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mfg eng

Standard Wiring Conventions

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Hello, I'm wondering if someone here might be able to give me some pointers on industry standards for control panel wiring. I'm looking for some of the basics. I have helped to wire a couple of panels for some inhouse built machines in the past, but we didn't follow any standards. 1. We typical use non-fused type AB 194R rotary disconnects on our machines. The line voltage coming into the control panel is 120VAC 1phase. Is it common practice to wire the hot and neutral lines thru the disconnect or just the hot line? I have seen it done both ways. 2. Is there a standard for wire numbering convention? For instance, how should the numbering label sequence for the control wiring be handled. How do you know how to label wires and when to change the number? Any info. would be greatly appreciated. Thanks

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First you need to get yourself a copy of the National Electric Code (NFPA70). As for examples of other panels you may wish to view our new gallery HERE. 1. Normally I just see the 120VAC ran through the disconnect. Come to think of it I don't think I have a single 120VAC system where I am now. But in the past the neutral was not ran through the disconnect. 2. This one is going to depend on how you do your wiring diagrams. You may look HERE for some recommendations on cad packages

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One method can be ... The wire numbers that we use are determined on what drawing sheet that derive from with reference. IE our drawings have 0-9 ref pos across the top of drawing. If on sheet 3 the wire number would be 030200 where 03 = sheet 02 = ref on sheet 00 = first in the sequence. Therefore if another wire exists in the same ref then if could be 030201 etc.... Other methods might be site specific...

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NFPA 79 applies to industrial machinery. It is complimentary to the NFPA 70.

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Please check accessories for 194R (look for 194RF...) to meet NFPA requirements. AFAIK new installation should have the NFPA handle and provision for lockout even if panel door is open (standard 194R didn't have that). Any 194R switch should be easily upgradable to 194RF through inexpencive kits. As for running power through disconnect, I don't see a problem - unless this is a fused disconnect (you cannot have fuse blow on neutral and have whole machine live). We usually use fused disconnects but you should be able to check the code or simply ask local inspector. Wire numbering in North America is usually done based on line number as mentioned by Sleepy Wombat. Wires of PLC I/O get the actual PLC address (or short form of it, since addressing on Logix CPUs for example is very long). Power is also usually exempt so the three phases become L1, L2 and L3 and this is then incremented as they go through devices such contactors etc. Single phase power is usually L and N or in case of split supply LA, LB and N. DC Power is usually labeled according to voltage of the particular PSU output. I've seen variations like +24 and -24, 24+ and 24-, 24V and 0VDC, 5VDC and 5COM, P and N, 24P and 24N. It all depends on how many different power rails you have (most machines will only have one powersupply), if the DC side is grounded or not and of course personal preference (not everyone thinks the same). I don't realy like the +24 and -24 if this is comming from single output power supply. When sign is before number, it looks like absolute value from reference point. Since voltage is potential difference, it could be expected to see 48V when measured accross . Reason I don't like it because I have worked on many machines that do have both +24 and -24V (among other voltages) and measuring from -24 to ground is actually 24V just like measuring from +24V to ground. For example, it could be that one of the components in the machine is using NPN I/O or machine is using NPN style I/O with positive side of 24V PSU grounded, but safety circuit is on separate power supply where negative is grounded etc. (need to make sure it is fail safe, accidental shorts to ground are detected and there is no uncontrolled motion or loss of safety function). Whatever you do, try to make sure it is clear and easy to follow, think how others will see it, after all we all think differently. Don't let someone shut the line down or get hurt because of misinterpreted drawing. Many companies have their own standard that more or less follow described or have particular preference. Sometimes the sequence number is replaced by letters (A, B, C...) and they index in different order. For example inxecing is not nececarily from left to right, it could start from the device and increment the further away from device particular wire is (imagine VFD or safety controler wiring where circuit is on the left side of device, A would be closer to the device which is on the right, B would be next to it but to the left etc.).

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Do you have a part number? I need to get some of them. We are getting ready to add a second disconnect for that reason

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194RF-30R1 ; 30 AMP Retro Fit Kit with a 10" shaft 194RF-30R2 ; 30 AMP Retro Fit Kit with a 13" shaft (only about 1 or 2 dollars more than 30R1) 194RF-60R1 ; 60 AMP, 10" 194RF-60R2 ; 60 AMP, 13" they are in order of $20 list and include besides shaft, pusher tube, lockout kit and NFPA handle: http://www.ab.com/en/epub/catalogs/12768/2...3908/print.html NOTE: One has to watch for more space on side of the disconnect where shaft enters the switch body. This is because of new lockout which is part of the kit. I am buying R2 versions and keep on my shelf since they are often longer delivery than the switch itself. Besides they are so inexpencive, I don't want to use pliers or wrench to operate disconnect ever again

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Thanks, I didn't know it was available as a retro. The problem I have with the pliers is people turning them the wrong way and when it doesn't switch not realizing that you don't have to put 500 lbs of force on it. You would be suprised how many we have had to replace where people break the linkage inside

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well, it's not as solid as it could be. i remeber using 194L on my first little project (panel was only 24x20" or so). the thing was busted (switch came apart) after just one day when someone pulled harder on the door. as for 194R, it's not too bad. i just wish they had better knob, something really solid. many knobs have been replaced because of screwdriver use to move defeater mechanism and open the door while machine is powered.

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