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10Amp Booster & HO

This section talks about the ABSOLUTE RULES needed to be followed without exception to be successful in using a booster who's current rating is greater than normal 5Amp rating with a HO layout.    In other words, if your using a booster rated at more than 5Amps on it track terminals with a HO layout, you need to pay attention to this section.

This information is based on my first hand experience with designing/engineering a successful system for a large HO club that has been in use since 2000.

This section assumes one is NOT USING COMMON RAIL.   For common rail applications, see special section on "CONCERNS FOR COMMON RAIL WIRED LAYOUT"

In this section:

1) GENERAL/SINGLE BOOSTER ABSOLUTE WIRING RULES
2) SUPPLEMENTAL MULTIPLE BOOSTER ABSOLUTE WIRING RULES
3) BACKGROUND OF THE SITUATION/MY DISCLAIMER
4) THE DCC MANUFACTURE'S LIABILITY ISSUE WITH SMALL GAUGE LAYOUTS
5) EXAMPLES OF WHAT HAPPENS WHEN NOT FOLLOWING THE RULES
6) BENEFITS TO USING A HIGH CURRENT BOOSTER WITH HO
7) THIS IS NOT NEW: SOME HISTORY WITH HIGH CURRENT BOOSTERS
8) SPECIAL CONCERNS FOR CURRENT BASED OCCUPANCY DETECTORS
9) SPECIAL CONCERNS FOR COMMON RAIL WIRED LAYOUT
10) KEY BASIC CONCEPTS THAT ALLOW HIGH CURRENT TO BE MADE SAFE WITH HO



1) GENERAL/SINGLE BOOSTER ABSOLUTE WIRING RULES  (not in any order)

1) USE DCC CIRCUIT BREAKERS:  ANY TRACK TO RECEIVE POWER FROM THE BOOSTER MUST PASS THROUGH A DCC CIRCUIT BREAKER WHO'S TRIP CURRENT IS SET TO 5AMP OR LESS.  The circuit breaker itself must be rated to support high currents so it can process the full booster current safely.  DCC Specialties PSX series or NCE's EB1 DCC circuit breakers are rated for a full 10Amps.

2) MINIMUM 12 AWG WIRE FOR ALL TRACK BUS DISTRIBUTION RUNS.    

3) USE TWISTED TRACK BUS PAIR WIRE RUNS.  Twisting the track bus wire minimize wire inductance the corresponding voltage spikes created by the wiring when dealing with short circuits.  Think "blowing up decoders" as in smoke.  HO Scale decoder decoders do not have the same maximum input voltage range as a O scale decoder.  Also the section below on current based occupancy detection and twisted pair wiring.

4) EVERY SECTION OF TRACK MUST HAS ITS OWN TRACK FEEDER.  You are not allowed to rely on any rail joiners for electrical connection.  If you build any large layout, you know that solder rail joint break at different points on the layout.  Weak or broken rail joints can have enough series resistance to preventing the booster from shutting down in a condition that would shutdown is that joint was still solder properly.  

5) USE 18 AWG FOR TRACK FEEDERS AND FROG POWER.  Solid wire works well for it is still very small.  Keep length to 18" or less.  This is all about keeping wire resistance to a minimum which maximizes the ability of the DCC circuit breaker to detect a short circuit in all conditions.  18 AWG is also the minimum wire gauge allowed for a ScotchLok 567 IDC suitcase connector tap connection.

6) PERFORM A SHORT CIRCUIT TEST ON EVERY SECTION OF TRACK BETWEEN RAIL JOINERS TO VERIFY BOOSTER SHUTDOWN PROPERLY.  This is also known as the coin test.

7) INSTALL A RC FILTER (TRACK BUS TERMINATOR) ON THE FAR END OF EACH TRACK BUS RUN.  These attack voltage spikes and clean up the noise on the track bus.   To learn more about the building the RC FIlter go here:
See section 6 for more information about the location of the filter.

8) KEEP ALL TRACK BUS LENGTH LESS THAN ~45 FEET FROM THE BOOSTER.  Precision length is not an issue here just keep it reasonable.  See reason for twisting the track bus wires.  Keep the wiring inductance to a minimum.

9) USE ONLY THE MOST RELIABLE HIGH CURRENT WIRE CONNECTION METHODS

a) If you crimp, only use a crimping tool with a ratcheting lock on it.  Use the correct lug for the wire size.  Never re-use a crimp lug or terminal...always use a new one for each new joint.  Although crimping is proven in the electronics industry to be 100% reliable if done properly, if you do not trust crimping, feel free to solder the lug to the wire.   

b) If you solder something, give the solder joint a tug to make sure it holds and the solder joint must be shiny/smooth solder.  If you do not like the joint, trust your feeling and redo it.  

c) If you use IDC "suitcase" connectors, use a IDC designed for 10Amps.  Only use the proper AWG (Wire Gauge) supported by the IDC.  IDC connectors are designed for narrow range of AWG wire for stranded or solid wire.  Failure to do so will result in a unreliable IDC connection.   When done with the crimping down of the wire blade, tug on the tap wire to make sure the wire does not slip out the IDC connector.  Take full advantage of the inspection window for the tap wire to visually inspect the tap before closing the lid.  If you do not see the wire in the inspection window, you missed the connection.   Remove the IDC and start over.

d) Do not use bare wire on a barrier terminal strip for wire connections.  Use a spade crimp lug on the end of each individual wire instead and screw the lug down on the terminal strip  Stacking lugs from two wires back to back to a screw terminal is acceptable.

10) TORTIOSE CONTROLED FROG POWER SHOULD HAVE SOME CURRENT PROTECTION.  A Automotive light bulb should be wired in series with the frog power wires to limit the current.  The current rating of the bulb should be sized for the running current of a single engine.  For a selection of bulbs to use go here: Light Bulbs

2) SUPPLEMENTAL MULTIPLE BOOSTER ABSOLUTE WIRING RULES (not in any order)

SAME AS SINGLE BOOSTER PLUS:

1) USE OPTO-ISOLATED BOOSTERS.  This prevents the booster's "control bus" ground from carrying any current between boosters.  All of NCE boosters meet this requirement.  Digitrax boosters are offered with this option but one must make a special order to get them.

2) YOU MUST INSTALL A #1156 LIGHT BULB IN SERIES WITH EACH INDIVIDUAL BOOSTER'S GROUND/COMMON CONNECTION BEFORE IT'S CONNECTED TO OTHER BOOSTERS.  This limits the booster exchange current flow when a short circuit occurs while crossing between two booster districts.

3) EACH BOOSTER SHALL HAVE ITS OWN DEDICATED POWER SUPPLY.  This prevents the power supply wiring itself acting as a poor common between boosters.  The only common allowed between boosters is the booster common.

4) NO EXPANSION BOOSTERS ARE TO BE EARTH GROUNDED.    The Earth Ground connection itself can act as another common with boosters exchanging current using you house wiring!  The only common allowed between boosters is the booster common.  It should be stated that there is no requirement for the layout to have ANY earth ground connection.  If you are going to establish a earth ground, do so only on the command


3) BACKGROUND OF THE SITUATION

BEFORE WE PROCEED, ONE MUST BE FULLY INFORMED OF THE RISK INVOLVED.

Boosters rated GREATER than 5Amps are designed to support larger scale railroads like O and G scale where everything gets bigger.  Bigger rail, bigger trains, bigger motors and hence more power it takes to run the engines.  This includes the locomotive's internal wiring by default.  Large scale layout owners know from experience that corresponding heavy duty layout wiring is also required.  Just the mention of a 10Amps, for example, is large enough for most people to at least think about using house hold wiring standards to wire the layout which leads to large gauge wiring.  Why? The number is high enough to remind them of those 15A circuit breakers in an AC panel.

1a) So what are the issues with using it with HO or smaller scales? 

THERE IS DEFINITE RISK OF DAMAGE OR FIRE TO THE LAYOUT OR ROLLING STOCK IF ONE USES A BOOSTER WITH A CURRENT RATING HIGH THAN RECOMMENDED FOR THE GIVEN SCALE WHEN DIRECTLY CONNECT TO THE TRACK.

IF you have a layout smaller than HO, STOP RIGHT NOW AND DO NOT EVEN CONSIDER THIS OPTION...PERIOD!! 

1b) Then why consider this option in the first place for the HO user? 

HO is the scale that is in the middle between OK (O Scale) and NOT OK (N scale) with respect to 10Amps.  Shades of gray so to speak.  Success depends on paying attention to all the wiring details to make is safe for the locomotive to play in so to speak.  It is all about consistent voltage-drop/resistance management so that when there is a short, it is a solid short circuit as possible.  


4) THE DCC MANUFACTURE'S LIABILITY ISSUE WITH SMALL GAUGE LAYOUTS

No DCC manufacture will recommend any booster with a current rating above 5Amps at the track terminal to directly connect to HO or smaller scales.   

Why?  

NCE, or for that matter any DCC manufacture, has no control over what people do with their products and how they are installed.   

What is the issue?

To do it right requires the HO customer to have a good level of electrical understanding and RESPECT for the power involved that is not taught using HO wiring techniques.  What does HO wiring teach?  Small gauge wiring is OK to use.

Why? 

2a) The current is very low.  DC power layouts because the currents involved were only high enough to run just one train which is about 1 Amp or so.    The power is so low it is NOT considered to be any electrical hazard at all.

2b) Most HO users who wired up their first DC layout often did so with purchased or surplus wires to save money.  If you purchase the wire commonly sold for model railroading at your local hobby shop, again small gauge wire is offered.  IF you used surplus telephone cable wiring which is easy to work with.  

2c)  Smaller gauge locomotive often presents you will even smaller gauge wiring than found on the layout.

2d)  Some high power accessories (Atlas Twin Coil) use small gauge wiring.
  
CONCLUSION:

One quickly accepts by default that small gauge wires are fine to wire up any HO layout under any all conditions.  

HENCE THE PROBLEM:

If you think the HO wiring techniques are OK for 10Amps, your thinking is very dangerous.  
10Amps will find your wiring weakness instantly with no warning and provide the conditions that can start a fire.

BOTTOM LINE: DCC manufactures simply issue a "DO NOT USE" statement due to the potential hazards when mixing high current booster and small scales starting with HO.   They will not offer an explanation because if you have to ask why, then by definition you do not understand the risk/respect problem.

MY DISCLAIMER: SINCE I CANNOT SUPERVISE OR CONTROL THE QUALITY OF THE WORK BEING DONE ON THE GIVEN LAYOUT, I TOO CANNOT ACCEPT ANY RESPONSIBILITY FOR ANY DAMAGE INVOLVED AS A CONSEQUENCE OF USING THIS INFORMATION.  THE USER OF THIS INFORMATION ACCEPTS FULL RESPONSIBILITY IN ITS USAGE.


5) EXAMPLES OF WHAT HAPPENS WHEN NOT FOLLOWING THE RULES

1)  Melted Loco Trucks.   Photos curtesy of Rex Beistle.

The two pictures on the left shows what can happen with a 8 Amp booster directly connected to the track to an engine involved in a derailment and corresponding short circuit.







2)  Story by NCE:

Jim Scorse, of NCE, related a story to me about a N scale layout owner who used a NCE 10 Amp booster.  He found out because the owner gave him a call to complain.

The owner had a sectional N-scale layout.  He purchased a NCE 10 Amp system rationalizing that by using a 10Amp booster, he would never run out of power.  He set up a loop in a room and started running his trains.   He left the room with the train running.  The train derailed creating a short circuit on the track.  When the owner came back some time later, he found parts of the engine and track had melted.  The resulting short circuit was NOT strong enough to trip the 10Amp booster into shutdown and so the booster happily supplied 150+ watts of power (heat) into the rolling stock and track.  Luckily there was no fire.


6) BENEFITS TO USING A HIGH CURRENT BOOSTER WITH HO.


1) Lower Booster Cost: A single high current booster cost less than two 5 Amp boosters.

2) More Power Districts/Booster.  You can MORE than double the number of DCC circuit breakers connected to a 10Amp booster than a dual 5Amp booster setup.  ANALOGY: This is like your AC circuit breaker panel for your house.  You have a 100Amp service (10 Amp Booster) feeding a bunch of smaller 15 Amp Circuit Breakers (3 to 5 Amp DCC Circuit Breakers) to power different appliances or rooms of the house (Power Districts on the layout).  The extra booster current can be better utilized to cover the peaks of more circuits.

3) Improve performance working with Sound Equipped Engines especially if you have a lot of them.  The extra current available from the booster is available as extra "peak current" that will allow sound engines to re-charge their on-board "hold up" capacitors faster in all conditions.  This is especially true if you have lots of sound engines on the layout.  You will also observe improved recovery from short circuits when using standard DCC circuit breakers.  However the benefit is not as great as what you gain in using DCC circuit breakers specifically designed to work with Sound Decoders such as DCC specialties PSX series of products.)


7) THIS IS NOT NEW: SOME HISTORY WITH HIGH CURRENT BOOSTERS

The concept of using a >5AMP high current booster with all scales is not a new concept and is still commercially available TODAY.  The difference is how the boosters are built.

NCE made a "Master Series" dual 5Amp booster called a PB205 (no "a" suffix). It shared the same internal 10Amp power supply as the 10Amp booster but offered two independent DCC outputs.  In other words it was a dual 5Amp with a 10Amp peak current capability.

System One's SBR-01/PSR01 was its own unique version of a NCE Dual 5Amp booster but it too used a 10Amp power supply and hence had the same 10Amp peak current capability as NCE's dual 5.

In other words, NCE and Wangrow did offer dual 5A boosters were really just a 10Amp booster feeding into two fixed 5A DCC circuit breakers all packaged in SINGLE BOX and sold for all scales including N scale.

TODAY CVP new ZoneMaster is the same concept. The DZB7 consist of a 7 Amp, 30 Amp peak, booster feeding TWO 3 Amp DCC circuit breakers in a single box and is usable with all scales. (3 Amps is the default setting. Range is 7 to 1.5A per output).

Today we use single booster feeding into multiple DCC circuit breakers.  It is simply a unbundled version of what was done before.  The problem is there is less control involved since the user is involved in setting this up.


8) SPECIAL CONCERNS FOR CURRENT BASED OCCUPANCY DETECTORS

1) If you have current based detectors, they must be set up to support the full booster current rating even if you have a DCC circuit breaker involved.  You run the risk of damaging the detector is you exceed it recommended current rating.

2) Make sure the location of the occupancy sensor is remotely located near the section of track it is intended to monitor.  The goal is to maximum the use of twisted pair wiring of the DCC track bus up to the sensor.  Why?  Twisted wiring will interfere with reliable occupancy detection on any wiring past the occupancy detector. 

3) The RC filter should only be installed on the NON DETECTED side of the occupancy detector.  If installed on the detected side, it will lead to false occupancy detection


9) SPECIAL CONCERNS FOR COMMON RAIL WIRED LAYOUT

Common Rail wired layouts introduce a modification of one of the rules in the wiring.  If you do not know what common rail wiring is, then you do not have it.  To learn more go here:

Most DCC manufactures assume and and in some cases do NOT support the use of common rail wiring with their DCC system products. right out of the box.  IN other words you need to order a special version of the booster.

1) NO BOOSTER COMMON.  With a common rail, the booster common now represent a second common connection.  Violated no mulitiple common rule.  The common rail connection takes priority.


10) KEY BASIC CONCEPTS THAT ALLOW HIGH CURRENT TO BE MADE SAFE WITH HO

1) SET DCC CIRCUIT BREAKER TRIP CURRENT TO 5A OR LESS:

WHY?  DCC Circuit breakers set to a trip threshold of 5A or below will limit the TIME duration of the any current flowing above the trip threshold.  DCC CIRCUIT BREAKERS DO NOT LIMIT THE ACTUAL CURRENT.  The booster does that all by itself.  DCC Circuit Breaker "BREAK THE CURRENT" which is why they have that name in the first place.   To be clear, the full current of the booster will flow through the DCC circuit breaker to the load or short circuit.  Some heat will still be generated.  The question is how much and where.  By cutting off any sustained current flow above 5A, we have re-created the same shutdown conditions that a 5A booster would provide which has been determined and demonstrated as being safe for HO operation by DCC system manufactures.

2) RELIABLE HIGH CURRENT LAYOUT WIRING:  Use a wire and connector system that supports and minimize resistance at 10Amps.

WHY? The weakest point in the current path that has the highest resistance will see the majority of the heat.  Stated another way, any wiring or connection that is to weak to work with the high current rating of the booster reliably can become thermally damaged.  Excessive wiring resistance can cause DCC circuit breakers to fail in protecting equipment.  10Amps of sustained current will quickly find your weakest wiring point and burn it up.

3) DO NOT USE FOR SMALLER SCALES THAN HO PERIOD:

WHY? When you go below HO, the wiring and connections inside the locomotives involved become to weak to support the high current.  The heat can become so concentrated so fast it will find a single point of potential failure.  I have seen the wire insulation melted in a HO locomotive even though it did not reach the point of burning.  It is a time bomb waiting to happen.  So the limiting the scale to HO or above and make sure all the wiring is designed for high current where ever possible will minimize that risk.


9/24/15