Nothing drops in. Honeywell's notice ending the Hochiki-based SD device line in 2023 says it has no exact replacement. To keep the panel, reprogram it for SK protocol and replace every SD device with an SK device, such as the SK-PHOTO-W.
SK and SD devices are not interchangeable and cannot share a system. The details below come from the Honeywell and Silent Knight documents listed under Sources.
Is the SD505-PHOTO discontinued?
Yes. Honeywell's Hochiki SD discontinuation notice (bulletin M23.1, issued in January 2023 through its Farenhyt Series brand, which uses the same SD part numbers) set December 31, 2023 as the date the line would be fully discontinued. The list covers the SD505-PHOTO and SD505-HEAT detectors, the SD505-4AB, SD505-6AB, SD505-6IB, SD505-6RB and SD505-6SB bases, the SD500 modules and pull stations, and the duct accessories. The SD505-DUCT and SD505-DUCTR were already discontinued.
The notice gives one technical reason worth knowing: the SD photoelectric detectors are listed only to UL 268 6th edition. It also states that the SD line has no exact drop-in device replacement, and that existing sites can keep the panel by replacing all SD devices with devices of the other protocol the panel supports. The notice is written for Farenhyt panels and names Farenhyt IDP devices. For Silent Knight panels, the compatibility chart shows the equivalent choice: SK protocol.
The SD505-APS is the earlier SD505 analog photoelectric sensor. Silent Knight's SD505 installation sheet lists it with the SD505-AIS and SD505-AHS on the same SD protocol and the same SD505 bases, so the answer is the same as for the SD505-PHOTO.
Which detector replaces SD505-PHOTO, SD505-APS and SD505-HEAT?
There is no SD-protocol successor. The table pairs each SD device with the SK-protocol device that does the same job, matched from the two Silent Knight datasheets. It is a functional pairing for a protocol conversion, not a Honeywell cross-reference table, and none of these parts works on a loop that is still programmed for SD.
| SD device | Function | SK-protocol device with the same function |
|---|---|---|
| SD505-PHOTO, SD505-APS | Photoelectric smoke detector | SK-PHOTO-W |
| SD505-HEAT | Heat detector | SK-HEAT-W (135°F fixed) |
| SD505-DUCT, SD505-DUCTR | Duct smoke detector | SK-PHOTO-R-W remote-test head in a DNR duct housing |
| SD500-AIM | Contact input module | SK-MONITOR |
| SD500-MIM | Mini input module | SK-MINIMON |
| SD500-ARM | Relay module, two Form C contacts | SK-RELAY |
| SD500-ANM | Notification module | SK-CONTROL |
| SD500-SDM | Two-wire smoke detector interface | SK-ZONE |
| SD500-LIM | Line isolator | SK-ISO |
| SD500-PS, SD500-PSDA | Pull station | SK-PULL-SA, SK-PULL-DA |
Are SK and SD devices interchangeable?
No. Silent Knight's compatibility chart states that the 5700, 5808, 5820XL, 5820XL-EVS, 6700, 6808, 6820 and 6820EVS support SK protocol or SD protocol, that the panel must be programmed for one of them, and that every device on the system must match. The 6700 manual puts it more bluntly: you cannot mix SLC devices of different protocols.
What changes when a panel moves from SD to SK:
- Every SLC device. One SD505-PHOTO cannot be swapped for one SK-PHOTO-W on an SD loop. The whole system converts.
- Addressing. SK devices are addressed with two rotary dials on the device. The SD505-PHOTO datasheet describes addressing without mechanical switches.
- Capacity. The 6700 supports 50 SK detectors plus 50 SK modules, or 50 SD devices. The 6808 supports 198 SK points or 127 SD. The 6820 expands to 1,110 SK points or 635 SD.
- Expanders. On the 6000 series, the 6815 SLC expander is for SK devices; SD devices still use the 5815XL.
- Wireless. SWIFT wireless works only with SK devices.
Which base does each detector use: SD505-6AB, B300-6 or B501?
The two families use different bases, so plan to replace the base with the head. SD505 detectors mount on SD505 bases: the SD505-6AB (6-inch), SD505-4AB (4-inch), SD505-6IB isolator, SD505-6RB relay and SD505-6SB sounder base. The SK-PHOTO-W datasheet lists System Sensor bases instead: the B300-6 (6-inch flanged), the B501 (4-inch), the B224RB relay base, the B224BI isolator base and the B200S and B200SR sounder bases.
Is the SK-PHOTO-W the same as the SK-PHOTO and the IDP-PHOTO?
The SK-PHOTO-W is the white SK-protocol photoelectric detector that Silent Knight's compatibility chart lists for every SK-capable panel. Its datasheet names the 6820, 6820EVS, 6808, 6700, 5700, 5808, 5820XL and 5820XL-EVS, and Silent Knight's own discontinued-products page now includes the older SK-PHOTO and SK-PHOTO-T. The SK-PHOTO-T-W adds 135°F thermal sensing, and the SK-PHOTO-R-W is the remote-test version for DNR duct housings.
IDP is the part-number prefix Honeywell uses for the same kind of device in its Farenhyt Series line. Order the prefix that your panel's own compatibility documents list.
Is a System Sensor SS-PHOTO a substitute for an SK-PHOTO?
On paper it is protocol-compatible. Listing is still per panel. System Sensor's SS-Series datasheet says the detectors support current SK, LiteSpeed and SS protocol systems, and the SS-PHOTO installation sheet says the device supports SS, LiteSpeed and SK protocol. Both documents send you to the compatibility chart or the panel's SLC wiring manual for specific panel compatibility, and the installation sheet limits use to listed-compatible panels. Honeywell's product page files the SS-Series under both the System Sensor and Silent Knight brands.
We did not find a Honeywell document that calls the SS-PHOTO a direct replacement for the SK-PHOTO or SK-PHOTO-W, or a chart that lists it against each Silent Knight panel and firmware. Check your panel's current manual or ask Silent Knight before ordering. The SS-PHOTO is not an SD device either, so it does not solve an SD505 problem unless the panel is converted to SK.
Confirm any device 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 parts
The store stocks the SK detector and module lines in the Silent Knight collection, along with smoke detectors and modules from other brands. For a full SD-to-SK conversion list or a part not shown, request a quote.
Sources
- Honeywell Farenhyt Series, Product Discontinuation Notice - Hochiki SD, Marketing Bulletin M23.1, January 2023 (revised February 2023)
- Honeywell Silent Knight, Addressable Detector and Sounder Base Compatibility Chart, 2019
- Honeywell Silent Knight, Hochiki SD Devices data sheet, 53624 Rev C, 05/18
- Silent Knight, SD505-PHOTO Addressable Photoelectric Smoke Detector data sheet, 350225 Rev G
- Silent Knight, Installation Instruction for SD505 Analog Smoke Sensors (SD505-APS, SD505-AIS, SD505-AHS), publication 150955, 2/01
- Honeywell Silent Knight, SK-PHOTO-W Series data sheet, 351634 Rev A, 04/18
- Honeywell Silent Knight, 6700 Installation and Operation Manual, LS10148-001SK-E Rev C, 09/28/2017
- Honeywell Silent Knight, 6808 data sheet, 351608:C, 3/10/2022
- Honeywell Silent Knight, 6820 data sheet, 351610:C
- Honeywell Silent Knight, 6000 Series sell sheet, Rev 03, 12/20
- Honeywell Silent Knight, Discontinued Products page
- Honeywell Farenhyt Series, IDP Ivory Detector Last Time Buy and Discontinuation, Marketing Bulletin M23.12, November 2023 (IDP part numbers)
- System Sensor, SS-Series Intelligent Detectors data sheet, SPDS-62164
- Honeywell, SS-Series Intelligent Photoelectric Smoke Detector product page
- System Sensor, SS-PHOTO installation and maintenance instructions, I56-1406-001