Recommendations for Circuit breaker for Lenz DCC set 02 running 2mm scale layout

[SandHutton]

Hello All, 

 

I recently converted my small layout to DCC with a Lenz set I bought a while ago.  The setup comprises

 

• A TR100 transformer 
• LV101 power amp and LH200 controller. 
• Small BLT style layout in 2mm finescale running converted N gauge or 2mm stock.
• Zimo Decoders - MX620N, MX617 fitting SACC16 and stay alive where I can

 

It runs well but after having a momentary short today I wanted to get some recommendations for a circuit breaker if indeed one is needed.  I am assuming its not ideal to rely on the inbuilt protection in the LV101 or the decoders themselves.   Also would I need a different circuit breaker for say powering a small 4mm layout from the aforementioned setup as the current draw will be higher?

 

Thanks

 

Guy

 

[Nigelcliffe]

I think the LV101 is 3Amp max, so that's reasonable for 2mm or 4mm scales.   Unless you have a large setup where it is sensible to isolate failures to particular areas (eg. up-main, down-main, fiddle yard, goods yard, etc.) it should be OK as it is. 

 

The LV101 should be fine to protect itself.   The decoders don't need "protecting", as they are not in the path of any short circuit - the short will occur through the loco's wheels and pickups, but doesn't go through the decoder.    Further, Zimo decoders are pretty well protected internally against a loco internal failure (eg. a motor self-destructing as an internal short-circuit, something which is a very rare occurance). 

 

Your locos wheels and pickups shouldn't suffer from 3A shorts, unless you make a huge habit of leaving locos shorting everywhere.    What does matter is that the system detects a short anywhere on the track: if it doesn't trip, you can have an "almost short" where most of the system current is flowing through the short, but not quite enough to trip the system.  That can heat up pickups (ruining them), melt bogies, etc..    So perform a "coin test" around the layout.  Use a coin to short the track, and the DCC system should detect it immediately.  If it doesn't, the first suspect is the quality of the wiring to that track.  

 

If you think you need extra cutouts, then you need something which trips at a lower current than your system, say 2A or lower. Commercially some of the Powershield range can be set to quite low currents.    I'd use a MERG kit build breaker (MERG = UK hobby organisation for model railway electronics), which in standard build will cut at 1.5A.  It can be easily modified to cut at 0.75A.     

 

 

[SandHutton]

Many thanks for the detailed advice.  The coin test reveals that the system trips without issue thankfully but I might get a MERG breaker in time just as a belts and braces approach.