Could use some help - 7 amp in-line fuses frequently blowing while running new engine

[Birds]

I am frequently blowing in-line 7 amp fuses when a brand new engine (pulling 5 lit passenger cars) traverses switches or crossings. Sometimes it happens when I stop on a switch or crossing and start up again or try to reverse the unit. Other times it happens if the train goes slowly over an O-22 switch or crossing. The 7 amp fuses don't blow all the time in each scenario, but it is frequent enough that I am trying to understand what is taking place, and trying to see if there is a problem in my wiring.

The setup:
I run a KW with the A & B posts protected by in-line 7 amp fuses.

Wiring is star wired and 16 gauge wire (which I understand should be able to safely handle 10 amps)

Tubular track.

I have two independent loops that interact at switches and crossings. The middle rails of the two loops are insulated at the switches and crossing where the two loops interact. The common rails of the two loops are connected together at the switches and crossings where the two loops interact.

The switches are powered with constant voltage from a secondary starter set transformer.

I have no operating accessories or operating cars.

What I've checked

The engine alone (no cars attached) typically draws between 1.4-1.8 amps running on regular tubular track. When it traverses crossings or switches the amp draw can jump up to 3-4 amps.

The engine has a 6 amp reversing unit. When testing the amp draw with a digital VOM while reversing, the draw appears to be under 3.5 amps

The five lit passenger cars add about 1 amp.

Questions:
What might be a cause for the amps to jump like this when a switch or crossing is traversed?

Is there a way to eliminate or even out the amps?

Should I insulate the common rails between the two loops?

Thanks,
Birds

[Big_Boy_4005]

It may be your passenger car lighting putting you over the limit. Are you powering your switches with fixed voltage from a separate source, or are they on track power? It doesn't sound like the engine is the problem, it sounds like a combination of things are adding up to more than 7 amps. Are you using slo-blow type fuses?

If this is only happening on the switches, check that the rails there are clean and the electrical connections are solid. In electrical terms, voltage is pressure, and amps are volume of flow. Since the volts are limited, and the train wants more power for whatever reason, it's making it up in amps. Why is it so "hungry" in those locations?

[Birds]

Thanks Bigboy.

• The switches are on fixed voltage powered by a second transformer dedicated to switch power.


• The total amps drawn by all five passenger cars are: 1.06 amps @ 14.25 volts.

The increase in amps while traversing 45 degree crossings also has me wondering what is taking place. The fuse will sometimes blow at 45 degree crossings when you stop the train and try to start up again, or try to reverse.

Would adding power drops before and after switches and crossings help even out the amperage draw?

Thanks,
Birds

[Big_Boy_4005]

Extra drops might help, they certainly couldn't hurt.

Starting from a dead stop, will generally draw more current because the motor is working harder to get the train rolling. A train moving at constant speed will draw less. This simple physics principle applies to your automobile and real trains as well.

Are the passenger cars fairly free rolling? More drag means more work required which translates to more amps. Electrical rollers and axel bearings might benefit from a little lube, thus reducing the drag.

The ultimate solution may be to change the fuse value to 8 or even 10 amps. As you mentioned before 10 amps is the safe limit 16 gauge wire. It doesn't sound like you are constantly drawing the higher current, but rather need it on start up.

[Anonymous]

I would look at dirty track or connectons especially in the center rail. Could be current is being drawn through the thin wire in the passenger car when the pickup rollers are on both sides of the crossing. Make sure the rails are feed on all 4 sides of the crossing from the transformer.. I would also go to a 10 amp fuse.

You could also convert your passenger cars to LED lighting to reduce current draw but I dont think your transformer is over taxed. LED lighting has other advantages as it reduces arcing and blade burning on your passenger cars.

Dale Hz

[Birds]

Thank you for the replies.

The engines and passenger cars have all been lubricated recently to reduce drag.

The passenger car bulbs are the mini-lights that have wedge bases (like Christmas tree lights). Each lamp draws .1 amps (.2 amps total per car). Haven't found LED replacements for these yet, but the mini-lights are more efficient than the regular bulbs.

The crossings and surrounding track are new and clean. Good tight connections too.

I will try adding drops before and after the crossings and switches.

Thanks again,
Birds

[wrmcclellan]

I have several trains with dual pickup rollers where one roller can short on a common rail while the other is still on the center rail, momentarily shorting the rails together. I also have a Weaver 060 brass loco that has really wide rollers that can short from the center raisl to common on a switch. I wonder if it is this scenario causing you the problem?

[trigtrax]

I think McClellan has your answer. Your normal current draw will not blow the fuses but when you pass switch tracks you are creating a short to ground. This momentary spike is what's doing the damage.
First take a passenger car and slowly push it over a switch. Then run your engine slowly over the same switch. You should see a spark if you're creating a short.

[Birds]

Thank you for all the responses.

Progress is being made.

The tips on looking for sparking and shorting are good ones. I'm not sure how to completely eliminate sparks on crossings and switches. It appears that there is always a small amount as the wheels and rollers traverse the gaps. If anyone has some suggestions to eliminate this I would appreciate the benefits of your experience.

I added four additional power feeds to the layout. What I noticed is that the amps from the transformer to the main feed wire (the portion before the terminal strip) stays the same - about 2.3 - 2.8 amps. But the individual power feed wires (which leave the terminal strip) each remain under .5 amps.

I found that the pickup rollers had become very greasy (new engine with lots of grease getting worked out), so I cleaned those up.

I also noticed that one of the pickup rollers was pitted all the way around. That would not make for a good contact against the track and it picks up and holds grease in the pits. I used a Dremel with a very fine emery disk and polished the roller smooth. That worked quite well.

[wrmcclellan]

Birds,

A pitted pickup roller can be evidence that the roller has been involved in short circuiting something on the layout. It can also be a symptom of dirty track.

Non-derailing switches will usually show a bit of sparking when the wheels complete the non-derailing circuit of the control rail. Thus some sparking on the outer control rail is normal.

Good luck.

Regards,
Roy

[Anonymous]

http://www.rossswitches.com/technical/rcsprem.jpg
Check this weblink to Rose Switches could be some help.

[trigtrax]

Your pitted roller is a place to start looking. Sometimes a tiny dab or paint on the ground spot that's hitting this roller (Paint track not roller [:D] ) ia all the insulation you'll need to solve the problem.

[lionelsoni]

"I run a KW with the A & B posts protected by in-line 7 amp fuses."

"I have two independent loops that interact at switches and crossings. The middle rails of the two loops are insulated at the switches and crossing where the two loops interact."

"When [the locomotive] traverses crossings or switches the amp draw can jump up to 3-4 amps."

"I also noticed that one of the pickup rollers was pitted all the way around."

Is it possible that you are running across gaps between blocks powered by different outputs of the ZW, thus creating a short circuit through the locomotive pickups or car pickups between two ZW outputs not at the same voltage?

[Birds]

Bob,

I am not sure if shorting by crossing a gap is taking place or not. I tried to isolate the center rails of the loops so that wouldn't happen, but I did not isolate the commons on the two loops – the commons are tied together. Would having the commons of the two loops tied together cause the short you are talking about even if the center rails are isolated? Should I also isolate the common rails of the two loops?

Here is a picture of the layout (click to enlarge):


There are two loops: Loop1 & Loop 2
There are three 45 degree crossings: C1, C2, C3.

Crossings C1 & C3 are where the two loops cross (C2 is only connected to Loop 1), and so these crossings have the center rails unsoldered underneath and they are insulated from each other with rubber strips. C2 is not insulated like this since all four sides are on the same loop. (picture below - click to enlarge)



When I do a continuity test of the crossed center rails, they no longer respond as being connected. Only the rails that are in a straight line respond as being connected (hope that made sense).

The train has shorted on switch "R5" (circled in blue and to the left of crossing C1) while running only on Loop 1. This switch does connect to Loop 2, but the center rail is isolated at the curved track outlined in red.

So I tried to eliminate the possibility of the train crossing gaps that have two different voltages.

[trigtrax]

The train has shorted on switch "R5" (circled in blue and to the left of crossing C1) while running only on Loop 1.

Make sure your fixed voltage Switch transformer and KW are in phase. I would remove the fixed voltage plug from the switch that shorted and run the engine through again. If it doesn't short check your phasing.

[lionelsoni]

I was worried that you were running between the two loops; but it seems that you are not.

The phase of the auxiliary transformer shouldn't matter.

Connecting the outside rails together between the two loops is correct.

Here are a couple of things to try:

Connect the entire layout to one output of the ZW and run long enough to see whether that makes a difference. If the problems clear up, then you are probably shorting the two ZW outputs together somehow. If not, the problem is probably a short circuit to ground. In that case:

Do what Trigtrax suggested, pushing a car or running a locomotive slowly over a trouble spot. But bypass the fuses first. You will be able to shut the transformer off quickly enough when you get a short circuit. Then tip or look underneath to see what's touching what it shouldn't.

[waltrapp]

Bob,

Agreed that the aux power transformer and the track power transformer don't have to be in phase.

BUT......
I don't remember the 'exact' rules for aux power for switches, but I was thinking that I recall reading a comment once that the transformer's ground for the aux power and the transformer's ground for the track power should be connected.

Not sure though.

- walt

[lionelsoni]

That's right, Walt. I assumed that his are connected, since otherwise the switches wouldn't throw at all.

[Birds]

Thank you for all the replies and help.

Yes the commons for the Aux transformer that provides track power, and the transformer for the track itself are grounded together. But it can be improved upon so I will work on that.

I checked for sparking on the switches with the constant voltage in and out (using track voltage). There was no increase in sparking using constant voltage versus track voltage.

It definitely is a short as opposed to just being a large draw because there was one time I was not using an in-line fuse (have to buy more now) and the voltage went up to 14.

The comments helped me find and address lots of small things that appear to have been building up. I am thinking they all came together at the right time and caused the shorting.

• The track was pretty dirty from the grease on the new engine so the track got a good cleaning.


• Since my layout isn't permanent yet, some of the track joints had loosened up with trains running and there were some gaps and there sparking on straight track sections. So they are once again pushed as tight as can be now.


• The phasing of the transformers was checked just as a precaution and they were in phase.


• More returns for common connections will be added.

The sparking is very minimal now. The lights have to be turned out and one has to be at eye level and really looking to see it.