# 3 source Transfer Switch mechanical Interlock



## Mista Bojangles (Feb 15, 2015)

Hey guys, 

I'm in the process of building a 3 source ATS out of 3 separate contactors. I am easily able to Electrically Interlock them, but when I attempt to find a way to mechanically Interlock them, I only find different ways to mechanically Interlock 2 contactors. Is there anything out there that will do more than 2? Any suggestions will be greatly appreciated!


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## inetdog (Apr 13, 2016)

You may have to build it in the form of one contactor selecting A or (B or C) and then using a second contactor to select between B and C.
Trying to do it by only allowing one of three parallel NO contactors to close sounds like the hard way to do it.
JMO.
You could build a "maximum one out of three" interlock using three pins and two sliding interposer links such that at most one pin can be down. You can see examples of that in old multi-button switches. But it would not be Listed and good luck getting it by an AHJ.


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## Bird dog (Oct 27, 2015)

Any way to group them? For example, if you have two backup gensets and utilty power, feed one ATS with the two gensets then send that output to the second ATS with the utility power.


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## Mista Bojangles (Feb 15, 2015)

Can't group the sources. It's for an inverter/generator/grid connection for a large RV.


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## donaldelectrician (Sep 30, 2010)

Build one yourself ... I do not think you will find one .




Don


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## AK_sparky (Aug 13, 2013)

inetdog said:


> You may have to build it in the form of one contactor selecting A or (B or C) and then using a second contactor to select between B and C.


Yup, exactly like this. It will take an extra contactor to do it though.


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## Pantera3k (Mar 10, 2016)

kind of three pole triple switch (by default mechanically interlocked)
maybe like that
http://www.amazon.com/dp/B00NG83MLW...SIN=B00NG83MLW&ascsubtag=-8898393763365099675


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