Single Phase motor breakers - 1 or two poles?

TimD

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Join Date
Aug 2007
Location
New Hampshire
Posts
235
Hi, I am going to build a small 2-starter motor control panel. I have built three phase starter panels before, but this is my first, using 230v single phase motors.

Granted, I'm no electrician, I like a lot of programmers like 24vdc! I probably shouldn't build this, but I've done a dozen three phase panels already, and this is small, and I'll learn something...

This panel will be inspected by a licensed electrician prior to service.

I have 2 questions:
#1 Should I use double or single pole breakers to protect the motors?

#2 If my service is 230v, is there an easy way to get 110v for my controller without using a transformer?

Thanks very much!

Tim
 
#1 230 Volt single phase = 2 pole breaker

#2 This depends on the service, if there is a neutral (white wire) available or not. Phase to neutral should read 115 volts on your meter. Or you could just order your motor starters with 230 volt coils.
 
Thanks 72hdflh,

I'll ask the electrician if he is bringing the neutral wire along, then I can tap off of it inside the panel or at the disconnect.

Thanks Again
 
My electrician mentioned not needing a transformer. Maybe I'll get one to be safe. Looks like AD has some for under a hundred bucks including fuses, cover and clips.

I am going to use 24vdc coils for the starters. I just like doing starters that way. Dunno why, but they have never failed me.

Thanks
 
Tim
230 volt control is not IAW with a NFPA standard (I forget number - 79??)for machinery.

The other thing I would consider is IF you are installing this in a wet or in a washdown area use 24 volt controls. Make sure you run motor feed conductors in one conduit and control wiring in another.

Dan Bentler
 
Hi Dan,

Yes, I'm using 24v starter coils, always do.

I also (usually) separate control from high voltage whenever possible.

Thanks!
 
When connecting Line to Line you must use a breaker with a pole for each line.

Line to grounded counductor, i.e. neutral, you can use a two pole breaker if your want but its not really necessary.

I recommend using a transformer to derive your 120 control voltage and I also recommend that you bond one side of the trasnsformer secondary to ground so that the secondary doesn't float.

A0505081.JPG
 
Don't do what I did, (QUOTE), "OOPS I should'nt have done that". Recently I was told to redo a machine that did'nt work. So I took everything off and reworked it. New controllers, New light curtians etc. The machine needed 230 volts single phase for the motor. And 120 volts for the controller and etc. In the shop, I Measured everything, Re-wired everything, And the bosses saw that this new rebuild was a new reliabile machine. So I moved it to the press, Where the 3 phase plug on the press was backwards. Using no transformer to get the 120 volts I found out that there is something called a wild leg on 230 volt to neutral. Which set fire to everything that ran off of 120 volts. Needless to say I reversed the plug.
 
What ndzied1 said. If all you have are the contactors, then just get a small 24VDC power supply. Automation Direct has some starting at around $60. The only time I ever even think about AC coils on contactors is if running something that requires an 80A or up contactor; small stuff is a lot easier on everyone at 24V.
 

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