neither panel can exceed 200 amps but both panels together can and thats why the meter base (that serves both panels) must be rated to carry the total calculated load.

I just wanted to add that I'm not 100% certain this is what you have .. pictures would help .. Your description though sounds like a 400 amp service using two 200 amp main breaker panels. If it is anything else someone got resourceful....

[quote=Jerry Peck;117418]Roger,

You do not understand why it is a point of concern because you have not been around here long enough to see that people STILL do not know how they are wired and where the neutral is isolated from ground (at the service equipment only).
nuetral isolated from the ground at the service equipment only?

Originally Posted by Jeff Remas

I will still call them sub-panels unless the NFPA decides to give them a name and a definition.

Jeff,

The NFPA gave them a name DECADES AGO.

They are called "panelboards".

If you want, though, call them "panels" for short.

Originally Posted by Chuck Miller

Now that I have thought about this situation more, my question is: if both panels are 200A, the total 400A. That is over the max for 4/0 alum. cable, right?

Chuck,

Actually depends on what you have and how you have it worded.

As worded, you are saying that one set of 4/0 aluminum service entrance conductors is feeding two 200 amp service equipment, and, yes, that would be wrong.

However, what I suspect you have is two sets of 4/0 aluminum service entrances conductors feeding two 200 amp service equipment, in which case that would be okay.

[quote=brian schmitt;117655]

Originally Posted by Jerry Peck

Roger,

You do not understand why it is a point of concern because you have not been around here long enough to see that people STILL do not know how they are wired and where the neutral is isolated from ground (at the service equipment only).
nuetral isolated from the ground at the service equipment only?

Brian,

I told you it was confusing.

Chuck Miller asked:

Now that I have thought about this situation more, my question is: if both panels are 200A, the total 400A. That is over the max for 4/0 alum. cable, right?

Not exactly. They can do a load calculation to determine that. You can have two 200A panels on a 200A service if your load calculation allows you.

Don't like it, don't agree with it but you can do a load calc to determine that.

Most double 200A panels that I see these days are part of a 320A continuous service.

First why is anyone opening a service panel that is that rusted. if the panel is wet it could be a shocking surprise. Second shouldn't this all be referred to a licensed electrician if for nothing more than what caused the rust and is it safe?

Originally Posted by Jeff Remas

Not exactly. They can do a load calculation to determine that. You can have two 200A panels on a 200A service if your load calculation allows you.

Not quite that easy: (underlining, bold and red text are mine)
- 310.15 Ampacities for Conductors Rated 0–2000 Volts.
- - (A) General.
- - - (1) Tables or Engineering Supervision. Ampacities for conductors shall be permitted to be determined by tables as provided in 310.15(B) or under engineering supervision, as provided in 310.15(C).
- - - - FPN No. 1: Ampacities provided by this section do not take voltage drop into consideration. See 210.19(A), FPN No. 4, for branch circuits and 215.2(A), FPN No. 2, for feeders.
- - - - FPN No. 2: For the allowable ampacities of Type MTW wire, see Table 13.5.1 in NFPA 79-2007, Electrical Standard for Industrial Machinery.
- - - (2) Selection of Ampacity. Where more than one calculated or tabulated ampacity could apply for a given circuit length, the lowest value shall be used.
- - - - Exception: Where two different ampacities apply to adjacent portions of a circuit, the higher ampacity shall be permitted to be used beyond the point of transition, a distance equal to 3.0 m (10 ft) or 10 percent of the circuit length figured at the higher ampacity, whichever is less.
- - - - - FPN: See 110.14(C) for conductor temperature limitations due to termination provisions.
- - (B) Tables. Ampacities for conductors rated 0 to 2000 volts shall be as specified in the Allowable Ampacity Table 310.16 through Table 310.19, and Ampacity Table 310.20 and Table 310.21 as modified by (B)(1) through (B)(6).
- - - FPN: Table 310.16 through Table 310.19 are application tables for use in determining conductor sizes on loads calculated in accordance with Article 220. Allowable ampacities result from consideration of one or more of the following:
- - - (and goes on and on)
- - (C) Engineering Supervision. Under engineering supervision, conductor ampacities shall be permitted to be calculated by means of the following general formula:
where:
- - - (provides formula for the engineering)

Want to have an engineer calculate the ampacity? Go for it.

Otherwise stick to the charts.

What I believe some here are thinking of is multiple mains in the SAME enclosure fed by one set of conductors, whereas what was described here are multiple mains in DIFFERENT enclosures, which quite obviously means they are not fed by the same one and only set of conductors.

One set of conductor may feed one panel, which is a feed-through style, with the conductors then feeding-through to the next panel. That means the conductors feeding the first panel must be rated for the 200 amp main at that main panel, but it also means that THE SAME 200 amp limitation applies to the second 200 amp panel, meaning the service is only 200 amps.

[IMG]file:///C:/DOCUME%7E1/Chuck/LOCALS%7E1/Temp/moz-screenshot.png[/IMG]I have tried to upload some pics. Lets see if it works.

Originally Posted by Chuck Miller

[IMG]file:///C:/DOCUME%7E1/Chuck/LOCALS%7E1/Temp/moz-screenshot.png[/IMG]I have tried to upload some pics. Lets see if it works.

Chuck,

When you make a post, scroll down a little when you have that screen open and you will see a button to click on which says 'Upload Photos', use that.

Thanks Jerry,
here they are

Can you tell I don't do this much.
How 'bout now

One more

Chuck,

Thanks for the photos, now it becomes clearer (if that is a word ) ...

My guess is:

From the meter to the wireway/gutter above the two panels is the properly sized service entrance conductors, which in the wireway/gutter is tapped off with the smaller service entrance size as required for each disconnect.

Or:

The service entrance conductors from each disconnect run up into the wireway and out to the meter through that large conduit, with (hopefully) proper terminals at the meter which allow for two conductors at each meter terminal.

Not sure which is 'most likely' in your area, I've seen both methods in the places I've been.

Thanks again, Jerry,
As you can see this is a pretty rust box, so I recommended that a qualified electrician evaluate and make necessary repairs.

Chuck

Good pics Chuck.
FYI for those concerned; the raceway in this situation is more than just a (2.5 inch?) raceway from exterior to the wireway (aka gutter) above the panels. The two (2) nipples that extend down to the panels are also 'service raceways'.
The reason for noting the proper definition is this case...

Service raceways (and the wireway) must be bonded by methods exceeding those of load side raceways, such as; bonding locknuts on fully punched holes, bonding type bushings and the like. Bonding conductors are to be sized per table 250.66 (this has been talked about many times here). If the raceways are not being used as the sole return path, only one side of each raceway/wireway need be bonded. This more stringent requirement is due to the fact that there is no overcurrent/ground fault protection ahead of the service conductors (I'm assuming).
This is a common rejection I write.

Note that all the bonding and the GEC's can be connected in the wireway pictured. This gets a little more complicated but is the method I personally prefer.
Bob Smit, County Electrical Inspector

If I understood correctly, the service is only 200 amps.

There a raceway feeding in to a Wireway. There below,
are two panels, each being connected to the Wireway
by use of Steel Threaded Couplings. Inside the Wireway
each panel Main is wired thur their raceway coupling
connected/splice inside the Wieway. Where the wire
may only be rated for 200 amps. The power meter is
an unkown for me, the power company meter may be
able to take 400 amps, with any problem. But I most
interested in the ampere rating the the service conductor.


My question how is allow in the NEC code that you can
do this type of service. And why aren't the panels
mains rated at 100 amps each. When you add the two
together it equal 200 amps. I would have problem
with this type of service. But please educated why this
allowed.


One last thing, most 100 breaker are not rated for continuous
load. So could you used two panels with 125 amp. rated mains.

Thanks to all who will know try to educated me.

Robert,

I'm not following your post or question, but here is what I *THINK* you *MIGHT BE* asking ...

PRESUMPTION #1: There is a meter on the other end of that horizontal metal raceway which goes into the wall to the right, and that the meter has terminals for TWO conductors at each terminal location, and that there are TWO sets of service entrance conductors connected to those terminals.

PRESUMPTION #2: There is a meter on the other end of that horizontal metal raceway which goes into the wall to the right, and that the meter has terminals for ONE conductor at each terminal location, and that there is ONE set of service entrance conductors connected to those terminals.

In #1 above, the TWO sets of service entrances conductors run into the wireway and split up, ONE set of service entrance conductors running down into each panel. Nothing wrong with that provided that each set of conductors is rated for the main service disconnect it is supplying.

In #2 above, the ONE set of service entrance conductors is run into the wireway and split up, with a set of service entrance conductors tapped/bolted to the main service entrance conductors and running to the panel to the right, and a second set of service entrance conductors tapped/bolted to the main service entrance conductors and running to the panel on the left. Nothing really wrong with that provided that each set of tapped off service entrance conductors is rated for the main disconnect it is supplying and that the main set of service entrance conductors is rated for what the two disconnects are rated for when added together.

The only way to have found out how that was wired would have been to have removed the wireway cover and looked inside.

Either of the above would have made that a 400 amp service, each main rated for 200 amps.

Example of Jerrys Presumption #1 (below) This is what we can't see outside at the meter only difference is the service entrance conductors share the same pipe at some point in situation we are talking about. The utility or the homeowner will supply that meter line side with conductors to meet the 320 class meter base for a 400 amp service. Load side it is split into two sets of 200 amp service entrance conductors in this case 4/0 aluminum if it was sized correctly.

The meter is double lugged as you can see to accomodate each set of conductors. I can't come up with a picture of mine or online for Jerrys Presumption 2 it isn't often done that way for a residence in my experience.. but the big wire would just continue on the load side of the meter and taps made in that wireway in the basement to each 200 amp panel.

You could also have two 200 amp service equipment disconnects in circuit breaker enclosures outside and each one of those with a 4 wire feeder to two 200 amp mlo panels inside.

Thanks, Jerry & Roger for your recent posts.

Rger, thanks for sharing the photo, very helpful.