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Electrical current from Flourescents (help needed)
I need the advice from the physicists and electricians reading this list.
I have a small current in all of the tanks on one iron rack. The current
is originating from one flourescent bulb circuit (maybe the ballast
itself). When I test with the volt-ohm meter, I get 32 micro amps (uA)
between the water and ground in the 125 gallon tank which is directly under
the bulbs. I can reduce the current to 14uA in the 125 when I connect a
grounding probe to that tank. All other tanks and the stand itself have a
few uA. If I shut off the offending circuit, the current goes to zero.
The lighting over the 125 consists of 2 sets of 6-foot bulbs. I wired them
myself, and they have been in operation for the past several years. They
use conventional, non-water proof ceramic end caps which are resting on a 2
inch wide wooden cleat which is on top of the plastic tank frame. One set
of bulbs is Normal Output (NO) (ea 55w) and the other is High Output (ea
85w). Both have electronic ballasts which are mounted to the wall behind
and above all of the tanks. The NO ballast has a ground wire which is
connected to ground.
The current only occurs when the N.O. lighting is turned on. No current
occurs from the HO side.[Other measurements with gr. wire connected: .07DC
volts, 3.5 V AC]. There is no change with the ballast's ground wire
connected or not.
I thought that the bulbs and ceramic end caps might be coated with salt and
somehow causing current to leak from the endcaps to tank... so I cleaned
the bulbs and endcaps -- no change. I tested for resistance between the
bulb's end caps and the water and there is a large but measureable
resistance (i.e. different than infinity). I even tested for current with
the bulbs out of sockets, but with the N.O. ballast on -- Current is still
non-zero --4 uA (without ground wire, 16uA). With bulbs out, I also get a
few uA current between the end caps and ground, and the same between the
insulated wires and ground. With bulbs in, no current from endcaps or
wires. Does this suggest that the induced current is coming from the
ballast itself?
I also observed a current between the large wrought iron stand and ground
(30uA), also caused by the N.O. flouresent circuit (ballast with bulbs.).
I checked all the other tanks on this stand which do not have a grounding
probe and there is also a current, much smaller but measureable = ~2uA.
The 280 watt lighting system has been great for my plants, but I recently
wondered if a voltage leak might be responsible for some peculiar behavior
with my fishes. This is when I discovered the "problem." The NO ballast
cost approximately $40-50, but will gladly replace it - if it is bad and
somehow responsible.
Your expert advice is appreciated. Has anyone else experienced this? If
there is anyone in RDU that wants to help, you can also see some great plants.
Neil