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Old February 23rd, 2018, 10:00 AM   #1
dcam
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115vac outputs on unenergized dig ouput card

Hello all, struggling with an intermittent issue where i have 115VAC on outputs that are not energized(no light, not called for by program) . I've swapped output modules, changed the TB3 and cursed fluently in 3 languages...Jk. I can log on and speak to any module with RS Logix (fire outputs, etc) on the flex I/O and module in question. This is not triac bleed by, the voltage will pull in the starters of associated equipment.(i see voltages with a wiggie)

There is a huge amount of contractor work happening right now, Im wondering if some how a neutral has been compromised? The problem is intermittent. I have attached a pict of module in question.
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Old February 23rd, 2018, 10:25 AM   #2
Ron Beaufort
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just a long shot GUESS - in case all else fails ...

this is just a GUESS based on what you've told/shown us so far ...

notice that the output bit addresses on the wire labels are numbered in OCTAL but the bit addresses on the module are numbered in DECIMAL ...

I'm just GUESSING that the system was originally controlled by a PLC-5 system (which uses octal addressing for its I/O signals) ...

considering your statement:

Quote:
There is a huge amount of contractor work happening right now
maybe (just MAYBE) the contractors are "swapping over" your system from PLC-5 control to ControlLogix/CompactLogix instead ??? ...

if so then it's not uncommon for the difference between OCTAL and DECIMAL addressing modes to cause confusion ... think: the I/O bit addresses above "7" can end up being "off by two" if the contractors/programmers/etc. aren't taking the various addressing modes into consideration ...

as I said this is all GUESSWORK and personally I wouldn't bet more than pocket-change that this is even related to your problem ... but ... I have had to help a couple of customers troubleshoot this same problem over the years ... I offer this as a straw at which to grasp ...

here's another thing to check (which is even less likely) ... sometimes when converting from PLC-5 systems to ControlLogix/CompactLogix systems the programmer will set up the I/O transfers by using the ControlLogix/CompactLogix default data-type setting of DINT (32-bit data) ... if the remote I/O is expecting to see INT (16-bit data) instead, then the transfers can get pretty wobbly with "overlaps" and "communication errors" etc. ...

TIP: the more you tell us about the DETAILS of your problem then the more details we can put into our answers ...

good luck with your project ...
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Old February 23rd, 2018, 11:30 AM   #3
Mickey
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1794-OA16 has solid state outputs, you are going to have leakage (with no load).

See pdf.
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Old February 23rd, 2018, 11:56 AM   #4
Ron Beaufort
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Quote:
This is not triac bleed by, the voltage will pull in the starters of associated equipment.(i see voltages with a wiggie)
that was the first thing that I thought of too - but it sounds like he's got that angle covered, Mickey ...

would be nice if we could see a copy of his program files - but I've given up on asking for those ...
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Old February 23rd, 2018, 02:09 PM   #5
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Quote:
Originally Posted by dcam View Post
Hello all, struggling with an intermittent issue where i have 115VAC on outputs that are not energized(no light, not called for by program) ....(i see voltages with a wiggie)
When you catch the problem, where you are seeing voltage with a wiggie, consider (very carefully) lifting the hot wire from the output module (using appropriate PPE for hot work). Then measure voltage on the lifted wire to see if it is being energized by someplace else.

And as you mention, a floating neutral could also be trouble. You might get some insight with the voltage reference used by the wiggie (ground vs. various neutrals).
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Old February 23rd, 2018, 03:41 PM   #6
dcam
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All great responses! This is a remote I/O flex rack with each module independently powered by a diff circuit for a peculiar E-stop MCR configuration and i believe the problem is here somehow. I cleaned up the Neutrals and some wiring and haven't seen the prob for a while. The control logix cut over is coming in a few weeks. Read something about neutrals from diff crkts causing issues on these dig output cards....going to MCC now to check...Thanks everyone!
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Old February 23rd, 2018, 07:37 PM   #7
agdacanay77
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Hi Sir,

I had similar problem(intermittent) that i encountered and troubleshooted found that there is a wire(power cable of motor) has scratch which is touching to the DIN rail. see attached photo for your reference.

Hopefully this will help you.

Thank you.
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