What Replaces the Notifier FSP-851, and Will the FSP-951 Fit My Base?

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Notifier FSP-951 intelligent photoelectric smoke detector

The Notifier FSP-951 Series replaces the FSP-851 Series; Notifier's datasheet calls the 951 detectors direct replacements. The catch is protocol. The FSP-851 ran in FlashScan or CLIP, the white FSP-951 is FlashScan only, and the ivory FSP-951-IV that covers CLIP was scheduled by Notifier for discontinuation at the end of 2024.

So the right part depends on how the loop is programmed, not on how the detector looks. The details below come from the Notifier documents listed under Sources.

Is the FSP-951 a direct replacement for the FSP-851?

Yes. The FSP-951 datasheet says so, and Notifier's SLC wiring manual states that the FSP-951 models update and replace the FSP-851, FSP-851T and FSP-851R, and that the FST-951 models do the same for the FST-851, FST-851R and FST-851H. The FSP-951 Series is designed to meet UL 268 7th Edition.

851-series model 951-series model What Notifier says
FSP-851 photoelectric FSP-951 (white) or FSP-951-IV (ivory) Direct replacement
FSP-851T photo with 135°F thermal FSP-951T or FSP-951T-IV Replaces FSP-851T
FSP-851R remote test, for DNR duct housings FSP-951R or FSP-951R-IV Replaces FSP-851R
FST-851, FST-851R, FST-851H heat FST-951, FST-951R, FST-951H (and -IV versions) Direct replacement
FAPT-851 Acclimate Plus FPTI-951 photo, thermal and infrared Replaces the FAPT-851 Series

Two legacy models have no replacement statement in the documents we reviewed. The FSC-851 IntelliQuad and the FSI-851 ionization detector are both described as FlashScan and CLIP capable. The current four-sensor detector is the FCO-951 fire and CO detector, but its datasheet does not name the FSC-851 as the model it replaces, and we found no 951-series ionization detector. For either one, ask Notifier which current detector your panel and firmware accept before ordering.

Can FSP-851 and FSP-951 detectors run on the same SLC, in FlashScan and in CLIP mode?

That depends on the loop's protocol, and this is where most wrong orders happen.

  • FSP-851 Series: FlashScan or CLIP.
  • FSP-951, FSP-951T, FSP-951R (white): FlashScan only.
  • FSP-951-IV and the other -IV models (ivory): FlashScan or CLIP.

On a FlashScan loop, the white FSP-951 is the documented replacement for an FSP-851. On a CLIP loop, only the -IV version of the 951 is listed to work, so a white FSP-951 is the wrong part. Notifier's SLC wiring manual lists both generations as intelligent detectors for its SLC, but the panel's own manual and firmware decide which device types a given panel accepts.

Is the ivory FSP-951-IV discontinued, and is the white one the same detector?

Notifier announced the end of its ivory detectors. The Ivory Detector Discontinuation Notice, document M23.18, set December 31, 2024 as the date the ivory line would be fully discontinued, with final orders due by December 1, 2024. The affected list includes the FSP-951-IV, FSP-951R-IV, FSP-951T-IV, FST-951-IV, FST-951R-IV, FST-951H-IV, FCO-951-IV and FPTI-951-IV. We have not found a later Notifier notice that reverses it.

The white FSP-951 is not the same detector in a different color. It is FlashScan only. The notice itself acknowledges that ivory detectors may still be needed for legacy CLIP installations, and recommends moving those systems to FlashScan rather than naming a CLIP substitute. That leaves a CLIP site with three options:

  1. Use ivory -IV detectors or FSP-851 detectors while they can still be sourced. Both are listed for CLIP.
  2. Convert the loop to FlashScan, if the panel supports it, and use white 951-series detectors.
  3. Ask Notifier what it currently recommends for your panel model.

If the only goal is an ivory finish on a FlashScan loop, the FSP-951 datasheet lists the CK300-IV color kit, an ivory cover and trim ring sold in packs of ten.

Will a 951-series head mount on an existing B210LP or B501 base, or do I need a B300-6?

For a new base, order the B300-6 (6-inch flanged) or the B501-WHITE (4-inch flangeless). Those are the standard bases on the FSP-951 datasheet, with B300-6-IV and B501-IV as the ivory versions.

For a base already on the ceiling, the Notifier documents point the same way without quite saying it in one sentence:

  • The SLC wiring manual describes the B300-6 as the replacement model for the B210LP, and the current white, ivory and black B501 bases as replacing the legacy ivory B501.
  • The intelligent bases datasheet covers one base family for the 900-series detectors and earlier generations, and lists the B210LP alongside the B300-6.
  • The FSP-951 datasheet lists the TR300 trim ring as a replacement flange for the B210LP.

None of them states outright that a 951 head is listed on an installed B210LP or legacy B501. Before reusing old bases across a building, check the detector installation sheet (I56-6519) and the base installation sheet, or confirm with Notifier. Relay, isolator and sounder bases (B224RB, B224BI, B200S, B200SR) are separate parts with their own limits.

What do R, T and -IV mean in the part number?

  • T adds a 135°F fixed-temperature thermal sensor (FSP-951T). Its operating range is narrower: 32°F to 100°F.
  • R is the remote-test version for DNR and DNRW duct detector housings (FSP-951R).
  • -IV means ivory, and on the 951 series it also means FlashScan and CLIP. No suffix means white and FlashScan only.
  • A marks the ULC-listed model (FSP-951A).
  • -SELFT is the self-test version, which the SLC wiring manual lists for the N16 panel only.

Confirm any detector against the control panel's listing and compatibility documents, and install it to NFPA 72 and the requirements of the local AHJ.

Where to find these detectors and bases

The store stocks the Notifier 951 and 851 lines in the Notifier and smoke detectors collections, and the matching bases. In-stock orders placed by 3 PM ET ship the same business day. For a retrofit quantity or a model not listed, request a quote.

Sources

Tags: Bases, Flashscan, Notifier, Replacement guide, Smoke detectors