Smoke detectors
- Thread starter nov0798
- Start date
Steve
Senior Member
Ummm, 2 wires???? 
Ok, seriously, there actually are several threads around that get into it, but that's ok. Without getting into the weeds with it, it really comes down to 1 thing. Do you want your smokes zoned separately or do you want them all on 1 zone? With 2 wire, they are all wired together in series and they attach to 1 special zone (16 on Elk or 1-4 on Omni). 4 wire smokes you can group or homerun them all to individual zones. They can attach to any available zone in the panel. Some people like 4 wire so that when one trips it can be announced quickly vs looking at the LED to determine what tripped. 4 wires can be a little more expensive because you use a power supervision relay on each one, not just a single reversing relay for the whole chain as in 2 wire. Hope that clears it up a little better.
Ok, seriously, there actually are several threads around that get into it, but that's ok. Without getting into the weeds with it, it really comes down to 1 thing. Do you want your smokes zoned separately or do you want them all on 1 zone? With 2 wire, they are all wired together in series and they attach to 1 special zone (16 on Elk or 1-4 on Omni). 4 wire smokes you can group or homerun them all to individual zones. They can attach to any available zone in the panel. Some people like 4 wire so that when one trips it can be announced quickly vs looking at the LED to determine what tripped. 4 wires can be a little more expensive because you use a power supervision relay on each one, not just a single reversing relay for the whole chain as in 2 wire. Hope that clears it up a little better.
AHH,
So if I want to use individual zones, such as individual rooms, wired into an input expander on my system, without having to run wires from the attic to the basement, then I would use a 4 wire. A two wire will just let me know that I have and alarm, but no necessarily where?
The 4 wire thing would definatley be easier for me.
Thanks
So if I want to use individual zones, such as individual rooms, wired into an input expander on my system, without having to run wires from the attic to the basement, then I would use a 4 wire. A two wire will just let me know that I have and alarm, but no necessarily where?
The 4 wire thing would definatley be easier for me.
Thanks
WayneW
Senior Member
True, but not for the reason I presume you are thinking. There isn't a difference due to 2-wire versus 4-wire technology. The difference is that 4-wire allows you to use multiple zones, whereas 2-wire is typically only usable on one zone. Think of it like security sensors... if you had all your doors, windows & motions wired to one zone, you would still have a security system, but when something went wrong, you would have no idea where. If you have those same sensors spread out over 5, 10 or 100 zones, you can see the increased level of detail available.
In the case of a fire when you & family are home, you probably shouldn't care which sensor is sounding, as you should be assuring safety first and probably evacuating. But if the house is empty, it MAY be very helpful when the alarm company calls you for you to know WHERE the sensor is to speculate if it might be a false alarm or not. Similarly, if the system gives a trouble alarm (a wiring problem, not a fire problem), it would be helpful to know which sensor to investigate. You may also be able to bypass one sensor without compromising the entire smoke system. With 2-wire units connected to one zone, it is basically all-or-nothing. I am a fan of 4-wire smokes, although I admit that is more expensive to use multiple zones.
PaulD
Active Member
If you are trying to decide which wire to run, that is easy...home run 4 wire. Leaves you the option of wiring 2 or 4 wire smokes. I made a huge mistake in my new house by letting the builder run 2 wire. I did not understand the difference at that point and as a result, I am locked into the 2 wire solution whereas when I finished construction, I understood the difference and wanted a 4 wire solution.
