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



"Proctologically Violated©®" wrote in
message ...
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. ouch
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.

--
------
Mr. P.V.'d (formerly Droll Troll), Yonkers, NY

Stop Corruption in Congress & Send the Ultimate Message:
Absolutely Vote, but NOT for a Democrat or a Republican.
Ending Corruption in Congress is the *Single Best Way*
to Materially Improve Your Family's Life.
The Solution is so simple--and inexpensive!

entropic3.14decay at optonline2.718 dot net; remove pi and e to reply--ie,
all d'numbuhs

"Tazz" wrote in message
...
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