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Individually labelling 0VDCs

Individually labelling 0VDCs

(OP)


G'Day All

In Oil & Gas projects I have seen the 0VDC 'feeds' individually labelled - see the photo above. All the 0VDCs, i.e. 0VDC1, 0VDC2, eventually connect to the same 0VDC on the power supply.

Why is this practice used? Does it provide some troubleshooting benefits?

Cheers Michael

RE: Individually labelling 0VDCs

Michael; It's not clear what you're asking. Separate grounds or separate labels?

On most things in field wiring you don't ever want daisy-chain wiring hence separate wires for a "star" pattern. You invite this by separate screw/terminal points.

Often the wiring in the control panel continues this scheme so the labeling does what it can to continue it. If the terminals were all labeled identically as 0VDC it would cause cheap installations where installers consider all the OVDC the same and they aren't really. Wiring may be twisted pairs clear into the controllers with the star point inside somewhere.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Individually labelling 0VDCs

(OP)
So you're saying they aren't all 'the same' 0VDC? Can you describe why? (not arguing with you - I need to know! :) - this is part of the question I am asking.

What do yuo mean when you say 'the star point inside somewhere?

RE: Individually labelling 0VDCs

One aspect of the separation, if I'm reading the drawing correctly, is that each 0V signal has its own fuse (F?) upstream. This might well be 2 pole breakers, it might be fuses, but full isolation of both poles and thus then separate connections is beneficial.

Single terminals for a signal wire with a common return is different to what you've shown in the drawing, as itsmoked suggested, you invite discrete pairs by putting discrete terminals in. Inadvertent 0V connections can do funny things with 4-20mA loops, voltage transducers and the like. Its also relevant with 2 wire sensors, each designation refers to the specific sensor return wire, not the common terminal its connected to.

RE: Individually labelling 0VDCs

The only advantage I can see is it makes it simpler to trace wires.
Normally I would jumper all the negatives down the RH side of the terminal strip with the bottom one going back to the point of origin for extra security, I assume -24 is grounded also.

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