Is a burglar alarm box a junction box? It's metal and has knockouts
just like a metal junction box. Is it sufficient to contain 110v
I'm only thinking of putting "a little" bit of 110 volts in the box,
110 coming in, the hot wire going to one side of a relay switch and
the other side of the relay switch sending the hot to the hall light
switch box and the dining room light switch box, a total of 230 watts.
The coil of the relay will be controlled by the burglar alarm, so that
these lights go on when I arm the alarm and when I come in the front
door. How does this sound? I plan to put the relay in its own small
metal box, lined witha non-conductor.
IMO you are treading on dangerous ground as you are putting 120 volt and
"control" wiring in the same box. Of course, that's done all the time in
appliances and furnaces but these "boxes" get some kind of UL or whatever
You have some options:
1) Be careful but go ahead and put both 120 and low voltage wiring in the
same container. Hope and pray you don't make a mistake and also that your
don't have problems which might expose you to some liability.
2) Buy some approved apparatus that has a "low voltage" side and a "high
2a) One example might be the X-10 gadget that plugs into the wall for the
"high voltage" side and has some screw terminals for the "low voltage" side.
These have options including send "ON" when an external contact closes and
"OFF" when the external contact opens. Other X-10 devices would switch the
lamp load. This is the quick and dirty "off the shelf" approach.
2b) A transformer/relay "package" that is approved and has isolated high
and low voltage sides. The "high voltage" wiring would come out in an
attached J-box. The "low voltage" stuff would be screw terminals. I have
seen this but would not know where to get my hand on it.
I didn't say so, but I actually had it running this way with the old
burglar alarm, which eventually failed (after about 18 or 20 years).
Doesn't X-10 all depend on radio transmissions. I'm going to use that
to flash the porch light when the alarm goes off, but that's not
critical. If at all possible, I like to use hard-wired things.
Well, what it has now, the professional quality alarm (used by a
friend with an alarm business and over 1000 customers) comes with its
own big wall wart, 16.5 volts. The 110 has to be the same phase as
what supplies those light bulbs at other times, through their
respective switches, because if the light is already on when I arm the
alarm, I have to have the same phase 110 going to the lightbulb
through both sources. I'm sure even one reading already knows that.
I guess I could use a big, 250 or more watt isolation transformer. I
think it would be expensive to buy and it would have to run all the
time, just for those 2 minutes when I leave the house or return.
Whereas, what I had in mind wouldn't cost any additional money for
installation or running.
X10 is a power line carrier system, where the signals are modulated on
121KHz bursts that are sent along the power line during zero-crossing.
This is an old, slow protocol with little error correction.
There are related devices that transmit through the air, but normally
X10 does not.
Because of the powerline dependence, you will not be able to use X10
across power transformers, and may have problems controlling devices
on the other AC phase.
On Fri, 12 Jan 2007 15:38:52 -0500, email@example.com wrote:
When I tried it, the capacitor would not work at all. The coupler
would, but only if it was an ACTIVE coupler (amplifies the X10
signal). There were still a significant number of annoying
intermittent problems. A hardwired system would be a lot more
reliable, or at least wireless using some more modern protocol.
That's my experience. The "Passive" couplers just don't work very well.
The "active" couplers sometimes work and sometimes don't.
X-10 could/can be very reliable if one creates an isolated wiring section.
For example, one can get a filter that blocks X-10 signals from passing.
Stuff on either side of the filter can communicate with stuff on the same
side but "other side" stuff can't communicate or interfere.
In the OP problem, the solution is a "relay transformer" package. It
allows low voltage control of a high power load.
You are supposed to have a barrier between the 120v side and the low
voltage side. It might be easiest to put all of the 120 in a separate
box and just feed it with the low voltage from the burglar alarm. Have
you looked at Solid state relays? They provide a great deal of
isolation and will work on very low currents from the low voltage
side. Hosfelt, AllElectronics and the other surplus sites sell them
about as cheap as a regular coil relay. They also have the advantage
that they are essentually an LED on the low voltage side so you can
drive them directly from "logic". The Opto22 and Crydom (and other
similar types) have the LV and line on opposite ends of the device so
you can arrange a barrier to be perfectly code compliant. If you mount
one horizontally in a 4x4 square box you can install the barrier made
for the purpose. You just have to cut out the section that fits over
the SSR. The other option is to mount them on the side of a deep box
and fabricate a barrier that screws into the back of the box dividing
the top and bottom. I can send you some pictures of some I have made.
On Thu, 11 Jan 2007 15:23:29 -0500, firstname.lastname@example.org wrote:
I used to get the AllElectronics catalog, but maybe I didn't buy
enough, or maybe they are all web now.
I'm actually only powering a reed relay directly from the alarm board
now. What I've been using is a quality brand relay more than rated for
the load, and that is powered by the output of a reed relay that
requires a very tiny input. Either the manual for the previous alarm
didn't say how much current could go through screw #7, or I was afraid
I would make a mistake about how much was used by the relay. But I
was just tremendously scared of burning out that part of the board,
and maybe more, so I made sure the output used was verrry low, by
putting the reed relay in the middle. Using two relays in sequence
seems to me like a Rube Goldberg machine, but there's no noticeable
delay in the light going on, and I think it worked fine for maybe 15
If that would make me code compliant, have I already succeeded in that
by the method I'm using now? I'll admit that the 12 volt power supply
that powers the alarm (and with the new one is integral with the alarm
board) also powers the circuit with the secondary of the reed relay
and the primary of the output relay.
I just happen to have a couple 4x4 boxes that I'm looking for a use
for. :) No kidding**. Can I put the 4x4 box in the old alarm box,
which now has plenty of room because it only holds a separate 18 volt
siren driver and the 18 volt power supply?
I'll admit that what I've been using up to know was a metal Band-aid
box lined with cardboard, with all the metal electrical parts covered
in silicone sealant, and arranged so that nothing electric touches
walls of the box anyhow. I guess that's not good enough 8~(
(18 volts makes the siren louder. Even though I'm getting monitoring
this time, I'm a big believer in sirens. After calling my house to
check for a false alarm, the monitoring will send the police, in 5
minutes if I'm lucky. The siren goes off immediately.)
**I think the 4x4 boxes came from the retired alarm guy, who rented a
ministorage unit from a friend of mine. Once in a while she lets me
clean out a unit when they move out and leave things behind (which
they're not supposed to do, of course, and few do.) I'm not sure what
standard she uses to decide when to let me do that. (I'm hoping it's
whenever there is something I would want that she doesn't.) I sold
for a dollar or two or gave away most of the alarm parts last summer.
I could do that too, if it turns out there isn't room for the 4x4 box
inside. Or it might even be better, not having to run the wires
through 2 layers of steel. Although then I wouldn't have the second
If it is not much trouble, I'm at mm2005 a.t bigfoot do.t com.
I would add another box, connected to the alarm box with a 1/2"
plumbing nipple and those thin nuts that fasten conduit fittings into
sheet metal boxes. Use two - one inside the box and one outside.
Run the low voltage into the added box through the nipple to
operate the relay there.
The installations I've seen of burglar alarms, fire alarms, pbx and
computer network boxes have all been set up with the electric
completely separate. Typically the electric is run in and terminated
with regular three prong 120 volt outlets. Then the alarm installers
(and other system installers) nail a hunk of plywood to the wall, hang
all their stuff on that, and plug it in to the 120 volt outlet just
like you'd plug in a toaster. Same was true in our parking lot with
the stuff all in the same large metal enclosure. Separate electric,
plywood bolted to the inside of the metal enclosure, etc.
That's how we do it.
_Years_ ago (decades, actually), alarms were wired with 120v directly into
the back of the box, either hard-wired or plug-in.
I prefer the current way of doing it - with a 16.5v transformer!
It seems likely that your burglar alarm should have an "output" set up
to control a relay. Just like it has an internal output that turns
the red light on to tell you it's armed. Assuming it has such an
output you would use that to control a relay in parallel to the hall
and dining room light switches. Alarm on = relay on = lights on.
Elbridge Gerry, of Massachusetts:
"What, sir, is the use of militia? It is to prevent the
establishment of a standing army, the bane of liberty. . .
Whenever Government means to invade the rights and liberties of
the people, they always attempt to destroy the militia, in order
to raise a standing army upon its ruins." -- Debate, U.S. House
of Representatives, August 17, 1789
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