Momentary vs Maintained In 3-Pos Switch

Mark Snodgrass said:

Hey guys, I am looking for your opinions on 3 position push pull switches. When using them for other than emergency stops, is it better to use momentary in or maintained in switches? We use both at different control panels, neither has caused much issue one way or another. Is it perhaps just operator preference or are there real pros and cons to each type?

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I'd say it's application dependant.

kalabdel said:

I'd say it's application dependant.

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Agreed.

But one thing I have done and like to do when that type of control is wanted, is to use a version that is momentary when pulled, i.e. Start, then maintained when pushed, i.e. Stop. The reason is that in a large PB console, by being maintained when pushed you know which button was the one that stopped a process. Lights can do that too, but lamps can burn out (or used to...) plus it's an issue when there are 50+ illuminated buttons on a panel.

Jraef, Your reasoning makes sense. Is there any kind of standard or code (NEC, NFPA 79, UL, etc..) that specifies one or the other in certain cases? I have looked and have not been able to find one, but maybe I am looking in the wrong places.

I always use maintained for emergency stops of course, and I find plenty of information on that.

Perhaps in the future as I design panels I will follow Jraef's lead and use maintained as a standard, his reasoning makes a lot of sense.

If you need to integrate an HMI into the mix, momentary is probably the better of the two.