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mehranalmasi 06-20-2007 06:20 PM

Problem with line voltage
Hi experts,
I am upgrading a swimming pool and have noticed a problem with the voltage to one of the pumps.
Basically there are two pumps for the pool. One is for filtering and one for the sweeper. The pump connected to the filtering wiring does not run but if I connect the same pump to the sweeper wiring, it works. I could see that both wires going to the filtering pump have power but when I looked closer and compared to the reading on the sweeper lines, the filtering lines register less voltage.

The filtering pump used to work. So the question is: could a slightly less reading on the voltmeter be the cause? if so how can I find the source of this problem? I have used a sandpaper to clean all the contacts between the pump and the switch.


Sammy 06-20-2007 07:20 PM

What kind of upgrade are you doing to the pool?

How much voltage difference are you getting between the two?

Most pool fliter and boosters pump/vacum motors run on the same line.

jwhite 06-20-2007 07:20 PM

As a general rule, a little less voltage is not a problem.

what are the exact readings, and where were you testing when you got them.

mehranalmasi 06-21-2007 11:54 AM

I measured the voltage at the timer's output and at the contact point on the pump. I have to go back and do an exact measurement to report back.
If the small difference is not the cause of the motor not turning, then what could possibly cause it?
The pool itself is getting replastered and I am replacing the filter pump.

NateHanson 06-21-2007 12:17 PM

If the voltage is substantially lower, the pump motor won't turn. Pumps and electronics are fairly picky about voltage.

However, if the voltage drop isn't enough to cause the problem you're having, then perhaps it's a loose neutral connection in the wires feeding the second pump's receptacle.

mehranalmasi 06-21-2007 05:02 PM

thanks Nate, to remove any wire or connection doubts, I replaced the line going from the timer box connectors to the pump itself. This basically replaced the three wires going from the timer to the pump with solid connections with neutral wire connected to the timer ground on one end and pumps ground at the other. This test made no difference.
Do you have any idea at about what voltage the pump would fail to turn? Also what could cause the voltage drop at I see it? I have not verified but I am assuming the wiring is typical for a pool, from the timer going to the breaker box.


joed 06-21-2007 07:01 PM

If you are using a digital meter you might not actually have any voltage. Digital meter sometimes read phantom voltages.

Sammy 06-21-2007 07:24 PM

I would test at the motor connections for the filter pump... Since you have switched motors and know the filter pump motor is good, you have eliminated that as an issue. I would temp wire out the filter motor at the pump without it being connected to the pump for a short time to see if you have a pump problem versus a motor problem. May be some construction debris in the pump thats keeping it from turning. Check the ground wires also.. Most pool installs have a seperate ground rod and a ground wire connecting both motors. Are you doing the pool upgrade or someone else i.e. why arent they handling this?

Speedy Petey 06-21-2007 08:31 PM

OK. First off, what does this mean??? Neutral and ground are NOT the same thing! Please explain further. Are the pumps 120v or 240v?

Originally Posted by mehranalmasi (Post 49970)
......with solid connections with neutral wire connected to the timer ground on one end and pumps ground at the other.

Also, most (CORRECT) pool installs do NOT have a ground rod (just) for the pumps. If they did it would have NO bearing on how the pumps run. All correct pool installs have a BOND wire connecting all metallic items associated with the pool bonded to create a level ground potential. This bond also has NOTHING to do with pump performance.

A loose connection somewhere might show proper voltage with no load, but as soon as a load is placed the voltage goes away. I suspect this is the problem.
Do not just throw fixes at this problem. Troubleshoot it and find out what is wrong. Check ALL connections and terminations, from the first breaker to the last pump.

mehranalmasi 06-22-2007 02:13 PM

Hi Speedy Petey,
sorry for the confusion. I should have said neutral since both pumps are 240v. As for your suspect cause, is there a way to verify it? If the filter pump is connected to the problem wiring and I turn the switch on, and still read about 120V on two lines powering the motor, does that help confirm or disconfirming what you are suspecting?
Maybe I should disconnect the wires at the main breaker box and see if there is still voltage at the pump timer?

Speedy Petey 06-22-2007 07:14 PM

If the motors are 240v then there is NO neutral. A 240v motor has two hots and a ground, only.

Do you read 240v line to line with the motor connected? If you are reading 120v to ground on each leg then you might be getting a backfeed through the motor.

Connect the motor, turn it on and test from line to line. Tell us the result.
Do the same test at the breaker connections.

mehranalmasi 06-26-2007 05:21 PM

I got a hold of digital meter and measured 122 to 125 V on each line, when not connected to the motor.
Speedy Petey, when you say line to line, do you mean one of the meter's probes connected to one of the motors connector and the other probe on the other, while both electical lines and the ground are connected to the motor?

Speedy Petey 06-26-2007 07:57 PM


Originally Posted by mehranalmasi (Post 50540)
Speedy Petey, when you say line to line, do you mean one of the meter's probes connected to one of the motors connector and the other probe on the other, while both electical lines and the ground are connected to the motor?

Also, so the same test but across the two feed wires, but disconnected from the motor.

mehranalmasi 06-27-2007 11:06 AM

I think you are on to something Speedy Petey. I just had a few minutes to test so I put my analog meter to the two wires going to the motor without the motor connected. The needle barely moved when set to 150 VAC Max I have on the meter.
I did the same thing for the other wiring going to the sweeper motor (that runs both motors) and the needle jumped!
What can this mean?


Speedy Petey 06-27-2007 01:22 PM

You likely have an open on one of the wires. Did you check each one to ground while disconnected?

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