Connecting Drain Wire

Hi to all,

Our company builds control panels. At present we provide two terminal block for each analog signal. The Drain/shield are terminated outside the panel.
Im want to re design the wiring.Im planing to add third terminal block to be located beside the signal terminal block so that the drain are terminated inside the panel to ensure a proper grounding of the signal wire.
Please comment on this. Much better if you can provide standard for panel wiring of analog signal.

Many thaks,

Lovington Dela Cruz

Google this topic and you'll find different opinions on what's the best way to eliminate ground loops. My current company's standard is to ground the shield inside our control panel and leave the field side floating. (Though a few times I've experimented in desperation with other configurations in the field with varying success).

We connect the shields to a third terminal inside the panel as you've indicated. We carry the shield signals all the way through to the card in the PLC rack, and terminate them to a ground lug on the subpanel directly under the rack (which is also connected to the main ground in the panel). The extra couple of feet inside the panel probably isn't a big deal unless you've got other high-voltage wiring or components.

Just $.02 from my limited experience. Curious to see how others handle this...

Ingat!

-- Dave

thanks for your contribution for this thread. I expect to see the standard of other panel manufacturer how do you deal with the shield/drain wire of a analog signal.


regards,

Our standards are just what Dave said. We use a third, bonded-to-ground (din-rail clamp) terminal right next to every signal lead that has a shield (or might potentially require a ground bond -- We also provide bonded-to-rail ground blocks for every motor and source of 120VAC or higher power).

The Bonded-to-rail blocks are only used at the customer connection point in the main equipment enclosure; in all other locations (for SIGNAL SHIELDS), yellow/green NON-BONDED (isolated) blocks are used. These may be in junction boxes, or operator stations, etc.

Of course, follow any and all local codes!

when I was a contractor, terminating the drain was always done in the panel with the field end 'floating'. Not sure if it's industry standard, but most places I've been prefer this method. In most machines & most cases, loose wiring will be found in the field, and wiring in the panel is usually secured, although this depends heavily on who is servicing the equipment.

We use a green/yellow bonded (metal clamped) to the DIN rail terminal in the panel for connecting the shields.

I refuse to use non-bonded green/yellow terminals in my panels because they rely on an external connection to ground. I once spent half a day chasing analog problems on a VFD control because they use non-bonded green/yellow terminals but left them floating.

I've always designed for the shield/drain wire to be terminated inside the control cabinet to a ground bus terminal strip.

As for terminating the field end, a lot of devices have no provision for terminating the shield at the device (just another thing to think about if you prefer this method).

Most of the time we terminate the shield on a ground bar in the panel but on occasion have gone to a terminal first and then bonded to the ground bar. Haven't ran into any issues so far. (knock on wood)

Mine also terminated in the panel. One thing to ensure is standardization. It'll prevent confusion later on where somebody might terminate the shiled at both end!

I use triple stack terminals that have the ground(bounded) as an integral part of the terminal. Eliminates the need for an extra terminal.

thanks to all for sharing your valuable information

Does this mean you typically ground the drain to the AC ground that's use for 120 and higher power? Somebody told me to keep the drain ground isolated.
Please advise.