Honeywell Sensepoint XCD SPXCDULNHX – Fixed H₂S Detector (0-50ppm, Electrochemical (Surecell™), UL, LM25, 3/4" NPT)
SPXCDULNHX is the Honeywell Sensepoint XCD transmitter factory-fitted for hydrogen sulfide, default 0–50 ppm electrochemical range, LM25 epoxy-coated aluminium and 2 × 3/4" NPT cable entries, UL / CSA certified. Specify it when a fixed H2S point must stay online at a wastewater headworks, sour-water pit or offshore well bay instead of sending a portable every shift.
Same gas, swap enclosure/approval: aluminium SPXCDALMHX, 316SS SPXCDASMHX, UL SPXCDULNHX. SPXCDALMHX · SPXCDASMHX · SPXCDULNHX
Part-number decode
| Segment | Meaning | This SKU |
|---|---|---|
| SPXCD | Sensepoint XCD series | SPXCD |
| A / U | Approval A=ATEX/IECEx/GB; U=UL | U |
| L / S | Enclosure L=LM25 aluminium; S=316SS | L |
| M / N | Entry M=M20; N=3/4" NPT | N |
| HX | Gas hydrogen sulfide, Electrochemical (Surecell™) | HX |
Same gas, swap enclosure/approval: aluminium SPXCDALMHX, 316SS SPXCDASMHX, UL SPXCDULNHX.
Technical specifications
| Target gas | H₂S / hydrogen sulfide |
|---|---|
| Principle | Electrochemical (Surecell™) |
| Default range | 0-50ppm |
| User FSD window | 10-100ppm |
| Resolution | 1ppm |
| Output | 4–20 mA sink/source + optional Modbus RTU |
| Supply | 16–32 VDC (24 VDC nominal) |
| Power | 3.7 W |
| Enclosure | LM25 epoxy-coated aluminium |
| Entries | 2 × 3/4" NPT |
| Display | Tri-colour backlight LCD |
| Relays | 3×5A@250VAC |
| Ingress | IP66 |
| Approvals | UL / CSA |
| Temperature | −40~+65 ℃ |
| Mass | approx. 2.0 kg (4.4 lb) |
Why this principle for this gas
H₂S is denser than air and collects in sumps, wet wells and trench bottoms. An electrochemical Surecell™ cartridge is used because it is selective at tens of ppm and supports Reflex™ electrode check; a pellistor would ignore the toxic risk and a semiconductor cell would drift in wet H₂S. Mount the sensor 300–500 mm above the lowest floor, never in the splash zone, and do not fit a weather cone that traps heavier-than-air gas against the sinter.
Sensor and replaceable parts
OEM cartridge SPXCDXSHXSS. Calibration cap S3KCAL. Fit a collecting cone on hydrogen; do not cone a heavier-than-air H₂S head. Pipe/duct kits: SPXCDMTBR / SPXCDDMK.
Typical applications
Typical fixed H₂S points are wastewater wet wells, refinery sulphur pits, landfill biogas headers and battery rooms with sulphide off-gassing. XCD stays on the wall, accepts a remote sensor up to 30 m if the transmitter must sit outside the splash zone, and is magnet-calibrated without opening the flameproof lid—none of which a portable can do on a 15-minute tour.
Selection contrast
| P/N | Gas | Range | Principle |
|---|---|---|---|
| SPXCDULNHX | H₂S | 0-50ppm | EChem |
| SPXCDULNCX | CO | 0-300ppm | EChem |
| SPXCDULNO1 | O₂ | 0-25.0%Vol | EChem |
| SPXCDULNRX | CH₄ | 0-100%LEL | IR |
| SPXCDALMHX | H₂S | 0-50ppm | EChem |
| SPXCDASMHX | H₂S | 0-50ppm | EChem |
Installation and wiring
Wall-mount SPXCDULNHX (hydrogen sulfide, LM25 epoxy-coated aluminium) through the one-piece plate with M8 bolts sized for that mass. This SKU uses 2 × 3/4" NPT entries: pipe kit SPXCDMTBR covers Ø1.5–3″, duct kit is SPXCDDMK, and glands must match—do not retap SPXCDULNHX. Land SPXCDULNHX 4–20 mA as three-wire and set Modbus address from the menu only. Magnetic wand calibration on the SPXCDULNHX lid stays non-intrusive. On SPXCDULNHX keep the H₂S head low and skip the weather cone.
FAQ
- Does SPXCDULNHX measure anything other than H₂S?
- SPXCDULNHX — No. The HX cartridge is H₂S-only. To change gas you replace the sensor housing SPXCDXSHXSS or order a different transmitter SKU.
- SPXCDULNHX: How does Reflex™ affect H₂S cell life?
- SPXCDULNHX — Reflex™ pulses the electrode and flags decline before the 2–3 year electrochemical life is exhausted. Budget a spare SPXCDXSHXSS at the 24-month mark for continuous H₂S service.
- LM25 or 316SS for SPXCDULNHX (hydrogen sulfide)?
- SPXCDULNHX ships in LM25 epoxy aluminium (~4.4 lb). For hydrogen sulfide in salt spray, caustic CIP or sour-water splash, switch to 316SS sibling SPXCDASMHX instead of painting this lid.
- Why is SPXCDULNHX NPT instead of M20?
- SPXCDULNHX is the UL/CSA hydrogen sulfide body and ships 3/4" NPT. Do not tap M20 on this lid—order ATEX sibling SPXCDALMHX if metric glands are mandatory.
- Can I retrofit Modbus on SPXCDULNHX after it ships?
- Modbus RTU on SPXCDULNHX is a transmitter sales option, not a jumper on the hydrogen sulfide lid. Confirm the option before the box leaves; 4–20 mA sink/source is already on this SKU.
Documents
Honeywell Sensepoint XCD datasheet / manual · On-site XCD selection matrix
Availability and enquiry
Stock is lot-based. If this aluminium ATEX box is out, jump to 316SS SPXCDASMHX or UL SPXCDULNHX rather than a dead SKU.