Pump Humming

[Riles_J]

I have a pool pump that was throwing the breaker after a few seconds. Thinking it was a short somewhere I began investigating and thought it was the wire connecting to the pump. I replaced that section of wire. Now it will not throw the breaker, but the pump will hum after about 2 minutes for around 5 seconds and then stop and then hum again about 2 minutes later. The pump does not shut off though during the hum. The hum can also be heard in the circuit breaker. I am guessing every time the pump hums the circuit breaker hums (but not throw) at the panel. I took some reading at the panel and I am getting 120v out of each side of the breaker and then when I hear the humming the voltage seems to drop on one side to about 115v and then increases on the other side to 124v. When disconnecting the pump altogether I do not get any hum at the breaker (I did not measure voltage on each side when disconnected so I don't know if there is still some fluctuation). This certainly screams a bad pump to me, but I am hoping it is a bad breaker. Any assistance out there is appreciated.

Riles

 

[tsunami]

When the contacts inside the breaker starts to fail, the breaker in question could feel noticeably warmer than the rest of the breakers. The heat is from the electricity trying to "arc" it's way across the bad contacts. Eventually, the contact burns open far enough that the electricity can no longer arc it's way across, and you'll get no voltage on the load side of the breaker. I've heard a failing breaker make a ticking sound when the contacts were arcing, but no hum. You could swap out similar breakers in your panel to test if it's your breaker or not. (not recommended for anyone without electrical experience)

Is the pumps breaker a 120v or 240v? Were the voltage reads that you were taking before and after (line side and load side) the pump's breaker or at the main breaker?

A bad neutral before your meter could cause the voltage on each of your 120v lines to fluctuate up and down, but you'd notice that throughout the house.

 

[Riles_J]

The pump is running at 240V from a 2 pole breaker in the panel. The voltage is reading 240 at the panel and at the pump, so I don't think I have a breaker problem. One interesting thing I found was that the previous owners had a switch run inside the house that we use to turn the pump on and off. Well they only interrupted one wire, or half the current and ran it up to the switch and back down. Could this have caused some issues with the pump motor? I have since taken the switch out of service and that is not causing the current issue the humming.

Riles

 

[spishex]

You are exactly right. Cutting off only one leg is a great way to cut the life of a motor short. What you are describing, the HOH or Hum-Off-Hum cycle, is created by a switch inside the motor that cuts it off when it overheats. Since your motor shaft isn't moving, it is constantly overheating.

You might open up the back of the motor and give the shaft a twist, minding the electricity of course. If the shaft still turns freely and the motor will run on a kick start, you can try replacing the capacitor, usually right there under that back plate.

 

[tsunami]

.....One interesting thing I found was that the previous owners had a switch run inside the house that we use to turn the pump on and off. Well they only interrupted one wire, or half the current and ran it up to the switch and back down. Could this have caused some issues with the pump motor?

Riles

I think it's very possible. You basically have a low voltage situation every time you turn off the pump, since you're not actually turning it off. Low voltage, as well as high voltage can damage equipment. I don't think that pool equipment would be any different. I'm new to pools so we'd have to see what the experienced pool guys say.

 

[Riles_J]

sphishex,

The pump seems to run fine when it is powered up. I get great flow through the returns. Even when the pump is humming it does not appear to be turning off the motor. At least the return flow seems uniterupted when the humming starts.

Aside from the humming the pump seems to operating as it should, however, I don't want to run it until I figure out what the problem is as I fear the electrical issue might cause some larger problems.


Riles

 

[spishex]

Ah, sorry about the misunderstanding! The voltage drop on one leg still sounds like a motor that is going bad thanks to that switch.

I'd assume the motor is going to fail soon and would recommend replacing it if you're planning on running through the winter. If not, shut it down and ride it 'til it dies. I'd just hate for you to be stuck for a week in January with no water flow while you wait for your new motor to arrive.