Is a 10 amp breaker too much?

Well, the classic breaker is heat activated, so it takes a short of some duration to trigger it.  The 10A breaker will require a dead short for a few seconds to trip as a rule.  If you need faster action, look for magnetic breakers, they're considerably more expensive than the thermal breakers and much faster acting.

Another thought, since you're running conventional, try reducing the breaker for each power district to around 6A, there will only be one train on the power district at one time, right?

When you go TMCC, consider something like the TMCC Direct Lockon, it has an electronic breaker that trips very fast.  For running DCS or combined DCS/TMCC, the MTH TIU has excellent protection and trips immediately on a short of any kind.  I like it's operation better than the TMCC Direct Lockon because it stays tripped until I power cycle the input power to the TIU channel.

You didn't explain where your 4 feeds go.

Each circuit breaker should feed an independent loop or block.  If multiple breakers feed the same area, the current in the breakers will be split up, and any one breaker may not reach its trip point.

Dale I wondered that my self,I thought I had way too much circuit breaker protection attached to just one output of my post war ZW.I have all these lines originating from one output by the way,there are no breaks.And my 4 feeds go to different locations of the track.2 of them go to the farthest outside corner of the loop.1 attached to my outer loop and 1 attached to my inter loop. And I have the same set up for the other 2 wires.Those 2 are attached to the closest inside corner of the layout.Within a foot or two of my transformer.I do understand that the circuit breakers are for the transformer protection and the TVS are for the electronics in the train protection.

Bryan

Thanks also gunrunnerjohn

Some things about your setup ar unclear as Dale indicated. That being said

10 qmpere breakers on each ZW terminal (A,B, C and D) should be OK. BUT, I use 7 ampere  breakers on each terminal of my ZW and it has been satisfactory for several

years.

Al W.

Remember that the external breakers are protecting your wire.  If you are using only one output of the ZW and it is protected at 10 amps, you are OK with transformer protection also, but if you have multiple outputs to breakers, the internal breaker in the ZW will need to protect the transformer when the sum of the external currents exceeds the transformer's rating.

Your absolutely right Dale,With all the breakers tied in I accidentally bumped my reading glasses on the track,and it fused my glasses right to the track.The Post war zw kicked in before any of the 10 amp breaker's tripped,actually they never did trip.I have a total of 4----10 amp breakers,so like you said that's the equivalent of one 40 amp breaker,and if I understood you right that's not going to work for wire protection.

Unless you have very big wires!

Nope the wires aren't that big John,should probably had just done what you had suggested and gotten those TMCC direct lock on breakers.Been a lot easier,or just plain bite the bullet and buy the MTH Z4000.

.

If you're running straight TMCC, the TMCC Direct Lockons work fine.  They are not compatible with MTH DCS or conventional operation, FYI.

Thanks John

If you want something that will pop right away on a derailed car (I do), I suggest using electromagnetic breakers (previously mentioned).

 I use postwar Lionel #91 adjustable electromagnetic breakers, one on each active terminal (A, B, C, D).  To those who use these breakers, please be aware that it is possible to turn the adjusting knob in far enough to render the breaker inoperative (will never trip). 

Also, whenever a thread about transformer protection comes up, I like to mention that the breaker inside most transformers, including the ZW, only protect circuits that run through the "U" (common) post. It is very possible to accidentally create a circuit between two active terminals (A,B,C,D) that is not protected.