System Sensor Smoke & Heat Detectors — Conventional & Addressable
System Sensor is the OEM behind a remarkable share of the conventional and 2-wire smoke detectors installed in US commercial buildings — and the dominant supplier of detector bases that interface with every major panel brand. QuickShipFire stocks System Sensor detectors, plug-in sensor heads, bases and duct detector housings across conventional, 2-wire, 4-wire, i3 and addressable platforms.
System Sensor: The OEM Behind Half the Detectors You’ve Ever Installed
System Sensor is a Honeywell business unit and the largest US OEM supplier of commercial smoke and heat detectors. The catalog supports every major branded panel manufacturer — Notifier, Fire-Lite, Silent Knight, Gamewell FCI and many others — plus stand-alone conventional product lines under the System Sensor name. The brand is also the dominant supplier of detector bases that interface across the entire industry.
System Sensor’s product depth covers four core lines:
- Conventional 2-wire detectors (2W-B, 2WT-B, i3 conventional) — the backbone of older commercial systems and the contractor go-to for cost-effective new installs.
- 4-wire system detectors (4W-B, 4WT-B) — for systems with separate detection and notification circuits.
- Plug-in sensor heads + bases (2151, 2151T, 5151 heads; B210LP, B501 bases) — the OEM platform behind countless branded detectors.
- Duct smoke detection (DH100, DNR, DNRW housings) — HVAC integration per IMC and NFPA 90A.
System Sensor Product Lines We Stock
Conventional 2-Wire Detectors
2W-B / 2WT-B photoelectric and photo-thermal detectors for 2-wire conventional zones. Compatible with the vast majority of conventional FACPs in service.
Conventional 4-Wire Detectors
4W-B / 4WT-B detectors for systems with separate detection power and signal circuits.
i3 Series Self-Diagnostic Detectors
i3 photoelectric and thermal conventional detectors with self-supervision, drift compensation and built-in synchronization.
Plug-in Sensor Heads
2151 photoelectric, 2151T photo-thermal, 5151 thermal heads — the OEM platform behind Notifier, Fire-Lite and many other branded detectors.
Detector Bases
B210LP and B501 6-inch and 4-inch plug-in bases; B210RB relay base; B524 sounder base; B501BHT high-temp base.
Duct Smoke Detectors
DH100ACDC duct housings with photoelectric heads; DNR / DNRW current housings with cover LEDs and remote test capability.
Notification Appliances (SpectrAlert)
SpectrAlert Advance horn strobes, speakers and ceiling-mount appliances — ADA candela compliant.
CO + Smoke Combination Detectors
Conventional and addressable CO/smoke combination detectors meeting NFPA 720 commercial requirements.
Most-Searched System Sensor Model Numbers
| Model | Description | Status |
|---|---|---|
| 2W-B | 2-wire conventional photoelectric detector | Active / legacy |
| 2WT-B | 2-wire photoelectric/thermal combo | Active |
| 4W-B | 4-wire conventional photoelectric detector | Active |
| 4WT-B | 4-wire photoelectric/thermal combo | Active |
| i3 Photo | i3 Series intelligent conventional, photo | Active |
| 2151 | Plug-in photoelectric sensor head | Active |
| 2151T | Plug-in photo-thermal sensor head | Active |
| 5151 | Plug-in heat sensor head | Active |
| B210LP | Plug-in base, 6-inch profile | Active |
| B501 | Plug-in base, 4-inch profile | Active |
| B524 / B524RB | Sounder base / relay base | Active |
| DH100ACDC | Duct smoke detector housing, AC/DC | Legacy / refurb stock |
| DNR / DNRW | Current duct housing, weatherproof option | Active |
| SpectrAlert Advance | Horn/strobe family | Active |
System Sensor Cross-Reference & Brand Interchange
Because System Sensor is the OEM behind many branded detectors, an “in-stock” plug-in head from System Sensor is often the direct equivalent of a branded sensor that’s on extended back-order. This is the single most valuable cross-reference in commercial fire alarm parts.
| Branded Detector | System Sensor Equivalent | Compatibility Notes |
|---|---|---|
| Notifier FSP-851 / FSP-951 sensor | System Sensor 2151 head | Same B210LP base; panel-firmware verification. |
| Fire-Lite SD355 / SD365 | System Sensor 2151 head | Same B210LP base; SLC polling differs by panel. |
| Notifier FST-851 / FST-951 | System Sensor 5151 thermal head | Same B210LP base; verify fixed-temp rating. |
| Fire-Lite H355 / H365 | System Sensor 5151 thermal head | Drop-in at base; verify panel compatibility list. |
| DH100ACDC duct housing | DNR / DNRW current housing | Cover LED added; remote test capability. |
| B501 (older rev) | B501 (current) | Drop-in; legacy and current production interchangeable. |
| 2W-B older rev | 2WT-B current | Verify panel compatibility list before substitution. |
| B524 sounder base | B524 (current rev) | Drop-in; sounder volume per NFPA 72 6.3. |
For deeper coverage of obsolete System Sensor inventory, see our Obsolete System Sensor Detectors page.
System Sensor Troubleshooting & Inspection Resources
- System Sensor False Alarm — Diagnosis & Fix — the high-volume troubleshooting article.
- How to Replace an Old Commercial Smoke Detector — step-by-step replacement procedure.
- Duct Smoke Detector Trouble Conditions — DH100, DNR, DNRW diagnostics.
Industries Where System Sensor Devices Dominate
Older Commercial & Class B Buildings
2-wire conventional zones with 2W-B / 2WT-B detectors remain the backbone of mid-century commercial stock.
K-12 Schools
Multi-decade conventional installed base; cross-building parity matters for district facilities teams.
Multifamily Mid-Rise
Common-area conventional systems with i3 retrofit potential; HUD-funded property managers depend on it.
Light Industrial & Manufacturing
4-wire system detectors with monitored interfaces; see industrial fire alarm.
Restaurants & Commercial Kitchens
Heat detectors and duct detectors for hood / Ansul integration; see restaurant fire alarm.
Retail Strip Centers
Conventional 2-wire zones for cost-effective single-tenant retail spaces.
Frequently Asked Questions
Is QuickShipFire an authorized System Sensor distributor?
No. QuickShipFire is an independent reseller. We stock System Sensor products but are not an authorized System Sensor / Honeywell distributor. We work in the secondary market — new, new-old-stock and refurbished — which is why we can also stock discontinued SKUs that authorized distributors no longer carry.
Can I substitute a System Sensor 2151 head for a Notifier or Fire-Lite branded detector?
Usually yes for the sensor head itself — many branded detectors are System Sensor 2151-platform devices in branded packaging. But always verify against the panel’s compatibility list before substituting. A device that’s technically interchangeable may not be on the panel’s listed compatibility document, which is what an inspector checks.
What’s the difference between 2W-B and 2WT-B?
The 2W-B is a photoelectric-only 2-wire conventional detector. The 2WT-B adds a fixed-temperature thermal element in the same housing, providing photoelectric and thermal detection on a single conventional zone. Both use the same 2-wire interface, and most modern panels list both as compatible.
Are i3 Series detectors backward-compatible with older conventional panels?
Yes, in most cases. The i3 family operates on standard 2-wire conventional zones and is listed compatible with the majority of conventional panels in service. The self-diagnostic features (drift compensation, dirty-detector indication) require the panel to support the i3 message protocol — without that, the detector still functions as a standard conventional smoke detector.
Do you stock System Sensor SpectrAlert notification appliances?
Yes. SpectrAlert Advance horn strobes, speaker strobes and remote strobes ship from our warehouse. ADA candela ratings, indoor and outdoor variants, and ceiling-mount appliances are all available. For full notification-circuit specifications, submit the bill of materials through our quote form.
How fast can you ship System Sensor detectors?
Most in-stock System Sensor items ship the same day if your order is placed before noon Eastern Time. Ground transit anywhere in the continental US is typically 2 to 5 business days. Expedited shipping is available at checkout for urgent jobsite needs.
Are refurbished System Sensor detectors code-legal?
We sell new and new-old-stock System Sensor detectors as the standard. We do not typically refurbish smoke sensor heads — UL-listing reasons make it impractical. For obsolete plug-in heads (e.g. older 2151 revs), we source from new-old-stock inventory.
Request a Quote on System Sensor Detectors
Send us the System Sensor SKU — or describe the panel you’re working on — and we’ll respond with availability, pricing and panel-compatibility notes. Most quotes go out the same business day.
Need a System Sensor Detector — Today?
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Request a Quote Call +1 (833) 747-7845