DCS and short circuits

Chuck,

If I lay metal across the tracks by accident what happens to the TIU?

If you do that while the tracks are powered, you better have good short-circuit protection either in the transformer or in the Hot wire between the TIU and the transformer.

 

Otherwise, you will most likely either blow the fuse in the TIU or risk damage to the TIU.

What size fuse would you recommend on the hot wire?  I am running the Z-1000 transformer. Do you think it's built-in circuit breaker protection is enough?

 

Thanks Barry.

The breaker is marginal.  I'd probably go for a 10A fuse in-line, that will go before the 20A one in the TIU.

 

 

That's what I'll do John. Thanks.

I have blown a few TIU fuses. I now use 15 amp fuses in my TIU instead of 20 amp.

I have 180 Lionel Powerhouses which trip very fast. I also use the TVS's recommended here in strategic locations.

I am pretty sure that using 15 amp fuses does not really change things electronically speaking. My idea to change to 15 amps is not based on anything other than it makes me sleep better. Funny the things people that don't know electronics will do to protect their babies based on nothing more than " it seemed like a good idea at the time".

Can someone tell me if using 15 amp fuses helps at all for any valid reason? If its just silly for me to do so please lie to me and say its a really great and smart idea. I like sleeping well.

Happy Holidays

If I lay metal across the tracks

 

I think about this every time I run my aluminum passenger cars

 

The other day I ran my passenger cars and forgot to throw a turnout, resulting in one of the cars "hitting the ground".

 

I have the TIU powered by a Lionel 180w brick, both units have circuit breakers.  I also have a TMCC Command Base-L connected, the base and the brick are plugged into one of those power strips that has 6 outlets and a circuit breaker.

 

When the car derailed, the engine shut down, not sure if the TIU, brick, or base powered down, but I turned off the power strip within 1-2 seconds of this happening (I didn't bother to see if any unit had powered down, moved too quick to take time to notice).  NONE of the circuit breakers were tripped, all I did was to rerail the passenger car and turn the powers strip back on.  I also had 3 other engines sitting on the tracks, not powered up.

 

I've had this happen 5-6 times with the same results.  Maybe I'm lucky or maybe the units did what they were suppose to do, but I find it strange none of the CBs had to be reset.

 

 

That's exactly my point... it's not the intentional screwdriver across the rails it's the UN-intentional screwdriver across the rails scenario.

 

I ran Digitrax for years and it would shut down the second it felt a short. Very reliable. I'm not knocking DCS it's my system of choice now that I'm running MTH loco's.

 

The goal is to ensure I don't do damage when I screw up. I'm liking the 10-amp in-line fuse idea and just ordered them.

 

Thanks!

I asked MTH about the 20 amp limit since the transformer normal limit is 10 amps.  The 20 amp fuse protects the TIUs internal traces from being damaged in the event of a short where high amperage could be sourced.  Think post war ZWs.

 

So back to you individual protections you want to fuse to protect your inputs.

 

If your using a Z-1000 and you want to trip before the breaker on the Z-1000 trips you might pick a 6 or 7 Amp fast blow fuse, not 10amps which is higher than the Z-1000 rating.

 

For Lionel PH which have super tripping capability, I don't think you need a fuse, but you could go with the 10amp.

 

Going to a 15amp in the TIU just protects the TIU traces a little better.  Voltage spikes are a whole different matter.   G

I don't see anything wrong with the 15A fuses in the TIU, but you may be taking it apart more often to replace them.  

All these fuses/circuit breakers we're talking about are on the INPUT side of the track and are fine for things like lightning strikes, but what about the scenario he/we are talking about where the short occurs at the track?  The fuses/CBs on the TIU and brick do little good when the short is on the OUTPUT side.

Bob,

 

When there is a short on the tracks, a fuse or circuit breaker protects everything between itself and the source of the short. That's why the closer the fuse or circuit breaker is to the transformer, the more effective it is.

 

The fuse or circuit breaker should always be wired into the Hot line. Don't depend on the TIU's fuse on the Common side to protect anything except the TIU.

I'm not sure what you're talking about here Bob.  My PH180 brick breakers trip on the spot for any derailment, that's a short on the output side.

 

The fuse in the TIU is on the output side as well.

 

The TIU has no current protection, other than the stopgap 20A fuses.  That's why it's recommended to have good circuit protection on the input side to avoid excessive current into the TIU.  Obviously, it won't hurt anything to have more protection on the output side.

 

EDIT: I see Barry slipped in with a similar answer while I was thinking.

Thanks guys (I'm thick as a brick sometimes )!  I'm still curious as to why the CB on the PH180 hasn't tripped.

I have seen a PH180 with a defective breaker circuit.  Since it's an electronic circuit that depends on the circuit's proper functioning to pick the relay to interrupt the power, a failure in the circuit will render the breaker in-op on that unit.

 

I think they would have been better served having the circuit hold the relay until the overload and then drop it out, it would have been more fail-safe.  However, Lionel didn't consult with me before producing the product.

 

MTH puts the fuses and breakers on the common side.  For a single transformer it doesn't matter.  When using multiple transformers with common "common" fusing the hot lead is more appropriate.  G

FWIW, I recently found these and then a discussion came up on the forum. (It's great how many times that happens around here for me.) During the discussion someone pointed me to this thread that I found interesting, you might also.

 

PSX-AC Demo

 

Don't have a layout set up right now, but have been playing with them using a Powerhouse 180 and they are very impressive! They always trip before the PH180 and the PH 180's are very fast!  May be maximum overkill, but I now have about a dozen PS2 & PS3 diesels and replacing them (even one) would be much more than a few of these things! Replacing a TIU would be more expensive as well. I plan to have 1 on each TIU channel if I ever get all of the TIU channels used.

 

The others in this thread got theirs elsewhere I think, believe their are links in the thread. I got mine at Tony's Train Exchange. Also more information on them at this site. I was happy with their service.

The MTH Z-1000 I have has a 7 amp breaker on it and it pops pretty quick when something happens.

 

I would go with a 7 or 8 amp breaker or fuse on each circuit from the TIU in the side of the red plug to track power.

 

After reading some of the posts on here, I now know that the TIU is fused on the common side if that is correct. Just my opinion but I would have fused each set of output terminals with a 10 amp fuse or breaker just to be safe.

 

Lee Fritz

phillyreading,

   If I remember correctly Scott made a 6 Amp breaker set that the guys were using for the Z-1000 and it worked really well. 

PCRR/Dave

I ran Digitrax (HO) for a decade before switching to MTH O diesels. Digitrax would shut down the instant a short was detected and would come back as soon as the short cleared. It's a nice feature that maybe could be replicated by MTH?

 

Every frog in my layout was powered via a Tortoise switch machine and I had to put car light bulbs in series with the wire running to the frog. The light would "eat" any transient shorts caused by the Tortoise and the turnout points not quite in sync with each other. Digitrax would not see these shorts because the light bulb took the short.

 

The light bulb would also light if a locomotive was driven into a turnout "against the points".

 

As we know shorts can cause enough heat to weld rails. I'd like to see MTH incorporate the technology Digitrax has?

 

Now this inspires me with another thought for my fellow railroaders: what if the car light bulb was placed in the outputs of the TIU? Would a short on the railroad be "eaten" by the bulb and it would light up indicating a problem?

 

What do you think?

 

G in your example could you tell me again which is the common side? Is it the red or black wire?

Red is called Hot and Black is called Common for our model trains.  G

OK thanks. I wired my entire barn in 120V and black was always the one that I knew would bite me...  In our case with trains it's the red one that's hot? And the black is common or can it also be called neutral? I know we're beating a dead horse but it's an important issue.

 

 

And the black is common or can it also be called neutral?

In the world of MTH and DCS products, BLACK = COMMON for our toy train, 3-rail wiring.

Re: Color Coding of wires and Terminals:

  See AC and DC Wiring Conventions with photos toward bottom of the page.

 

"The lockons show a very good example of two different Color Code conventions.

   The AC convention that I use is based on 120V residential and commercial wiring postwar toy train wiring. My outside rails/commons are tied in with white wire and variable voltage/center rails are black wire. The AC convention is handy when you get into more than one circuit because there are a lot more colors available.
   The DC convention that is being use with modern toy train wiring applies to low voltage wiring and electronics. Their outside rails/commons are tied in with black wire and variable voltage/center rails are red wire.
Use the Color Code convention that makes sense to you."

Susan,

 

My post was intended to be taken in the  context of DCS, where MTH consistently uses RED for Hot and BLACK for Common across their product lines of TIUs, transformers and lockons.

 

I can accept that Barry and thanks for always taking the time to help. It looks like the red wire is the one that carries the electrons full of energy to our layout and the black wires carry the tired electrons that have done the work on the layout back to the power company.

 

Close enough?

 

 

Not just MTH uses the convention of Red as hot.  Obviously any wiring colors can be chosen, but I think most layout builder avoid trying to match household 120V convention.

 

If you need to use household wire because of gauge required I think I would still chose black as common and use the white as hot.  It seems to be a  convention for model trains.  The best thing to do with a larger layout is make up an index and stick to the colors chosen.  Track power, switch power, track activated accessories, stand alone accessories, etc...  G

 

Others with the same Z-1000 brick have reported that the TIU fuses go, so there is some variability in the circuit protection.

 

A Z4000 plus two Z750 Transformers power my trains. The circuit breakers in these MTH transformers have saved the TIU on my layout many many times from derailment short circuits. Thus it would be wise to use a circuit breaker with the same operating characteristics as those in the MTH transformers.

 

 

Best to use as small an external breaker as will reliably run trains.  On 5 of my 6 circuits, I use 5 amp breakers; the 6th uses 7.5 as I often run 3 or more trains on it.  POwer is a Z4000 and two postwar ZWs.  I don't use smoke, which draws much power.

 

Breakers in the long run are cheaper than fuses.  For pure redundancy, I also have 10-amp fues in line with the breakers, and have never had one blow

 

In household 120-volt wiring, black is "hot" and white is common, known as "neutral."  Where there are multiple hots (as between 3-way switches) red is also used for hot.