Isolation to prevent ground loops

[jakematic]

Background:
- WS-6-Mini powered by WS-12-250-AC
- No utility power in close proximity to the WS-6
- Everything connected to WS-6 is PoE powered
- Devices are at locations on different sub-panels
- Desire is to add a non-PoE device to the WS-6
- WS-12 is already using both SFP in a LAG back to core fibre switch

So I've been looking for ethernet opto isolators but can only find magnetic ones like:
https://www.blackbox.com/en-us/store/De ... kV-/SP427A

From the tech tip:

Isolators place a physical barrier... Only data can travel across this barrier through the coupling of magnetic fields.

Is this just marketing or do these work any differently than the magnetic coupling already in the switches ?

I've got media converters but that won't work since they'd electrically connect things still.

Thoughts / Suggestions ?
Thanks-Jake

[sirhc]

So yes we have Ethernet Transformers which are magnetically isolated but since UBNT bond DC negative to rail in all their radios and ToughSwitch we did as well so the center tap of the transformer has access to the DC negative which is bonded to the AC Earth ground same as UBNT radios and ToughSWITCH.

Running a copper cable between 2 differnt earth grounds that are not bonded is bad.

[lligetfa]

From the tech tip:

Isolators place a physical barrier... Only data can travel across this barrier through the coupling of magnetic fields.

Is this just marketing or do these work any differently than the magnetic coupling already in the switches ?

That isolation only works on data lines that don't have POE. As soon as you add DC power, it's faggeddaboudit!

[jakematic]

Running a copper cable between 2 differnt earth grounds that are not bonded is bad.

Yep, that's why I have no intention of using an AC powered device on the remote switch, hence the search and question.

From the tech tip:

Isolators place a physical barrier... Only data can travel across this barrier through the coupling of magnetic fields.

Is this just marketing or do these work any differently than the magnetic coupling already in the switches ?

That isolation only works on data lines that don't have POE. As soon as you add DC power, it's faggeddaboudit!

If you read back.... I want to add a NON PoE device to this setup as well.
Without creating a ground loop.


EDIT: Maybe I'm not explaining this well, but the isolation would be AFTER the WS-6


WS12 ------- WS6 ---- Isolator ----- AC powered device

[sirhc]

SO it all depends if the AC device on the far side is isolated. From my experience most Ethernet devices provide minimal isolation and ground current can be many AMPs and can arch across magnetic coupled zone.

[jakematic]

Thanks Chris - that is what I was thinking too and it's just not worth the risk.

After our phone call last summer we ran about half a km of fibre and did serious work on our ground rods.

Will see if I can come up with an alternate design that will work. Probably with fibre LOL

[sirhc]

WHat would work here is if we had a WS-6-MINI with SFP slots.

Then you could power WS-6-MINI in far building from near building. DO NOT LOOK UP CHASSIS GROUND LUG ON WS-6-MINI then run fiber from MINI to switch in far building.

Wonder if anyone makes a media converter that is powered via POE?

IF NOT MAYBE WE SHOULD MAKE ONE LOL

[sirhc]

If your just out of SFP slots and you want to run fiber you could use a media converter in near building to convert copper port to fiber then run fiber to far building.

[jakematic]

A WS6 with SFP would be AWESOME... as would a POE powered media converter.

[lligetfa]

Wonder if anyone makes a media converter that is powered via POE?

IF NOT MAYBE WE SHOULD MAKE ONE LOL

You mean like this?
https://www.ubnt.com/accessories/fiber-poe-accessory/

IgniteNet also make one.