Spa Bonding at 300mV

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FionaZuppa

FionaZuppa

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Location
AZ
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Part Time Electrician (semi retired, old) - EE retired.
LA Spas Maui, UL listed, measures 11kohm in the water, went to measure ohms from water to bonding wire and i cant, there's +300mV between wire and water (+ on the wire). bonding is also tied to service gnd. so why the voltage here?
 
ActionDave said:
I'm going to take a stab and say chemicals in the water.
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that means what? if the water (a liquid metal at this point) is elctrically connected to the bonding bar, then how can there be potential diff?
 
edlee said:
What are you using to test this? For example a digital multi-meter probably wouldn't be reliable in this case.
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yes, a fluke digi meter. why would it be not reliable.
i measured 11kohm in the water where probes were about 8" apart from each other. water to bonding is probably a good 6-7ft from probe in water to other probe on bonding bar of spa itself.
 
FionaZuppa said:
that means what? if the water (a liquid metal at this point) is elctrically connected to the bonding bar, then how can there be potential diff?
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I can measure voltage using a digital meter just waving my arms in the air. If I did not get some kind of reading doing a test like yours I would be inclined to think my meter was not working.
 
ActionDave said:
I can measure voltage using a digital meter just waving my arms in the air. If I did not get some kind of reading doing a test like yours I would be inclined to think my meter was not working.
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so what test do you do? equi-bonding means everything on that wire is at same potential, i have a diff between water and bonding.
 
Not code required

Not code required

FionaZuppa said:
so what test do you do? equi-bonding means everything on that wire is at same potential, i have a diff between water and bonding.
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Everything in the wire should be at the same potential. There is no requirement for testing from anywhere the water to anywhere. Water is not a suitable conductor, hence the need for bonding in a plumbing system (here we go again).

Try filling the hot tub system with pure distilled water...then tell us what your readings are.
 
cuba_pete said:
Everything in the wire should be at the same potential. There is no requirement for testing from anywhere the water to anywhere. Water is not a suitable conductor, hence the need for bonding in a plumbing system (here we go again).

Try filling the hot tub system with pure distilled water...then tell us what your readings are.
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so a tad confused. pools require bonding plates to be installed so that the water is bonded to all metal per NEC.

so if my spa water has 1meg ohm to the bonding lug and the water to gnd or bonding shows say 120v, is this an issue? voltage doesnt always mean squat as it could just be static charge with little coulombs of energy, etc.

i will run some other tests to see how conductive the water-to-water really is, i would then expect to see same conductance between water and bonding lug if the water is properly bonded, etc.
 
Spa Bonding at 300mV

Distilled water is an excellent insulator as opposed to potable water. Potable water due to all minerals diluted in it has a grater degree of conductivity that distilled water, the conductivity varies with the amount of minerals. So because potable water is a conductor we need to bond it to the circuit equipment grounding conductor supplying the spa. All metal parts in the spa, around the spa and the equipment used for the circulation and sanitation of water for the spa should be at the same ground potential. I think in your case you are reading 300 mv dc due to capacitance.
 
Turnpike15w said:
Distilled water is an excellent insulator as opposed to potable water. Potable water due to all minerals diluted in it has a grater degree of conductivity that distilled water, the conductivity varies with the amount of minerals. So because potable water is a conductor we need to bond it to the circuit equipment grounding conductor supplying the spa. All metal parts in the spa, around the spa and the equipment used for the circulation and sanitation of water for the spa should be at the same ground potential. I think in your case you are reading 300 mv dc due to capacitance.
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so yes, i know all about H2O and how it becomes conductive.

the same gnd potential? thats not definition of bonding, but i understand your point. bonding just keeps things at same potential, thus the diff between any two items is zero.

my next test will be a mA test from water to bonding wire. this will show me the resistance through water path. i also have a LCZ meter, i will attempt to measure LCZ between water and bonding lug. i also have portable o-scope, so maybe i will look at whats there from scope view.... my last test i didnt ascertain if it was a dc or ac voltage.

and to note, the unit is UL listed and in my locale bonding is not required, but i did anyways.

the bonding looks like this:
  1. 50ft #6 laying under spa pad in coil fashion
  2. two 10ft gnd rods, one next to disco/breaker box (5ft from spa), and another on opposite side of spa but is touch closer to spa
  3. #6 connects gnd rods, spa bond lug, and service gnd together
 
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yah...

yah...

Yah, I know about the water...that's why I suggested it off the cuff. I was building on a point from earlier in the thread where someone mentioned water content (dissolved solids in the water) as a factor to conductivity...which it is.

What I am wondering is why the OP is sticking a probe in the water to begin with.

What standard is this test performed in? What standard is he trying to achieve?
 
cuba_pete said:
Yah, I know about the water...that's why I suggested it off the cuff. I was building on a point from earlier in the thread where someone mentioned water content (dissolved solids in the water) as a factor to conductivity...which it is.

What I am wondering is why the OP is sticking a probe in the water to begin with.

What standard is this test performed in? What standard is he trying to achieve?
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Well, for one thing, the test will most likely detect the presence of energized unbounded metal in contact with the water somewhere in the system, leading to further troubleshooting.
Now if the chemical composition of the metal probe is right and the water is horribly acidic or basic you will get a small DC voltage just because you have made a battery (voltaic cell.)
 
Yes, but...

Yes, but...

Yes, but why? Is some AHJ making them do this? To what standard is this test being performed?

One would have to ensure a homongenous mixture of dissolved solids, pH, etc. were being met. and that each and every connection in the spa/hot tub was bonded throughout...which it likely is not.

I don't see the point of the test other than the OP ensuring the realization that the bare minimums of the NEC do not necessarily prevent someone from getting shocked. After all, none of the plumbing in most hot tubs is metallic anyway and water is not a reliable conductor of current...hence bonding to begin with.
 
i already posted the why's.
its a UL listed spa, my locale does not require bonding beyond what manufacturer has done. this means the water be gnd'd or bonded to the "bonding lug" the spa has.

there can in fact be a voltage generated by the free ions in the soup mix of chemicals in the water, and since the water from top to bond lug is a "variable resistor" i can measure a voltage diff.

i am more curious to know actual resistance, and for this i need to do a current test from water to bond lug.

but as you can see, the bonding doesnt completely fall in alignment with the definition of bonding, etc. the water should be at same potential as everything it is bonded to, but obviously wont be if the soupy battery (water) has resistence between it and the out or water bonding lug, etc.


cuba_pete said:
I don't see the point of the test other than the OP ensuring the realization that the bare minimums of the NEC do not necessarily prevent someone from getting shocked. After all, none of the plumbing in most hot tubs is metallic anyway and water is not a reliable conductor of current...hence bonding to begin with.
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plumbing? why would you worry about plumbing? almost every manufactured spa (if not all) has a heater that is a metal, that metal must be gnd'd, and the very conductive water touches the heater.
 
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My point was that even if all metal connected to (touching) the water is metallically bonded, you can measure a DC voltage when you stick a probe into the water which depends on the alloy of the probe. Resistance does not come into play.
 
GoldDigger said:
My point was that even if all metal connected to (touching) the water is metallically bonded, you can measure a DC voltage when you stick a probe into the water which depends on the alloy of the probe. Resistance does not come into play.
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if there is no resistance between end points then you have a short, and thus zero voltage, etc. so, i would have to say that resistance between the meter probes is a critical # when measuring voltage.
 
Not if the voltage is the result of a chemical reaction (electrochemical potential). If you also bond your meter probe you will no longer measure a voltage. But the open circuit voltage of a battery does not depend on its internal resistance.
One electrode is the material of the piping, etc. The other electrode is your meter probe.
If they are different metals, there is your battery.
 
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GoldDigger said:
Not if the voltage is the result of a chemical reaction (electrochemical potential). If you also bond your meter probe you will no longer measure a voltage. But the open circuit voltage of a battery does not depend on its internal resistance.
One electrode is the material of the piping, etc. The other electrode is your meter probe.
If they are different metals, there is your battery.
Click to expand...

bond my meter, you mean one probe on the bonding lug??
 
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