# Definite purpose contactor/ motor



## Funksparky (Nov 8, 2017)

Hey guys,
I know that you would not want to use a definite purpose contactor to control motor loads, but could you use one in a motor circuit if it never was doing any of the make or break operations? Starting and stopping would be done by the motor starter. The DP contactor would carry the current but would not open/ close under load. It would already be closed before the motor starter closed, and wouldn't open until after the motor starter did. Thoughts?


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## VELOCI3 (Aug 15, 2019)

What is the purpose of that contactor and why does it have to be in series with that motor



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## joe-nwt (Mar 28, 2019)

More info please.


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## Funksparky (Nov 8, 2017)

Load shedding. If motor A is running, motor B cannot be started and vise versa.


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## VELOCI3 (Aug 15, 2019)

Funksparky said:


> Load shedding. If motor A is running, motor B cannot be started and vise versa.



Do it on the control circuit not the motor circuit using a relay. 


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## VELOCI3 (Aug 15, 2019)

Have the coil of starter A energize the coil of a relay in starter B. That relay wi have the run command voltage on the NC of the relay. When A runs it opens the start signal for B. B can only run when A is off. 


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## Funksparky (Nov 8, 2017)

Ok thanks @VELOCI3


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## JRaef (Mar 23, 2009)

The problem with DP contactors is that they are designed to operate just long enough to satisfy a machinery OEM's warranty period, no more. It's not just electrically, it's mechanically too. They are going to cause you more grief in the long run than the money they save is worth.


I take it this plan of yours does not require UL listing as well? Because DP contactors are not UL listed, they are UL Recognized (backward UR symbol), which means they can ONLY be used as part of another UL listed assembly, they cannot be used on their own in the field.


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## VELOCI3 (Aug 15, 2019)

Also some starters have interlocks like E stop etc that are jumped out in the starter because they are not being used. Thats another spot you can break the start command. 


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