The SF152Y thermal fuse is commonly rated 15 A, 250 VAC with a nominal cutoff temperature typically listed at 157 °C (315 °F). This numeric snapshot matters because the device serves as a last-line overtemperature cutoff in many household and light‑industrial heating appliances, protecting against sustained overheating that other controls may miss.
This article delivers full thermal and electrical specs, performance limits, installation/testing guidance, cross‑references, and a sourcing/safety checklist so engineers and technicians can apply the correct part and avoid failures.
Point: The SF152Y is an axial, metal‑can thermal cutoff in the “jet” style with insulated axial leads or bare terminals. Evidence: Typical markings on devices include the SF152Y type code, a three‑digit temp code, and a small approval/lot stamp as shown on standard datasheets. Explanation: Photographic identification and checking the stamped cutoff code against the datasheet are essential to avoid substituting parts with different trip temperatures or tolerances.
Point: SF152Y sits in the SF-series family alongside SF152E and other variants that differ mainly by nominal cutoff and tolerance. Evidence: Distributor and manufacturer datasheets list SF152E at a lower nominal cutoff band and slightly different tolerance limits. Explanation: A short comparison helps a technician choose SF152Y when a higher nominal trip or different tolerance is required; always match the temp band rather than form factor alone.
Point: Nominal cutoff for SF152Y is typically 157 °C (315 °F); manufacturers list variants in roughly the 152–157 °C band. Evidence: Datasheet tables distinguish cutoff (the irreversible open) from allowable operating/hold temperature, and list tolerances ±3–5 °C on many parts. Explanation: Designers must quote vendor datasheet cutoff and convert units; do not use the part at sustained ambient temperatures near cutoff without derating.
Point: Rated current is 15 A at 250 VAC; rated values indicate maximum steady‑state limits under specified ambient and mounting conditions. Evidence: Datasheets specify continuous current, recommended max steady‑state current, insulation resistance and dielectric strength figures, and sometimes interrupting capacity. Explanation: “Rated” does not guarantee tolerance to large inrushes — confirm interrupting ratings and consider series protection or contactors for inductive loads.
Point: Trip time depends on heat source, ramp rate, ambient, and mounting; a slow ramp near cutoff can cause long residence times before trip. Evidence: Time‑to‑trip curves in vendor literature show wide variance with mounted heat sinking and airflow. Explanation: For validation, perform ramp tests at controlled rates and report sample size and statistics to capture spread and avoid nuisance trips in production.
Point: Humidity, vibration, and elevated ambient reduce margin; derating extends life and reduces false trips. Evidence: Typical limits list non‑condensing humidity, vibration resistance levels, and recommended max operating ambient. Explanation: Use rule‑of‑thumb derating (see table) and reduce continuous current at higher ambient to maintain safe margin.
| Part | Nominal Cutoff | Tolerance |
|---|---|---|
| SF152Y | 157 °C / 315 °F | ±3–5 °C |
| SF152E | 152 °C / 306 °F | ±3–5 °C |
| Ambient (°C) | Suggested continuous current derate |
|---|---|
| ≤25 | 100% rated |
| 25–50 | Reduce 10–25% |
| >50 | Consult datasheet; use next higher rating |
Point: Correct lead length, orientation and thermal isolation prevent premature trips. Evidence: Vendor application notes advise keeping the fuse away from direct soldering heat and suggest heat‑sleeves and strain relief. Explanation: Follow a step‑by‑step checklist: allow cooling after soldering, use heat‑shields, secure leads to prevent vibration, and avoid direct mounting on heat sinks unless specified.
Point: Bench verification requires a calibrated oven and thermocouple; in-system testing emphasizes safety. Evidence: Recommended ramp rates and oven procedures are provided in standards and vendor test guides. Explanation: For bench test, use a controlled ramp (e.g., 3–5 °C/min), attach thermocouple at the device body, record trip time and temp, and establish pass/fail acceptance criteria tied to datasheet tolerance.
Point: Typical uses include small ovens, air fryers, heaters, and power supplies where a compact, high‑current cutoff is required. Evidence: Application notes list motor/element cutoff examples showing SF152Y selection for its 15 A rating and axial form. Explanation: Selection rationale combines desired trip temp, current capability, and mechanical fit; SF152Y is chosen when mid‑150s °C cutoff and 15 A rating align with the thermal design.
Point: Equivalents exist across families; replacement rules require matching cutoff, current, approvals and fit. Evidence: Cross‑reference tables in distributor catalogs list family equivalents and variant codes. Explanation: Replace only with parts matching cutoff temp, continuous current rating and safety approvals (UL/CSA/VDE) and verify mechanical fit and lot traceability to avoid counterfeit or mismarked parts.
Point: Obtain from authorized distributors or OEM spare channels and verify incoming markings and certifications. Evidence: Procurement best practices call for certified vendor lists, lot traceability and sample inspection. Explanation: Sample PO checklist: part number, vendor name, lot number, date code, test report, and certification marks; check packaging counts and perform incoming inspection on first lots.
Point: Compliance requires datasheets, safety marks and in‑system testing. Evidence: Product safety files list required reports and test evidence. Explanation: Must‑do signoff includes: verified datasheet copy, UL/CSA/VDE marks, bench trip records, installation photos, and disposal handling per local regulations.
The key thermal fuse specs are nominal cutoff temperature (~157 °C / 315 °F), rated current (15 A), rated voltage (250 VAC), tolerance band (typically ±3–5 °C), and documented insulation/dielectric figures. Verify these on the official datasheet and use controlled bench ramp tests for validation before field use.
SF152Y is specified for 15 A resistive loads at 250 VAC, but inductive loads with high inrush may require additional protection. Confirm interrupting capacity and consider series devices (fuses, contactors) for inductive circuits; always validate under worst‑case inrush and ambient conditions.
Use a calibrated oven and thermocouple mounted to the device body, apply a controlled ramp (3–5 °C/min recommended), record trip temperature and time across multiple samples, and compare to datasheet tolerance. Maintain pass/fail logs, lot numbers, and installation photos for compliance and traceability.