Seal leak detection for submersible pump

[Dsg319]

I have installed submersible motor in a sump pump with both thermal switch, and seal leak detection.

From which it uses a 5VDC sense voltage from a probe inside to the metal chassis of the motor to test for leakage.. The product is a 8pin relay with adjustable settings. 201-100-SLD (will leave. Website for info)

I have no experience with this device, and first time dealing with sump pumps.

Question is, I have the seal leak detection conductors (everything single conductors) installed with the power conductors 208v/3ph, the sump pump only has 1port for entry. Do you think I will have problems with false seal leak detection due to induced voltages from the power conductors?

The common/input back to the relay that tells it there is a leak is bonded to circuit EGC from being attached to the motor chassis, will that take care of any induced voltages?

Fell free to correct me on anything as I really have not had much research in to how this thing works exactly.

201-100-SLD

<p>201-100-SLD is a single-channel, seal-leak detector with input voltage ac of 110–120 nominal and sensitivity at 4.7 k–100 kΩ.</p>

m.littelfuse.com

 

[Dsg319]

Here’s some images.

 

[gar]

211003-1018 EDT

A DC probe electrically conductive type liquid level sensor is not generally a good approach. Their pulsing approach my somewhat reduce the problem of polarization.

Their resistance sensing range of 4.7 to 100 ohms seems to be way off base.Take an ohmmeter and put two wires into tap water and see what resistance you read.

If one uses DC, a long enough test pulse, and substantial filtering noise may not be a problem.

I think a higher probe voltage might be desirable.

.

 

[Dsg319]

211003-1018 EDT

A DC probe electrically conductive type liquid level sensor is not generally a good approach. Their pulsing approach my somewhat reduce the problem of polarization.

Their resistance sensing range of 4.7 to 100 ohms seems to be way off base.Take an ohmmeter and put two wires into tap water and see what resistance you read.

If one uses DC, a long enough test pulse, and substantial filtering noise may not be a problem.

I think a higher probe voltage might be desirable.

.

Thanks for the info, and this come built into an explosion proof motor starter. So this will probably stay unless the customer decides to change it.

In laymen terms is this leak detector basically just preforming a continuity test?

 

[Dsg319]

Also the 4.7-100ohms is incorrect. I must have the wrong model number because I remember it having a much higher range. Will be there tomorrow to look.

 

[gar]

21003-1303 EDT

Dsg319:

I looked at your data sheet. The resistance set point range is 4.7 k to 100 k. That make more sense.

A probe type liquid level detector typically consists of some reference conductor, in this case the enclosure the probe is in, and an insulated probe. With no liquid contact with the probe the resistance between the reference conductor and the probe should be very high. Then if a conductive liquid, most normal water is moderately conductive, comes in contact with both the reference electrode and the probe, then a lower resistance occurs and can be detected,

.

 

[Dsg319]

21003-1303 EDT

Dsg319:

I looked at your data sheet. The resistance set point range is 4.7 k to 100 k. That make more sense.

A probe type liquid level detector typically consists of some reference conductor, in this case the enclosure the probe is in, and an insulated probe. With no liquid contact with the probe the resistance between the reference conductor and the probe should be very high. Then if a conductive liquid, most normal water is moderately conductive, comes in contact with both the reference electrode and the probe, then a lower resistance occurs and can be detected,

.

Thank you for the explanation, makes more sense now. Do you think being in the same raceway with the motor branch circuit conductors will have any effect on this detection circuit?

 

[don_resqcapt19]

I have never seen a submersible pump with leakage detection that was not oil filled and did not have a factory installed cord. Seems strange to me.

 

[Dsg319]

It

I have never seen a submersible pump with leakage detection that was not oil filled and did not have a factory installed cord. Seems strange to me.

It does have 50’cord for power conductors and another 50’cord for thermal switch and leak detection. But only one conduit for them to exit the sump and next to the power conductors back to the motor starter.

 

[ZZZ]

It is very unlikely that the probe circuit would be electrically connected to the pump housing in any way. The probe has two wires and it is sensing the resistance of the oil between two closely mounted electrodes, and it is not sensing anything to the motor housing. It is looking for a drop in resistance (due to moisture) in the oil that allows the 5 volt current to flow between the electrodes and actuate the relay. If there was a chance that the power wires would influence the sensing current, the manufacturer would have used a shielded cable for the probe to avoid that from happening. Contact Littlefuse Technical support to be sure.

 

[gar]

211003-2334 EDT

ZZZ:

Second paragraph of post #1 says

"From which it uses a 5VDC sense voltage from a probe inside to the metal chassis of the motor to test for leakage."

.

 

[Dsg319]

It is very unlikely that the probe circuit would be electrically connected to the pump housing in any way. The probe has two wires and it is sensing the resistance of the oil between two closely mounted electrodes, and it is not sensing anything to the motor housing. It is looking for a drop in resistance (due to moisture) in the oil that allows the 5 volt current to flow between the electrodes and actuate the relay. If there was a chance that the power wires would influence the sensing current, the manufacturer would have used a shielded cable for the probe to avoid that from happening. Contact Littlefuse Technical support to be sure.