Where you're trying to troubleshoot a problem and every time you think you have it solved it isn't? And to make matters worse it just goes on and on and eventually you start dreaming up wild theories because you've exasperated all other rational thinking?

I mentioned in another topic about the steam appliance that a plumber and I were working on and how we worked together to troubleshoot why it was shutting down. After several attempts and returning numerous times to stare at this miserable piece of equipment we are back at square one. I've exhausted the electrical end and he's gone through the plumbing numerous times. Together with advice from people who understand boilers we've tried to figure if there's a problem involving that piece of the puzzle and it still has us beat. I hate giving up but I'm almost there.

Now, if someone can direct me to a boiler guru.....

I'm not a guru but I understand that it's nice to have a little moral support.

Is it domestic water, space heating, or both?

Gas?
Did you throw a thermocouple at it yet? If it doesn't see heat pretty soon after the gas comes on it shuts down.
(my trick for today)
The first thing you have to do on a problem like this is figure out what CAN shut it down, then start eliminating those things.

The last time something that zany happened, the plumber had thrown his shut-off valve - CLOSED - even as the GC thought that it was left open -- since the plumber had promised the GC that he would do so.

Poof, the gen-set started up.

It's often the case that a trooper forgets a commitment -- or gets a phone call from his office instructing him on 'house' policy: his own boss insists that the gas cock be turned off. Rather than explain this policy to the GC, the dude just split.

(This particular GC superintendent was a screamer... and in w-a-a-a-a-y over his head.)

It's only funny years later -- to those who didn't have to endure him.

&&&&&

With modern digital controls, you may have to jumper past such logic to establish that the 'dumb' aspect of the device/ machine actually fires up.

And as Greg has pointed out, always be suspicious of safety over-rides. These are now standard fare for all ignition schemes for fixed equipment -- especially in confined spaces.

You might find that the logic is set up with even remote air quality sensors to prevent detonations.

ANYTHING burning LP is ESPECIALLY touchy about gas build up.

These air quality monitors are touchy enough to even trip out over sewer gases -- or if they are still wrapped in anti-dust barriers. (In the manner of smoke alarm heads.)

And, ...

Why rack your brains when the production factory has FREE TECH ADVICE direct to your location -- by cell phone. With modern smart phones, you can even video the gear and the tech can see what you're seeing.

The way you're acting the factory tech is as busy as a Maytag repairman. These fellows are DYING to hear from you. If you never do, they're sure to lose their jobs.

So think about that.

The plumber and I have both talked to tech support and they have the same answer - replace part A, B, and C. Those parts have already been replaced and I doubted the originals were faulty to begin with but when you start running out of ideas...

But to let you know specifically what we're dealing it's a Cleveland CSM24 Steam Coil Convection Oven. It uses building steam that runs through a coil in a boiler beneath the two heating compartments to heat the food grade water in the tank into steam. The building steam itself is not food safe which is why this system is used.

The basic problem is that the appliance operates for 3-4 hours and then shuts down. During the period of time when it fails we see the water in the sight glass go down but it doesn't appear that the probe in the tank that maintains the water level is signalling the circuit board to open the water fill valve. It takes approximately 20 minutes for the water to almost disappear from the sight glass and then the steam shuts off and it goes into a MANUAL reset mode. After it does it the first time it tends to happen every hour thereafter.

I placed 3 DMM's on the high probe, low probe, and water fill valve to see what was happening as far as if the signals were being sent. Every time we watched it shutdown we observed no change in voltage which despite the water level in the sight glass the water in the tank appeared to be covering the 2 probes and the water fill valve remained closed. We kept working on it from the point of that probes or circuit board were faulty but only during this time for reasons we could not explain.

The other day I came up with an idea that there was a counter pressure forcing the water in the tube to go down while the water in the tank remained high and eventually this mystical pressure caused it trip out on high limit. I metered the high limit during failure only to be proven wrong. But despite being told that my basic idea was scientifically impossible I found the smoking gun. Last night after posting this topic I finally found the supporting science to prove that water level can be high in the boiler while the sight glass level is lower and this eventually leads to a shutdown!!!

https://www.youtube.com/watch?v=a0xZPl_bwHI&feature=youtu.be

https://www.youtube.com/watch?v=tI3tWuSsX7c

It's tripping out on a high temperature limit or high pressure?

Oddly enough, I once encountered a similar problem with the water heater in a restaurant. The problem proved to be .... cardboard taped over a wall vent grill.

That's right. Even though the heater was located within feet of an open door, it was necessary for the vent to be unblocked for sufficient fresh air to reach the burner ... even though the vent was just as far away!

It appears that the vent was covered in the winter without causing problems- but, let summer come, and the combined draws of the cooking hoods and the air conditioning were able to starve the water heater.

Go figure.

Great website for problems like this is www.heatinghelp.com

It is full of heating professionals who work on primarily water based systems like steam, various flavors of baseboard, and solar.

It's tripping on LLCO.

But as I posted previously it's a far more complex situation that eventually leads up to that. So in order to come up with a solution we need to verify that what I now believe is happening is really happening and more importantly why is it happening.

I have already attempted that but haven't received a response yet. Beyond that I talked to an acquaintance who teaches power engineering at a technical school. He wasn't too sure of what to make of it but at least he offered some suggestions that might help. It's a tough problem to describe in a short period of time. Would be better to have someone right there on site when it shuts down.

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.