House wiring mystery!

Posts: 3 · New Forum Member Joined: Dec 15, 2003 Posts: 3

Does anyone out there know what the upper limit of allowable voltage on house wiring is with the Motorola VT1000 unit plugged in? The reason I ask is that I disconnected my POTS at the NID outside the house and I am still getting, somehow, six to seven volts on the line. I have disconnected everything - every phone, the answering machine and the alarm system - and I am still getting this mysto voltage from somewhere. I was expecting the line to show no voltage, and when I do plug a standard phone into the house wiring I am indeed getting nothing (Not even that slight click you get when dialtone has not been connected but you are still connected to POTS). I am a little concerned that this voltage is a short that will hose the ATA. The voltage never exceeds seven. Any thoughts out there?

Posts: 41 · Full Forum Member Joined: 1064934432 Posts: 41

I don't have any idea how many volts the ATA can handle, but this thought did pop in my head:
Have you checked to see if, for some strange reason, the phone lines are grounded to the house plumbing? It is common practice to ground the house's electrical system to the plumbing and I'm just thinking maybe someone decided to ground the phone system as well and there is voltage back-feeding from the ground.

I'd say it's a long shot because I don't even know if the phone system would work if it was grounded somewhere, but you just never know... Question

Posts: 3 · New Forum Member Joined: Dec 15, 2003 Posts: 3

Hey, Bob, you da man! It is indeed grounded to the pipes. I have a distribution panel (mega-biscuit jack) whose center wire is tapped onto the inbound hot water heater feeder pipe. But, jeez, don't I need that to be grounded? That is how POTS was installed... I went from the NID to this screw-down connector jack to distribute through the house. I can disconnect and see if the voltage goes away, but I would like to know if I am doing myself a disservice by taking that ground out... Thanks man!

Posts: 41 · Full Forum Member Joined: 1064934432 Posts: 41

First, let me say that I am not a phone system expert, so please don't take my word as gospel (I know there's some phone system experts hanging around here - maybe they'll chip in...)

Having said that:
I don't believe your phone lines need to be grounded. My brother (who has a lot more knowledge of phone systems than I do) helped me wire my house when I built it eight years ago. I don't have any ground wires running from my punch-down terminal blocks. What I can't tell you off the top of my head is whether or not the phone company ran a ground line from the NID box. I don't remember seeing one, but that doesn't mean it's not there... Confused

If I were you, I'd disconnect the ground and see what happens Shocked

Hope this helps!

Posted: Tue Dec 16, 2003 11:52 pm Post subject:

It might be worth noting that external electrical items could be causing enough induced voltage in the lines to cause this level of electrical voltage, albeit at a very low current. It might be a good idea to disconnect the individual lines and see if the phantom voltage is limited to one specific leg of the residential telephone wiring.

Brian

Posts: 3 · New Forum Member Joined: Dec 15, 2003 Posts: 3

Bob, Brian, gentlemen, thank you for your replies. If I wasn't such a big fat dummy this would have taken care of itself in my feeble mind. One plate of crow coming up!! I had a closer look at that "ground line" and realized that I was taking a voltage reading off of the wrong screw mount connectors. Yeah, Bob, that was a residual voltage measured off of the water pipes because that was what I was unwittingly measuring! Doh! When I took a measurement from the correct two mounts I saw the voltage spike to 20V! Yikes! I then remembered that the ATA was still connected, so I unplugged the ATA and made another measurement. This time I saw the voltage bleed down to zero. Exactly what I was expecting to see, and what I would have seen if I just wasn't being such a dope. Can't see the forest for the trees, I guess! Anyway, mystery solved (I am an idiot) and thanks for your time!!

Posts: 41 · Full Forum Member Joined: 1064934432 Posts: 41

Glad to hear it worked out all right! Very Happy

It might help to know you're not alone - the other day I was working from home when I lost my internet connection. Multiple reboots of the hardware didn't help, so I called the cable company. "Are all your cable connections tight?" they asked. "Well, it's been working all morning" says me, "but I'll check if it will make you happy...". I checked the cable going into the modem and was able to turn the connecter another 1/2 turn tighter. Sure enough, it all worked fine after that. DOH! Razz