Fixing Stray Voltage?

[jballa15]

So I got a multimeter for a keyboard project I'm working on and decided to test my 30g reef tank for voltage...it totals 40V. Basically both my main pumps (mag 5 to skimmer and quiet one 1200 return) and stealth (i think) heater each give off about ten volts. The rest is from powerheads and t5s which add about 3V each.

So, is my equipment too old (all unknown ages of between 1-4 yrs), or is it just crappy?

And which heater or pumps have you guys found not to give off voltage if I wanted to replace them?

How well does a ground work for this level of voltage?

Thanks ahead of time....

 

[gwhiz]

Unless your T5's are in the water I don't see how they're contributing to voltage in the tank, nor how they'd contribute 3 volts. Can you explain how you're testing?

 

[cr500_af]

All a ground probe will do is complete the circuit and trip your GFCI.

 

[ichthyoid]

Gwhiz;621058 wrote: Unless your T5's are in the water I don't see how they're contributing to voltage in the tank, nor how they'd contribute 3 volts. Can you explain how you're testing?

With alternating/varying voltages, there are two other ways that an electrical potential (voltage) can be transmitted, besides conduction.

1) Conductance- is familiar to us all. Hook up conductors/wires to a source of voltage and it will conduct, so long as you are connected between any two points that have a difference in potential/voltage. Why?-The universe wants everything to be equal, so electrons/current will flow from an area/object of greater concentration to one of less concentration, until both are equal.

Also of interest to us are two other methods by which a voltage may be measured from one point across a nonconductor to a second point.

2) Capacitance- this happens when:

A) there are two conductors closely separated by an insulator, AND
B) a varying voltage is present on one of the conductors, THEN
C) that voltage may be superimposed/measured on the second conductor

In this example,
A) is our lights, air gap above water, and the water
B) is the high frequency voltage in the lamps
C) is the tank water

3) Inductance- this happens when:

D) there is an alternating/varying voltage, producing an electrical field, AND
E) a conductor enters this varying field, THEN
F) that voltage may be superimposed/measured on the second conductor

In that example,
D) is the voltage in the electrical coil of a pump or heater
E) this could be a screw on the outside of the pump housing,
F) the pump screw touches the water, so the voltage can be measured in the water

I hope this helps.

 

[jballa15]

Right, thanks for the explanation, but I guess the question is more, am I at the normal range for an aquarium or can I find some equipment that reduces the voltage significantly?

My mag has plastic screws and the quiet one has none. I'm guessing the easiest thing would be a heater with an external transistor right? What about an external pump?

Don't wanna get too complicated in changing my system that has performed reasonably well, but if it makes a difference, then I'm all for it.

 

[cr500_af]

bratliff;621094 wrote:
I keep all other electrical devices in my sump or refugium (pumps, PH's, additional heaters, etc.). My thought is to limit how much potential voltage can be introduced into your display as much as possible.

Hope this helps.

With a continuous water connection inside your return plumbing, wouldn't it make no difference either way?

 

[ichthyoid]

It's not unusual to measure voltage in a tank, even 40 volts. Many of us have run tanks with grounding probes to eliminate 'the reading' (FWIW- I currently do not). My thought is that if you have no obvious problems don't seat a little voltage.

I strongly encourage you to use a GFCI on the circuits feeding your system, and that is especially true if you decide to use a ground probe. Not using a GFCI with a ground probe presents a greater hazard to you, IMO.

Example: you touch a light that has voltage on it AND touch the grounded tank water, then you just became part of the circuit with no GFCI to protect you. -JMHO

Edit:

bratliff;621094 wrote: One of the main reason I use Vortech mp40w's in my tank is the fact that the motor sits outside. No heat transfer and no possibility of electricity in the tank from the PH. Highly recommended.

The only other thing in my display is a single titanium heater. It's on my RKE controller and the thermostat is external as well. If my tank ever shocks me this will be replaced asap.

I keep all other electrical devices in my sump or refugium (pumps, PH's, additional heaters, etc.). My thought is to limit how much potential voltage can be introduced into your display as much as possible.

Hope this helps.

Not completely accurate, IMO. True enough for voltage from direct conductance. You could still get voltage from capacitance and/or inductance.

Barry's point about flow from the DT is a good point. It's all still in the circuit/contact, so to speak.

 

[gnashty]

ichthyoid;621096 wrote:
Example: you touch a light that has voltage on it AND touch the grounded tank water, then you just became part of the circuit with no GFCI to protect you. -JMHO

been there, done that...it will change the way you smile for a few seconds

 

[cr500_af]

gnashty;621099 wrote: been there, done that...it will change the way you smile for a few seconds

220v will change the way your arms work for a few minutes.

 

[ichthyoid]

I agree that the likelyhood is much lower, but still possible,

I would be very interested to see what you get with a vortex on a tank with seawater and nothing else while it's running. Thanks for the idea, and please post your results if you do this.

Also, I suggest that you ground the tank before energizing the Vortex, so that we know exactly how much voltage, if any, is generated by the Vortex.

 

[cr500_af]

Assuming you can keep the water in the tank.

 

[wayb]

I had this same problem and it turned out my outlet that every thing was plugged in was not properly grounded. Fixed that and all voltage went away.
Wayne

 

[rockdog]

cr500_af;621104 wrote: 220v will change the way your arms work for a few minutes.

480V will change the way 1/2 your body works for a couple days!
Been there done that!! NOT fun!!

Jason

 

[ichthyoid]

Rockdog;621291 wrote: 480V will change the way 1/2 your body works for a couple days!
Been there done that!! NOT fun!!

Jason

+1 on that one, but I have to say that the 400 VDC hurt more.

 

[rockdog]

ichthyoid;621292 wrote: +1 on that one, but I have to say that the 400 VDC hurt more.

DC alwayd hurts more!! It is just a long hard pull and that SU X!!

Jason

 

[darcurr]

cr500_af;621104 wrote: 220v will change the way your arms work for a few minutes.

+1

480 will change the way that side of your body works for a few minutes:confused2:

Edit:

wayb;621141 wrote: I had this same problem and it turned out my outlet that every thing was plugged in was not properly grounded. Fixed that and all voltage went away.
Wayne

This sounds like a probable culprit. If your reference is a solid ground, but your outlet isn't (or vise versa), then you can get some wild readings.

 

[ichthyoid]

Yes, if your reference is 'floating' then your voltage 'reading' is pretty much meaningless. That's why the generally accepted reference is an 'Earth ground'.

Edit: FWIW-

~2 KV DC in your pinkie and out your elbow will get you real close with your Higher Power (in more ways than one).

(900 watt CO2 laser cathode to ground...ooouuuwweee!)

The automatic ground strap failed to maintain contact (but I did not)! :doh:

 

[darcurr]

ichthyoid;621781 wrote:
~2 KV DC in your pinkie and out your elbow will get you real close with your Higher Power (in more ways than one).

(900 watt CO2 laser cathode to ground...ooouuuwweee!)

The automatic ground strap failed to maintain contact (but I did not)! :doh:

WOW. I got "fuzzed" once switching 12Kv in misty conditions, but that was just a scare.