Hot Box LVZ100 and complete shut downs

[250BOB]

Hi Guys......

This morning I was operating the layout....it had 3 locos running for about an hour while I got on with some maintenance off track.  One loco had sound on too.

 

After an hour or so.......I had a fault appear...everything stopped, but on pressing the red button after 10 seconds or so, everything set off again.  This then continued for about 30 seconds......then all stop again.  This then was repeatable time after time.  I took each loco off in turn, and even with only two non sound locos, the problem kept recurring after about 30 seconds of running.

 

By elimination, I ruled out it being any one of the locos, I took each one off in turn, and it kept happening.

 

A quick check around other areas revealed that my LVZ100 box was really hot.....the 5 amp transformer just barely warm.

 

I assume that the box is overheating and must have a cut out operating when it gets too hot.???

 

But I have never had this problem occur before in over 7years.....that said, I have never felt the box before, or if I have, I havent known it this hot.

 

I dont run anything else from the power bus other than the locos themselves.

 

Non of the three locos seem to be warmer than normal in the area of the decoder.

 

Any thoughts please.

 

Thanks...........................Bob.

[250BOB]

Check the layout for a hidden short. That could be in the wiring under the baseboards, a faulty frog-juicer or similar failures.

 

If its a hidden short......wouldnt the system shut down, and I wouldnt be able to run anything at anytime.??

 

Or......if I just switch on the system, and dont run any locos, switch all locos lights off ...would you expect the LVZ100 box to remain cold.

[250BOB]

There's an option the LVZ100 itself might be faulty. Disconnect the layout and leave it on for a while. If it gets hot, return the unit to your dealer for repair.

 

I noticed I had also got about a dozen locos on the layout, with lights on, but not running.  Could that have added to the overheat.?

[250BOB]

There's an option the LVZ100 itself might be faulty. Disconnect the layout and leave it on for a while. If it gets hot, return the unit to your dealer for repair.

 

I have the layout switched back on again now...........no locos running....all lights off.......I'll see what happens after about an hour. I'll check how warm it gets.

 

Thanks for your suggestions.....process of elimination.

 

Bob

[RFS]

You could have a problem with your wiring - ie you have a short somewhere but the wire is too thin at that point to draw all of the current from the booster.  Hence it sees no short and does not cut out.

 

Try the coin test - go round the layout and place a coin across the rails to force a short.  Does the booster cut out immediately? If not there could be a problem with the wiring somewhere leading up to that point. Try it at the points furthest from the booster.

[Izzy]

Logically, if it's worked okay till now, and no changes have been made to wiring etc, then I would tend to think that perhaps some fault with the unit has developed, a component failed.

 

Izzy

[250BOB]

You could have a problem with your wiring - ie you have a short somewhere but the wire is too thin at that point to draw all of the current from the booster.  Hence it sees no short and does not cut out.

 

Try the coin test - go round the layout and place a coin across the rails to force a short.  Does the booster cut out immediately? If not there could be a problem with the wiring somewhere leading up to that point. Try it at the points furthest from the booster.

 

 

Wow.............I've not seen that before...!!!

 

The coin shorted out my system immediatley........except the further away I got from the LVZ100......it didnt.

 

Quite a lot of the track which a compressed up and over figure of 8, will not short out with the coin test.

 

But what on earth do I do next.?????  How the heck do I start looking for the fault.

 

Bob.

[RFS]

This can happen if your DCC bus has wire that is too thin and you are encountering voltage drop.  The further away from the booster the greater the voltage drop.  A point can be reached where the drop is such that the wire can't take the full 5 amps from your booster, so the booster doesn't see an overload.

 

I can only suggest laying a new bus with thicker wires - mine's 2.5mm solid copper from B&Q "twin and earth".  You could try looking at the wires in the area where the coin test fails and see if any of them are warm.  But I would advise caution: if some wires are indeed heating up then that could be dangerous so don't leave the layout switched on unattended!

[Phil S]

As the coin test result shows - in the further parts of your layout has too much loop resistance - so that even a track short (coin test) will NOT ALLOW ENOUGH current to flow to trip the safety circuitry - this shuld be remedied asap by paralleling or replacing the bus wiring with something which CAN SUSTAIN  a CURRENT IN EXCESS of the contoller's MAXIMUM (because the MAXIMIMUM IS NOT A FAULT !!.   The intent is that when the 'maximum' current is flowing, the voltage does not drop more than a couple of volts anywhere on the layout - or sound decoders etc might  stop working.

 

It is very likely that, you DO have a 'short' or excessive load on your track ( PART of which may be static locos, lit coaches. accessory decoders etc, BUT THERE MAY ALSO be a SPECIFIC problem such as a SINGLE STAND OF WIRE across a track ... perhaps at a point and in the track bed where it is difficult to see.   [i last happened to me when I put a metal-clad battery down (on track) when distracted elsewhere by a derailment ! .... the short was NOT anywhere nere the derailment !!!   A short can be located by using an ohm-meter (resistance range on a  multimeter) and looking for the LOWEST value .... simply disconnect the Dcc source, and progressively hunt for it .... it helps if geographical areas (such as boards) can be isolated to laid localisation of the fault.

 

One possible source is from Steel-Wool which some people used to use (and some still do !!! ) for trees  (despite the fire risk when it comes into contact with live track)

Many years ago I had a internal point-switch fail, and allow a 3.5A current to flow continuously through it .... melting adjacent plastic! -- it was insufficient to trip the safety cutout, because the NORMAL MAXIMUM current of the ZTC511 was 5A!    

 

Don't forget that the 'fault'/'short' current is IN ADDITION to the current being taken by other devices on the track. 

Once you have removed other locos etc, with the high loop resistance you have identified by failing the coin-test, there may be insufficient 'fault current' to cause the trip again.

 

Some power supplies my have automatic resetting. Some a temperature sensor. 

On 'Plug-top' or some sealed-unit devices like transformers, they may rely on a THERMAL FUSE ... which, when it has failed, fails permanently.  (DO NOT solder in a replacement ... without using a heat sink !!!)  When teaching electronics at school, in the 80's, I had some of these fail because they were left by sunny windows in the lab!!

[250BOB]

Many thanks for replies guys......really appreciated.

 

I'm not an electrician so be gentle with me.

 

My compressed figure of 8 up and over, measures about 128 feet in length.......I have used the express models power bus kit, of which the bus wire is pretty substantial wire.

 

I have put droppers in only where necessary (minimum possible).....and I think all are within about 20 feet of the booster box,in each direction.  So that means I have about 80 feet of double track that just relies on the rails for electrical conductivity....and it is only in these areas where the coin test doesnt cause a short.

 

The wire from the power bus to the rails is only the thinner typical layout wire....but there are not many....only done where required.

 

If I went about an excercise of introducing power from the bus at more regular intervals over the 80 foot that doesnt have droppers, will that overcome the problem, or help to.??

[RFS]

If your droppers are thin - usually that means stranded 7x0.2 or solid 1x0.6 - then it is generally recommended that they should not be more than 300mm in length.  Rail joiners themselves can also cause voltage drop which is why it is often recommended to have a dropper on every piece of rail, especially in areas where the rail is painted or ballasted.

 

I would start by adding more droppers until you get to the point where the coin test always works in every part of the layout.  5 amps @ 16 volts is 80 watts of power, and that's enough to power a pair of 40 watt incandescent light bulbs, and think how much heat that generates - and almost instantly!  Get a short with a typical model loco, with plastic underbody and track, and a great deal of damage can be done quickly. That's why DCC systems are so sensitive to shorts.

 

If your wiring is then adequate you may then find your short starts to trip the booster, which makes it easier to find.  I once had a problem with a Peco PL-13 polarity switch where it was routinely resting with the wiper touching both sides internally.  I only got to investigate when the frog was dead, and when I opened the PL-13 it had practically melted! So you may have a bit of detective work to do. I would suspect the short is somewhere near a point, for example a failed IRJ, PL-13 wiring etc..

[Tony_S]

I had a fault that confused me for a while as I had dutifully snipped the little wire links on a Peco Electrofrog point but the frog rail was a bit loose and sometimes made contact across what should have a been a gap. It actually looked OK but wasn't.

While I agree with what everyone else says about needing more wires to the layout if you just want to reassure yourself that the Lenz LVZ100 is OK you could disconnect it from the layout and connect it to a couple of yards of plain track and put a couple of locomotives on it.

 

Tony

[250BOB]

I had a fault that confused me for a while as I had dutifully snipped the little wire links on a Peco Electrofrog point but the frog rail was a bit loose and sometimes made contact across what should have a been a gap. It actually looked OK but wasn't.

While I agree with what everyone else says about needing more wires to the layout if you just want to reassure yourself that the Lenz LVZ100 is OK you could disconnect it from the layout and connect it to a couple of yards of plain track and put a couple of locomotives on it.

 

Tony

 

Hi Tony

The LZV100 is fine.......locos running as we speak........the problem was the box got very hot this morning......then the system cut out, dispalying AUS as in a short, I suspect the box overheated, as 10 seconds later when the red button was pressed, everything back to normal.  About 30 to 60 seconds later, same again....and so it goes on repeating itself.

 

I suspect after the cut out.....10 or 20 seconds later its cuts back in again for about a minute, then trips again cos its still hot.  After cooling for 20 mins...its ran for ages without any problems, and is still running now.

 

Bob

[250BOB]

After running the same three locos for the last hour, without any problems, the LZV100 is only mildly warm, normal I expect.......but I had turned off the lights on all 15 stationary locos.

 

After an hours running, I have now switched on all the loco lights again....I am now waiting to see if the box heats up as before.

 

 

 

So....if I dont have a short......would the lack of droppers on my quite large layout be a cause for the LZV100 to heat up like it has...????

[Tony_S]

After running the same three locos for the last hour, without any problems, the LZV100 is only mildly warm, normal I expect.......but I had turned off the lights on all 15 stationary locos.

 

After an hours running, I have now switched on all the loco lights again....I am now waiting to see if the box heats up as before.

 

 

 

So....if I dont have a short......would the lack of droppers on my quite large layout be a cause for the LZV100 to heat up like it has...????

Well if something conductive had been on that section of track that has now been moved (a bit of thin wire or whatever) perhaps the problem has resolved itself but it does sound as if some more wiring is required! I have based my bus on that of the modular layout of the club I used to be in. Each board has a bus with droppers to the track but each boards bus is connected to the next one by jumper cables using XLR connectors. This makes fault finding easy as my Lenz can be plugged into each individual board for testing.

Tony

[RFS]

If there's anywhere on your layout where the DCC booster doesn't trip using the coin test then that's where you need to add more droppers.  Otherwise you run the risk of serious damage to a loco that shorts there, as it may not trip the booster and the current it's taking will dissipate as heat. 

 

Sounds to me like you might have a transient problem, eg caused by a point set a particular way, and once you change the point the problem resolves itself. 

[Sunnysa]

It has been said many times, do not rely on rail joiners (fish plates) to carry current.

 

Sure they may do for a reasonable time but more times than not the joiners will fail.

 

Which you say your layout has started to do.

 

 It may be APITA to do but to help bullet proof a lay out, irrespective  of size, power feeders need to be attached to every piece of track including points.

 

Cheers

 

  Ian

[34theletterbetweenB&D]

...So....if I dont have a short......would the lack of droppers on my quite large layout be a cause for the LZV100 to heat up like it has...????

No. With no short circuit present, increased impedance on some sections of your layout due to lack of track feeds will not cause the unit to heat up.

 

But, as others have already pointed out, with some sections of your layout having enough impedance that a dead short (the 'coin test') doesn't cause the unit's short circuit protection to trip, you are permanently at risk of heating the unit if a short circuit occurs in this section. There's no real alternative: improve the layout wiring until a short created anywhere on the layout immediately causes the system to trip.

 

You may well find that improving the wiring leads to a near inoperable layout, because the unit keeps tripping out with a short. That would be an indication that something currently in the high impedance section causes a standing short circuit (possibly when activated or selected) the effect of which is at present masked by the high impedance limiting the current draw to a value within the constant supply capability of the power unit.

[Neil Rogers]

we suffered a similar problem with RS Tower,

 

1- we had a load of approx 3.5 amps, the problem is you don't exceed the 5 amp limit but when you get close the system warms up, then trips out. Its the thermal cutout trip that protects LZV100 from doing any damage.

 

this is what we did to cure the issue!

 

1- reduce the load on the LZV100 i.e. power districts, boosters, circuit breakers etc. (on RS Tower we use a mixture of LV102's & Tam Valley Dumb Boosters, and the LZV100 has no load on it).

2- how well is the LZV100 ventilated? we now have a cooling fan on all the time. one of those small 12v cooling fans out of an old PC will do the job, if not there about £5 from Maplins

 

HTH

 

regards

Neil

[Crosland]

I have put droppers in only where necessary (minimum possible).....and I think all are within about 20 feet of the booster box,in each direction.  So that means I have about 80 feet of double track that just relies on the rails for electrical conductivity....and it is only in these areas where the coin test doesnt cause a short.

 

That's a bad situation...

 

The wire from the power bus to the rails is only the thinner typical layout wire....but there are not many....only done where required.

 

...made worse A classic ilustration of what many of us have said, time and again, about wiring DCC layouts, and what can happen when you don't follow best practice

 

If I went about an excercise of introducing power from the bus at more regular intervals over the 80 foot that doesnt have droppers, will that overcome the problem, or help to.??

 

Yes, droppers should be local, short, connections from the bus to the track. The bus (or sub-busses) should reach all parts of the layout.

 

Andrew

[royaloak]

It sounds like you need decent sized bus lines running around the layout and some more droppers further away from the booster, I dont think your bus wires are thick enough even though your existing droppers are.

[250BOB]

That's a bad situation...

 

 

...made worse A classic ilustration of what many of us have said, time and again, about wiring DCC layouts, and what can happen when you don't follow best practice

 

 

Yes, droppers should be local, short, connections from the bus to the track. The bus (or sub-busses) should reach all parts of the layout.

 

Andrew

 

Ok Andrew......I feel totally ashamed.!!!!   How many times have heard the tale about droppers to each piece of track, and then ignored it.

 

I have this evening began the process of putting in more droppers to reduce the run of 80feet with no feeds........I have now reduced the gaps to 20 feet, by putting in direct bus droppers at 3 places, on both rails and both up and down lines.

 

the layout now passes the coin test with flying colours.

 

It might be difficult to do every piece of track, because of how the layout is built up with walling etc.,  But I intend to divide the 20 feet sections again, so that I have no more than 10 feet runs without power feeds. 

 

For the booster to heat up like it did, I must have had an undetected short.   The trains are running as we speak....and the booster box is not hot, just mildly warm as per usual.

 

A lesson learned for me........wrist well and truly slapped.

 

And to everyone else who has helped with advice....a big thankyou.!!   

 

RMweb scores again......the best possible advice from some of the best people.

 

Bob

[tractor_37260]

Being a Lenz LZV100/TR150 user I've found this thread very interesting.  I'm aware of the need for droppers ideally for each piece of track/points etc, to combat any possible future rail joiner issues. As for the main bus wires, what is the recommended minimum cable size ? Is current/best practice still to keep the 2 bus wires separate from each other, or to wind them together lightly ?  And bus termination, is that only really needed on very large runs ?

I've a new project to start wiring up shortly, so any comments would be appreciated.

TIA

Ken

[melmerby]

Being a Lenz LZV100/TR150 user I've found this thread very interesting.  I'm aware of the need for droppers ideally for each piece of track/points etc, to combat any possible future rail joiner issues. As for the main bus wires, what is the recommended minimum cable size ? Is current/best practice still to keep the 2 bus wires separate from each other, or to wind them together lightly ?  And bus termination, is that only really needed on very large runs ?

I've a new project to start wiring up shortly, so any comments would be appreciated.

TIA

Ken

I use 2.5mm T&E cable laid flat i.e not twisted (It was recovered from a house re-wire, so free.)

Best practice is to twist wires together, but it may make little difference in the world of model railways.

Bus terminators do not exist as has been mentioned several times before, there is no determined impedance to terminate.

However a "snubber" to remove unwanted spikes at the end of a long run could be beneficial, although most find it unnecessary.

 

Keith

 

EDIT I have droppers to every piece of track and every point and running is near perfect, in comparison to some of my previous efforts where I relied on fish-plates for contact!

[34theletterbetweenB&D]

In support of what 'Melmerby' has posted, I reckon the most important element is large cross section copper wire. I am likewise on salvaged T&E house wiring (30A), with most of the insulation stripped off and spaced apart somewhat so that everywhere you go the two busses are available to be soldered to.