The CST-FF20 float level switch is a heavy-duty side-mounted (horizontal) float switch for high/low level alarm, pump control and overfill protection in industrial and marine tanks. A stainless-steel float follows the liquid surface and actuates a magnetic mechanism to switch an SPDT 250 VAC – 5 A contact. Rated up to 300 °C and PN40, with R2″, G, NPT threads or DN40–DN150 flanges – suitable for boiler water, hot water, thermal oil, diesel, fuel oil and chemicals.
Equipment Industrial Solution Co., Ltd (ISE) supplies the CST-FF20 with all float types, arm lengths and connections, and selects the right model for your medium, temperature and pressure.
Key features of the CST-FF20 float switch
- Microswitch or reed switch contacts; SPDT microswitch version rated for ambient up to +100 °C.
- Three temperature classes: L up to 100 °C, M up to 200 °C, H up to 300 °C for hot oil and boiler water.
- Flanges to EN 1092-1 (DIN), ASME B16.5 (ANSI) or JIS B2220.
- Several float sizes for liquids with specific gravity from 0.6 (oils, water, chemicals).
- Wetted parts in 304 or 316 stainless steel.
- Robust aluminium housing, G½ or ½” NPT cable entry; Ex d explosion-proof version on request.
CST-FF20 specifications
| Parameter | Value |
|---|---|
| Principle | Magnetic float, side (horizontal) mounting |
| Contact type | Microswitch (SPDT) or reed switch |
| Contact rating | SPDT, 250 VAC / 5 A (resistive) |
| Wetted material | AISI 304 (1.4301) or AISI 316 (1.4401) |
| Minimum specific gravity | 0.6 g/cm³ – float selected to application |
| Process temperature | L: −30…+100 °C; M: −30…+200 °C; H: −30…+300 °C |
| Ambient temperature | Up to +100 °C (SPDT microswitch version) |
| Operating pressure | PN5, PN10, PN16, PN40 (others on request) |
| Process connection | Thread: R2″ (ISO 7-1), G (ISO 228-1), NPT; Flange: DN40…DN150 (1½”…6″), PN10…PN40, Class 150/300 |
| Arm length (L) | 250 mm standard; max. 690 mm (L/M) or 700 mm (H) |
| Cable entry | G½ (L/M types); ½” NPT (H type) |
| Housing | Aluminium; Ex d on request |
Three temperature versions
| Type | Temperature | Typical connection | Application |
|---|---|---|---|
| L – low temperature | −30…+100 °C | Threaded | Water tanks, wastewater, fuel oil |
| M – medium temperature | −30…+200 °C | PTFE thermal isolator | Hot water, return tanks, hot oil |
| H – high temperature | −30…+300 °C | DN40 PN16 flange (EN 1092-1) | Thermal oil, boiler water |
Ordering code
Structure: CST-FF20 – [T] – [F] – [C] – [X]. Example CST-FF20-L-D-F-Q: low temperature, float D, 2″ (DN50), taper R thread.
| Position | Options |
|---|---|
| T – temperature | L: −30…+100 °C; M: −30…+200 °C; H: −30…+300 °C |
| F – float (Ø × length) | B: Ø75 × 120 mm; C: Ø41 × 150 mm; D: Ø50 × 150 mm; G: Ø41 × 125 mm; H: Ø41 × 100 mm |
| C – connection size | E: 1½” (DN40); F: 2″ (DN50); G: 2½” (DN65); H: 3″ (DN80); I: 4″ (DN100); J: 5″ (DN125); K: 6″ (DN150); L: square 92 × 92 |
| X – pressure / thread | M / N: PN5 / PN10; O / P: ASME Class 150 / 300; Q / R: taper R (ISO 7-1) / parallel G (ISO 228-1); T / U: BSP / NPT; W / X / Y / Z: PN10 / PN16 / PN25 / PN40; S: special |
When ordering please specify: medium, specific gravity, operating temperature and pressure, switch point / arm length, connection type and any explosion-proof requirement.
Applications of float level switches
- Boiler feedwater and condensate tanks: level alarm and feed-pump control.
- Thermal oil: return and expansion tanks of thermal oil heaters (H version up to 300 °C).
- Diesel, fuel oil, fish oil, fuel and chemical tanks.
- Clean water and wastewater tanks; ballast, bilge and service tanks on ships.
- General industrial process vessels and tanks.
Standards and approvals
| Item | Standard |
|---|---|
| CE | Low Voltage Directive 2014/35/EU (EN 61010-1, switching ≥ 50 VAC) |
| RoHS | 2011/65/EU and (EU) 2015/863 |
| Pressure equipment | 2014/68/EU – Sound Engineering Practice, Article 4(3) |
| Hazardous areas | ATEX 2014/34/EU – Ex d version on request |
| Flanges | EN 1092-1 / ASME B16.5 / JIS B2220 |
| Material certificates | EN 10204 3.1 on request |
FAQ
Can the float switch be used on thermal oil?
Yes. Choose the flanged H version (up to 300 °C) with a float matched to the oil’s specific gravity (typically 0.8–0.9).
How does specific gravity affect selection?
Lighter liquids need larger floats for sufficient buoyancy. The CST-FF20 works with liquids of SG 0.6 and above; ISE selects the float for your medium.
Can the contact switch a pump directly?
The contact is rated 250 VAC – 5 A resistive. For larger pumps, use it to drive a contactor coil or send the signal to a PLC.
Related products
- CST-MLG magnetic level gauge – continuous indication for boilers and pressure vessels
- CST-05 liquid level controller relay – electrode pump control
- DMS-XLT paddle level switch – bulk solids and silos
Where to buy the CST-FF20 float level switch?
EQUIPMENT INDUSTRIAL SOLUTION CO., LTD (ISE) – Ho Chi Minh City, Vietnam – supplies genuine the CST-FF20 float level switch with technical consulting, fast quotation and on-site commissioning support across Vietnam and Southeast Asia.
Contact us: Sales +84 909 617 185 – Technical +84 979 117 185 – Email: [email protected]
