Here's an interesting problem I had recently, during new construction. I'll give you the basics of the issue, and you can ask me questions about any other troubleshooting evidence you can think of. What would you check? What course would you take to find the problem? I'll answer your t/s questions, as if you are working on the equipment.

First, the job. 2500# car, 3 stop, direct bore hole jack, adjacent machine room. 25 hp, submersible hydro, Maxton valve. All new equipment, oil and tank as clean as a whistle. Motor was Direct coupled to a small Allweiler screw pump. Very standard stuff for the USA. No weird stuff that would trick you. As common as a Big Mac.

Imperial brand motor draws about ~350 amps when starting up, on each leg. It was a constant draw, not just the in-rush. Made a HUGE humming noise, like it was under a great load. Slightly worse when running backwards!

Full Load Amps data on motor tag says 68 amps, iirc. 230 vac 3 phase coming from the disconnect.

Using Seimens 75G solid state starter, set at various starting currents, like 350%, and 200%. Didn't change problem much at all. Tried CBA and ABC rotation setings.

Checked all motor wiring for proper identification, grounds, and check motor for forward rotation. There were no grounds, and all the T #s were correct. (T1 thru T6) Motor windings read very low like they should, and did not read to each other, nor ground.

Pump wasn't turning under power, but with the power off, I could reach into the tank, and just manage to grab the motor shaft with my fingertips, and easily turn the motor/pump by hand. Should I stop now? Have I aroused some interest in this little troubleshooting example? Anybody wanna play my silly game? :^)

Well to eliminate as many parts as quickly as possible I would wire the motor directly to the mainline. Turn her on and see what happens.If the motor still wont turn I would be looking for improper wireing or physical binding.

This is assumming that you have checked your 3 phase power and it is the correct phase and voltage configuration for your motor.But as you say new construction I would be surprised to hear that phaseing was the problem but the wrong voltage is quiet possible.

Yea, a participant! Thanks for checking in. You do understand I'm talking about a problem that has since been fixed, right? It was actually about a year ago. This was an intriguing problem for me, and no one I talked to had ever heard of it happening. A once-in-a-career thing.

I like your train of thought. Yes, I had tried wiring the motor directly to the mainline disconnect. When I turned it on, the fuses in the disconnect blew immediately. The fuses were the correct type for motor rated duty, and the correct amperage, etc, per the NEC. I'll go ahead and tell you that it had nothing to do with the problem. The 3 phase supply in the disconnect was of the proper voltage and phasing. The power supplied was proper in every way, and had nothing to do with the problem. But yes, I sure did a lot of checking on the power, during the course of this issue..lots of head scratching...

Just as an aside, it was interesting that fuses of the same rating DID NOT blow while the power was going through the Seimens solid state starter. Its' current limiting abilities acted like a safety valve. It would allow a certain steady state of current, hundreds of amps even, depending on what allowable percentage of FLA you set in the parameters, but no more than that. But this also had nothing to do with the problem, I thought it was just interesting.

What would you do next?


(oh, boy, got one on the "hook"!) :^)

I probably should mention at this point, that I traced each and every wire, from the T1 terminal on the Seimens starter, to the T1 metal tag on the motor leads, then T2, etc, did each one, one at a time, all were correct. Single voltage motor, 6 leads. At some point, this question will cross anyones' mind, who is wrestling with this issue.

some imperial ac motors were wound to otis spec/labeling. if hooked up incorrectly like it was a nema spec the fields fight each other and create high current and a loud humming. is that the problem?

what about the freq of the motor? was it less than 60hz?

Mr Greenpants got the problem! One of the three fields was fighting the other two. Depending on how the motor last came to rest, it might get hung up in a dither ansd not turn, or it might rotate forward, albeit at high current, with two windings fighting the third backwards one, like two men dragging a third man, hence the great current draw.

The 6 metal "T" numbers were installed in China for Imperial Electric, but not for Otis.

Each of the three windings had a metal NEMA tag installed on each end. And each winding had the correct pair of metal designations on its' leads, but-

On one winding only, the two NEMA metal tags were installed swapped from end to end. The motor was wound correctly, and the windings each had the correct pair of NEMA metal tags crimped onto its leads, but just one winding was labled backwards. So if you wired it according to the drawing, the magnetic force of that one winding ended up bucking the rotor rotation. Two windings made the rotor turn forward, sometimes...Other times it would not turn at all...depending on the exact degree of rotation as the motor last came to rest.

Greenpants, it sounds like Otis had an issue with this before, eh? I had never seen it in my 25 years, neither did the tank manufacturer, nor the Imperial rep. But if they don't get the Chinese up to speed, me thinks they/we will see it more often.

Looks like everything is being made in China now, the default, low-cost labor factory for the world.

sccjr, it was 60hz. Good thought, because if you apply too low a frequency, (or if the motor was designed for a signifigantly higheer frequency) it doesn't create enough impedance to limit the current flow, so there is some validity to that. IDK how far off the rating would have to be to cause a problem, but I dont think the delta from 50 hz to 60 hz would be much of an issue, but Id have to look that up. Aircraft usually use 400 hz transformers, and motors, because due to the greater reactance at the higher frequency, they convert more efficiently, so they can be made smaller and lighter than 60 hz X-frmrs. It was said to me many years ago in aircraft school, if you put 120 vac, 60 hz, onto the primary of a 120vac, 400 hz aircraft transformer, you will draw massive current. (understatement!)

Which makes me wonder, when powering a 60 hz AC motor with a VVVF drive, what limits the current flow at lower frequencies, when the motor is turning slowly? I imagine the currrent sensing coils around the three phase feeders tell the drive board to chop the sine wave earlier and earlier, resulting in less RMS voltage accross what is essentially lower peaks.

I hope everybody found this intriguing! I like to solve and write about stuff like that. And I've got a couple more weird ones, if anybody is interested.

Greenpants has been around the block a couple of times. I first ran into this on a elevonic 401, the ac end of generator burned up and it was rewound. the repair crew hooked up the wiring per the dope sheet only to encounter vics problem. after going through the nema wiring diagrams it became obvious that the windings were not labeled the same as the original otis set up. we just rewired per nema standards and all is well. I have had this problem come around about a half dozen times in the last few years. as soon as you show up on an otis job with rewound ac motor, and they cant get it to run, you will look like a hero when you rewire it to nema standards. this is a good one to remember, as it will happen again.

hey vic, bring on the other wierd ones, im interested

Scott, I'm amazed it's happened to you at all! I had never seen it, or even heard about it. I thought it might have been a one-off problem.

When I was at Otis, I was compounding the generator on an MRS unit. It was 1990...Gas was a nickle, and dinosaurs ruled the earth..where was I? Oh, yes, for every turn we added in the series field, we should have gotten a linear effect in the base speed, but the speed jumped wildly when adding what should have been just another turn. Sure enough, the series field taps were mis-marked, and there was a couple of markers in the wrong place. I thought it was a neat problem, because the empirical evidence demanded a rational answer, even if that answer contradicted assumed constants. God, I love that sh*t! fun to think about, fun to solve. Sometimes daunting! Gets your brain working! Still hate Sudoku, though.... :^)

Here's one, also on a hydro- The job was a brand new 5 stop, standard bore hole, submersible, Maxton UC5, 60' remote m/r, with an MCE PHC 1000 control. The machine room was hot, because being the Marine Corps, the Feds didn't have to comply with the code mandated temperature maximum. They stuck the tank and control in a boiler room! The Federal Government is exempt from common sense, you know..

Customer would call and say the elevator just wouldn't respond. Everytime I got there, the thing had already cooled down. It kept shutting down on a maximum number of relevels. I forgot what that fault is called, but after 60 relevels, it triggered the MLT shutdown routine. I'd reset the fault, and run it for a bit, but it always ran great, with no problems. Then after I left, it would happen again. Where would you start?

I guess I would first start by making sure the valve would relevel properly, many overload and mlt trips that are intermittent can be solved by making the car relevel and be sure that the car does not overshoot up relevel, or overshoot down relevel, causing a jerking off sequence that eventually trips ol or mlt. Most guys will check this so I don't think it could be this easy. I have had one motion control do what you said and the onlynway we found it after many months of taking guesses was to put a analyzer on the system and check as ,any signals we thought appropriate. After a couple weeks it failed, and we played back the analyzer to find that during the night some one would take the car to the op floor and it would sit there for an hour or so and slowly leak down, and start chattering the Lu signal, this should have releveled the car, but the up normal limit was set incorrectly, and Lu could not move the car up, it would then mlt. Set limit correctly and that was the end of many months of calls. Ok now I'm thinking it can't be that easy, let me think about this awhile .. Ok how about the intrnal motor overload getting to hot and opening, then get a Lu signal and the car won't run up until thermal cools down, then it starts up, but thermal opens again and continues this cycle until mlt

Hmm, good ideas there. Was that the Wurtec S3 analyzer? I'm not fond of it, because it has high impedance inputs, that can't tell the difference between just noise, and a bonafide high state. Wurtec was designing a new analyzer, last I talked to them, and I asked them to include the option of drawing just a little test current on the inputs, so it won't be fooled by noise.

That's an interesting situation you had there, where the car is trying to level up, but hitting the top normal limit. I've seen 'em where they won't make the floor, if the limit is set too tight, but never seen it generate many relevels. Cool, thanks.

Here's another clue, that came to light during long marathon periods of observation.

On the rare occasion it was still hot when I got there, and I'd reset it, it would run on automagic just fine, but every couple of minutes, you would hear it relevel. Seemed to taper off after a couple of hours. (Yes, I sat there in front of the controller until my butt had a Home Depot bucket halo permanently imprinted on it. Too much info? Ok, right) Noticed tiny air bubbles seeping through the jack packing. Never releveled when reset after sitting for a while.

If I give too many clues, you won't have the fun of solving it, but it could get stale if I don't offer evidence that would be evident if you yourself were working on it.

This one threw me for a loop, because there was actually two separate problems, that both caused the same relevel/MLT symptom. Solved one first, then got a crushing dose of humility, when even after fixing one problem, the exact same fault did not go away. It was really strange, becuase I found a definite problem, that could absolutely cause that fault, and it had been identified and corrected. Yet it had the same exact fault again! Defied common logic!

You want more clues? Or is this pace about right?

Before I forget, there was another hydro issue where there were a plethora of door zone faults, always at the top floor. Oh, yeah, another one that ran with the doors open! Scary sh*t. And another one that blew the entire buildings' instantaneous circuit breaker, intermittantly. They're coming back to me now..like old friends, are the battles won.

A little more-

Opening the boiler room door cooled the machine room until I could stand the sweltering heat, but then that changes the ambient temperature, changes the exact operating conditions, and that's not good, because to find the problem, it has to be in its' failure mode, with the m/r door closed! Must observe, without affecting. It was some real "hot" troubleshooting!

Ok Vic, how about this, when the tank was hot, it expanded, and the oil level was lower then when the tank was cool. Not likely, but you said it was a dose of humility. Ok just give us the answer I can't wait any longer. Ha ha.

Whoa, I almost thought you were gonna guess the answer! It had to do with temperature, definitely. I'll let you off the hook in a second- But first, here are some things I did to ascertain the problem.
1. I sat there for hours, and recorded the time that relevels occured, put 'em on a time-based chart, and found that relevels generally subsided logarithmically, meaning the incidence of relevels was high after a reset, but dropped off quickly, continued to decline at a diminishing rate, like an olympic ski jump. That rate of decline reminded me of temperature based issues.
2. But I still had the bubbles escaping from the jack packing! That loss of volume would cause it to relevel. Bubbles never subsided, they just kept coming "forever".

So where was the air coming from? After all, the pump is submersed in the oil, and the only suction is at the end of the pump, everything after that is pressure only. I theorized about a multi-sectional piston, with loose joints, where the oil is entering the piston cavity through a lower joint, and pushing air out of the upper joint. Sounds good, except this was a one-piece piston. Hmm.. I even looked at the pit pump return line into the tank, but that was way across on the other side, away from the pump inlet. Yes, on the other side, until the pump started! The suction and/or turbulance pulled the long return line hose all the way over to the other side, where it got sucked up to the pump inlet. Since this was a new job, there was no oil in that line, just air, and it sucked that air into the pump, blew it into the jack, filled the jack with bubbles, and the car would sink as the air escaped through the packing. Then the whole process would start over again, and it basically would just keep releveling until it faulted out. Cut hose shorter, no more bubbles. Thought I fixed it, but the exact same fault came back. Still releveling, still faulting out. Weird.. Conclusion tomorrow. I really gotta go.

So, we got the bubbles problem out of the way, and still have relevel issues.

I was doubting the sealing of the Maxton check valve, and so took that all apart, cleaned it up, and replaced the valve stem seats, but it still releveled. Like always, it would initially level into any floor just fine, cycle the doors and park. Then after a couple of minutes, you would see the LU relay come in, and she'd relevel up. The packing was oil tight, no oil in the pit return sump, no oil going over the top of the jack. Everything was bone dry. Where was the volume of oil going?

I tried a pressure test, chained the push plank down to the pit channels, and put 400 psi on it. Watched the gauge, no bleedoff.

One day I put the car at the top floor, closed the gate valve in the machine room, yanked the power, then disconnected the feedline from the valve. Not a drop of oil came through that Apollo ball valve, all night long. Dems some great sealing ball valves, rite dere. Even with the ball valve closed, the elevator dropped 4" !!!

Where is the damn oil going, that is allowing the car to drift downward? It's not going back into the tank, it's not going back into the pit can, the jack's not leaking! Arrgh!

I consulted an engineer. Yeah, I'll admit this one had me baffled, and no, I didn't solve it without help. Wish I did. But the engineer measured the temperature of oil in the tank, and the temperature of oil at the jack, and we found that it had a difference of over 40 degrees! Sometimes much more, depending if the boiler room was hot where the tank was located, and if the elevator was being used a lot, etc. But generally, this point is that the hot oil would go through a long feedline, dissapating heat like a radiator, and then into a pit that was cold as a witches' tit. Must have been a high water table, bcause that pit was unusually cold.

Hydro oil, aka "32" oil, or ASO 150, has a coefficient of volume expansion of 0.027% per degree of Farenheit, (iirc, was over 10 years ago) and the contraction is the same when cooling. So for the given volume of jack oil, when the elevator is at the top floor, plus the feedline, equals "X", times 0.027%, times the degrees of temperature shift, equals "Y" volume lost, which came out to about 4" of piston length, when cooling over night, in worst case conditions.

It was just the conditions the job was installed under, and nothing at all was wrong with the equipment in any way. Chalk it up to the Fed's divine right to put the tank unit in a boiler room.

So I took the "FLO" fan/light output timer, which changes states after demand ceases according to the set time value, and drove a relay with it, which I used to inhibit the LU signal from getting to terminal 26, or up level input. When the car was running, FLO is dormant, car levels normally. After sitting for one minute, FLO changes state, the LU signal is inhibited, car drifts below floor level. It might drift even a few inches off floor level, but that's ok. There is no way to get into the car without having it relevel itself back flush with the floor, because any form of demand, whether Phase 1, hall call, car call, MLT, etc, would cause FLO to change states again, then it would level up flush. Even if the car had drifted out of the door zone, it wouldnt matter, because it won't open its' doors until it's in the door zone, after leveling in.

I don't reccomend modifying controls without getting the OEM to sign off on the change, because you could incur liability on yourself, even if some accident has nothing at all to do with the change you made. Liars, oops, I mean LAWYERS will distort anything if they think they can win a judgement. Draw it up, then send it to the OEM for an offical blessing.