ground question for sirhc

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Mike
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ground question for sirhc

Sun Dec 02, 2018 2:45 pm

I have read through some ground links but this is an unusual setup that I lost a couple radios. Both times upon power outage and generator use. I am using the ws6 mini with poe power not barrel.
Wondering what best ground option is to save radio.
Details
Rocket radio with sector on metal tower 150 feet high.
Base of tower surge protector grounded to tower ground and Ethernet goes through that.
No power at tower site.
Then the Ethernet cable goes 150 more feet to Netonix ws6 mini.
Tough cable used with drain connected all ends.
No bonded grounded between.
Netonix POE power goes to UPS battery backup also.
There are other things plugged into wall outlet and UPS that should have ground.

Not sure just whats going on but 2 radios died in last month both during power outages so maybe generator power is effecting things but right now it does have a cat 5 between with ground on both ends which is a NO NO so I have to eliminate one end somehow.

So it appears in this case is to leave tower radio grounded to tower and at base of tower but eliminate ground at power end?
It seems it may be easiest is to go to a POE for that radio instead of Netonix and cut off the 3rd prong ground on the power cord? Will that work?

Any other thoughts or recommendations?

EDIT,
Got to thinking, this may be the case if switch was getting affected but if the radio is its probably nothing to do with switch being 300 feet away?

Mike

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sirhc
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Re: ground question for sirhc

Mon Dec 03, 2018 11:03 am

So from reading your description I "think" you are not bonding tower grounds and electrical service grounds so the bond between 2 different ground potentials is the Ethernet cable.

When hooking up a generator it is important to bond the generator to the tower ground before using.

Everything you need to know about grounding is in my posts.
Also you should not use Ethernet Surge protectors with "passive" POE switches like Netonix and ToughSWITCH.

99% of all WISP equipment damage is from ground current (I own a WISP)

Here are some good posts on grounding:
viewtopic.php?f=30&t=2786#p19279
viewtopic.php?f=30&t=1816
viewtopic.php?f=30&t=188
viewtopic.php?f=17&t=1786&start=30#p13447
viewtopic.php?f=30&t=1429

Read the posts above but the basics are as follow:
Tower ground rods must be bonded to electrical service ground rods HEAVY #2 wire.

I always add 1 or 2 “new” ground rods to older existing electrical services.
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Re: ground question for sirhc

Tue Dec 04, 2018 12:39 am

I didn't know about not using Ethernet surge suppressors with poe switches. Can you tell me the harm and problem with that and also is a regular POE better or the same? Ubiquiti makes surge suppressors and recommends them so how can it be bad?

Like I said I am not bonded so I have to eliminate ground at one end I chose to use tower ground and get rid of ground at POE side is what I assume is correct?

There is a typo in this post below, neutral is white and hot is black you have colors reversed.
-----------------------------------------------------------------------------------

"When you draw power from another electric service that does not have its Earth Ground bonded to the tower ground system your mounting on you only want the HOT (WHITE) and NEUTRAL (BLACK) wire and then you use the ground from your tower."

CLICK IMAGE TO VIEW FULL SIZE
Image

Mike

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Re: ground question for sirhc

Tue Dec 04, 2018 2:50 pm

How Ethernet surge protectors work is they clamp all 4 pair together and to ESD drain wire if ESD compatible. When this happens you create a dead short.

99% of WISP equipment is damaged from GROUND CURRENT not ESD or surges so the surge suppressor is useless as clamping all 4 pair together will not stop ground current and to be quite frank it rarely occurs.

Look if your tower suffers from ESD which enters into the radio on the radio side would FRY the radio side yet most WISP equipment suffers Ethernet port damage which is from GROUND CURRENT.

You can use Ethernet surge suppressor with "active" POE and or POE bricks because they use active over current protection and shut down POE fast enough to prevent damage "most times".

Netonix switches and UBNT ToughSWITCHES use "passive" POE and poly-fuses to protect against fire in the event of shorted cables but Poly-fuses open too slowly to prevent damage to switch.

UBNT, MIMOSA, Ignite, Cambium, and so on use "passive" POE.

Now our next generation of switches the WS2 and WS3 line we designed our own "active over current protection" but not so much so you can use Ethernet Surge Suppressor as this simply is not the cause of most damage but so people stop frying switches with shorted cables.


I do not have a single Ethernet Surge Suppressor in my entire WISP and I have lost 2 pieces of equipment at towers in 2+ years and both times were because site owner messed with grounding improvements we put in.

The discussion of Ethernet Surge Suppressors has been discussed on this forum, UBNT Forum, and many Facebook WISP groups.

As far as not using service ground OK that is fine but I would ADD a couple NEW ground rods to the electrical service ground rods.

I would also make sure generator ground lug is bonded to tower ground before you fire it up.
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Re: ground question for sirhc

Wed Dec 05, 2018 12:49 am

Interesting that ubnt even sells surge suppressors and they have passive poe on everything. I have several SS in place at towers all grounded and never lost any equipment at towers except this one which has electric service ground 150 feet away horizontally not up the tower. Generator is 150 feet away from tower too so not grounded to tower. I do have SS grounded at this particular tower would I be better off with a coupling and get rid of that grounding there?

UBNT poe's are tough because I had a dead short and the light would just blink and never killed the poe so it has some protection built in.

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Re: ground question for sirhc

Wed Dec 05, 2018 10:26 am

Mike wrote:Interesting that ubnt even sells surge suppressors and they have passive poe on everything. I have several SS in place at towers all grounded and never lost any equipment at towers except this one which has electric service ground 150 feet away horizontally not up the tower. Generator is 150 feet away from tower too so not grounded to tower. I do have SS grounded at this particular tower would I be better off with a coupling and get rid of that grounding there?

UBNT poe's are tough because I had a dead short and the light would just blink and never killed the poe so it has some protection built in.

Mike


A dead short would not damage any Ethernet Surge Suppressor.
What they do is clamp all wires together in the event of high voltage.

Read what I said, the POE bricks will also not be hurt from a dead short they simply shut off.

Our next model of switches have that same type of design, our current models deal with shorts the same as the ToughSWITCH, we used polyfuses which are too slow to open to protect the switch, they are there to prevent fires in the event of a dead short.


The reason we did not have active over current protection in the first models is it required us to invent and design circuits that could be done cheap enough and small enough to be viable.

Active 802.3af/at switches utilize a controller chip that had active over current protection built in so all the design work was done on a larger scale for a larger market whereas we had to design our own as the controller chip was designed for "active" POE not "passive" POE.

Add a couple NEW ground rods to electrical service.

Bond generator to tower ground before use but you said it is too far away. SO make sure your binding to electrical service grounds then just make sure the service grounds are over kill that way it will never see the tower grounds as a better path.

My guess is when the generator starts up it has extra current it tries to shunt to ground but that current is seeing the tower grounds as a better less resistant path so again adding new electrical service ground rods may help this as I assume you are binding the generator to service grounds? You should always provide a connection to earth ground for generators before use as what do you expect them to do with excessive voltage/current it has? It needs a path to ground to discharge that voltage/current too.
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Re: ground question for sirhc

Wed Dec 05, 2018 11:10 am

Like I mentioned I am not bonding these grounds 150 feet apart and don't want the Ethernet cable to be the ground link between (like it was) so I chose to eliminate service ground of POE and have the radio only to the tower ground. I asked before if I can just cut off 3rd prong on POE on service end and let radio ground to tower? Im trying to protect radio the most so I don't have to climb. Its the radio that blew twice in a month.

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