Interconnecting Smoke Alarms, And Capacitive Coupling ?

[Robert11]

Hello:

Have been going around the circle with this, and would sure apprciate any
thoughts, or help.

Moved into a new house, and replaced some really old smoke detectors with 3
new Kidde AC wired-in ones. There is a three conductor (plus gnd wire)
running between them.

When hooked up as individual units, all is fine.

When interconnected via the red wire in the cable, they all just keep going
off.

To the best of my knowledge, there is absolutely nothing else on this line.
When the smoke detectors are not hooked to it, it is truly floating, I
believe.

But, with nothing on it, I measure about 2 to 4 volts AC, which is
apparently
enough to trigger them., when they are hooked to the line in interconnect
mode.

Voltage seems high, but others have told me that it is possible via
capacitive coupling.
True ?

A kidde engr told me that when NOT triggered, the interconnect line has 0
volts on it.
So, how can they ever work ?

Any thoughts on this, and hopefully suggestions on how to interconnect these
units without them always going off would be most appreciated.

Thanks,
Bob

 

[Robert Baer]

Hello:

Have been going around the circle with this, and would sure apprciate any
thoughts, or help.

Moved into a new house, and replaced some really old smoke detectors with 3
new Kidde AC wired-in ones. There is a three conductor (plus gnd wire)
running between them.

When hooked up as individual units, all is fine.

When interconnected via the red wire in the cable, they all just keep going
off.

To the best of my knowledge, there is absolutely nothing else on this line.
When the smoke detectors are not hooked to it, it is truly floating, I
believe.

But, with nothing on it, I measure about 2 to 4 volts AC, which is
apparently
enough to trigger them., when they are hooked to the line in interconnect
mode.

Voltage seems high, but others have told me that it is possible via
capacitive coupling.
True ?

A kidde engr told me that when NOT triggered, the interconnect line has 0
volts on it.
So, how can they ever work ?

Any thoughts on this, and hopefully suggestions on how to interconnect these
units without them always going off would be most appreciated.

Thanks,
Bob

See if you can, at minimum, get a wiring diagram for multiple units.
Look for a "termination device", as well as daisy chaining of that
red wire.

 

[Fred Bloggs]

Moved into a new house, and replaced some really old smoke detectors with 3
new Kidde AC wired-in ones. There is a three conductor (plus gnd wire)
running between them.

When hooked up as individual units, all is fine.

When interconnected via the red wire in the cable, they all just keep going
off.

To the best of my knowledge, there is absolutely nothing else on this line.
When the smoke detectors are not hooked to it, it is truly floating, I
believe.

But, with nothing on it, I measure about 2 to 4 volts AC, which is
apparently
enough to trigger them., when they are hooked to the line in interconnect
mode.

Voltage seems high, but others have told me that it is possible via
capacitive coupling.
True ?

A kidde engr told me that when NOT triggered, the interconnect line has 0
volts on it.
So, how can they ever work ?

Any thoughts on this, and hopefully suggestions on how to interconnect these
units without them always going off would be most appreciated.

Yeah- RTFB!- either you have a gross wiring error, different AC
circuits, or something else on the interconnect line. The
interconnection puts out 9VDC referenced to the incoming neutral line-
steady in smoke detect and pulsed in CO mode- so if your neutrals don't
match it will nusiance trip. http://www.kiddeus.com/bulletin1.rsf. Your
4VAC reading, measured with respect to neutral I assume, suggests that
there is some other load on the line/neutral circuit, remove it.

 

[[email protected]]

Bob,

Some smoke detectors operate on two wire systems and some on four wire
systems. The difference between the two is that one type needs to be
powered to operate. Therefore, if you have a four wire system, two
wires are to power your smokes. Now, smoke detectors as well as burg.
detectors use wire color codes as in DC to low voltage systems which is
different than house wiring color codes. So your red wire is power and
your black is ground. That leaves the other two wires. I'm sure that
instructions came with your smokes and that you wired your smokes
correctly. So this is not the problem. What you don't know is that your
smokes operate on resistance which controls the amount of current
passing through them. The old smokes operated on a different resistance
than your new ones and when you hooked them up and powered them they
all did their stuff. What you have to do is determine the current
difference between the two smokes. If the specifications are not
written on the old smokes than you have to place one of them into the
circuit and using a multimeter measure the current through the device.
If you don't have a current reading on your meter you can place a 1 ohm
resister in series with the smoke and measure the voltage across it.
The voltage will equil the current. Make sure that you pick a resistor
that is rated for the wattage of the circuit. Then all you have to do
is determine the current difference between the two smokes.If he new
smokes pass less current than you have to add some value of resistance
in series with the smokes and if they pass more current than you have
to place some resistance in parallel with the smokes. You see the
circuit has to see some constant resistance in order for it to
determine that all is right. When smoke enters the detector the
resistance changes within the decector and more current is allowed to
pass causing the alarm to sound. The resistors you choose have to be
determined by the series, parallel resistance equations. I really hope
that I have explained clearly enough for you to understand. Please
excuse my spelling.

Paul