System Sensor CO1224TR — round-profile 12/24 VDC system-connected carbon monoxide detector with an electrochemical sensing cell, RealTest functional gas testing, a local 85 dBA sounder, a Form C alarm relay and a Form A trouble relay. The manufacturer describes it as a six-wire, system-monitored detector.
The CO1224TR is the round-footprint member of the CO1224 series, intended for locations where the rectangular CO1224T would be visually obtrusive. It is not a stand-alone CO alarm: it wires to a fire alarm, security or combination control panel so that both a CO event and a detector fault are reported off premises, which is what UL 2075 and NFPA 720 commercial installations require. A Form C alarm relay signals CO and a separate Form A trouble relay reports sensor failure or end of life — under UL 2075 that trouble signal is mandatory. RealTest allows the sensing cell itself to be functionally verified with canned CO rather than only exercising the electronics, and a Test/Hush button silences the sounder for five minutes. An internal ten-year end-of-life timer opens the trouble contact when the cell expires. The base mounts to a single-gang electrical box or directly to a wall or ceiling; drywall anchors are included.
Specifications
| Model |
CO1224TR (US only) |
| Sensing technology |
Electrochemical CO sensing cell |
| Wiring |
Six-wire, system monitored |
| System voltage |
12/24 VDC nominal; minimum 10 VDC, maximum 33 VDC |
| Average standby current |
20 mA |
| Maximum alarm current |
40 mA (75 mA in test) |
| Maximum start-up capacitance |
20 µF |
| Alarm relay |
Form C, 30 VDC @ 0.5 A |
| Trouble relay |
Form A, 30 VDC @ 0.5 A |
| Audible signal |
85 dBA minimum at 10 ft, ANSI temporal 4 pattern |
| Operating temperature |
32°F to 104°F (0°C to 40°C) |
| Operating humidity |
22 to 90% RH |
| Sensor life |
Approximately ten years; built-in end-of-life timer opens the trouble contact |
| Diameter |
6.0″ (round) |
| Height |
1.25″ |
| Input terminals |
14 to 22 AWG, SEMS screws |
| Mounting |
Single-gang back box, or surface mount to wall or ceiling |
| Certification |
UL 2075, Gas and Vapor Detectors and Sensors |
| LED — normal standby |
Green blinks once per minute; red off |
| LED — alarm |
Red blinks in temporal 4 pattern; sounder in temporal 4 |
| LED — RealTest mode |
Green blinks once per second |
| LED — CO trouble |
Red blinks once per minute; green off |
| LED — end of life |
Both LEDs off |
Installation notes
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Six wires, not four: the manufacturer’s ordering information and installation manual both describe the CO1224TR as a six-wire system-monitored detector — power, a Form C alarm relay and a separate Form A trouble relay. Listings that call it four-wire understate the terminations required.
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The trouble relay is mandatory: per UL 2075 a trouble signal must reach the panel on CO cell trouble or end of life. Terminating only the alarm contact does not satisfy the certification.
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Placement: on a ceiling keep the detector at least 12 inches from any wall; on a wall mount it at least as high as a light switch and at least six inches below the ceiling. Install per NFPA 720, which since 2009 covers both commercial and residential applications.
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Ten-year replacement is absolute: the electrochemical cell has a finite life and is not field-replaceable on this model. When the end-of-life timer expires the trouble contact opens and the whole detector must be replaced. Check the “Replace by” sticker under the cover.
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Hush has a ceiling: Test/Hush silences the sounder for five minutes while the red LED keeps flashing, but hush will not operate above 350 ppm CO.
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RealTest is a gas test: hold Test/Hush for two seconds to enter RealTest, spray canned CO agent, then verify sensing at the panel; the detector exits automatically after roughly 20–60 seconds. Confirm with the AHJ whether a functional gas test is required.
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Altitude: the data sheet states testing to 12,000 feet above sea level for the CO1224T specifically. For high-altitude work verify the CO1224TR’s rating with the manufacturer rather than assuming it carries over.
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Environmental limits are narrow: 32°F–104°F and 22–90% RH, ordinary indoor locations only. Garages and attics are generally outside that range.
Related models
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CO1224T — the rectangular version of the same six-wire system-monitored detector with RealTest; 3.3″ W × 1.3″ H × 5.1″ L, tested to 12,000 ft above sea level
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CO1224A — Canadian model, ULC certified to CSA 6.19-01
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CO-PLATE — replacement plate covering the footprint of previously installed competitive CO detectors on a retrofit
Specifications taken from the manufacturer data sheet “CO1224 Series Carbon Monoxide Detectors with RealTest Technology,” document 9021-60937 Rev. A (2016), and the System Sensor installation and maintenance instructions “CO1224T/CO1224TR Carbon Monoxide Detector,” document I56-3111-012. Manufacturer specifications are subject to change without notice.
Documents
FAQ
How is the CO1224TR wired to a panel?
It is a six-wire, system-monitored detector: 12/24 VDC power, an alarm contact and a Form A trouble relay. Per UL 2075, the trouble relay must be wired so CO cell trouble or end of life reaches the panel.
How long does the detector last?
The electrochemical sensor has a lifespan of approximately ten years. At end of life the trouble contact opens, and the detector must be replaced by the date on the "Replace by" sticker under the cover.
Can it be tested with real CO gas?
Yes. Hold the Test/Hush button for two seconds to enter RealTest mode, then spray canned CO into the detector; it alarms and automatically exits RealTest after 20 to 60 seconds.
Where can it be mounted?
On a single-gang electrical box, or surface mounted to a wall or ceiling.
