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Joined: Dec 2001
Posts: 50
Within our manufacturing plant over the years as the plant expanded we have expanded our distributions system (loadcenters, panelboards, etc.)as well. Unfortunatly We ended up with somewhat of a haphazard identification system for them. Even though it is working, I don't like it.

I would like to know what kind of a system you find works best.

For instance in our case a breaker panel loacted at the fartherest end might start off from the MDP go through a 480 volt panel, through an in house transformer and through another panel or two till it finally comes to this panel. If I simply label this last panel "Panel G" it really tells me nothing except that it is panel G.

Should not each panel be ID'd in such a way that be reading the ID a person can tell which panels it is fed from?

I'd just like to know if there is a good straight forward system that works good.


Joined: Apr 2002
Posts: 7,336
Likes: 7
For an existing facility it's not easy. We usually start at the switchgear, and ID the feeders "MDP-1" etc. The sub-panels are tagged either MDP-1-A, or DP-x with suffixes as required. Xfr's are tagged "Xfr-x" "Pri: DP-1" "Sec:LP-1" or whatever logic is suitable to you.

We ID discos as to line source by panel ID. We ID all sub-panels as "Line from xxxx"

Hope this helps you.

Joined: Jul 2003
Posts: 394
In addition to the originally designed scheme, we have added labels on every panel that say "Fed From XXX". With 2 HV feeds, main gear, and 5 substations feeding 1500 feet of bus duct down the middle of the building, it's really handy to be able to work your way backwards sometimes.

Joined: Apr 2002
Posts: 2,527
A start at documenting a building electrical system may be the use of some record-keeping materials like Scott35's panel-schedule spreadsheets at

We in the trade need to be acutely aware of poor recordkeeping and the problems it can cause. Since day one there have been obvious safety implications, but nowadays in the 'digital world' loss of production from even the shortest outage also becomes important to managers.

Joined: Oct 2000
Posts: 2,722
Broom Pusher and
The way I setup Distribution lines is:

Main Service Equipment = MSB-# (Main Switch Board),

Distribution Equipment = MDP-# (if large distribution equipment for both high and low voltage sides, then the number is appended with "H" or "L"),

Transformers - T-# (if isolation transformers are included, then "TP-#" for normal power systems, and "TI-#" for isolated systems),

High Voltage Subpanels (i.e. 480Y/277) = "HP-#",

Low Voltage Subpanels (i.e. 208Y/120) = "LP-#"
*** BTW:
if a Subpanel is fed from another Subpanel, then it receives an alphanumeric designator - such as:

"HP-1A" is fed from panel "HP-1"

Good luck with this task.


Let me know if the spreadsheets found at the link Bjarney has listed are of use.

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Joined: Jul 2002
Posts: 8,432
Likes: 3
Having just gone back into Faults work,
The permutations of having an inadequately marked Industrial installation are only realised during break-downs.
If I am the Line Mechanic that connects the new Distribution Panel up, before I do, I ask if the Installation has been labelled properly, I usually go and check this too, the days of poorly sized fuses and having them blow out our Secondaries, are well upon us.
And try and find the offending fuse!.
No labelling, no connection.
If we can label all of our poles and Air-Break switches and other equipment, spanning an area in miles, not feet or yards, why can't a factory be labelled properly?.

Joined: Jun 2001
Posts: 141

For commercial buildings, here's how I do it, and how I wish everyone else did!

Each tranny gets a number (T-1 etc), then power panels are PP-1, PP-2 etc (for power panel #1), which feed lighting panels marked as LP-1, etc. If there's another power panel fed from a power panel (say from
PP-4), the sub is PP-4B.

Each ungrounded branch circuit conductor is numbered at the breaker, and at each j-box. And, every j-box cover is labelled in BIG printing, with the panel of origin and the circuit numbers.

I don't have to tell you how much time the j-box labelling saves when making modifications, adding a circuit, or troubleshooting! Pop one ceiling tile, use a good flashlight to look around, and you can usually see the j-box you need right off the bat.

Work safe,


p.s. Don't forget to keep the panel schedule up-to-date...CP

Joined: Jul 2002
Posts: 241
SJT Offline
Hello Amp-Man,
That sounds like THE WAY to identify everthing. LP1, PP2, etc. I agree, it's too bad things are not labeled right after the job is installed. I have a job now, where I have to label transfer switches. Normal, Generator power and load terminals feed out to panel xyz.
Have you had to label transfer switches? I like to see alot of Labels myself. Its important.

Joined: Jun 2001
Posts: 141

Yea, it's amazing how there's never time to label stuff as it's installed/pulled, but there's always time to trace it for troubleshooting when part of a building is dark (or a production line is down)...clearly, we work better under pressure!

As far as transfer switches, it's an easy time of it if the conductors for the grid power, the genny power, and the load are all in separate conduits. I label the outside of the pipe with SMUD (for Sacto muncipal utility district) or PGE (Pacific Gas & Electric, our local PoCos), GEN, & LOAD (or FEEDER 1, 2, etc.). I've thought of using "GRID" for the poco supply, but it seems too similar to GEN for my taste. Too easy to mix up under stress.

If two of these sets of conductors run in a single pipe or bus duct, then you have to label the conductors themselves. I've had little luck finding a good place to attach a label inside the transfer switch can.


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