schematic design

georgia boy · May 15, 2005

hi everyone

i have a project installing new controls on some old assembly equipment . slc 5/05 plcs new control cabinets . new prints the whole deal . my question is on drawing the prints and layout of the physical wiring . on standard prints wire numbers go in sequence from left to right and top to bottom with all wires connecting to the same point such as L1 marked the same on the old panels all wire connecting to L1 are numbered 1 and all wires connecting to L2 numbered 3 . troubleshooting wires on the L1 side is easy each wire is fused in the control cabinet before it goes to its field device . but if you loose L2 on a field device you have no idea which one it is because all L2 terminals are marked number 3 so you have to start pulling wires and opening wiring ducts . is there a better , standard method ? i was thinking of using something like L1.1 , L1.2 , L1.3 AND SO ON . anyone have any ideas

rsdoran · May 15, 2005

L1 and L2 imply main feed, they are always L1 and L2 but anytime you branch the feed thru fuses they should be designated, ususally 1L1 and 1L2, 2L1&2L2 etc etc..this designates its a branch of line feed.

Depending on situation its common when going thru a 120vac transformer to use 1 & 2 then sequence the numbers as you stated. With a 24vdc power supply its common to start at 100 with the power feed. With PLC inputs its common to start at 1000 or 10000.

The attached pdf is a simple example.

georgia boy · May 15, 2005

reply to rs doran

i looked at your attached print. looks like after your 480x120 transformer x1 and x2 you use 1 for x1 and 2 from x2 this is very common basically what i have . my question is from your print i see you have pilot lights 1lt ,3 lt,4lt lets say these and ten other pilot lights were mounted in a remote cabinet 20 feet away from the main cabinet . the energized conductor to all these pilot lights could possibly have a different conductor wire number correct but the the neutral side of all these lights would bemarked as 2 right . if you had a broken neutral wire on one of the pilot lights how would you know which wire to test from the main panel as in the terminal blocks they would all be marked 2 ? this gets hard when you have multiple conduits going from one panel to another .i want to designate on my prints which netral wire goes to 1 LT,2LT 3 LT . but also designate that they all connect to x2 .

rsdoran · May 15, 2005

Its virtually impossible to designate a common any other way. Even if the device is located a long distance there may be other devices connected to the same common...ie one wire may go from panel to a terminal block then its again distributed.

A broken neutral should be simple to determine.

leitmotif · May 15, 2005

Semantics maybe BUT

georgia boy said:
i looked at your attached print. looks like after your 480x120 transformer x1 and x2 you use 1 for x1 and 2 from x2 this is very common basically what i have . my question is from your print i see you have pilot lights 1lt ,3 lt,4lt lets say these and ten other pilot lights were mounted in a remote cabinet 20 feet away from the main cabinet . the energized conductor to all these pilot lights could possibly have a different conductor wire number correct but the the neutral side of all these lights would bemarked as 2 right .
REPLY Yes.

if you had a broken neutral wire on one of the pilot lights how would you know which wire to test from the main panel as in the terminal blocks they would all be marked 2 ? this gets hard when you have multiple conduits going from one panel to another.
REPLY the three lites would have 3 different "hots". Each would hva common (I DO NOT want to call it a neutral maybe grounded conductor is a better term). In conduit feeding lites in panel you hve the 3 hots and one grounded (2). In the panel 2 would go to a separate power strip and branch off from there (or could daisy chain from lite to lite). To find broken "grounded conductor ie 2) test from "hot" side of lamp to the grounded @2 side get 110 youre OK if not test the hot to another #2 if 110 then you know that your #2 is broke. As a note I like to use a white conductor with a color trace on it for the GROUNDED CONCUCTOR - whether 120 or 24 control power voltage (piece of tape works well) ESPECIALLY if there is a real true blue NEUTRAL in there.

Sometimes a good test for neutral (GROUNDED conductor)
IF you have a GROUND (green) is to
check for potential from GROUNDED to GROUND.
IF no potential then
switch to resistance and
read resistance between GROUNDED and GROUND.
IF thre is only one panel then this value should be close to zero.
If you have a large system with lots of sub panels and sub subs and or sub sub subs then this resistance will be higer of course because you have to go all the way back thru the subs to the main panel where the neut (GROUNDED CONDUCTOR) is bonded to ground.

.i want to designate on my prints which netral wire goes to 1 LT,2LT 3 LT . but also designate that they all connect to x2 .

They will all be the same guess that is why they call it common. Just make sure as described above to make all of em a different color than your "hots".

Dan Bentler

JohnW · May 16, 2005

One method of cable numbering is to mark the cable with the equipment and terminal it goes to i.e. lamp H1 the common would be marked H1-N. if you need a wire number just add it on so it becomes 2-H1-N.

Another way is to put terminal links to each group of commons and call the links L1.....Lx then the main common is N0 and the common after the link becomes N1...Nx so the connection to H1 becomes N1 the connection to H2 becomes N2 etc.

For supply cables use the MCB or fuse number so L1 before fuse F1 becomes L1-1 after F1, L1-2 after F2 etc.

georgia boy · May 16, 2005

thanks john w

i think the method you described will work great in this application . i just wanted to do it in a manner that would make my prints to or above code / standard

TConnolly · May 16, 2005

When there is the possibility of confusion I designate the termination number (Device tag + term) on the wire marker as well. I only do this if there can be some confusion, otherwise, its extra work. On my drawings every connection point designates the terminal number.

Also, where-ever possible, the device tag, the wire number, and the PLC IO address are the same, for example PBI008, I008, and I:0/08. Also, when the wire does not go to a PLC input, then the wire number matches the drawing line number on which the wire originates. This means that you no longer just sequentailly assign wire numbers, but it sure makes it easier to find it in the drawing. For example, wire #511 will be found to originate on page five, line eleven of the drawing set.

I use heat shrink wire markers and I have a printer for these, so its not too hard to do, but if you are using pre-printed wire number stickers this might be harder.

Edited to add sample files, I stripped the title block off these sample drawings so that the customer remains annon.

schematic design

georgia boy

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rsdoran

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georgia boy

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