Honeywell SF20-B54 (VF20A) pipe surface temperature sensor, NTC 20 kΩ, IP54
- Type: NTC 20 kΩ (25 °C), passive
- Measuring range: -30…+110 °C
- Protection class: IP54
- Mounting: strap-on pipe up to Ø 110 mm
Where SF20-B54 is used
This sensor measures pipe surface temperature and is most commonly used as heating supply-line or DHW temperature feedback for Honeywell Smile, Excel, or CentraLine controllers. Strap-on (non-immersion) mounting allows installation without draining the system and without a separate pocket — the strap wraps around the pipe and presses the sensor housing against the surface. Additional wrapping with insulation is recommended so ambient temperature does not distort the reading.
Technical specifications
| Parameter | Value |
|---|---|
| Code | VF20A (legacy) / SF20-B54 (current) |
| Manufacturer | Honeywell |
| Sensor type | NTC 20 kΩ (nominal 20 kΩ at 25 °C) |
| Measuring range | -30…+110 °C |
| Accuracy | ±0.2 K at 25 °C |
| Temperature coefficient | -934.5 Ω/K at 25 °C (non-linear) |
| Connection | 2 terminals, non-polarised |
| Protection class | IP54 |
| Dimensions (L × H × D) | 56 × 81 × 40 mm |
| Mounting | Strap-on pipe (max Ø 110 mm) |
| Housing material | Plastic |
| Contact material | Aluminium plate for heat transfer |
When to choose SF20-B54 (VF20A)
- Heating supply/return temperature sensing with Honeywell controllers
- Retrofit without system drain — when a pocket cannot be installed
- DHW system average return temperature monitoring
- When simple, reliable mounting is needed without thread work
- Compatibility: Honeywell Smile SDC, Excel Web/Falcon, CentraLine Merlin, Falcon controllers with NTC 20 kΩ input
B2B delivery and logistics via Amegata.lt
- 24-hour delivery across Lithuania (from our warehouse in Vilnius)
- Competitive B2B pricing — often below market average
- 30-day payment terms for companies (per contract)
- Free technical consultation on surface vs immersion sensor selection
Official Honeywell catalogue: products.ecc.emea.honeywell.com/SF20-B54
Frequently asked questions
What's the difference between VF20A and SF20-B54?
Same product — VF20A is the legacy Honeywell code, SF20-B54 is the current one. New catalogues and warehouses list it as SF20-B54, but it is often ordered by the VF20A code from older project drawings. Directly interchangeable.
Is it compatible with Danfoss ECL 210/310?
No. Danfoss ECL uses Pt 1000 (platinum), while SF20 is NTC 20 kΩ. For Danfoss systems, choose ESM-11 surface sensor (SKU 087B1165); Ouman — TMS-4M/NTC10; Siemens — QAD22.
How to mount correctly on the pipe?
Clean the pipe surface where the sensor will sit (paint, corrosion). Apply a thin layer of thermally conductive paste (silicone). Press the sensor with the strap, then wrap with insulation — without it, ambient air draws heat and readings will be too low.
What cable length is allowed?
Up to ~50 m of 2 × 0.75 mm² shielded cable without meaningful error. Ground the shield only at the controller end — dual grounding creates a noise loop.
When to choose an immersion sensor instead?
When media temperature must be measured with <2 K accuracy — e.g. DHW return limitation, minimum return protection. In such cases, choose VFF20-75P65 (SKU T7425A1005) — immersion sensor with 75 mm probe and G½" thread.
