ECN Forum Forums General Topics of the Trade General Discussion Area Have you ever had one of those jobs.....

A recording volt monitor might be handy for this

It might help.

We've determined that the appliance failure has a pattern of shutting down approximately every 3 1/2 to 4 hours if you completely drain it, allow it to go through it's 3 minute blowdown cycle, and then start it up from that point.

With that knowledge I have the meters in place ahead of time and we can view the voltage change while it fails.

After spending a few hours working on it today I'm almost 100% certain this problem is in the realm of a tradesman with knowledge of how steam in boilers can do things that people like myself have no knowledge of. The 2 links I posted earlier of what it looks like in a boiler during various circumstances have me convinced that this is not an electrical problem but rather a steam problem.

I was once told that novice tradesmen like myself often look for the difficult answer to what often is a simple problem. I'm convinced that we covered all the simple solutions a long time ago as far as what plumbers and electricians are trained to understand.

Do Cleveland not offer a technician call out service, either direct or through agents? These services tend to be expensive but it sounds like this job is costing a great deal of your time already. In my experience manufacturers' technicians know most of the tricks.

Super simple problems you just can't lick are horrible. Here's the situation:

HAZMAT shed, 3 phase, three 120V circuits. Incandescent light going through bulbs. Voltage varied at the light like 109-150 volts while the line to ground volt on all three . Lost the neutral within 10 feet of the panel. Could not find it. Everything appeared wired and metered correctly. Even rung out the wiring, nothing was coming back bad.

After a few hours of pulling out what little hair I had left and cosidering a career change because I couldn't fix something so simple and after starting over for like the 20 time, I FINALLY figured it out. Typically on a 3 phase label, the three legs are on the same horizontal plane and rip the neutral lug is off set. How ever, this particular panel, two of the 3 legs were on the same horizon plane while the 3rd leg was offset. Adding to the confusion, the neutral busbar going to the terminal bus for the circuit neutrals was covered by the panel guts just like the ungrounded bus so at first glance, the neutral terminating looked like termination for one of the phases. As a result, one of the legs and neutral were cross wired when it was connected years prior.

At first thought, this don't sound right and it did not sound right to me either. I dug deeper in the panel,verified the panel was indeed terminated wrong, scratch it all out out on paper, and even talked to the users over the years because it was never a problem, until now. It turned out, the planet was align all these years and someone desired to start using the heater I think which changed the condition which threw the voltage at the light in a tizzy.

Whomever wired it initially apparently assumed the three legs on the same plane and wired it as such.

I think I can beat that:

I had a weird, general purpose auditorium -- whose structure was such -- and my bosses were such -- that the most important branch conductors were run the L O N G way around a not so small building. (35,000 sf)

At issue: two 277VAC critical lighting circuits that feed ganged switches at the FAR side of the basketball court/ auditorium. These were re-engineered by me to be on the exact same phase so that there was no NEC violation in the switch box. Standard 277 switches controlled the overhead HO T-5 lights. (At the time, the latest 'thing') They really kicked out the lumens.

Because of the loading -- and distance -- I upgraded the neutral returns to #8 on both 20 breakers.

Now, get this, half-way around the building it was necessary to splice both hots, both neutrals -- on their home run back to the panel. My dufus apprentice made up this simple box.

Well, not so simple: AFTER getting the 'hots' properly wired through, under my specific direction from the floor, I turned my head, and he made up both neutrals --

Naturally he wired BOTH line-side returns to each other -- and BOTH load-side returns to each other. Obviously, the massive light array had not return to the Service panel as a result of this.

So, instead of failing to fire off, to light up, the entire array fired up PERFECTLY!

This strange situation lasted for FOUR months!

That January, I get a very long distance phone call from my boss. (a genius, IMHO) He's on the scene because the lights are SUDDENLY acting up. (!)

Pulling on my memory cells - and gagging on the tale I'm hearing - I instruct him to the magic, offending box, the ONLY box that had any splicing whatsoever. I hate to splice on a 'dedicated' home run -- but these were truly long. (These two lighting circuits were the only runs in the 3/4" EMT, period.)

It's at this time, my field superintendent informs me of my man's boner.

Which left BOTH of us stumped: how in the world did the system run for me?

&&&&&&&

I had to conclude that the weather had changed.

Further, that the lights ran back in August because the extreme length of the neutrals acted -- for a while -- as a 'sink' for the harmonics. This effect was so pronounced because of the size of the returns -- #8 -- that they were able to bleed off their harmonics into the inductance of the very long EMT run.

Wetter air changed this equation enough to cause the electronics to shut down, entirely. (High quality electronic drivers will shut themselves down when they sense that something is really goofy with the wave form/ current differential.

As for the electronics, they HAD been able to draw out enough energy to pump the fixtures until then.

Why?

They actually constitute micro Secondarily Derived Services for each fixture. Each, in turn, was capturing energy and transforming it into a 'bucket' of DC -- in a series of capacitors. (A higher power version of the switching logic inside a DMM.)

It's from this source that the solid state logic builds a totally new wave form.

In sum, electronic 'ballasts' can tolerate pretty filthy AC power. Beyond some set limit, their logic shuts off any attempt.

This is fundamentally different than analog systems -- IE real world systems. For them, the gear tries -- and FRIES.

{ As an aside: you wouldn't believe the grief I had getting the crew to wire these lights. It was one of the first critical efforts that I didn't have the time to scissor up and inspect every box. I had to re-cap my boots after that marathon.

I'd SWEAR that the crews were gaming me: I was treated as a shuttle cock between 'crisis' after 'crisis.'}

That would have definitely been a head scratcher. That is why it is called electrical theory, be cause, in theory, it shouldn't have worked... but it did...

Like that HAZMAT shed. It was hooked up wrong for years and never was a problem until a conditioned changed.

A case of the EMT doing the 'n' job!

I had a 120 volt circuit that had only one (1) THHN conductor. On the cb, and on the receptacle, the 'n' of the receptacle was bonded to the 4 sq box, the EMT to the panel. Worked fine for a while until the loose setscrew couplings started arcing!! Could have been the cause of a fire, as the EMT was on wall behind clothing racks.

You know, that was actually acceptable practice in Germany eons ago! And by that I mean well before WWII. Some of these installations have actually survived and stump modern electricians.