# Magnetic starter- wiring an Allen-Bradley 709 3-phase starter for single phase 220v.



## portsample

Hi-
I've got an Allen Bradley (AB) 709-BOD size 1 starter that I'd like to wire for use as a starter on a single phase Baldor 5HP motor. I've got a remote AB "start" and an AB "stop" push button switch that are appropriate for this unit. Is anyone familiar with this application? I've reviewed this wiring diagram:


and am about 80% sure that I've got it figgurd out. 
I'm hoping someone here who has experience with these units can help me with the other 20%. 
Thanks in advance...


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## JimDawson

Use only L1 and L2, don't connect anything to L3

The motor connects to motor terminals T1 and T2, nothing connects to T3

Wire the transformer as shown in the 220V diagram, and you should be good to go. It is a bit confusing when the transformer ''T'' terminals are labeled the same as the motor terminals.


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## portsample

Here is what I have so far. 
View attachment 92900


Am I missing anything here?
I'm slightly fuzzy on the START switch wiring: see comments under the picture.
Note: wiring used in the picture are for conceptual purposes only. Appropriate wire will be used for application.

Thanks a million for taking the time to look this over.


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## jim18655

The power flows through the stop normally closed (NC) contacts and powers both the switch and the #2 terminal on the starter. The #2 terminal supplies power to the operating coil on the starter through the auxiliary normally open (NO) contact mounted on the side of the main contactor. The jumper from the NC stop switch to the NO start switch provides power to the start button. The other side of the start button connects to terminal #3 on the starter. That terminal is connected directly to the operating coil. When you push the start button the contactor coil moves and closes all three main contacts and the auxiliary contact. The auxiliary contact then supplies power from the stop button directly to the main contactor coil and keeps the contactor turned on. Pushing the stop button interrupts the the latching or holding circuit and drops the contactor turning off the power to the motor.
A common mistake is the motor only runs when the start button is pressed and held. This indicates a wiring mistake or faulty parts in the latching circuit.
Please check the coil voltage before you power the circuit since it could have been changed to a different operating voltage. It's not uncommon to find 120 v coils on motor starters. If it is 120v then you need to make sure the L2 jumper has been removed and the neutral connected to the overload relays.
The other thing is I would use L1 and L3 to power the motor. Put a jumper from L2 line to L3 line at the top of the contactor that way you can use both overloads to protect the motor. Size them by the full load current of the motor and the chart that should have come with the starter. You'll need to have both heaters in the starter to make it work so might as well use them.


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## portsample

Okay- I've modified the wiring per above suggestions: 1)moved STOP switch wire to L1, 2)connected the other wire from the STOP switch to one of the Normally Open (NO) contacts on the START switch bundled with wire going to contact #2, the other START switch wire still goes to the terminal shown in the picture, this is just below contact #3. Plugged it in, nothing happened...pressed the START button (closing this switch) and did not hear the magnets closing the circuit. Using a multimeter,  I've confirmed power going through STOP switch and into #2 and START switch, as well as power going through START switch (when held) and into #3 (via the terminal just below #3). 
Shouldn't I hear the switch close at this point and have power going into the heaters? I've attached 2 pictures taken a moment ago. Thanks again for taking a look at this.


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## JimDawson

Does the coil voltage read 120 or 240, I can't quite read it.  And:


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## portsample

It's 120v. Thanks.


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## JimDawson

portsample said:


> It's 120v. Thanks.



Is the input voltage 240? If so then you will burn up the coil wired this way.

You will have to bring in a neutral the get 120 volts to run the start circuit.  Connect the neutral in place of the wire above at the O/L contact, and do not connect to L2 as shown in the picture.


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## jim18655

If the coil is 120v then you'll need a neutral connected to the overload relay circuit. You'll also need a 4 wire cord - 2 hot, 1 neutral, and a safety ground. The overload contacts are the two NC contacts shown after the main coil usually located near the bottom of the contactor assembly.


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## portsample

JimDawson said:


> Is the input voltage 240? If so then you will burn up the coil wired this way.


Negative, this is standard single phase residential to power a 5hp Baldor motor (L3608T).


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## JimDawson

If I understand correctly, you are planning on running a 5 HP motor on 120V?  That is about 50 amps.  It can be done, but is very unusual.  Normally you would run that motor on 240V, that's still about 25 amps.  Also that motor starter might be a bit light for 50 amps.  I think you need at least a NEMA 3 starter for that much current.  Your  (NEMA 1) starter is rated at 27 amps continious.


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## portsample

(2) 120v wires are what the motor is designed for and what is currently running it. The switch on it now is a Grizzley paddle switch (non-magnetic) w/contacts too small for this motor.


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## JimDawson

portsample said:


> (2) 120v wires are what the motor is designed for and what is currently running it. The switch on it now is a Grizzley paddle switch (non-magnetic) w/contacts too small for this motor.



I think there may be some confusion in the terminology here.  At least I'm a bit confused) Does each wire measure 120 volts to ground or if you connect the volt meter across the two wires, does it measure 240 volts?  If so then it would be 240 volt, single phase, standard house wiring.


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## jim18655

If you follow the diagram in your first post the neutral connects to L2 and the 2 hots to L1 and L3. The motor connects to T1 and T3 for 240v.
Jim D. is correct about the large current draw on that size 1 starter. I think you'll need a larger size even at 240v.

*Single Phase Motors*

 Maximum horsepower, full voltage starting, two pole contactors, are       indicated below:

Maximum Horsepower (hp) NEMA Size115 Volts230 Volts001/31012123237.537.515


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## portsample

JimDawson said:


> I think there may be some confusion in the terminology here.  At least I'm a bit confused) Does each wire measure 120 volts to ground or if you connect the volt meter across the two wires, does it measure 240 volts?  If so then it would be 240 volt, single phase, standard house wiring.



My mistake, yes it's 2 x 120v.


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## JimDawson

Gunrunner you need to order a set of these for the Z axis hand crank. Bill did you just spit coffee on your monitor? :rofl:

View attachment 253356


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## portsample

This works.


Thanks for the help.


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