Stray current? How to test for/acceptable levels

[Bri Guy]

I was wondering what is the best way to test for stray current? And what levels of current are acceptable.

I have a chiller (1/10 Current prime) that when plugged in causes my pH probe to give false readings. Im thinking stray current, but it could just be electrical disturbance. How could you narrow out the possibilities of each?

I have a multimeter with 12+ different settings, I have read something about hooking one to the ground and one to the water, but on what setting?

The chiller does NOT trip my GFCI

Thankx

 

[jdieck]

Black on ground red in water. Have your lights ON and start by measuring AC Voltage starting with a setting of 250 Volts and switch to a lower setting one at a time until you get a reading, repeat the process but measuring DC Volts. Tur off your lights and repat the process. Repeat the process with the chiller ON and OFF.
Depending on the system voltage is usually 1 or 2 volts and have seen it up to 20 but as far as it has no current capability then there is no issue.
To test for current use AC Amps and start at the highest setting (Probably 10 Amp. and keep lowering the scale. You should get no current at all even if you have a voltage reading, if you do then turn each piece of equipment off until it disapears to find the culprit.

If you find no current and your PH probe is still unstable there is a chance your system might have a ground loop where two or more different devices are grounded to different ground levels (usually when grounded to two different circuits.

 

[Bri Guy]

Thankx!

I had already narrowed it down to my chiller being the culprit.

The first reading I got off my tank was with the chiller UNplugged, DCV 20, and my reading was -0.14, then I plugged in the chiller (now I am plugging it into an aquacontroller DC8, so even though its "OFF" it still has the trickle of electricity going to it) and my reading was -0.46! Twice as much as everything else in my tank just from the chiller.

I have not tested it with the chiller running yet, but just plugging it in is enough to make my pH reading go from 7.89 to 9.86

Any cures for this?

 

[jdieck]

<a href=showthread.php?s=&postid=12925960#post12925960 target=_blank>Originally posted</a> by Bri Guy
Thankx!

Any cures for this?

The DC8 might be connected to a different house circuit with a different quality of grounding than the controller so there could be a ground loop. If it is not already in the same circuit try connecting the DC8 to the same house circuit (outlet) than the controller.

Another possibility is to check if your chiller is connected to either outlet 4 or 8 of the DC8, if not then use any of those two outlets (4 or 8) for the chiller.
In newer DC8, the outlets number 4 and 8 are actuated by a relay that positively disconnect the devices plugged to them. All other outlets 1-3 and 5-7 are actuated electronically (triacs) and may still have a small amount of leaked voltage into the device.

 

[Bri Guy]

The chiller is plugged in to outlet #1, Ive tested with the multimeter with it plugged into a totally different outlet, and the readings I get are the same as through the DC8. So I can rule out the plug in on the DC8.

The ACjr. is plugged into a power strip which is in a GFCI outlet, the DC8 is plugged into the same GFCI outlet, if that helps clear up my possible "ground loop"

The current jumps to all 3 of my tanks in the system, and my two ground plugs do not effect the current levels when I take them out, they don't raise or lower.

Nothing in my tank was ill effected during the week it ran this way, except for my off pH reading.

Would neptune's Ground Isolated Serial Connector work in my situation?
http://www.reefgeek.com/equipment/C..._Isolated_Serial_Connector_by_Neptune_Systems

 

[jdieck]

The Ground Isolated Connector is only needed if you have a computer connected to the controller via the serial port. If you do then you need to install the isolator.

Ground Probes should affect the readings if they are properly grounded.
Did you tested current or only voltage?
Can you test for current with and without the chiller connected and without the probes in the water?
Note that if there is a current leak into the tank while the probes are out, the test may trigger the GFCI.

What is the current level?

 

[Bri Guy]

<a href=showthread.php?s=&postid=12927131#post12927131 target=_blank>Originally posted</a> by jdieck

Did you tested current or only voltage?

What is the current level?

Im not sure the difference or how to? I used the DCV 20 for the readings above, the meter comes with settings for DCV, ACV (but only 750 or 200), DCA, and a horse shoe looking symbol with a range between 2000K and 200. Should I be using one of these settings instead?

I tested out my ground plugs, they do work, and do make a very small difference when I put the meter on DCV 2000m, should they be making a larger difference?

A reading of -0.46 on DCV 20, would this be the equivalent of like 9 volts?

thank you for all your help jdieck!!!

 

[USC-fan]

Yeah could someone show what setting to use on a volt meter.

I have the Black in [com] and the red in [v]

With the voltmeter set at ~v I get 000, should I remove my ground probe?

With the voltmeter set at -...v I get .346

 

[jdieck]

<a href=showthread.php?s=&postid=12928073#post12928073 target=_blank>Originally posted</a> by Bri Guy
Im not sure the difference or how to? I used the DCV 20 for the readings above, the meter comes with settings for DCV, ACV (but only 750 or 200), DCA, and a horse shoe looking symbol with a range between 2000K and 200. Should I be using one of these settings instead?
No, DCV and ACV are both for voltage. DCA is for measuring current (Amps) but only for DC the the reanges are most probably milliamperes which is too low of a range and may damage the meter. It does not have measurement of ACAmps which is what you need.
The one with the Omega symbol is to use for measure electrical resistance and should be used only on systems with no power (disconnected)

I tested out my ground plugs, they do work, and do make a very small difference when I put the meter on DCV 2000m, should they be making a larger difference?
How did you tested them? at 2000 millivolts if you measured between the probe (submerged) and the ground outlet you should have exceeded the scale maximum as you will be measuring the tank DC voltage

A reading of -0.46 on DCV 20, would this be the equivalent of like 9 volts?
This reading of negative 0.46 tells that the polarity was inverted (no issue) and that the DCV is only 0.46 volts (half of a volt or 500 millivolts) which may show only that there is electrical noise in the system. This noise is usually created by ballasts and sometimes by DC motors which you might have none in the system)

thank you for all your help jdieck!!! [/B]

Do you have a computer permanently connected to the aquacontroller? If so, disconnect the cable from the computer and see if the problem persists. If the problem goes away after disconnecting the computer then you need to get the ground isolator.

The interference can also come form a different source and there is a procedure to try to detect it but if you have a connected computer try that disconnecting test first.

The procedure to check for interference from a device with the aquacontroller is:

In the aquacontroller go to the SECOND screen of “self test”.
1. Scroll to self test. Press select (first screen of selftest), press select again (second screen of selftest)
2. Press up button twice, down button twice, and then the select button

You are now at the manual calibration screen. See if there is a variable (Sy) whose value should be steady and it is typically at 63 or 64. Some appliance (most likely an electronic ballast or the chiller) is generating a great deal of radiate EMI (Electro Magnetic Irradiation), and interfering w/ the operation of the AquaController. Shut equipment off one at a time, and until the Sy value goes steady at about 63 or 64. Once the problem equipment is identified physically route the telephone cord between the AquaController and DC8 and the PH probe cable as far away possible from the device causing the interference.

 

[jdieck]

<a href=showthread.php?s=&postid=12928199#post12928199 target=_blank>Originally posted</a> by USC-fan
Yeah could someone show what setting to use on a volt meter.

I have the Black in [com] and the red in [v]

With the voltmeter set at ~v I get 000, should I remove my ground probe?

With the voltmeter set at -...v I get .346

All test should be done iwth the ground probe removed.
Because all equipment we use is AC (except PH, conductivity and ORP sensors) the voltage is any will be AC (alternating current also indicated with a tilde ~)
Voltage for direct current (indicated by DC or three dots with a horizontal line on top) in an AC systems is detected usually due to electrical noise in the line that can be created by ballasts, PC or VHO bulbs and motors.

Try both tests but with the probes removed.

By the way, for this kind of test the conection of the meter leads make no difference in AC although there is a preference to use the com for the black lead conecting to a potential neutral and the red to V and conected to were the hot wire might be.

For DC the conection of the leads make a difference, If as you described the black (negative terminal) lead is in Com and the red one in V; if you get a positive number that means that the voltage being read is higher at the point were the red lead is connected. If you get a negative number the voltage being read is lower at the point were the red terminal is connected to the system being measured.

 

[rick s]

jdieck,

I'm thinking that: If I have ground probes in both my sump and display tank, and everything is run through GFCI's, then I can't have any voltage or current at a level that would be of concern to fish or corals (or me) because if I did, it would trip the GFCI. Is that true?

 

[jdieck]

<a href=showthread.php?s=&postid=12973478#post12973478 target=_blank>Originally posted</a> by rick s
jdieck,

I'm thinking that: If I have ground probes in both my sump and display tank, and everything is run through GFCI's, then I can't have any voltage or current at a level that would be of concern to fish or corals (or me) because if I did, it would trip the GFCI. Is that true?

Yes in general that would be true unless the grounding of the probes is not optimal or the GFCI is defective and do not trip.

 

[rick s]

Thank you Sir.

 

[jdieck]

:thumbsup: