ECN Forum Forums General Topics of the Trade General Discussion Area motor starter overload

I think you should try to simplify the wiring in your own mind first.

You have your line voltage to the motor connected to L1, L2, L3. Your load out to the motor on T1, T2, T3. The load current goes through the 3 heaters and out on the T1, T2, T3 terminals.


Now your control voltage usually has one side of the control power (we'll call L2) connected to one terminal of the overload block. The other end of the overload block connects to one side of the coil. That way if the overloads are ok your coil sees L2 and if the overloads trip it will kill L2 to the coil.

Now you need to take your L1 control side through whatever controls the motor to start it. In this case it might be a pressure switch or an alternating relay. L1 will connect to the other side of the coil from L2 when the pressure switch or relay makes.

The N/O contacts that you describe are usually used when a starter needs a latch-in circuit. I don't believe that is the case here. They also can be used as auxilliary contacts to power other things like indicator lights or open dampers, etc.

Edit: Sorry Don, I didn't mean to jump in on your reply. I was typing (slowly) while you answered.