Simplex 4098-9845 — a weatherproof duct housing enclosure that protects a TrueAlarm addressable duct sensor housing mounted on an air duct exposed to outdoor environmental extremes.
Duct smoke detection on rooftop and other exterior air handling equipment presents a problem: the duct sensor housing itself is only listed for a comparatively narrow indoor temperature band, while the duct it monitors may sit in weather ranging from deep cold to summer roof heat. The 4098-9845 solves this by circulating conditioned air drawn from the duct itself around the internally mounted sensor housing. That circulating air holds the sensor housing within its rated temperature range while the enclosure body takes the weather, and it is why enclosure performance depends on duct air velocity as well as outside temperature.
The enclosure is a solid nonmetallic body and door in light gray PBT/PC blended plastic that does not require painting, with captive cover screws so the door hardware is not dropped off a roof during service. Intake and exhaust tubes for the enclosure and all required gaskets are supplied, and the internal mounting plate is removable so it can be used as a drilling template. The duct sensor housing itself is ordered separately.
Specifications
| Function |
Weatherproof enclosure for TrueAlarm addressable duct sensor housings |
| Compatible duct sensor housings |
4098-9755 Standard Duct Sensor Housing; 4098-9756 Duct Sensor Housing with Relay Output (both ordered separately) |
| Air velocity range |
300 to 4000 ft/min (91 to 1220 m/min) |
| UL listed external temperature range |
-40° to 158°F (-40° to 70°C) |
| UL listed external humidity |
Up to 100% RH |
| NEMA enclosure category |
4X |
| Construction |
Solid body and door, light gray, PBT/PC blended plastic, UL94-5VA flammability rating, UV stabilized |
| Dimensions |
22 1/8 in. W x 15 in. H x 7 1/8 in. D (562 mm x 381 mm x 181 mm) |
| Supplied with |
Enclosure air intake and exhaust tubes, required gaskets, removable internal mounting plate |
| Mounting |
Four mounting holes; preferred and acceptable vertical orientations shown in the data sheet |
| Installation instructions |
574-922 |
| Listings |
UL listed to Standard 268A; UL, ULC, CSFM Listed (CSFM 7300-0026:245); MEA (NYC) Acceptance MEA35-93E |
Enclosed duct sensor housing ratings (4098-9755 / 4098-9756)
| UL listed temperature range |
32° to 100°F (0° to 38°C) |
| Operating temperature range |
32° to 122°F (0° to 50°C) |
| Storage temperature range |
0° to 140°F (-18° to 60°C) |
| Humidity range |
10% to 90% RH, non-condensing |
Installation notes
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Airflow is what makes the enclosure work: the enclosure protects the sensor housing by circulating duct air around it. Duct air velocity must be between 300 and 4000 ft/min, and the required velocity rises as the outside ambient temperature moves further from the duct air temperature. Consult the temperature versus airflow graph in the data sheet before committing to a location.
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Enclosure only — order the rest separately: the duct sensor housing, its photoelectric sensor, and the sampling tube sized to the duct are all separate orders. The enclosure supplies only its own intake and exhaust tubes and gaskets.
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Seal the conduit entrance: use flexible conduit with weatherproof fittings (not supplied) and seal the conduit entrance with 3M Weatherban sealant #606 or equal (not supplied). NEMA 4X is only achieved if the entry is properly sealed.
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Orientation matters: the data sheet shows a preferred orientation and an acceptable vertical orientation. Mount the enclosure so the intake and exhaust tube locations align correctly with the duct.
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Use the mounting plate as a template: the internal mounting plate is removable and doubles as a drilling template, which is the practical way to lay out the four mounting holes.
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Duct detection is supplementary: the manufacturer states that duct smoke detector effectiveness depends heavily on air handling system design and operating conditions, on smoke dilution and stratification, and on placement, and that it must never be regarded as a substitute for the building fire alarm and detection system.
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Not FM approved: this product was not FM approved as of the data sheet revision date.
Related models
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4098-9755 — standard TrueAlarm addressable duct sensor housing, supplied with photoelectric sensor and exhaust tube; mounts inside this enclosure.
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4098-9756 — the same duct sensor housing with a relay output, for local fan shutdown or damper control.
Specifications taken from the Simplex data sheet "TrueAlarm Analog Sensing — Weatherproof Duct Housing Enclosure 4098-9845," document S4098-0032-3 (10/2011). Duct sensor housing details are given in data sheet S4098-0030. Manufacturer specifications are subject to change without notice.
