atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Outside Plant OSP Construction Porta System BET ground causes big voltage drop

Hi guys,

Couldn't get Samsung digital keysets to come up today over a 600' 50-pair OSP feed cable today. After some troubleshooting, another tech found when he removed the ground wires that go on the SIDE of the Porta Systems unit, the phones would come up. The cable shield is grounded also.

The voltage of the keyset is 48v. When one side is grounded, it drops to 28v, if both, 10v or so.

The ground sucks the life out of it.

So, when the shield is grounded only, all is OK. But we can't run phones and have the side ground lugs attached.

One side looks like this:



Problem solved if we remove that ground lug connection. Probably not great to leave it that way. Are the Red 'fuses' the wrong type?

Is the Earth round?

The shielding and lug are grounded to the same point on both sides. One side has a ground rod clamp, the other side to a steel girder frame (building is grounded itself according to electrician there).

So, if you remove the "Reds" and connect to the feeder side, do they work?

Disconnecting the ground says your protectors are grounding out the system....or causes too much resistance......what is the value of the protectors?

That is a good question ? The modules are likely not the proper rated ones. I would get with PORTA SYSTEM and relay this information to them. I think you are clamping at the wrong voltage.I know they make a great product but never use them.

Research your SAMSUNG manual and see what the voltage is on the station side. Go up in voltage
what ever is next rating, i assume around 50v or
75v. by any means do not eliminate the protection
just find the right shoe seize for the foot.

All 5 pin protectors are available in several different clamping voltages. It's up to the installer to determine what is proper for the equipment that the protector will be used with.

-Hal

Those look to be Porta Systems MLVP27 which have 27 volt clamping, really just for unpowered data. Somebody screwed up bad and those are expensive!

Replace them all with 105SCG-75V or 105SCG-240V (assuming normal 5-pin not the Porta "pogo stick" style).

-Hal

Hals hit it. The 27 is the clamping voltage, If your system requiremets are 48v I'd go as close to that as possible to protect the equipment.

I'd be worried about that exposed icky-pic indoors and unbonded cable sheath too. Those are both definite no-no's. That cable should be terminated on a BET, not a secondary protector.

Yeah, I saw that too but didn't comment. Also, even though the cable sheath is only partially visable I don't like what I see going on there either.

-Hal

Oh well - we learned something then. I will place all the blame on the installer. He is on this forum also.

Will call Porta Systems. If the keyset measured voltage is 48v right out the system we'll get something above it. We were told these are being correct for 'digital phones' - our fault for not knowing exactly what we were buying. Guess '27' on the red fuses wasn't obvious enough for us.

Look at the bright side: The modules were doing exactly what they are made to do. At least you know that their stuff works.

If the keyset measured voltage is 48v

I wouldn't trust measuring it. You never know what else is going on. Get with the manufacturer for their recommendation or play it safe and go with 235.

For instance with Partner and some Panasonic with the phone plugged in a 75 volt protector will work fine. Measure the voltage and it's well below 75 volts. But disconect the phone and the system assumes you will be connecting a standard SLT device and puts ringing on the pair. So now you have a ring/trip whenever a line assigned to the disconnected extension rings. That can put the whole system out of service.

-Hal

And to cut the original installer a little slack, those 27 volt protectors will work fine for some systems. Omega IV 616 and ZTD systems, for example. But not the larger Omega IV systems! All of which are manufacturer disc for 15+ years, before someone else points that out! Anyhow, that's why ya gotta know what your doin'! John C.

Thanks - the Samsung manual says 48v also - we will get ones rated significantly higher.

LH - "We don't know what the hell we are doing and we are scared" (Credit Chris Elliott)

75 is the next one up.

-Hal

Well - got lucky and found two for a good price. The good news is we'll swap out the data ones for another install. One of those mistakes we won't make twice.

https://helpdesk.portasystems.com/download/Copper/PSC_BET_Series24.pdf

Like I've said before you guys are the best.

I've always had good luck with the 235v.

That's what we use also. I figure if it can't handle 235 volts it's the manufacturer's problem.

-Hal