Series-L4

Supported Applications

The Dwyer Series L4 Flotect® Float Switch is a rugged, magnetically operated point level switch designed to automatically indicate tank levels. The series operates by using a free-swinging float that attracts a magnet within the solid metal switch body, actuating a snap switch via a simple lever arm without bellows, springs, or seals. Documented applications include direct pump control (starting or stopping pumps), automatic tank dump operations, level control, valve control, and triggering level alarm signals.

Specific process environments cited for the Series L4 include sumps, scrubber systems, hydro-pneumatic tanks, boilers, and water/wastewater treatment processes. The switch is suitable for liquids compatible with its wetted materials.

Operating Conditions & Performance

The series features a weatherproof and explosion-proof enclosure rating. Standard units are listed with UL and CSA for Class I, Groups C and D; Class II, Groups E, F, and G. ATEX certified models carry the designation 2813 II 2 G Ex db IIB T6 Gb (-20°C≤Tamb≤73°C) under EU-Type Certificate No.: KEMA 03 ATEX 2383, adhering to standards EN 60079-0:2012+A11:2013 and EN 60079-1:2014. IECEx certified units are rated for Ex db IIB T6 Gb (-20°C≤Tamb≤73°C) under Certificate of Conformity IECEx DEK 11.0071, adhering to standards IEC 60079-0:2011 and IEC 60079-1:2014.

Temperature limits vary by configuration:

• Ambient Temperature (Standard): -4 to 275°F (-20 to 135°C).
• Ambient/Process Temperature (ATEX and IECEx options): -4 to 163°F (-20 to 73°C).
• High Temperature Option (MT): Rated up to 400°F (205°C); note that the MT option is not UL, CSA, ATEX, or IECEx listed.

Pressure ratings depend on body material: Brass bodies are rated for 1000 psig (69 bar), while 316 SS bodies are rated for 2000 psig (138 bar). The standard float is rated for 100 psig (6.9 bar) with a minimum specific gravity of 0.7. Optional floats support higher pressures and lower specific gravities, such as the 50 psi (3.5 bar) option requiring > 0.5 s.g.

Electrical ratings for UL, FM, ATEX, and IECEx models are 10A @ 125/250 VAC (V~). CSA models are rated at 5A @ 125/250 VAC (V~) or 5A resistive / 3A inductive @ 30 VDC. The standard dead band is 3/4" (19 mm).

Configuration Options

The Series L4 offers extensive configuration options for construction, wetted materials, switching logic, and mounting.

• Construction & Mounting: Standard side mount with brass body; optional top mount (L4-TOP) requiring specified rod length. Flange process connections are available in 2", 3", or 4" sizes with Carbon steel or 316 SS materials and ratings of 150 #, 300 #, 600 #, or 900 #.
• Wetted Materials: Standard body is Brass; optional -SS provides a 316 SS body with a 430 SS magnet keeper. The float and rod are standard 316 SS. Magnet keepers can be upgraded to 316 SS or Nickel 20.
• Switch Options: SPDT snap switch is standard; DPDT (-D) is optional. Gold plated contacts (-MV) are available for dry circuits (not UL/CSA/FM/ATEX/IECEx listed).
• Float Options: Standard float rated 100 psig. Optional spherical floats include: -50 (304 SS, 50 psi), -150 (316 SS, 150 psi), and -300 (304 SS, 300 psi).
• Process Connections: Standard is 1-1/2" male NPT. Optional floats support 2-1/2" male NPT. The -BSPT option provides a 1-1/2" or 2-1/2" male BSPT process connection with an M25 conduit connection.
• Electrical Connections: UL and CSA models feature 16 AWG, 6" (152 mm) leads. ATEX and IECEx units utilize a terminal block.

Special Service Options

• Hazardous Location: -AT for ATEX compliant construction; -IEC for IECEx certified construction.
• Environmental Protection: Epoxy coated housing (-EPOXY), Neoprene boot (-NB).
• No Housing: Option -NH removes the electrical housing (no approvals apply to this configuration).
• Time Delay Relays: Adjustable 0-1 to 0-31 minutes for increasing flow (-TRI) or decreasing flow (-TRD). These options are not UL, CSA, FM, ATEX, or IECEx listed.

Key Product Differences

The Series L4 distinguishes between standard side-mount configurations and top-mounted vertical flange installations (L4-TOP), where the distance from the flange face to the centerline of the float must be specified up to a maximum of 20" (508 mm). Variants differ primarily by body material (Brass vs. 316 SS) and hazardous location certification status.

Units without the 'AT' suffix are not Directive 2014/34/EU (ATEX) compliant and are not intended for use in potentially hazardous atmospheres in the EU, though they may be CE marked for other Directives. The -NH option removes approvals entirely. High temperature (-MT) and gold contact (-MV) options also carry specific limitations regarding UL, CSA, FM, ATEX, or IECEx listings.

Standard models utilize a 3/4" female NPT conduit connection; the -BSPT variant changes this to M25 x 1.5 with corresponding process connections.