Home Forums General Discussion Technical Questions Otis mcs 220 RSL fault

Hello good people, i am currently inspecting the weirdest fault i have ever seen so far.

I have an otis mcs 220 with RSL faults, and after hours of tracking down whats disturbing the bus i accidently stumbled into the "problem/solution".

The remote station on floor 3 call button is dragging the whole bus, making me loose the connection to most RS cards.

Now this is where it gets odd, if i plug in the bus cable for the shaft going into LCB2 about 1/4 of the way the elevator goes on normal and starts a correction run. But looses connection if u plug it in too far. And it ONLY works if i have the RS(remote station) on floor 3 plugged in, if i plug it out i cant get the elevator to run however much i yank on the plug.

I have tried switching buttons with different floors, plugging out all RS in shaft and changed the termination card at ends. now i cant hold it for too long in that exact 1/4 of the way in for too long, but as long as i keep it there elevator works flawlessly. I have no clue what to even try next exept continue looking more. But im at loss for what more to try...

I have already changed some RS cards on roof 16 and 17 to no help.

Any tips is appreciated

The RSL relies on a specific differential voltage being present between the L1 and L2 signal lines in order to detect clock pulses and data.

It also relies on proper power getting to each Remote Station (the "RS" boards). If you have a lot of current draw on those power wires you can end up with different "reference" voltages (the common 0V) at each Remote Station. Remember Ohm's Law, V=IR ! This is typically a problem with very high rises or where you have some power-hungry fixtures attached to the Remote Station power, or perhaps a bad connection. The original AMP insulation displacement "IDC" connectors were notoriously unreliable if you didn't use AMP's special tool and tried to push the wires into the "V" shaped insulation piercing pieces.

And there's also proper Line Termination. Depending on whether you have "Master In the Middle" (e.g. LCB or LCB II with a single RSL) or "Master At The End" (RCB or RCB II and most later GCS-based systems with separate Car, Hall and Group RSLs), you need to be using the right terminator board.

Lastly, there's also the issue of proper RS board addressing. If you have duplicate boards you can get parity errors if the active inputs are different between the two boards. Have you verified that all the RS boards in the system are correctly addressed?

It sounds like that one board on floor 3 is, as you say, dragging down the entire RSL. The real question is what is so "special" about that one board? If you disconnected the buttons from it, does it still drag down the entire RSL? If you move that board to a different floor, or put a brand new RS board onto floor 3, does that change anything?

I suspect that when you've got the hoistway RSL connector 1/4 of the way into the LCB II that you are possibly not powering up that segment of the RSL properly, or maybe the L1 and L2 signals are not fully connected in some weird way. Unless you run the Self Test and look at which missing RS boards are there, you don't really know if the hall button RS board for floor 3 (or for some other floor) is communicating or not.

I do not understand your comment about changing RS boards on "roof 16 and 17", which maybe is a typo for "floor 16 and 17". Without knowing EXACTLY how many floors you have, and what other RS boards are connected it's a bit hard to say for sure. Perhaps you can share more details about ALL the boards on the RSL.

One more thing - are these "genuine" RS boards? There was a time when Chinese-produced Otis controllers were being shipped with locally-made "clones" of the RS boards. Some of them even had similar part numbers as the German-made ones, but they were prone to all sorts of weird failures, including bringing down the entire RSL bus.

Im going there now but yes i have checked most RS boards for their adresses, im not fully understanding the RSL parity fault, how can a board change adress after elevator has been running for 20 years. Its a single rope elevator with 9 floors, what i meant is we changed 16 and 17 is we changed the rs14 boards on the car adressed 16 and 17 because they came up in the selftest and i couldnt get the TCI signal to show on rs14 board 16 so elevator wouldnt go away from inspection led, but no diffrence happend after changing them.

The RS board on floor 3 is just the board dragging the bus not the button, i can disconnect it and still if only board is plugged in, fault happends. I havnt tried putting brand new board in, but the odd thing is bus is completely bugged out if i remove the board on floor 3, so even if thats the problem, its not fixed if i remove it.

If i run selftest with everything connected it looks like all of the shaft boards is missing and half or if not most boards on car too, but i cant hold the plug still for too long to do the test while i have it in that position.

in car junction box i have RS14 board with adresses 16,17,20 and behind car panel 4,5,6,7,8 and in shaft 21-29 for buttons, and i have rs18 adressed 60 in the controller that splits the bus to the car

About the "genuine boards" i wish i could say i knew but i would hope so, they are ordered from the most used elevator parts seller in sweden but even they are a bit sometimes not so honest where their parts come from or quality...

The elevator can change a parameter by itself if it gets a surge (often through the old phone line on the REM).
If you have 2 rs boards programmed the same it causes parity errors, can happen on lifts with 2 cop panels in the cabin.

But I think you should measure the voltage on the data of the rsl before and after disconnecting the button board (needs to be 0.32v). I think you probably actually have another hall button board dragging down the rsl line. It's only 9 floors so you could disconnect them all and reconnect them one by one if you have to.

I'm certain the Swedish supplier is not using Chinese boards.