​McDonnell & Miller Flow Switches

McDonnell & Miller Flow Switches

Flow switches perform the function of protecting the flow service of fluids. A flow switch monitors and controls the flow of air, steam or liquid through a pipeline. It sends a "trip signal" to the various devices in the system, such as a pump. The flow switch can signal the pump to turn on or to turn off. Some of the universal uses are for protecting the pump, for cooling-circuit protection and to indicate during too high or too low flow rates.

The flow of various fluids in pipelines has a crucial part in various industries. It is a must to ensure a safe flow of fluids in the pipelines. This is the motive behind the development of the  McDonnell & Miller Flow Switches.

McDonnell & Miller, are suppliers of liquid and air flow switches. Liquid flow switches can be used for

• Air Conditioning
• Hot Water Space Heating Systems
• Hot Water Supply Systems
• Pump Systems
• Water Cooled Equipment
• Blending or Additive Systems
• Liquid Transfer Systems
• Fire Sprinkler Systems
• Water Treatment Systems
• Swimming Pool Chlorination
• Industrial Laser Coolant System

The McDonnell & Miller Air flow switches can be applied for clean room filter systems, duct type heating, exhaust ventilating, air supply systems and air treatment systems.

The McDonnell & Miller Flow Switches are manufactured with either one or two SPDT switches apart from the Model FS7-4A (Pneumatic). McDonnell & Miller Flow Switches are suitable for pipe sizes between 1/2" - 36" NPT.

These flow switches can create or break the electrical circuit when flow begins or when the flow stops, and can also be used to:

• Activate a signal when flow stops
• Start a motor with flow
• Stop an alarm when there is enough flow
• Stop a motor when there is no flow

Technical Specifications

• Two SPDT switches to make or break two separate circuits
• Materials of construction suitable for corrosive liquids
• BSPT threads
• Minimum temperature (fluid or ambient) 32°F (0°C)
• Maximum temperature 300°F (149°C)
• Maximum pressure 160 psi (11.3 kg/cm2)
• Two electrical knock-outs allows connection from either end
• Sensitivity adjusting screw makes flow adjustment easy
• Single pole, double throw snap switch
• Hardened stainless steel bearings minimize friction
• Sealed Monel bellows
• Four stainless steel paddles included -1″, 2″, 3″ & 6″ (25, 50, 80, & 150mm)

McDonnell & Miller Flow Switch models are available with wetted parts of brass, Monel or stainless steel. This is to ensure that there are models available for different purposes such as to be used with water, viscous fluids, some oils, various caustic solutions etc.

Installation

For best and proper functioning, the paddle type flow switches need to be installed in a horizontal pipe in the vertical position. It has to be installed in a threaded pipe tee on 2" or smaller pipe or a welded half coupling if it is to be installed on big welded pipe.

In case of installation in copper pipe, you will have to be extra careful. The use of thread to sweat adapters to put in the flow switch can make the paddle arm to be outside of the flow of water. The paddle and paddle arm has to be in the run of the pipe to ensure a proper functioning.

How does it work?

The flow switch has a sensor and it is fitted in the pipe network for both heating and DHW circuits, it is a usually open switch. When the pump operates it moves the fluid around every circuit and the sensor on the flow switch monitors the fluid movement. This device measures the fluid flow and in case of abnormal fluid levels the switch turns off or turns the pump or sets off an alarm.

The Mcdonnell & Miller Flow Switches Models

• Series FS4-3
• It serves a wide range of applications. It is best used in starting or stopping electrical equipment such as signal lights, alarms, motors, automatic burners etc
• Series FS8-W
• It is used in applications that work with environmental exposure, or those that need a water-tight, dust tight, or a NEMA 4X rated flow switch.
• Series 250
• This flow switch model can also be used for starting or stopping electrically operated equipment.
• Series FS7-4
• It is also used in large pipe applications, such as heating and hydronic systems, air conditioning, refrigeration and process work.
• Series FS7-4E
• It is applicable in hazardous environment which needs a NEMA 7 (Class I, Group C or D) or NEMA 9 Class II, Group E, F, or G) rated flow switch.
• Series FS7-4W
• For applications that need a water-tight, dust-tight or a NEMA 4X rated flow switch.
• Series FS5
• For applications that need low flow rate sensitivity