How did you connect them to the panel, and where (at what point) are you taking the voltage measurements?
Are you using EOL resistors? Where are they located and how did you wire them into the system?
The detectors are CO8RD and has the following contacts: COM,NO,NC,GND,12V,24V
EOLR installed on NC and NO contacts
COM to NEG on panel
NO to Zone on panel
Power connect to GND and 12V going to panel VAUX power
Here is the device spec sheet:
http://www.nadi.com/...RD_CDN_spec.pdf
Your EOL resistor isn't completing a circuit connected to the NC and NO contacts of that sensor. The relay on the sensor uses EITHER the NO and Common (for Normally Open circuits) OR NC and Comman (for Normally Closed circuits).
Also, the EOL needs to be in 'series' with the circuit.
Doing a quick search it appears the best way to wire this would be to use a normally open circuit with the EOL resistor installed in the NO and COMMON terminals of the CO sensor.
I would first make sure you have no wiring problems as I'm nervous about the fact that you have similar sensors wired and set up the same with different results. Do you have a multi-meter to test your cabling?
Actually this is exactly how I have wired mine (!). Putting the EOL resistor across the NO and NC contacts is a convenience, because it lets you avoid a flying splice connection. The relay when deactivated (non-alarm) has the resistor in series with the zone (because COM=NC) exactly as if ir were discretely wired in the circuit in series. It certainly works -- has worked here for years. I can't think of a reason not to do it this way. Maybe it is even a little bit better in "keeping an eye on the relay?"EOLR installed on NC and NO contacts
COM to NEG on panel
NO to Zone on panel
Power connect to GND and 12V going to panel VAUX power
Putting the EOL resistor across the NO and NC contacts is a convenience, because it lets you avoid a flying splice connection. The relay when deactivated (non-alarm) has the resistor in series with the zone (because COM=NC) exactly as if ir were discretely wired in the circuit in series.
Actually this is exactly how I have wired mine (!). Putting the EOL resistor across the NO and NC contacts is a convenience, because it lets you avoid a flying splice connection. The relay when deactivated (non-alarm) has the resistor in series with the zone (because COM=NC) exactly as if ir were discretely wired in the circuit in series. It certainly works -- has worked here for years. I can't think of a reason not to do it this way. Maybe it is even a little bit better in "keeping an eye on the relay?"
So unless jsp's low-reading relay is faulty, it would seem that there is some issue with the wiring, poor electrical contact somewhere, wrong resistor value, etc. etc.
Wow, I never thought of that, but you are correct! I initially pictured the other end of the resistor just hanging out in the open when I first replied. Thanks for pointing out my mistake as I obviously should have thought about this some more! :blush:
Your 4V value suggests that you're possibly seeing 2 resistors in series, basically a high resistance fault showing.
CO's should always be wired as a NO circuit with the EOLR across the circuit at the last device. That's how the panels expect them, just like a fire alarm. Also, if the unit has trouble relay contacts, they should be wired in series with the circuit to remove the EOLR so the panel recognizes a trouble.