Using ground probes in aquariums

Discussion in 'Reef Aquarium Discussion' started by Brew12, Oct 20, 2016.

  1. marvelousone

    marvelousone Active Member Louisiana Reef Club

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    I had my hand in the tank today. While my hand was in the water my shoulder hit my light fixture. I got a shock. It is a 8 bulb t5 fixture. Does that mean my light fixture has a short even though all bulbs are working.
     

  2. Brew12

    Brew12 Electrical Gru R2R Supporter R2R Excellence Award Reef Squad Leader Article Contributor Build Thread Contributor Partner Member 2018

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    More than likely it is the other way around. You probably have something faulted in your tank and the light fixture provided a path to ground. I'm assuming you don't have a ground probe.
     
  3. marvelousone

    marvelousone Active Member Louisiana Reef Club

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    No do not. I did not know there a such thing till tonight. I put my hand in the sump and I don't feel anything.
     
  4. Brew12

    Brew12 Electrical Gru R2R Supporter R2R Excellence Award Reef Squad Leader Article Contributor Build Thread Contributor Partner Member 2018

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    Unless you are on a concrete floor odds are you have enough insulation to prevent you from feeling a shock. To be shocked, you need a path for current to flow through you. Wood, tile, shoes, and dry carpet provide insulation that protects you by blocking current flow. The metal housing of your light fixture connects to ground. Current can flow from your tank, through you, through the light fixture, to ground.
    I recommend getting something like this and plugging your aquarium equipment into it one at a time to see what trips it. Keep in mind you may need a ground probe or provide another path to ground for a GFCI to trip.
    https://www.lowes.com/pd/Shock-Bust...-Single-to-Single-Yellow-GFCI-Adapter/1135923
     
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  5. marvelousone

    marvelousone Active Member Louisiana Reef Club

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    I have one of those gfci on my pump that I use for water changes. Thanks Yall are awesome. I will do that.
     
  6. marvelousone

    marvelousone Active Member Louisiana Reef Club

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    not to highjack your thread Brew12 but this is helping me. I tested my tank today. the meter read 87.1. Turning off switches one at a time. One power head when turned off it dropped to 17.4. So bad power head. I tested the rest and it never would drop below 17.4. So do I have still some voltage in the tank. I touched the light with the volt meter and it read 17.1. I order a grounding wire. I guess I need to throw that power head away.
     
  7. marvelousone

    marvelousone Active Member Louisiana Reef Club

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    I put another powerhead and it went up to 18.6
     
  8. Brew12

    Brew12 Electrical Gru R2R Supporter R2R Excellence Award Reef Squad Leader Article Contributor Build Thread Contributor Partner Member 2018

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    That sounds very normal. Looks like you do have 1 bad powerhead. Glad you found this helpful!
     
  9. Cnidoblast

    Cnidoblast Active Member

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    Will plugging the ground probe into a apex controller unused outlet be okay? (I'd hope that ground is always connected regardless if the outlet control relay is on or off!!!!!!!) @Brew12
     
  10. Brew12

    Brew12 Electrical Gru R2R Supporter R2R Excellence Award Reef Squad Leader Article Contributor Build Thread Contributor Partner Member 2018

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    Yup, that is just fine. Until next week when you decide you need to use the switchable outlet for something! :p
     
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  11. kecked

    kecked Active Member R2R Supporter Build Thread Contributor

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    I had a bad shock about six months back from three faulty heaters. I removed them all and put new ones in and then found about 20v. It was the return pump. Went dc. Voltage gone. I still want to see a dc heater.

    I now have a volt meter in my tank and look at it before touching the tank. I measure current and voltage.

    Now I read the start of this thread about ground probes acting as heaters. Rubbish. And I’ll prove it now.

    Say you have dead short 120v and a leakage current of 100ma. This is really nearly impossible. Power is voltage times current so you have 12w. Dissipation in the tank as heat isn’t a big deal. Figure the resistance of seawater and then the disapation current across that as a resistor. Just treat it as dc. Ac gets into reactance which makes this harder. So you have this current in this giant box all spread out. What you get in heat from this is going to be nothing compared to the room itself. As for the probe, the resistance is micro ohms if that. There is effectively no heat possible from the probe. I can do the math if you want.

    GFI or die.
     
  12. Brew12

    Brew12 Electrical Gru R2R Supporter R2R Excellence Award Reef Squad Leader Article Contributor Build Thread Contributor Partner Member 2018

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    Just want to clarify a few things for people reading this.

    First, DC pumps can induce AC voltages into an aquarium. You need a True RMS voltmeter in order to read it accurately but it does happen.

    It is correct that the ground probe cannot act like a heater. It can, in some very unlikely situations, allow the source of the fault to generate heat. For this to happen you would need to not be running a GFCI and have a relatively high resistance fault at the source. In theory, a fault like this could generate over 1800W of heat.

    But again, this is incredibly unlikely. Most failed electrical devices in salt water will trip the circuit breaker on overcurrent if a GFCI isn't used.
     
  13. HKfshkpr1

    HKfshkpr1 Member

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    OK, I am ready to install one( at least). My question is: my "system" also has a refugium and a sump all linked together, totalling about 250 gal.
    Do I need 3 probes or just 1?( the heaters are in the sump but there are powerheads in the display and refugium). Thank you!
     
  14. Brew12

    Brew12 Electrical Gru R2R Supporter R2R Excellence Award Reef Squad Leader Article Contributor Build Thread Contributor Partner Member 2018

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    You should be fine with just one in the sump. The only time it won't cover all 3 is if the return pump isn't running.
     
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  15. kecked

    kecked Active Member R2R Supporter Build Thread Contributor

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    Put one in every box of water. You can’t have to many
     
  16. Fliper

    Fliper Member

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    I bought one too. Good idea. Why do many people are against them is beyond me? Anyhow, I’ve been in this hobby for 12yrs and never even heard of using one. But, I have one now. Also, I checked my stray voltage and it was 12v. It’s now 0. Thanks! I’m sure my fish are thankful too lol.
     
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  17. jasonrusso

    jasonrusso Valuable Member Build Thread Contributor

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    I had one in my second tank on day 1. It saved my in my first tank.
     
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  18. HKfshkpr1

    HKfshkpr1 Member

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    Ok I think I'll go with only 1. In the 25 years of freshwater fish keeping I have never used one and had no problems. But now I'm keeping saltwater fish...........
    Thank you!
     
  19. Brew12

    Brew12 Electrical Gru R2R Supporter R2R Excellence Award Reef Squad Leader Article Contributor Build Thread Contributor Partner Member 2018

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    Yup, a ground probe is absolutely worthless in freshwater. I consider them vital in saltwater.
     
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  20. dwwataz

    dwwataz nuttier than a squirrel turd R2R Supporter R2R Excellence Award Build Thread Contributor

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    Does your apex then connect to an in-wall gfci receptacle?
     
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