Author Topic: Should a 555 PBX be grounded  (Read 451 times)

Offline trainman

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Should a 555 PBX be grounded
« on: March 24, 2017, 07:32:12 PM »
If you are using your 555 with a key system power supply, should it be grounded? And what should be grounded to what?

Im using an Elgin Electronics EAK 4 power supply.

Offline Fabius

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Re: Should a 555 PBX be grounded
« Reply #1 on: March 24, 2017, 09:09:02 PM »
And what should be grounded to what?

I believe the best place to get ground would be at the incoming metal water pipe.
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Victor Laszlo

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Re: Should a 555 PBX be grounded
« Reply #2 on: March 24, 2017, 10:11:48 PM »
According to the BSP's a key system power supply should be grounded using the third prong of the power cord, only, unless the outlet is a non-grounded one, in which case an alternate method is prescribed, such as a cold water pipe.

That is the requirement for safety. If the circuits are ground referenced, such as CO trunks, and require a ground for proper operation, the key system ground screw can be connected to the center screw of the outlet plate, but that's not a substitute for the safety ground.

Offline trainman

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Re: Should a 555 PBX be grounded
« Reply #3 on: March 24, 2017, 10:56:52 PM »
Ok. We have the power supply grounded, but what about the pbx itself? I mean should the frame of the pbx be grounded, or not.

Offline dsk

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Re: Should a 555 PBX be grounded
« Reply #4 on: March 25, 2017, 07:02:10 AM »
Grounding should be for a reason.  Why should we ground it?  Is it a risk for connection to live power supply in th system, and will this cause any risk if you touch something? what about protecting the equipment, will a grounding decrease, or increase the risk of frying the equipment?  (GFCI on the supply side?)  Statics, lightning etc. ???.

I have my sxs grounded via a high ohmic restor (390k), it discharges statics, the first fault will not affect the system. The mains side of the power supply is grounded, and protected by a GFCI. I deem the risk of lightning to about zero!

The maker had an idea of battery + to ground, and for a huge exchange with lines on poles, or running along, or across high voltage etc. It is a lot of other reasons too, galvanic corrosion etc.  Every line here was terminated with 400k ohms (390k) to keep a sealing current on bad splices.  The telco's in Norway used this up to about 1980-something.

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Offline trainman

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Re: Should a 555 PBX be grounded
« Reply #5 on: March 25, 2017, 10:46:25 AM »
Ground post on power supply connected to pbx frame doesnt make grounded ringing trunk units work. grounding tip on each individual trunk line to the pbx frame makes the grounded ringing trunk units work.

Of course using the PBX on trunk calls makes my Uverse internet act all weird.

Victor Laszlo

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Re: Should a 555 PBX be grounded
« Reply #6 on: March 25, 2017, 05:32:41 PM »
"Ground post on power supply connected to pbx frame doesnt make grounded ringing trunk units work. grounding tip on each individual trunk line to the pbx frame makes the grounded ringing trunk units work."

1.  I did not recommend grounding the power supply to the PBX frame.  I recommended grounding the power supply to earth.

2.  Go tie the T side of all your trunks to ground. Let me know how that sounds. 

Generator on the R side, thru a condenser, thru the R relay, to ground, is what makes a CO trunk, arranged for grounded ringing, ring.  The T side has nothing to do with it.
« Last Edit: March 25, 2017, 05:53:30 PM by Victor Laszlo »

Offline trainman

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Re: Should a 555 PBX be grounded
« Reply #7 on: March 25, 2017, 08:53:56 PM »
Yes. I reread what you wrote. Power supply is not grounded to   PBX frame.

The documentation I have, which matches my grounded ringing trunks does say it will ring with either Tip or Ring referenced to ground.

And  yes, i cant recall, but I think i did tie Tip to the pbx frame and it did make the CO trunk R relay pick up.

I just couldnt figure what should be ground in regards to the power supply, if anything should be, in regards to making the CO trunks ring.
« Last Edit: March 25, 2017, 08:56:23 PM by trainman »

Victor Laszlo

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Re: Should a 555 PBX be grounded
« Reply #8 on: March 25, 2017, 09:20:41 PM »
"referenced" is not the same thing as "connected."

Offline Jim S.

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Re: Should a 555 PBX be grounded
« Reply #9 on: March 25, 2017, 09:27:31 PM »
"referenced" is not the same thing as "connected."
Would that be "system ground" and "Earth Ground" ?
Jim S.
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Offline dsk

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Re: Should a 555 PBX be grounded
« Reply #10 on: March 26, 2017, 04:43:05 AM »
If you are using your 555 with a key system power supply, should it be grounded? And what should be grounded to what?

Im using an Elgin Electronics EAK 4 power supply.

Back to the original question:
Yes, the power supply should be grounded, and preferably protected by a GFCI. The board it-selves does not strictly need a bonding to earth ground. The frame will work as system ground, and could easily be connected to any ground via a resistor, just to discharge statics.  The resistor may burn at a large over current caused by high voltage, and should be located at a suitable position.  I  have just made this grounding to the power supply ground, and it is not making any noise in my system, that may be a problem if the mains has a failure pretty distant, or close. Grounding to a suitable grounding rod, metal cold water pipe or other suitable point of grounding may eliminate this risk of noise.  It is many ideas about grounding, and the different power companies, states, countries etc will never agree about one solution, maybe because local need may be of  most importance.

dsk

PS
This grounding is made with priority of a smooth operation, risk of electrocution caused by e.g. a live wire gets in contact with one of your telephone wires.  If you are reasonably well isolated from ground, you will be safe, you may increase the safety by putting up an alarm bell  telephone ringer coping with 120V 60 hz instead of the resistor. This will alarm you when the failure starts, but not protect you.  If you deem the risk of such failure to be larger than you are willing to risk, you have to bond the battery + and the frame to ground, direct, or via a ground idolator equal to those used on boats, strapped with the resistor to reduce noise.   You may read more about those isolators here: http://www.pbase.com/mainecruising/galvanic_isolator
DS
« Last Edit: March 26, 2017, 05:04:57 AM by dsk »
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Offline Phonesrfun

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Re: Should a 555 PBX be grounded
« Reply #11 on: March 28, 2017, 12:46:30 AM »
should it be grounded?

It should sit squarely on the floor and not hanging in mid-air.  From that standpoint, "grounded" is preferred.   ;D
-Bill G