Irritating short circuit

[Magpie473]

I would welcome comments on my irritating short. I have a 00 DCC layout controlled by an NCE Power Cab. It has three    reverse loops that were controlled by 3 Gaugemaster DCC 40’s. When the 20 points were manually operated all was well. I then motorised the points using the Rails connect surface mounted points feeding into the DCC Concepts ADS-8SX all running from the same track bus, which caused a system short. Discussed this with DCC Concepts and Digitrains without any sensible resolution other than to change the DCC40 for Tam Valley Depot Frog Juicers. That appeared to cure the fault but the system was drawing almost 1 amp without any trains running. 
Next idea to uprate the power using the Tam Valley 5amp booster. This caused a dead short. Nothing worked at all. I then Unhooked the ADS units and all well. I tried all my knowledge to isolate the fault with no success. However, the system ran ok without the power booster. So I gave in and ran the layout without the booster. 
Yesterday I hooked up the NCE Auto Switch to create the program track. As soon as I tried to program the CV’s the Power Cab flashed a Short Circuit message. It allows me to continue and it appeared to work ok. But the evidence is there that the short is still an issue. 
1. Can anyone offer any advice?
2. should I run the 20 points from an accessory bus?
3. I select to train routing using the macro facility so I need to understand how I can run both buses from the same hand set.
4. should I use a circuit breaker?

[Nigelcliffe]

Your description makes me think "wiring messy", and its going to take time to isolate the issue.   

 

Your report says it gives the impression of overloads with just the PowerCab.  And substituting a 5A booster sees a complete short.  To me, that means "look for where power is leaking".  Which could be quality of wiring, or could be errors in wiring.  

 

Start from disconnecting the reversing loop switch over devices, and see what happens to current consumption on the layout with no trains running.  Then reconnect the reversing devices one at a time, looking what happens.  If a big jump in current, that's a clue as to where the problems may be - somewhere in the wiring into that reversing loop.  

 

Similarly, disconnect the ADS-8SX, and go through the same process, noting the current changes when they are connected, and not connected.    Again this will give clues as to where to look for current losses.   I'd be looking closely at any other connections (except DCC track input signal) to the ADS-8SX, such as switch outputs to frogs on turnouts, etc.. if used (those need to be disconnected as part of these tests).   

 

 

An "accessory bus" is just another pair of wires from your command station/booster.   Without a circuit breaker, it won't do anything to fix things (except you'd be re-wiring some stuff, so may, inadvertently, remove something which was (part of) the fault).  With circuit breakers in place, you'd know which half contained the fault from which breaker was tripping - track wiring or accessories - but no more.  

 

 

 

[rogerdee]

I had a similar problem with my NCE unit. I ended up splitting the feed from the booster to the track and to a separate accessories bus bar,the track feed then goes into a circuit breaker for each district of track. My has been working fine now . The point decoders work fine now and don't overloaded my system. Did you wire the auto switch correct as I remember some were sent out with the wrong wiring diagram .

[RAF96]

I thought ‘slow’ leak as well, one that wasn’t enough to trip the kit as was. Best of luck finding it.

The other thing is maybe acc decoder inrush current is making the unit think there is a short. Try firing these up in batches using isolation switches.

[Ron Ron Ron]

1 hour ago, Magpie473 said:

3. I select to train routing using the macro facility so I need to understand how I can run both buses from the same hand set.
4. should I use a circuit breaker?

 

35 minutes ago, Nigelcliffe said:

An "accessory bus" is just another pair of wires from your command station/booster. .....

 

As Nigel says, an accessory bus would just be another pair of wires from the same track output, but to make it worthwhile, you really need the circuit breaker.

 

Ordinarily, you wouldn't need to put a circuit breaker on the accessory bus, but the PowerCab doesn't have proper protection against shorts (there are warnings on the NCE web site), therefore I'd suggest running the accessory bus through a separate circuit breaker channel from the one for the track bus feed.

 

Just throwing this point in, for anyone reading this topic who isn't sure....

If it isn't blindingly obvious, DCC commands sent out to both loco decoders and to accessory decoders, are transmitted on both (or all) buses connected to the track output.

Only the addressee decoder (whatever it is) will respond to commands addressed to it.

 

 

 

 

.

[Ron Ron Ron]

39 minutes ago, RAF96 said:

 

..............The other thing is maybe acc decoder inrush current is making the unit think there is a short. Try firing these up in batches using isolation switches.

 

One solution to inrush currents, is to fit a soft start, or surge protector device.

These are fitted just after the track output from your Booster(s). In the PowerCab's case, just after the track output port on the PCP.

There are at least a couple on the market.

DCC Concepts are one company selling these.

 

https://www.dccconcepts.com/product/surge-protector/