Smole Detectors / Texecom Premier 48

[james.wilson]

i thought they did

[NitroN]

That depends on the model of the smoke detector. Normally I would not try to explain this on an open forum, but seeing as I do not have access to the trade forum and that Redbull and Angus have asked...

Two wire 12v smoke detectors, when wired to a 2 wire smoke detector circuit will go open if there is no voltage.

Four wire 12v smoke detectors typically have a built in relay, but this is normally designed to trigger a remote indicator. (i.e. a strobe outside the area that the smoke detector is installed in.

While many installers just connect the suitable resistor in parallel to the normally open smoke detector circuit, this will work, but the panel will not be able to monitor power (as this is a NO Circuit).

To do this correctly:

1. The smoke detectors power should be connected to a resettable panel power supply, this is normally either a dedicated smoke detector power supply or a programmable output.

2. The smoke detectors are connected in parallel to the panel, but in series to the required resistor connected to a relay powered from the same power line as the smoke detector(s).

3. The smoke detectors zone circuits should be connected to the Com & NO terminals on the relay. (NO & Com terminals are shorted when the relay is powered

[NitroN]

I forgot to mention, that most alarm panels will monitor two conditions on a fire zone.

1. A short circuit will activate a fire alarm - Big trucks, bar-ones, pole sliding, big false alarm fines, etc.

2. An open circuit will activate a fire trouble, Red-eyed techs, call out fees, no big false alarm fines, etc.

NitroN

[Guest anguscanplay]

ah I see - the detectors were talking about are totally different to the detectors your talking about. I wondered which alarm panels detected 2 wire ....

yes your right viz fire alarms, but these are intruder panel fire detectors - NC going open (different product)

[NitroN]

The problem with using normally closed smoke detectors is that these can cause false alarms if a wire is broken or if there is no power.

If you wire them this way, (depending on how your panel's fire zone works), you will only get a fire alarm if the smoke detectors circuit goes closed.

A wiring or power problem with create a fire trouble.

2 wire smoke detectors monitor this automatically and do not need a relay.

[aptsys]

The Premier 48 accepts up to 10 2 wire smoke detectors connected between Aux 12V+ and Panel O/P 1.

Obviously 4 wire smokes can be connected to a standard zone.

[InspectorGadget]

That depends on the model of the smoke detector. Normally I would not try to explain this on an open forum, but seeing as I do not have access to the trade forum and that Redbull and Angus have asked...

Two wire 12v smoke detectors, when wired to a 2 wire smoke detector circuit will go open if there is no voltage.

Four wire 12v smoke detectors typically have a built in relay, but this is normally designed to trigger a remote indicator. (i.e. a strobe outside the area that the smoke detector is installed in.

While many installers just connect the suitable resistor in parallel to the normally open smoke detector circuit, this will work, but the panel will not be able to monitor power (as this is a NO Circuit).

To do this correctly:

1. The smoke detectors power should be connected to a resettable panel power supply, this is normally either a dedicated smoke detector power supply or a programmable output.

2. The smoke detectors are connected in parallel to the panel, but in series to the required resistor connected to a relay powered from the same power line as the smoke detector(s).

3. The smoke detectors zone circuits should be connected to the Com & NO terminals on the relay. (NO & Com terminals are shorted when the relay is powered

[james.wilson]

you can also program the sensor to auto reset