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No luck, no change, calling in the big guns. We called the electric testing Co. that tested the building originally and they are coming out to check the grounds between MCC's and the Mains and the building ground. They should have the original data and we can then compare if there has been any degradation.
I kept coming back to ground issues and an idea that has been percolating in my mind. A grounding issue if that's what it is, may not be as localized as we have been thinking. I've begun to suspect the building service entrance grounding resistance has been slowly increasing to the point where it is just now becoming apparent in it's effects on our equipment. The areas outside and parallel to the main electrical room were, for the longest time so heavily irrigated and plagued with leaks that the ground was always saturated to the point that we had developed a sink hole in the center area right outside the main electrical room and we had lime leaching out of the concrete walkways along the edges. Over the last year changes to, and failures of the irrigation system has allowed these areas to dry out. This has also been the driest year weather wise for quite a while.
Since I started typing this a field engineer stopped in to look over the situation. He said that this area of Auwatukee/Phoenix has some of the highest ground resistance readings in the city and a super market about 5 miles away had to add earth grounding conductors for the same reasons. This was before I mentioned the irrigation theory. So it's plausible that this may put us on the right track.

“Within the last 60 days our cooling tower Lakewood TDS meter's operation became erratic.” “There has been no significant maintenance or changes to the system other than the usual monthly cleaning”

“No new equipment has been added and the system has been running trouble free for over six years.”

SOMETHING HAPPENED WITH IN THE LAST 60 DAYS!


The drying out of the soil and the high ground resistance are issues, but SOMETHING HAPPENED WITH IN THE LAST 60 DAYS!

"I used a pair of jumper cables and grounded the conduit to the lighting arrestor earth ground in the tower yard as far from the affected area as I could manage, which was about 15 feet off the ground and 10 feet from the tower and first meter. Not great surface area contact but enough to have an effect. Both meters now read approx the same and though there is still some drift it has been reduced substantially."

The results of the jumper cable test shows that the TDS meter EMI issue is an internal problem, independent of the changing ground resistance. SOMETHING HAPPENED WITH IN THE LAST 60 DAYS!


"All grounds tested .2 ohms or less between the fan, all the way back to the service entrance."
Was this resistance check done with a multimeter? When dealing with RF, low voltage DC measurements don't always mean anything. When you are dealing with RF noise, the long run of pipe looks like a high impedance path. Low DC resistance doesn't mean that the RF impeadance is equally low.


_______________SEPARATE ISSUE________________

"In addition, our BAS went berserk every time we opened or disturbed a ground anywhere. It apparantly relies heavily on grounding for communication and is very touchy. Even loosening a ground screw connection and teaking the wire was detected and we received a communication alarm. This would seem to indicate that the grounding system is fine or we would have had other problems."

I disagree. I think that means that the BAS signals are running thru your grounding system. Should the BAS signals be referenced to ground? That doesn't sound like a reliable design for a multi-structure system. That means whenever there is a voltage difference between the 'ground' of structure A and the 'ground' of structure B, the BAS signals change too.

LarryC

Here's an update: All ground resistances as measured with a megger 4 Wire bridge were .2 ohms or less including the main grounding conductor to earth.We haven't recieved the report yet but as I recall THD at the drive inputs was 1.26% or lower wave for was clean. The ouput of the drives had mutiple harmonics in varying percentages. Figures will follow when we get the final report.