What Is a Maintained Push Button? Types and Selection Criteria
A maintained push button is a panel and machine control button that stays in the pressed position and keeps its contact changed until it is pressed again.
A maintained push button (push-push button) is a control button that stays in the pressed position when pressed and keeps its contact in the changed state until it is pressed again. It is used to switch a load that stays on for a long time, such as lighting, a fan, a pump or a heater, on and off without building a separate sealing (self-holding) circuit. It is a different product from a spring-return or emergency stop button.
Maintained vs spring-return push buttons
| Maintained button | Spring-return button | |
|---|---|---|
| When pressed | Stays pressed, the contact stays changed | The contact changes only while the button is held |
| Return | Returns on the second press | Returns by itself when released |
| Typical use | Lighting, fans, heaters, operating mode | Motor start/stop, contactor sealing circuit, reset |
| After a power cut | The contact stays closed, so the load restarts by itself | The sealing circuit drops out, so the load waits for a new start command |
Types of maintained push buttons
- By contact: A 1NO (normally open) model closes the circuit when pressed, a 1NC (normally closed) model opens it.
- By protection rating: In the catalogue, the EMAS B and MB series are IP50 and the CP series is IP65. IP65 suits washed, dusty or outdoor-facing panels.
- By mounting diameter: The EMAS and Schneider Electric maintained buttons in the catalogue are for a 22 mm hole.
Selection criteria
- Task: Will the button set a lasting state (light on, fan running) or give a start command? Motors and machines are started with a spring-return button and a contactor sealing circuit; a maintained button suits loads that may safely restart when power returns.
- Contact type: Choose 1NO if the button has to close the circuit and 1NC if it has to open it.
- Contact ratings: The control circuit voltage and current must stay below the contact rating. For inductive AC loads such as contactor coils, use the AC-15 rating, and for DC coils the DC-13 rating; for example, the catalogue data for the Schneider Electric XA2AH gives 3 A at 240 V AC (AC-15) and 0.27 A at 250 V DC (DC-13). These ratings are defined in IEC 60947-5-1, the standard for control circuit devices.
- Colour: IEC 60204-1, the standard for the electrical equipment of machines, recommends white, grey or black when the same button alternately starts and stops; red, yellow and green are not used for this task. In the catalogue, the model that fits this task on a machine panel is the black Schneider Electric XA2AH021.
- Mounting diameter and series: Match the hole diameter (22 mm or 16 mm) of the other buttons in the panel and, where possible, the series; heads, labels and contact blocks of different series do not fit each other.
Common mistakes
- Starting a motor with a maintained button: When power is cut and restored, the motor restarts by itself; an unexpected restart on a machine is dangerous.
- Using a maintained button instead of an emergency stop: Emergency stopping is done with a separate mushroom-head, latching device with an NC contact.
- Not showing the state: The position of a flush push-push head is hard to read from a distance; show that the load is running with a pilot light or a label.
Maintained push buttons in the Welibaba catalogue
The Maintained Push Buttons category has 8 active products from EMAS (4) and Schneider Electric (4):
| Brand | Model | Colour | Contact | Feature |
|---|---|---|---|---|
| EMAS | B100FY | Green | 1NO | B series, 22 mm, IP50 |
| EMAS | MB100FY | Green | 1NO | MB series monoblock, 22 mm, IP50 |
| EMAS | CP100FY / CP100FK | Green / Red | 1NO | CP series, 22 mm, IP65 |
| Schneider Electric | XA2AH021 / XA2AH031 / XA2AH051 | Black / Green / Yellow | 1NO | Push-push, flush |
| Schneider Electric | XA2AH042 | Red | 1NC | Push-push, flush |
Buttons that return when released are in the Spring-Return Push Buttons category, emergency stop devices in Emergency Stop Buttons, and maintained selections whose position can be read at a glance in Selector Push Buttons.
Frequently asked questions
What do 1NO and 1NC mean on a maintained push button?
A 1NO maintained button closes the circuit on the first press and opens it on the second. A 1NC maintained button opens the circuit on the first press and closes it again on the second.
Can a motor be started with a maintained push button?
It is not recommended. When power is cut and restored, the contact of the maintained button stays closed, so the motor restarts by itself. Motors use spring-return start and stop buttons with a contactor sealing circuit.
What colour should a maintained push button be?
On machines, if the same button alternately starts and stops, IEC 60204-1 recommends white, grey or black; red, yellow and green are not used for this task. In circuits outside machinery, follow the project's colour scheme.