Q-16 Flow Switch Max RELIABILITY – Min COST

MODEL Q-16 Q16webThe “Harwil” Model  Q-16. Maximum Reliability at Minimum Cost.

The Q-16 is the newest addition to Harwil’s heavy-duty line of flow switches. The switch is used to signal, start, or stop electronically operated equipment when flow or no-flow conditions occur. The Q-16 benefits from 40 years of flow switch development experience for every conceivable application.


Harwil’s patented elastomeric sealing system is superior to the metal bellows that are subject to metal fatigue and corrosion. This seal system has been field-proven for over a decade.

q16_plrd_0 The Q-16 can be used in pipes 1 inch and larger, with set points as low as 4 GPM (15 L/m) to over 500 GPM (1,893 LPM) in larger pipe sizes. The Q-16 uses a 15 amp SPDT micro switch that can control a 1⁄2 horsepower motor.

Key Features:

  • Multiple Quick-Change Paddles
  • Patented EPDM Seal, Superior To Metal Bellows
  • Industry-Leading 3 Year Warranty
  • Field Adjustable Set Points
  • Field Adjustable Paddles
  • Direct Replacement For Most Paddle-Type Flow Switches
  • Best Flow Sensitivity Among Paddle-Type Flow Switches
  • High Pressure (200 psi) and Temperature (250 ̊F)
  • Stainless Steel Paddles and Shaft
  • NEMA 1 Enclosure
  • UL 508 & UL 353

Vital Stats:

  • Process Connection 1” NPT
  • Working Temp ( ̊F / ̊C) 32 ̊–250 ̊F (0 ̊–121 ̊C)
  • Pressure 200 psi
  • Enclosure NEMA 1
  • Conduit Opening 1⁄2” Conduit
  • Pipe Size 1”–6”

Flow Range. Water calibrated at 70 ̊F (21 ̊C):

Flow Range. Water calibrated at 70 ̊F (21 ̊C) Q16_1



Typical Uses: The Q-16 was designed for any fluid that is not corrosive to brass, stainless steel, or EPDM. Examples include:

  • Cooling Tower Water
  • Glycol Solutions
  • Irrigation
  • Process Water
  • Wastewater
  • Other Non-hazardous fluids
  • A low-voltage, low-current model is available for microprocessor or control signal applications.

Industry Ideas:

Typical industries include:

  • BOILERS – Verify critical flow in tube-boilers or boiler feeds.
  • CHILLERS – Protect coils from freezing at low flow. WATER
  • TREATMENT – Verify flow for chemical feed, UV, ozone
  • IRRIGATION – Protect pumps and verify flow for fertilizer injection.

Electrical Switch Characteristics:

  • Single-Pole, Double-Throw (SPDT) 15A, 1⁄2 HP @ 125/250 VAC 1⁄2A @ 125 VDC, 1⁄4A @ 250 VDC
  • Switch can interface with microprocessor based controllers and related computer circuits.

Wetted Materials:

  • Body: Brass
  • Shaft: 304 Stainless
  • Paddles: 316 Stainless
  • Seal: EPDM

Installation Dimensions: Q16-Diagram-for-Web-01


Here you will find the the most current copies of all our technical data sheets, organized and collated for your perusal. Click on the link to view the PDF in your browser, or right click on it and save it to your hard drive.

We’ll denote the name of the PDF and the date it was last updated. If you have any questions or special requests, you can reach us through our contact page.

Full Catalog Last Updated
Catalog Jan. 25, 2013
Flow Switches Last Updated
Q-1 Sept. 21, 2012
Q-4 Sept. 21, 2012
Q-5 and Q-5SS Sept. 21, 2012
Q-8N and Q-8CR Aug. 26, 2013
Q-8DS and QD-8DS Aug. 26, 2013
Q-10N and Q-10VCR Sept. 21, 2012
Q-12N and Q-12VCR Jan.  17, 2012
Q-16 Jan. 25, 2012
Level Switches Last Updated
L-5, L-5SS Sept. 21, 2012
L-8N, L-8CR Sept. 21, 2012
L-21N, L-21VCR, L21 PLUS Sept. 21, 2012
L-30N, L-30R Sept. 21, 2012
L-40N, L-40VCR Sept. 21, 2012
Controllers Last Updated
CF-112 Sept. 21, 2012
LC-1 Sept. 21, 2012
SDC-101 Sept. 21, 2012
Series 27 Sept. 21, 2012