What Are Push Buttons and Selector Switches?

Push buttons and selector switches are manual control operators that let a person send a command to a machine or control system. A push button is usually pressed and released for a temporary action such as start, stop, reset, or test. A selector switch is turned to one of two or more positions to choose an operating mode or circuit state. These devices are commonly built from a front operator, one or more contact blocks mounted behind the panel, and optional legend plates, guards, illumination modules, or key operators. In practical panel work, they are part of the control circuit rather than the power circuit, so the important checks are usually pilot duty rating, contact configuration, mechanical action, and physical compatibility.

Where Are Push Buttons and Selector Switches Used?

These devices are used anywhere an operator needs a simple manual interface. Common examples include motor starters, conveyor controls, pump stations, compressor panels, fan controls, generator auxiliaries, irrigation systems, wash bay controls, and OEM machinery. In commercial buildings they are often used for exhaust fans, lighting control stations, door release functions, and mechanical room equipment. In industrial settings, selector switches are common for Hand-Off-Auto, Local-Remote, Auto-Man, and Forward-Off-Reverse functions. Push buttons are common for Start-Stop, Jog, Reset, Lamp Test, and Emergency Stop stations. The application matters because a clean indoor panel, a washdown area, and an outdoor enclosure may all require different operator constructions and sealing levels.

How To Choose Push Buttons and Selector Switches

Start with the control function. If the command should happen only while the operator is pressed, use a momentary push button. If the operator must remain in a selected mode, use a maintained selector switch. Next confirm the number and type of contacts needed, such as 1 normally open for a start signal, 1 normally closed for a stop signal, or mixed blocks for interlocking and status logic. Then check the mounting format and operator family so the front operator, contact blocks, lamps, and legend plates all belong to the same series. For retrofit work, verify the panel hole size, anti-rotation notch details, and rear clearance. Also confirm whether illumination is needed, whether a key-operated selector is required for restricted access, and whether the environment calls for oil-tight, dust-tight, or washdown-suitable construction. If the device is part of a safety function, do not assume a standard operator is acceptable without reviewing the control design and applicable standards.

Trade Rules Of Thumb

As a typical rule of thumb, use momentary green push buttons for start and momentary red push buttons for stop only when that colour scheme matches the machine standard or customer preference, because colour conventions vary by plant and OEM. For mode selection, a 2-position selector often suits Local-Remote or Hand-Auto, while a 3-position selector often suits Hand-Off-Auto or Forward-Off-Reverse. On replacement jobs, matching the existing operator family is often faster and cleaner than mixing brands, even when another brand is electrically comparable. For new builds, leave enough rear panel depth for stacked contact blocks and wiring bends. Another practical rule is to order spare contact blocks and legend plates on jobs with multiple identical panels, because these are common service items. These are practical field guidelines only and not a substitute for the equipment design, manufacturer instructions, or applicable Canadian code and safety requirements.

Sizing Guidelines

Push buttons and selector switches are not sized by conductor ampacity in the same way as feeders or branch circuits. Instead, selection is based on control duty. Confirm the control voltage, whether the contacts are switching a PLC input, relay coil, contactor coil, pilot light circuit, or another control load, and whether the device rating is suitable for that duty. Count the required contact states carefully. A simple start station may need only 1 normally open contact, while a stop station may need 1 normally closed contact. A selector used for Hand-Off-Auto may need multiple contact blocks to provide separate outputs and interlocks. If illumination is required, verify lamp or LED module voltage separately from the contact rating. For crowded panels, also check the operator diameter and rear stacking depth. Where exact ratings affect safety or reliability, use the manufacturer data and the control schematic rather than a rule of thumb.

Common Installation Practices

Typical installation practice is to group operators logically by function, keep legends clear and consistent, and maintain enough spacing for gloved operation where needed. Start and stop devices are often placed near the associated pilot lights or status indicators so troubleshooting is easier at the panel door. On selector switches, installers usually verify the maintained positions and contact action before energizing, especially on Forward-Off-Reverse and Hand-Off-Auto circuits where a misapplied contact block can create confusing operation. It is also common practice to torque terminals correctly, dress control wiring so contact blocks remain serviceable, and label both the front legend and the internal wire numbers. In wet or dusty locations, installers should confirm the operator sealing and enclosure arrangement are suitable for the environment. Follow manufacturer instructions and applicable Canadian requirements for installation, guarding, and safety functions.

Common Mistakes

One common mistake is ordering only the front operator and forgetting the contact blocks, lamp modules, or legend plates needed to complete the assembly. Another is assuming all 22 mm or 30 mm devices are interchangeable across brands when the mounting details and accessory systems differ. Buyers also sometimes confuse momentary and maintained action, which can cause immediate control issues on startup. On selector switches, the wrong cam arrangement or contact sequence can break the intended logic even when the switch looks correct from the front. Another frequent issue is using a standard operator in a washdown or outdoor location without checking sealing suitability. On retrofit work, replacing a single failed operator with a different family can create spacing, appearance, and spare parts problems for the next service call.

Brand Comparisons

Noark is commonly considered a value-oriented option for standard industrial control components and may be a sensible choice for new panels where the design is being built around the selected product family from the start. Telemecanique, ABB, Eaton, and Lovato are widely cross-shopped in industrial control work and are often preferred where a site already standardizes on those lines, where a specific accessory ecosystem is required, or where maintenance teams want exact continuity with installed equipment. Schneider is also a major name in this space, and many buyers specifically seek matching parts for existing Schneider or Telemecanique installations. If the job is a replacement in an established plant, matching the installed brand can reduce field modification and spare parts complexity. If the job is a new build with common control functions and the ratings line up, Noark may offer a practical alternative. Brand choice should be based on compatibility, accessory availability, service expectations, and the installed base, not just the front operator appearance.

Related Products

Push buttons and selector switches are often purchased with contactors, overload relays, control transformers, pilot lights, terminal blocks, relays, enclosures, legend plates, control stations, and emergency stop devices. For panel builds, buyers may also need DIN rail, wire duct, ferrules, control wire, and engraved identification. If the operator is part of a motor control scheme, review the full control package so the push button station, selector logic, contactor coil voltage, overload arrangement, and indication devices all work together. On replacement jobs, it is often worth checking whether spare contact blocks, lamps, and operator caps should be stocked at the same time.

Frequently Asked Questions

What is the difference between a push button and a selector switch?

A push button is usually pressed for a temporary action, while a selector switch is turned to a position and commonly stays there until changed. Push buttons are typical for start, stop, and reset. Selector switches are typical for mode selection such as Hand-Off-Auto or Local-Remote.

What does momentary versus maintained mean?

Momentary means the operator returns to its normal position when released. Maintained means it stays in the selected position. This matters because the wrong action can change how the control circuit behaves.

Do I need to buy contact blocks separately?

Often, yes. Many operator families are modular, with the front operator, contact blocks, lamp modules, and legend plates ordered as separate parts. Always confirm what is included before placing the order.

Can I mix brands if the mounting hole is the same?

Sometimes physically, but it is not usually the cleanest approach. Even when the panel hole matches, the rear accessories, contact blocks, legends, and operator depths may differ. For replacements, matching the installed series is usually the safer choice.

When should I use a key selector switch?

Use a key selector when access to a control mode should be limited, such as maintenance override, local control enable, or restricted operating modes. Confirm the keying style and whether the key can be removed in all positions or only selected positions.

Are illuminated push buttons useful on control panels?

Yes, when the operator also needs to provide status or when visibility is important in low-light areas. Check the lamp or LED module voltage separately from the contact rating, and make sure the colour and legend match the intended function.