End Switch

Suppose you have a modulating motor with an arm that can rotate back and forth over a 90-degree range.

Suppose you want to control dampers that will bind up if they are moved more than an 80-degree range

An 'End Switch' is an electric switch mounted on the motor linkage that will stop the motor movement when it reaches that 80-degree limit by opening the electrical circuit to the motor.

Most companies that make the modulating motors supply these switches as an accessory.

Actually, the linkages on the damper and motor are adjusted so that the damper movement is limited to something less that 90 deg, and that it does not stop on dead center.

End switches are adjustable, auxiliary switches mounted externally on motor operators to provide additional control sequences. Example would be a hot water heating valve with an aux. end switch that would de-energize the hot water pump when the valve reached the closed position. Or, a switch mounted on a damper operator, to energize an exhaust fan when the damper opened. There are infinite uses for end switches. Check with Honeywell Control Co. or Johnson Control Co.

Try "limit switch" instead of "end switch".

My doubt is this only in HVAC system why they using end or limit switch, they need only circuit breaker or isolators only isn`t, i think it may be related like that one only. any way we need input from the guest who posted this article for further discussion.

You are right: I don't see the link between a limit switch and HVAC.

Would it be that some valves have a position indicator? Could be important in shutters that regulate the amount of fresh air that is mixed in.

When you would use parallel electrical tracing, you could add a Relay to the end: the switch tells your control unit that the order has been translated into power on the bus wires.

Limit switches are built into the motor operator,interrupting the internal motor circuit to stop motor rotation, and generally are not adjustable. There are many varieties of auxiliary switches, everything from SPST, DPDT, through modulating type circuits and with about all amp and voltage ratings. These switches are mostly used in commercial or industrial applications, where complex control sequencing is required. In micro processor electronic control systems, which in a sense are less complex, sequencing is accomplished through programming.

An end-switch is a one that makes or breaks to indicate positive proof of equipment position such as a damper. Ex. in HVAC control systems they are used to prove a damper to be open before a fan starts. They may also be used to illuminate position indicating lights or signal an automatic control system of some action.

There is a nice discussion, diagram and explanation of the function of an "end switch" in a zoned circulated hot water heating system on the Bell & Gossett web site: http://www.bellgossett.com/homeowners/BG-ElectricZoneValves.asp

You lot seriously are idiots.

An end switch is a device that is commonly used to indicate whether a damper is open or closed. They come in various flavors (so to speak). There are mercury end switches that are attached to a bracket that clamps on to a damper shaft. When the damper rotates the mercury makes an electrical switch within the device. Ther are also end switches that utilize an arm attachment. At the end of the switch arm there is a roller. The switch would be mounted in an area of the damper that would allow the damper blade to move the switch arm which in turn makes a switch within the device. End switches are also used in automation equipment such as packaging conveyors.

Hope this helps.