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Top-Mount Liquid Level Control, SPST/SPDT, 0.5 SG, 12 ft Depth, NEMA
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Series-301

Top-Mount Liquid Level Control, SPST/SPDT, 0.5 SG, 12 ft Depth, NEMA

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  • Top-mount float control for tanks or sumps; depth up to 12 ft with low-gravity liquid capability
  • SPST/SPDT or optional DPDT switch with mercury, snap, or hermetically sealed contacts
  • NEMA 1, 4, 7, 9 enclosures available for general, outdoor, or hazardous installations
  • Stainless or copper float options handle fluids to 0.50 SG; durable rods and stops in 316 SS
Series-301
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0 Variations available
See all series options below
Series-301Data Sheet

Data Sheet
Top-Mount Liquid Level Control, SPST/SPDT, 0.5 SG, 12 ft Depth, NEMA Series-301 Series-301

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Product Overview

The Series 301 Top-Mount Float Type Level Control provides a reliable, economical solution for liquid level monitoring and alarm functions in open or closed tanks, sumps and vessels - particularly where side-mounting is impractical. It is designed for single-stage operation (pump control or alarm) and supports top flange mounting with float travel up to 12 ft (≈3.66 m). 

Installation flexibility is a key strength: the unit mounts via a ¾″ NPT connection or optional flanges (various sizes/materials), making it compatible with a wide array of tank configurations. The Series 301 is offered with multiple enclosure types—from general-purpose painted steel (NEMA 1) to weather-tight (NEMA 4/4X) and explosion-proof (NEMA 7, 9) versions - ensuring suitability for industrial, outdoor or hazard-rated environments.

Material and performance options allow tailoring to various fluid types and service conditions. Choose from 304SS or copper floats, rods/extensions in stainless or brass, and stop rods in 316SS. Pressure and temperature ratings depend on selected float/rod/stop combinations with maximum process temperatures up to ~500 °F (260 °C) in some configurations. Specific gravity minimums depend on float size and rod length but can reach down to ~0.50 for certain models - making the Series 301 suitable for lighter oils or similar fluids. 

Switching options include mercury contacts, snap-action contacts, hermetically sealed contacts (for higher reliability or special environments), and optional two-stage configurations (consult factory). The Series-301 is a robust top-mount level control device that delivers durability, flexibility and cost-effectiveness for alarm or single-stage pump-control applications.

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Can replacement floats, rods and clamps be purchased ?

Asked by: Kelly H
Unfortunately, we do not offer replacement parts for this series.
Answered by: AD Application Engineer
Date published: 2025-09-30
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EXAMPLE 301 G 4810 AS 15 1.0 2 STW 301-G-4810-AS-15-1.0-2-STW Top mount Float Type Level Control, NEMA 1 enclosure, single stage mercury switch, 3-1/2" x 6" 304SS float, 316SS stops, 304SS extension, 1.0 specific gravity, 4" 125# cast iron flange, with SS tag.
SERIES 301               Top Mount Float Type Level Control
ENCLOSURE   G             General Purpose, NEMA 1
  WT             Weather tight, NEMA 1, 2, 3, 4, 4X
  E             Explosion-proof, NEMA 7, 9, Class I Groups B, C, D, Class II Groups E, F, G, Div. I & II; CSA approved Groups C, D, E, F, G only
  EV             Explosion-proof/Vapor-proof, NEMA 7, 9, Class I Groups B, C, D, Class II Groups E, F, G, Div. I & II; CSA approved Groups C, D, E, F, G only
CIRCUITS     48XX           Single Stage Mercury Switch, see chart A
    78XX           Single Stage, Snap Switch, see chart A
    78XXHM           Hermetically Sealed Snap Switch, see chart B
    98XX           Single Stage, High Capacity DC Snap Switch, use heat fins (HF) if process temperature exceeds 350°F (177°C), do not exceed 450°F (232°C), see chart B
FLOAT/
STOP/
GUIDE ROD 		      00         No Float, No Guide Rod
      AS         3-1/2" x 6" 304SS Float, 316SS Stops, 304SS Extension
      BS         4-1/2" Copper Float, 316SS Stops, 304SS Extension
      CS         4-1/2" 304SS Float, 316SS Stops, 304SS Extension
      DS         7" 304SS Float, 316SS Stops, 304SS Extension
      ES         7" Copper Float, 316SS Stops, 304SS Extension
      A0         3-1/2" x 6" 304SS Float, 316SS Stops, No Extension
      B0         4-1/2" Copper Float, 316SS Stops, No Extension
      C0         4-1/2" 304SS Float, 316SS Stops, No Extension
      D0         7" 304SS Float, 316SS Stops, No Extension
      E0         7" Copper Float, 316SS Stops, No Extension
OPERATING
POINT		         XX       ≥12 or ≤96. See Dimensional Drawing.
SPECIFIC
GRAVITY		           1.0     1.0 Specific Gravity
          .9     0.9 Specific Gravity
          .82     0.82 Specific Gravity
          .75     0.75 Specific Gravity
          .62     0.62 Specific Gravity
          .50     0.50 Specific Gravity
FLANGE             0   No Flange
            7   4" 150# RF Carbon Steel
            8   5" 150# RF Carbon Steel
            9   6" 150# RF Carbon Steel
            10   8" 150# RF Carbon Steel
            12   4" 300# RF Carbon Steel
            13   5" 300# RF Carbon Steel
            14   6" 300# RF Carbon Steel
            15   8" 300# RF Carbon Steel
            7S   4" 150# RF 316SS
            8S   5" 150# RF 316SS
            9S   6" 150# RF 316SS
            10S   8" 150# RF 316SS
            12S   4" 300# RF 316SS
            13S   5" 300# RF 316SS
            14S   6" 300# RF 316SS
            15S   8" 300# RF 316SS
OPTIONS               HF Heat Fins
              STW SS Tag Wired
              01 Breather Only (E-Housing only)
              02 Drain Only (E-Housing only)
              12 Breather and Drain (E-Housing only)
              14210.40 Spec. 14210 for Sch 40
              14210.80 Spec. 14210 for Sch 80
              23720 Fungus Proofing
*Not supplied if insertion depth is less that 15".

 

CHARTS A & B - ELECTRICAL CIRCUITS AND RATINGS
SWITCH TYPE
SWITCH ACTION
ELECTRICAL RATINGS IN AMPS
ORDERING CODE
AC
DC
SINGLE STAGE
120V
240V
440V
30V
125V
250V
CHART A
Mercury Contacts		 SP-ST open on level FALL
10
5
3†
 
10
5
-4821
SP-ST open on level RISE
10
5
3†
 
10
5
-4820
SP-DT one switch
4
2
1†
 
4
2
-4810
SP-DT two switches E.I.*
10
5
3†
 
10
5
-4815
DP-ST two switches E.I.* open on level FALL
10
5
3†
 
10
5
-4813
DP-ST two switches E.I.* open on level RISE
10
5
3†
 
10
5
-4814
DP-DT two SP-DT switches
4
2
1†
 
4
2
-4806
CHART B
snap action contacts		 SP-DT one switch
12
5
3†
 
0.5**
0.25**
-7810
DP-DT two SP-DT switches
12
5
3†
 
0.5**
0.25**
-7806
SP-DT one hermetically sealed switch
5
5
 
5**
 
 
-7810HM
DP-DT two hermetically sealed SP-DT switches
5
5
 
5**
 
 
-7806HM
DP-DT two SP-DT switches
10
3
 
 
10‡
3‡
-9806
SP-DT one switch
10
3
 
 
10‡
3‡
-9810
†Available on special order, change 1st digit in ordering code from 4 to 5 or 7 to 8, i.e., -4820 becomes -5820, -7810 becomes -8810, etc.
‡10 amp inductive (polarized) at 125 VDC.
*Electrically Independent.
**Resistive.
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