Electronic Alarms and Home Security Devices - Smoke and CO2 on DSC 832

I have (6) 4-wire DSC FSA-410 smoke detectors and (1) 4-wire GE 240CO CO2 detector. A single 18g five wire cable was daisy run through all 7 locations and back to the panel during construction because I hadn't considered using a monitored CO2 at the time. I wired them as indicated in the DSC 832 reference, parallel with EOL Relay and Resistor. I used a standard 12v relay from Radio Shack because I couldn't find the part they suggested in the manual and the diagram looked just like a standard relay. As I was installing, it occured to me that it would be more beneficial to have the CO2 on a seperate zone so that if ever reported during an actual problem, the fire department would know ahead of time that they were dealing with CO2 and not to be surprised not to see smoke and nobody answering and just leave. This is where my amateur assumptions may be askew. I figured since I had an extra wire in the cable, I could use the same power and ground, and same common as the smokes by using adjacent zones on the panel which share a common anyway... and use the extra wire for the unique zone signal loop. When I finished all my wiring, and started programming... the instant I assigned the fire zone... it tripped and went into alarm and I had to reset with user code... it didn't do that again. However, I continued to get an open trouble on the CO2 zone. I tried with and without a resistor, and I tried switching from NO terminal to NC terminal on the CO2 detector, but it always showed open. I gave up and wired into the Fire Zone loop and I have no trouble on that zone.

So my first question is... is it simply not possible to pull off with only one extra wire?

My second question is... although I have no trouble indications for the fire zone... should they all go off and the panel go into fire alarm when I hold down the test button on one of the detectors? Because they don't... and I'm not sure if this is a problem.

I appreciate your help and patience with the long thread.

Q) When you say one extra wire.

Do you mean:

A) a pair of wires?
B) a single wire?

You shoud be able to use a pair of wires and connect the CO to a zone on your panel with a resistor using the the NC and Common on your CO detector. Just place the resistor in series with the detector.


Like this:

http://i89.photobucket.com/albums/k205/Old_Navy_Guy/SafeAir240-CO.jpg

Actually, no. A CO detector typically wires as a NO loop, just like a 4 wire smoke. Since you have the option of using it as a NC loop, there is actually a bit more flexibility. Sharing the common on one leg _shouldn't_ be a problem. The question is the details of _how_ the resistor for the CO zone was wired in, and how the zone was programmed.

It is pretty common, by the way, for smoke detectors to go into alarm when first powered up on most security systems. I learned the hard way to power them up first, _then_ change the zone type. (It's annoying in a residence; it can get the lynch mob fired up in an office....)

Thanks for your comments, I didn't think that there would be an issue in sharing a common, especially since they are adjacent zones (3&4) which share a common on the board anyway.

To answer your question about the resistor. On the Fire part of the parallel run, it is wired with the relay on the last smoke and a resistor between the relay and the common of the smoke. On the CO2 NO run, I had put the resistor between the common wires and the common tap on the unit.

My confusion, is how this truly effects the shared common. The way I wired it ended up with a resistor at the end of the common loop between the last smoke and the relay... and now also one on the unit side of the CO2... so I don't know how this creates an "open" trouble on the CO2 zone, and not the Fire.

As far as programming... I had the Fire Zone as [07] Delayed 24 Hour Fire Zone, and the CO2 zone as [08] Standard 24 Hour Fire Zone. I tried making them both [07] and both [08], but it didn't affect the "open" trouble on the CO2 zone.

BTW - Should the Alarm System react and all smokes emit when I use the test feature on one of the smokes? I thought that this was part of the reason to have the EOL relay. Each one of my units will test and emit when I hold it down for 5 seconds... but it doesn't trigger anything on the alarm or other units.

"To answer your question about the resistor. On the Fire part of the parallel run, it is wired with the relay on the last smoke and a resistor between the relay and the common of the smoke. On the CO2 NO run, I had put the resistor between the common wires and the common tap on the unit."

Your description is a little confusing, but what I would do is (not knowing where in the loop this CO detector sits), Power runs from unit to unit until you get to your EOL. Relay common runs to the common side of all of the alam relays on all detectors. Alarm loop line A runs through all of the smoke detectors and just passes through (wirenut or crimp connected) the CO detector (if it's not the last device). Alarm line B connects to the NO alarm relay on the CO detector with an EOL resistor across the the common and NO Relay terminal.

Assuming that your 5th conductor has continuity all the way back to the panel, then it should work.

The model smoke detector you have can be set up to sound their individual sounders on an inteconnect, but takes an additional piece of hardware. If you aren't getting your fire alarm trip when you press the test button, then you may have something wrong in your wiring or programming of the zone you are using (which also may apply to your other issue).

Wow... thanks for the quick response. I guess I made my mistake by not bridging the resistor across the common and NO terminals on the CO... I only put a resistor betweent he common wire and the common terminal. My best guess is that this will fix my problem... thanks.

As far as the Alarm not tripping when I test the smokes... I'll have to work on that one... perhaps I have something messed up with the EOL relay. I just bought a standard 12 volt relay from Radio Shack... might this be the problem? I couldn't find a source for the DSC RM-1 unit described in the reference.

Also you mention a separate piece of hardware required for my model smokes to initiate their sounders together during an alarm initiated by one... can you point me in the right direction as far as how to purchase this hardware?

Thanks Again... I'll dig into the smokes not tripping the alarm on test and report back.

The interconnect module is a PRM-4W, it's listed on the installation sheet for the smoke detectors, but is buried in the paragraph on interconnecting the smokes.

Pretty much any relay that opens on loss of power will work for the purpose of supervising the power supply. That one's just the particular DSC part number.