Single phase manual motor starter

[Tazz]

I have installed 120v manual motor starters forever. Also install magnetic 3 phase motor starters forever

I recently bought a 230v motor for a pump for the deerlease and wanted to install a manual motor starter for it. I sized the overloads according to the nameplate and Sf etc etc.

But what got me was that the manual motor starter only takes out one leg of the 230v when it trips on overload.

I think this is a bad thing. Although the motor wont work on one leg of 115v Why would anyone engineer it that way?

I thought it was code that you had to open ALL legs to motor when it trip on overload.

If you have a 3 phase motor on a magnetic there are 3 sets of overloads that will trip the system. Any of them that will take out all 3 phases

[RBM]

The idea is to stop the flow of current to the motor before damage occurs, which it does. You are still required to have a disconnect within site from the motor, which will disconnect all power to the motor

[Proctologically Violated©®]

I think you are confusing legs w/ phases. Altho there are, in fact, two legs going to your 230V motor, it's only one phase (two legs in series), and interrupting either one will do the job. This is not at all unusual. Altho, most shut off swtiches will be double pole. Altho, you could get away w/ a single pole switch as well--just not entirely safe, as parts of the motor are always then "hot". Sorta like putting a swtich on a lite fixtrue on the neutral side. In 3 ph, the situation is not so simple, and heaters, etc. are req'd on all three legs. Altho I have seen starters where only 2 of the three legs were protected. :)

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[Tazz]

Completely understand that single phase will have two legs. I just am suprised that is is not against NEC to open all the conductors ( excluding the ground) for the exact reasons you mentioned below. There is the potential there of 115v. at the motor that in my opinion just doesnt need to be there in an overload situation.

Thanks for the reply

[RBM]

A 3 phase started needs to monitor all three legs, because the motor will run, and burn out on single phase. A single phase motor, regardless of voltage, only needs to disconnect one leg to kill the circuit and protect the motor. Motor starters are strictly for motor protection, disconnect switches which disconnect all non grounded legs are for people protection

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