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What would happen if you exceed your layout's amp capacity?

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  • From: Southeast Texas
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What would happen if you exceed your layout's amp capacity?
Posted by mobilman44 on Wednesday, February 29, 2012 10:26 PM

Hi,

No problem here, just a "what if" question that came up today.  

In example, if we have a DCC layout with a 5 amp booster/power supply that is run through a circuit breaker, and we have a concentration of locos that exceed those 5 amps, what will happen?

Will the locos just barely move or light?   Will the breaker be tripped?   Or ?????

 

ENJOY  !

 

Mobilman44

 

Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central 

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Posted by maxman on Wednesday, February 29, 2012 10:46 PM

The command station booster will trip at 5 amps, or probably some number less depending on what the setting of its internal breaker is.  However if your system is set up correctly, that additional circuit breaker you mention (hopefully one that is designed for use with DCC systems) will trip at a lower value than the internal breaker.  Many, if not all, of the DCC breakers have an option to allow them to be set at varying values.  I think that maybe 3-1/2 amps or so should work okay for your 5 amp system.

Once the breaker trips, no light, no sound, no movement, no nothing.

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Posted by retsignalmtr on Thursday, March 1, 2012 5:00 AM

My club was using the Digitrax 5amp SEB at a show. We had several HO locos with sound running and a few lighted Passenger cars too all at the same time. The DB150 circuit breaker did not trip, but the command station cut off the track power when it got too warm stopping the entire layout until it cooled off a little. It happened several times that day. After the show I installed an old computor chassis fan to blow air over the heatsink on the command station and the problem hasn't reoccured. We have since upgraded to the 8amp Super Cheif and haven't had any problems. The fan remains in place.

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Posted by MisterBeasley on Thursday, March 1, 2012 6:23 AM

I had a slightly different problem.  I've got a Lenz System 100, 5 amps, but it requires an external power supply.  I was driving it with an old train transformer that probably only put out 1 amp or so.  It seemed great, but once I had a sound engine and a few lighted passenger cars running, along with a 4-car lighted subway train, I noticed that everything was just running slower.  I'd maxed out the power source, even though I was nowhere near the 5-amp capacity of the DCC system.

A proper 5-amp supply fixed the problem.

It takes an iron man to play with a toy iron horse. 

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Posted by richg1998 on Thursday, March 1, 2012 9:11 AM

The breaker will trip or the booster will trip. Happens at our club once in a while. Same thing if you ever do a "quarter test". I can hear the next question, what is a quarter test.

Rich


If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.

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Posted by ATLANTIC CENTRAL on Thursday, March 1, 2012 11:19 AM

mobilman44

Hi,

No problem here, just a "what if" question that came up today.  

In example, if we have a DCC layout with a 5 amp booster/power supply that is run through a circuit breaker, and we have a concentration of locos that exceed those 5 amps, what will happen?

Will the locos just barely move or light?   Will the breaker be tripped?   Or ?????

 

The circuit breaker in the booster will trip, but this is actually one of the possible short comings of some DCC installations, and one of the hidden cost factors as layout size or complexity increase.

Lots of sound equiped locos, sitting on live track, can and do draw a lot of current even sitting still. And can cause VERY big power surges on system start up.

Many will counter my comments by suugesting that few people leave that many locos on the layout all the time, or that they have installed kill switches to storage yard areas - that seems to fly in the face of the "two wire simplicity" thing.

As layout size increases, seperate power districts and sub districts with circuit breakers are the best precaution against such problems, but do add to the cost and wiring complexity.

Also the higher fault current of an 8 amp booster seems pretty scary to me. That's about 130 watts available during a short circuit - that can easily melt something before the breaker trips.

On my DC powerd layout, each of eight throttles has its own seperate 5 amp power supply, fused at 4 amps and only working at 13.8 volts max. Max available fault current at any one spot is 4 amps or 55 watts.

BUT, as a total the layout has 32 amps of train power. So four or six unit diesel lashups even with older motors are no problem. 

If I was using DCC, I would have five or six boosters and each would have multiple circuit breakers to limit current in any one area of track.

One more thought, I have about 120 powered locos/units of one sort or another. In operational mode they are all on the layout were they belong. They all serve a purpose in the operational scheme. Even at 1/10 of an amp, that is 12 amps of locos if I used DCC and sound, with a likely startup surge that could hit three times that.

Just a few thoughts from an electrician,

But what do I know, I'm just hick with a pickup, a few guns and some little trains without brains.

Sheldon

 

    

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Posted by mobilman44 on Thursday, March 1, 2012 1:14 PM

Thanks all for the input - and the good news is there is a lot of consistency.

I've got two 5 amp boosters/power supplies, 8 power districts with two PSX-4 sets of breakers.  I also have shut off switches for steam and diesel terminals, and freight and passenger staging/storage. 

I tend to "over kill", but after 3 years with the layout and accumulating a number of sound units, I think I'm not all that over powered afterall.

Installing gauges has been a question in my mind, but with 8 districts that (I think) would be 8 sets, unless I used some kind of rotary switch to route a given district thru the gauge to see what I'm pulling.  I realize one can "ballpark" a particular units draw, but if the unit has a problem and pulled more, you wouldn't know w/o gauges.   Am I just looking for work and a place to spend money here, or ???

 

ENJOY  !

 

Mobilman44

 

Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central 

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Posted by maxman on Thursday, March 1, 2012 1:56 PM

mobilman44

 Am I just looking for work and a place to spend money here, or ???

 

Yes

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Posted by ATLANTIC CENTRAL on Thursday, March 1, 2012 1:58 PM

With respect to gauges, I may be wrong, but the nature of the DCC signal/power and the nature of most gauges, may not really be a friendly or accurate combination.

Sheldon

    

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Posted by maxman on Thursday, March 1, 2012 4:04 PM

Unless you are going to have a single, isolated, unit in any particular power district , you won't be able to tell what it's electrical performance is anyway.  If you really want to make a science project out of this, what I'd suggest you do is set up a test track.  Then you can put each unit individually on that track and measured the out of the box curent draw, and have a baseline value for each of the units.

As far as getting an "accurate" reading, Tony's Train Exchange sells several styles of what they call a RRampmeter that is designed to give the correct voltage and current values for DCC.  The link is here: http://www.tonystrains.com/products/pop-meters.htm

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Posted by richhotrain on Thursday, March 1, 2012 6:25 PM

mobilman44

Installing gauges has been a question in my mind, but with 8 districts that (I think) would be 8 sets, unless I used some kind of rotary switch to route a given district thru the gauge to see what I'm pulling.  I realize one can "ballpark" a particular units draw, but if the unit has a problem and pulled more, you wouldn't know w/o gauges.   Am I just looking for work and a place to spend money here, or ???

 

mobilman,

If you use the RRampMeter, you will only need one "gauge" as you call it.

The RRampMeter is designed so that it can be quickly unplugged and moved anywhere on the layout.
 
You simply disconnect two RCA type plugs on the left side and two RCA plugs on the right side of the meter and remove the meter.  Then with the meter in hand, you go to any point on your layout and place the two leads from the meter on the rails and get readings for volts and amps.
.
The link that maxman provided shows that being done.
 
Rich

Alton Junction

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Posted by rrinker on Thursday, March 1, 2012 9:28 PM

 Not very convenine tif you have 8 power districts, to disconnect the wires adn connect int he RRampmeter to test, then reconnect. Unless you make a plug panel with somethign like PowerPole connectors or good old banana plugs. Jumpers complete the circuit under normal conditions, unplug jumper, plug in RRampmeter to test.

 One meter per district woudl be the ultimate - and ultimate expensive. Rob Paisley has a circuit on his site you can buy which gives accurate DCC amp readings (liekly the same part is built in to the RRampmeter).  A built-up circuit is $14, plus $9 for a suitable digital meter to attach to the circuit., slightly less in quantities. SO basically 23 buck per section. A power supply is needed to drive the meters.

http://home.cogeco.ca/~rpaisley4/DCCammeter10.html

         --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by richhotrain on Friday, March 2, 2012 6:19 AM

rrinker

Not very convenient if you have 8 power districts, to disconnect the wires and connect in the RRampmeter to test, then reconnect.  

Randy, the whole process is pretty simple with the RRampMeter.

There are four plug in cables, two on the left side and two on the right side. You just grab the cables with your fingers and pull them out of the sides of the RRampMeter.  Walk along your layout with the RRampMeter in hand and place it against the rails in any or all of the power districts to get readings.  When you are done testing, plug the four cables back into the RRampMeter.

No tools required.  No screwdrivers, no nothing.

What could be simpler?

Rich

Alton Junction

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Posted by rrinker on Friday, March 2, 2012 6:56 AM

 You can't just walk around the layotu and touch the RRampmeter to the rails to measure amps, it has to be in series with the track power to measure amps, like any other ammeter. WIth poer routed through a quad breaker like a PSX-4, that means disconencting 4 pairs of feeders and inserting the RRampmeter in each of the paths. Installing plugs like I suggested makes it a plug in operation, but you still need jumpers when the RRampmeter is not connected. Plus you might want an extra set of connections at the input to measure total amp draw on the booster. Then all times 2 since the OP has two boosters and two PSX-4's.

For VOLTAGE measuremeant, indeed, it is as simple as either using wires or the version of the RRampmeter with the contact strip on the back and setting it on the rails.

                 --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by richhotrain on Friday, March 2, 2012 7:55 AM

Randy, you are correct. 

As a portable unit, the RRampMeter only serves as a voltmeter.

Let me ask this question.

Is it possible, and economical, to set up 8 amp meters on a control panel so that the amp usage in each power district can be viewed simultaneously?

Rich

Alton Junction

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Posted by BroadwayLion on Friday, March 2, 2012 9:53 AM

LION has one power district covering 1000 actual feet of tracks.

LION has one regulated power supply providing 15 amps of power.

Since LION has track resistors to regulate train speed into stations, the 1/2 watt resistor is sufficient for a train coming into the station: it is only on the block for a few seconds. BUT A SHORT on the block will cause the resistor to catch fire: the resistor eats enough of the amps while cooking that the breaker in the poser supply never sees it, the ammeter never going above 8 amps.

LION installed a 5 amp breaker in front of his power supply but is still worried. Him is thinking of putting an automotive brake light in series with each feeder which will both prevent the short and tell me where on the layout the problem is.

LION runs 8-12 trains at one time from this supply.

ROAR

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Here there be cats.                                LIONS with CAMERAS

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Posted by rrinker on Friday, March 2, 2012 2:25 PM

richhotrain

Randy, you are correct. 

As a portable unit, the RRampMeter only serves as a voltmeter.

Let me ask this question.

Is it possible, and economical, to set up 8 amp meters on a control panel so that the amp usage in each power district can be viewed simultaneously?

Rich

 That's why I posted what I did about Rob's circuit. About $23 per meter, so for 8 or even 10 of them, not horrible. Overkill perhaps, but it would certainly look cool to have a bank of monitors for all districts.

 For just checking things now and then, a few buck's worth of connectors and some time making the jumper cables I mentioned, and buyign just ONE meter, would be much more economical and plenty useful, the slight nuisance of unplugging jumpers and inserting the meter when attempting to get a reading beign the tradeoff for the higher cost of equipping each section with a permanent meter.

                         --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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