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Electrical Question - Handling old intercom panel

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  • Jul 21st, 2020 11:25 pm
[OP]
Jr. Member
Apr 12, 2004
144 posts
56 upvotes
Montreal

Electrical Question - Handling old intercom panel

I've decided to paint my basement and am prepping the walls. I have an old intercom system (think 70's) that is on the wall and I was planning on removing. I just checked the wire and realized that the unit it powered (not sure if it's normal voltage or it's convert to a low voltage somewhere upstream). For context, the cable is a thin grey cable (much smaller than a typically electrical outlet cable).

In terms of being compliant with the electrical code, can I simply cap the cable and patch the wall? Or because it's a live wire I need to terminate it in the junction box?

Thanks for the advice!
12 replies
Deal Addict
Nov 17, 2012
4594 posts
4020 upvotes
Toronto
Find the other end - it likely connects to a transformer, like a doorbell. Is it a 2 wire kind of thing like speaker cable? Or is it a round cable with a DC plug on the end to plug into the back of the intercom?

Should be low voltage, look like speaker wire (2 wires) and there is no harm in capping it and leaving it in the wall. Disconnect the transformer at the other end and cap the 120v circuit / leave in a junction box or use it for something else like an outlet or light in the area it is in (hopefully not in a wall).
[OP]
Jr. Member
Apr 12, 2004
144 posts
56 upvotes
Montreal
Thanks for the input. The other end is likely in a wall somewhere where I don't have access.

The cable is a flat grey cable (with 3 wires). It's fairly small It looks like this.
https://www.gexpro.com/usg/Root-Categor ... d-/p/33820
The 3 wires are connected to the intercom at points labelled "copper", "silver", "center".

Is there a minimum voltage a cable needs to be in order to be safely capped and buried in a wall? I can check with my multimeter tomorrow.
Deal Guru
Jan 25, 2007
11947 posts
7119 upvotes
Paris
I don’t think you should cap any live wire in a wall. What about a fake switch or a blank wall plate?
Penalty Box
Jun 24, 2015
7196 posts
2232 upvotes
0 downvotes
usually intercoms have live wires but the transformer is almost NEVER Burried, mine was in the furnace room connected to the junction box of the light fixture so its almost always accessible, no one puts a ceiling in a furnace room so you almost never have to worry about it being buried. just trace the wires, i bet anything its also terminating to a 12 or volt transformer in the furnace room or maybe your hydro panel area, just check it
Say NO to the WAR!
PEACE is the answer!
Deal Addict
Nov 16, 2011
1509 posts
1224 upvotes
HAMILTON
Not that it has anything to do with the op's question, I have a finished ceiling in my furnace room and most folks that I know also have one.
Deal Addict
Nov 24, 2015
1462 posts
1219 upvotes
Durham Region
GoodFellaz wrote: usually intercoms have live wires but the transformer is almost NEVER Burried, mine was in the furnace room connected to the junction box of the light fixture so its almost always accessible, no one puts a ceiling in a furnace room so you almost never have to worry about it being buried. just trace the wires, i bet anything its also terminating to a 12 or volt transformer in the furnace room or maybe your hydro panel area, just check it
For my old intercom, the 12 volt transformer was right next to my electrical panel. I doubt it would be hidden somewhere

Not sure about capping the wires, that’s not the most ideal solution unless you absolutely can’t find the transformer
Deal Expert
Feb 7, 2017
22782 posts
21625 upvotes
Eastern Ontario
luckystrike1 wrote: Not that it has anything to do with the op's question, I have a finished ceiling in my furnace room and most folks that I know also have one.
Lol, really

How old is your house ?

Most houses, old or new that I have been in don’t have a finished ceiling in their furnace / utility rooms. Bare concrete walls, bare concrete floors, and straight up to the joists / floorboards.

Either cuz no one bothered to do any finishing in the space ... older houses .... Not sure WHY anyone would bother
Or a newer house, and no ones gotten around to it yet ... with tons of other higher priority projects / monied projects to do

Still don’t see WHY anyone would finish this space
Hey ... but maybe that’s just me
Not that gentrified ala HGTV
Deal Guru
Jan 25, 2007
11947 posts
7119 upvotes
Paris
luckystrike1 wrote: Not that it has anything to do with the op's question, I have a finished ceiling in my furnace room and most folks that I know also have one.
I dont know what kind of crowd you hang out in but as a window contractor im in quite a few houses in a given day and Ive literally never seen a finished ceiling in a furnace room. Its makes zero sense as when you get a new furnace it might have to all come down.

I will start paying more attention and report back if I see a single one. I did see a window that was basically inaccessible because it was weirdly behind the furnace once.
Deal Addict
Nov 16, 2011
1509 posts
1224 upvotes
HAMILTON
crowd that I hang out with ?????? now that is a stretch LOL.....

Yes, the ceiling and walls are finished. Was that way when I moved in and is still that way.....

Home previously had an electric furnace which I had changed to a gas furnace. Installers had no issues nor have an service people ( regular maintenance ) nor when I had furance upgraded to high efficiency had any issues or concerns....

Home is about 30-35 yrs old.
Deal Expert
User avatar
Jun 12, 2007
18602 posts
6029 upvotes
London
Jerico wrote: I dont know what kind of crowd you hang out in but as a window contractor im in quite a few houses in a given day and Ive literally never seen a finished ceiling in a furnace room. Its makes zero sense as when you get a new furnace it might have to all come down.

I will start paying more attention and report back if I see a single one. I did see a window that was basically inaccessible because it was weirdly behind the furnace once.
Maybe a rough in for a basement rental apt. A finished furnace room ceiling is required by fire code if you want to build a new basement rental apt in many municipalities now
Penalty Box
Jun 24, 2015
7196 posts
2232 upvotes
0 downvotes
wow, thank the lord the ceiling in my furnace room is unfinished, i have duct work there which is in all sizes and shapes and dampers and water shut off valves in the ceiling, i have a saddle valve (which i also plan to replace with a proper shut off valve, come take a look at my ceiling, if soneone forced me to drywall over that, you would probably laugh your pants off, theres absolutely NO WAY to drywall my ceiling with all these pipes and vents and cold air return ducts and valves and wires and furnace power vents and bvents and stuff,
Say NO to the WAR!
PEACE is the answer!
[OP]
Jr. Member
Apr 12, 2004
144 posts
56 upvotes
Montreal
So a quick update, I did find a transformer (in my garage, no furnace room here) which read 19V .... so guessing it's an 18V transformer. However, when the breaker that kills the power to the intercom was off, the transformer was still reading 19V. So, I think the garage transformer fed power to the old main unit (which was removed several years ago) and there is another transformer hidden in the wall somewhere that is powering the intercom.

I did also take a reading at the intercom and for some reason it showed less than 1V. This was based on different combinations of the 3 wires. I'm not really sure how that works, but given it was such a low voltage, I capped it for the time being.

Thanks again for everyone's help!

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