Author Topic: Safety issue: Grounding the Panasonic PBX  (Read 2717 times)

Offline cloyd

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Safety issue: Grounding the Panasonic PBX
« on: April 18, 2016, 07:40:44 PM »
Hi all,
I need your input on a safety issue.  The installation manual for my Panasonic 616 emphasizes grounding it.  There is a specially marked screw on the outside for grounding.  Can I ground it to the metal in-wall cable organizing box where I put the connections between Cat5E and the PBX?  There is a grounded electrical outlet in there too.  For that matter, the PBX electrical cord is grounded and plugs into that same electrical outlet.  Is that sufficient?  Surely, I don't have to take a grounding wire all the way to the grounding rod outside???  I am interested to know what others have done with their PBX boxes.

Thanks,

Tina
-- I am always doing what I cannot do yet, in order to learn how to do it. - Van Gogh -- 1885

Victor Laszlo

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #1 on: April 18, 2016, 08:17:15 PM »
The installation manual will probably state that you should use ONE of the two possible grounding methods, but NOT both.  Check to see if the manual says the following:

Generally, the grounding conductor (that third prong on the plug) is sufficient in a building whose electrical wiring is up to modern standards. In the event that the grounding conductor in the receptacle is not present, then you would use the external grounding screw/wire combination. It is a NEC violation to use both.

Offline Jack Ryan

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #2 on: April 18, 2016, 08:45:57 PM »
Generally the manuals say to use a mains cable with a ground and to ground the frame. Both grounds should be to the same point.

I believe the additional frame ground is a safety feature. The PABX is connected to CO and extension lines that may contact high voltages not associated with the telephone system. These connections remain even when the power cable is removed - the frame ground covers this situation.

Jack

Offline Jim S.

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #3 on: April 19, 2016, 05:54:26 PM »
Older digital phone systems were more likely to have interference trouble (like crosstalk, mis-dials ect , due to electrical interference). A lot of the interference is due to the phone station cables being ran next to electrical lines. I think for your set-up the 3rd prong on your cord is fine. If the prong is broken off I still doubt if it will be an issue.

JMO,
Jim S.
You live, You learn,
You die, you forget it all.

Dominic_ContempraPhones

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #4 on: April 19, 2016, 07:22:00 PM »
Hi all,
I need your input on a safety issue.  The installation manual for my Panasonic 616 emphasizes grounding it.  There is a specially marked screw on the outside for grounding.  Can I ground it to the metal in-wall cable organizing box where I put the connections between Cat5E and the PBX?  There is a grounded electrical outlet in there too.  For that matter, the PBX electrical cord is grounded and plugs into that same electrical outlet.  Is that sufficient?  Surely, I don't have to take a grounding wire all the way to the grounding rod outside???  I am interested to know what others have done with their PBX boxes.

Thanks,

Tina

Is the exterior chassis plastic or metal?  If it is plastic, there is no risk of electric shock.  The procedure (at least with Meridian) is to plug the unit (3-prong) into an outlet that comes straight out of your electrical panel.  Chassis ground (the screw) goes to a grounding terminal in the electrical panel.  Don't attempt to do this yourself if you're not familar with the procedure.  Have a qualified electrician do it.

Offline andre_janew

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #5 on: April 20, 2016, 12:01:45 PM »
I've heard my dad talking about grounding his crystal radio set by clamping the ground to a copper water pipe.  Could the same be done with a PBX?

Dominic_ContempraPhones

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #6 on: April 20, 2016, 12:25:23 PM »
I've heard my dad talking about grounding his crystal radio set by clamping the ground to a copper water pipe.  Could the same be done with a PBX?

No -- the chassis should to be grounded to the electrical panel it's powered from.

unbeldi

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #7 on: April 20, 2016, 01:02:17 PM »
These Panasonic PBX systems don't actually have a "chassis", at least not what one commonly calls a chassis.  The system is entirely constructed by mounting all components onto the plastic shell.

So by that virtue there is never a danger for operators to touch metallic parts under high voltage.

The installation manual states that the separate ground connection is to protect the system.  It does not say to protect an operator.

From looking at the schematics of the V2 and V3 KX-T61610 units, it appears that the ground terminal is direct connected to the ground lead in the power cord.  From my pictures when working on units I see that this is extended with a few thick green-insulated wires to a couple of places on the large main PCBs.

I think the extra grounding is provided to protect the unit from voltages entering through either the CO lines or the extension connectors, independently from the grounding through the power cord, which may perhaps not always be plugged in.  On the other hand if someone has a miswired power lines on their premises, or doesn't bother to plug the unit in, why would one assume that they went through the trouble of providing extra grounding on the ground terminal.

« Last Edit: April 20, 2016, 01:06:21 PM by unbeldi »

unbeldi

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #8 on: April 20, 2016, 01:04:40 PM »
I've heard my dad talking about grounding his crystal radio set by clamping the ground to a copper water pipe.  Could the same be done with a PBX?

A crystal radio can use ground to act as a giant antenna, because the radio is not otherwise grounded for power reasons.

unbeldi

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #9 on: April 20, 2016, 01:11:58 PM »
It is pretty common for telecom equipment to have separate grounding screws or bars.  With these, several units in a rack can be directly interconnected on a ground bus to provide a high quality means of eliminated any ground loops through extended or elaborate wiring through conduits, walls, and what not, wiring that could be an opportunity to pick up inductive noise.  A separate ground would cut that short and prevent humming in the talk circuits.


Dominic_ContempraPhones

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #10 on: April 20, 2016, 02:25:40 PM »
These Panasonic PBX systems don't actually have a "chassis", at least not what one commonly calls a chassis.  The system is entirely constructed by mounting all components onto the plastic shell.

So by that virtue there is never a danger for operators to touch metallic parts under high voltage.

The installation manual states that the separate ground connection is to protect the system.  It does not say to protect an operator.

From looking at the schematics of the V2 and V3 KX-T61610 units, it appears that the ground terminal is direct connected to the ground lead in the power cord.  From my pictures when working on units I see that this is extended with a few thick green-insulated wires to a couple of places on the large main PCBs.

I think the extra grounding is provided to protect the unit from voltages entering through either the CO lines or the extension connectors, independently from the grounding through the power cord, which may perhaps not always be plugged in.  On the other hand if someone has a miswired power lines on their premises, or doesn't bother to plug the unit in, why would one assume that they went through the trouble of providing extra grounding on the ground terminal.

That's against code because the ground could become live if a fault occurred and that would electrify the chassis, but if it's plastic ... I dunno, weird.  If it's plastic, then it's more for signal integrity and a reference point for the electronics in the PBX itself.  We would measure the resistance on the chassis ground ... if it was higher than 5Ω, it could cause glitchy behavior on the electronics.  Dunno, I have small PBXs (BCM) that don't require any special grounding other than a 3-prong plug.  For a home hobbyist, having to locate everything near the electrical panel would be a colossal pain.

Offline Phonesrfun

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #11 on: April 20, 2016, 09:32:03 PM »
I think this topic has been over analyzed.  Yep, plastic case.  Grounded plug.  I don't think it needs any more special grounding than your average desktop computer.  (Unless your house is an older one without grounded outlets.  Then you might consider a ground because you might have some noise on the lines.  Maybe, maybe not)
-Bill G

Dominic_ContempraPhones

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #12 on: April 21, 2016, 06:45:22 PM »
I think this topic has been over analyzed.  Yep, plastic case.  Grounded plug.  I don't think it needs any more special grounding than your average desktop computer.  (Unless your house is an older one without grounded outlets.  Then you might consider a ground because you might have some noise on the lines.  Maybe, maybe not)

All I know is we were told to never connect a chassis ground to the ground on the plug, and to not plug the system in until the chassis ground was connected.  Whether this was to protect the electronics or us was never made clear.  I suspect it was the latter.  This is Option 11.  Panasonic ... dunno.  There must be instructions indicating whether it is optional, mandatory, etc.

Offline dsk

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #13 on: April 22, 2016, 03:51:19 AM »
Many of us remember how sensitive the electronics was, regarding static electricity, proper grounding reduced this risk.
In Norway we have had traditions of local grounding, with no common ground, and isolated power supplies (mains) with no Neutral. 
Telecom systems used to have their own ground rods, due to signalling via ground might be used, (grounded ringers, or a button connecting one leg of the telephone line to ground) 
The Panasonic do not need the last type of grounding so my guess will be grounding via the power system does it well enough.

My mechanical exchange is grounded via a resistor to  + battery. The resistor prevents the statics, and protects the unit against the first error if a live wire should touch the telephone wire.

dsk

I have even got a regular New York number :-) 646 570 1796

Dominic_ContempraPhones

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Re: Safety issue: Grounding the Panasonic PBX
« Reply #14 on: April 22, 2016, 02:25:44 PM »
Many of us remember how sensitive the electronics was, regarding static electricity, proper grounding reduced this risk.
In Norway we have had traditions of local grounding, with no common ground, and isolated power supplies (mains) with no Neutral. 
Telecom systems used to have their own ground rods, due to signalling via ground might be used, (grounded ringers, or a button connecting one leg of the telephone line to ground) 
The Panasonic do not need the last type of grounding so my guess will be grounding via the power system does it well enough.

My mechanical exchange is grounded via a resistor to  + battery. The resistor prevents the statics, and protects the unit against the first error if a live wire should touch the telephone wire.

dsk

I still have to put on an anti-static strap