Problem with T5 flouresent lights and AC3 Orp/PH /Temp/DO and Conductivity readings

[chriscolt]

Curt: I am a long time AC3 user - this problem started happening when I installed a T5 electronic ballast 72", 8 bulb (48" x 8, staggered) fixture alongside my Metal Halides over a 180 gallon Oceanic tank (72 x 24 x 24) - the AC3 is under the tank in the stand - right now these lights are controlled via a mechanical timer (until I get the problem fixed) - every time they turn on the AC3 goes nuts - all readings on all probes - the DO goes to 0 (normal 5.5 to 6.5), the conductivity reads around 42 (normal is 52), PH goes to 7 (normal is 8.2), ORP goes to 480 (norm is 340), even the temp is off by about 4 degrees. The AC3 has all probe options equipped and also is connected to the LAN via the RJ45, no serial connections. DO and conductivity probes are in one of the overflows to isolate from the PH, ORP and Temp probes which are hanging in the main tank in the back I have a grounding probe plugged into the same outlet as the Neptune and T-5s - removing it makes no difference. Circulating pumps are all Tunzes (3 6100s and a Tunze wavebox) - using their 7095 and wavebox controller - will move to Neptune controller once this problem is fixed. Right now none of the lights (4 x 250 Watt MH, 8 x 54 Watt T-5) are controlled by the Neptune yet.

The Neptune is plugged into two different outlets (main and backup) and the cords are neatly bundled away from everything - the T-5 ballasts are built into the fixture - so the 110Volt plug does share the same outlet as one of the power feeds to the Neptune. The probes are about 7 inches below the T-5 fixture. The Metal Halide lights have no effect only the T-5s - How can I fix this?

Chris

[Tech Diver]

You didn't mention if you are using a DC8, DC4, or X10 to switch the power. In any case, if you are using a DC8 or DC4 you could try using the Socket Expansion box. Since it uses a relay, the power between the DC8/DC4 and the lights are completely isolated. But do remember to plug the thin power cord (relay control) into the DC and the thick power cord (supply power) into an uncontrolled outlet.

[clp]

It sounds like the T5 ballast is generating a significant amount of radiate EMI. Make sure that the ballast, and the reflector are all electrically grounded. Physically separate the probe cords from the ballast. Shield the ballast cords is necessary.

Curt

[chriscolt]

Thanks - How would I sheild the ballast cords? I know how to ground the ballast and reflector - no problem there - just not sure how to shield the actual power cord from the ballast - foil wrap to the ground pin?

BTW - A agree it must be the EMI interference since I am not even using the Neptune to control these lights (yet) ala thru a DC8 or DC4 - until we get this problem solved - so it must be radiant EMI that is feeding back through the probe cords

Chris

[clp]

You can shield the ballast wiring with conduit, foil, or even by wrapping the wiring w/ a ground wiring. EMI chokes may also be used to reduce the radiate emissions.

Curt

[Roy G. Biv]

Originally posted by clp
You can shield the ballast wiring with conduit, foil, or even by wrapping the wiring w/ a ground wiring. EMI chokes may also be used to reduce the radiate emissions.

Curt

It is worth mentioning that you must ground the shielding. Ive seen too many people just wrap aluminum foil around things and expect it to work.

[Kengar]

you might also want to add a titanium ground probe. I had similar experience with halides causing spurious readings. moved the probes well away from the ballasts/lamp cords, added a grounding probe, and problem resolved. good luck.