Flow Switch
Model Q-12

#1 Flow Switch

Since the mid 1980’s the Harwil Q-12 flow switch has been used by some of the largest companies in the Pool & Spa and fluid control industries. The Q-12 has several factory adjustable parameters that provide the flexibility to meet the requirements of almost any application. The Q-12 verifies fluid flow, typically in conjunction with another device. For example most of swimming pool salt chlorine generators use the Q-12 to verify sufficient flow before the generator is energized. In a spa or hot tub the Q-12 ensures sufficient flow to prevent the water heater from a meltdown. In a chiller the Q-12 prevents the system from freezing. At home the Q-12 turns on the water disinfection system when someone is getting a glass of water.

  • Max. flow may be five times normal flow.
  • Positive stop eliminates fatigue effects of turbulence, vibration and flow surge on flow detecting element.
  • Very low pressure drop – typically less than 1.0 psig at normal flow rate.
  • Small size and low profile provides easy mounting in crowded installations.
  • Power the driving coil of small ice cube relays as well as some 30A power relays.
  • Switches 5VDC to 240VAC.
  • Switch employs magnetic coupling.
  • Can be used in ¾ inch to 6 inch pipe.

Flow Range

0.7–590 GPM (2.6–2,233 L/m)

Working Temp

200˚F (93˚C) Maximum

Working Pressure

250 psi (1.724 kPa)

Process Connection

1/2″ NPT, 3/4″ NPT

Electrical (Reed) Switch

SPNO (single pole normally open) 0.5A*

Enclosure

NEMA 4X / IP 66

Uses

Monitoring flow of coolant supplied to:

  • Brakes and Clutches
  • Emergency Wash-Down Showers
  • Computer Systems
  • Marine and Stationary Engines
  • Diodes, SCRs, Triacs, etc.
  • RF and Radar Transmitters
  • Electromagnets
  • Spot welders
  • Fire Sprinkler Flow Alarms
  • Transformers
  • Lasers
  • Vacuum Systems

In Water Treatment:

  • Irrigation Systems
  • Salt and Fresh Water Systems
  • Chemical Feed Pump Control

In Chemical Processing:

  • Fluid Blending Systems
  • Liquid Transfer
  • Heat Transfer Fluids
  • Monitor Filter Clogging
  • Liquid Scrubbers
  • Starting back-up pumps
  • Monitoring pump output, valve position, systems flow status

In Pool and Spa:

  • Protect water heater in Spa
  • Protect water heater in Pools
  • Turn on Salt Chlorinator
  • Turn on UV System
  • Turn on Ozone System

Models

PIPE SIZE NPT NOMINAL ON/OFF SWITCH POINT RANGE (GPM) PADDLE NUMBER
ON OFF
3/4” 0.9 0.8 3 (.7SM)*
3 2 3SM
11 10 6S
1” 1.1 1.0 3 (.7M)*
4 3 4S
6 5 6S
1 1/2” 2.8 2.5 4 (.7L)*
13 12 4S
16 15 6M
21 19 6S
2” 4.9 4.4 4 (.7L)*
15 12 4M
23 18 4S
27 22 6M
3” 11.0 9.9 4 (.7L)*
33 25 4M
57 45 4S
65 58 6M
82 78 6S
4” 19.6 17.6 4 (.7L)*
56 43 4M
95 83 4S
120 108 6M
150 140 6S
5” 30.6 27.5 4 (.7L)*
92 69 4M
150 130 4S
180 170 6M
230 220 6S
6” 135 95 4M*
220 180 4S
260 220 6M
340 310 6S

 

Q12
Group
Q-12 Q-12CR Q-12DS-50 Q-12N/SPDT
Q-12 Wireless Q-12CR/NC Q-12DS-C2 Q-12N-50
Q-12/NC Q-12CR/NO Q-12DST Q-12N-C2
Q-12/NO Q-12CR/SPDT Q-12DST-C2 Q-12NT
Q-12/SPDT Q-12DS Q-12N Q-12NT-C2

Specs

ELECTRICAL (REED) SWITCH CHARACTERISTICS

SPNO (single pole normally open) or also available with NO, NC or SPDT Reed Switch

Contact Ratings:  N50 C2
AC Voltage (max. switching) 300VAC 24-30
DC Voltage (max. switching) 350VDC 24-30
Current (max. switching) 0.5A 0.1A
Power (max) (VA, W) 50 watts 10 watts

OPTIONAL: SPNC or SPDT, 3 watt, 100VAC/VDC.

INDUCTIVE LOADS

Switch contacts have been tested with small relays and 30A J-C relay inductive driving coils at 120/240VAC to 500,000 operations without failure.

Q-12N (NORYL®) 

  • WORKING PRESSURE: 200 psig max. @ 70˚F
  • WORKING TEMPERATURE: 180˚F @ ambient pressure
  • WETTED MATERIALS: Body: Noryl® (PPO) (10% glass fibers) Paddle: 316 stainless steel Seal: Epoxy
Q-12CR (FORTRON®)

  • WORKING PRESSURE: 250 psig max. @ 70˚F
  • WORKING TEMPERATURE: 200˚F @ ambient pressure
  • WETTED MATERIALS: Body: Fortron® (PPS) (40% glass fibers) Paddle: HASTELLOY® C. Seal: Epoxy

Diagram

q-12-diagram