New Century Pump Motor - Has Power - Won't Start

something_amusing

New member
Sep 2, 2020
3
Daphne, AL
I just installed a new Century UST1102 motor on my Hayward Super Pump. Actually the second new motor today. I think I blew the first one when I had it set to 115 when it was actually wired for 230. Anyways, the newest new one is set to 230 and all hooked up. I can test the connection points on the back of the motor and I show about 115V on each leg. So I've got power. But the pump doesn't do anything. No noise, movement, nothing. Any suggestions?
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
19,155
Bedford, TX
SA,

Having 120 volts on each leg is not the correct way to test for 240 volts.. When the pump is hooked up you can get a false reading doing to that way.

The only way to test 240 is to measure between L1 and L2.. and get 240 volts..

Test again and tell us what you get..

Thanks,

Jim R.
 

something_amusing

New member
Sep 2, 2020
3
Daphne, AL
Well, learn something new every day. Had no idea that was how to measure 240. I checked across both hot leads and got 0 voltage. Not sure what that indicates.

If it matters, the 240 comes from a tandem set of breakers.
 
Last edited:

JamesW

TFP Expert
Mar 2, 2011
20,757
One of the power wires is not getting power. You will have to check the voltage at the breaker. If the voltage is not 240, the breaker is bad. If the voltage is 240 at the breaker, you have to check the voltage at the switch.
 

JamesW

TFP Expert
Mar 2, 2011
20,757
You can check each wire to ground if the wires are disconnected from the motor.

If the wires are connected to the motor, the voltage will transfer through the windings and show up on the other terminal.
 

workedonthousandsofpools

In The Industry
Jan 9, 2020
10
Phoenix
You have to use a 240v breaker, you cant use two 120v breakers and think of it as adding up to 240v, this is what it sounds like possibly based on the measurements you took at the pump, if you had a reading of 120v on L1 to ground, and 120v on L2 to ground, but 0v on L1 to L2 this would explain 0v

On a 240V breaker, when connected at the motor, doing the same test would show 120V at L1 and ground, 120V at L2 and ground, and most importantly show 240V at L1 and L2.

you cant take two 120V hot wires each connected to there own breaker and get 240V when probing each wire you would get 0V, but each wire tested against ground will show 120V because there 120V circuits, so two hot wires each connected to there own 120v breaker will not equal 240V together.

in order to get a reading off of 2 wires that will show 240V on the meter the 2 wires have to be connected to a 240V breaker

Its not that testing each leg or line independent of the other is wrong, being that they each read 120V, when measured together they both would read 240V, if there on a correct 240V circuit with a 240V breaker. ....if I didn't get 240V on L1 to L2, then I wont get 120V when testing L1 to ground or 120V on L2 to ground on a correct 240V circuit
 
Last edited:

conedman54

New member
Jun 7, 2020
3
Sarasota
Your measuring correctly but your circuit is probably wired to the same 120VAC phase. You need a 120V source from each phase or hot leg. Use a 240Vac breaker, having 2 separate breakers is a code violation and dangerous if you ever forget to shut one off or shut an incorrect breaker instead.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
19,155
Bedford, TX
SA,

Just to be clear... When the pump is installed and connected to the input power line, measuring L1 to ground and L2 to ground and adding the two voltages together to get 240 is absolutely wrong... With the pump installed, you will measure 120 Volts on both L1 and L2 even if one of them is missing.. With the pump installed you must measure L1 to L2..

If the pump is not installed, then measuring L1 to ground and L2 to ground will work just fine.

Since everything was working before your original pump went bad, then I doubt it has anything to do with original wiring being connected to the same phase of AC.

Most likely one side of your breaker has opened or there is an open in either the L1 or L2 line going to the pump. Let's hope it is at some timer or switch, because the other option is an open wire.. We just recently saw one where the wiring inside a metal conduit had shorted to the conduit and burned in half. ☹

Thanks,

Jim R.
 

something_amusing

New member
Sep 2, 2020
3
Daphne, AL
To be clear, its two breakers stacked one over the other with a piece connecting the switches so they always move together. This ensures they are on different poles/phases and you can't turn just one off. I'm not sure about everywhere else, but in the houses I've owned, that has been common practice for all 240V appliances. Never had a single 240V breaker. On the other hand, I'm no electrician. Fairly obvious given I didn't know how to test 240V at the motor.

The pump is installed, so the L1 to L2 is what I should measure according to what I'm seeing here. And that shows 0V. Gonna check the breakers next. Hopefully one of them shows 0V. Much easier to replace that.
 
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JamesW

TFP Expert
Mar 2, 2011
20,757
Your measuring correctly but your circuit is probably wired to the same 120VAC phase.
The voltage being measured at both terminals is coming from the same 120 VAC phase, but it's not because the wires are connected to the breaker panel incorrectly. It's because one wire has lost connection with the panel. The voltage being measured at both terminals is coming from the live wire. The voltage transfers through the windings from the live wire terminal to the dead wire terminal. If you take the wires off of the motor terminals, then you would measure 120 volts on one wire and 0 volts on the other wire.
 

JamesW

TFP Expert
Mar 2, 2011
20,757
If you have a live wire connected to motor terminal L1 and a dead wire connected to terminal L2, and you disconnect the dead wire from terminal L2 and measure the voltage from terminal L2 to ground, you will get 120 volts. The voltage is coming from the live wire. Terminal L1 and terminal L2 are connected together by the motor windings. So, the voltage is the same at both terminals when there is no current flowing.

The windings have resistance, which causes a voltage drop, but only when the motor is working correctly and current is flowing.