Been reading a lot on here about the TVS Diodes and fast breakers..... and

The TIU has built in TVS diodes, the PSX have built in TVS diodes, so IMO no you don’t need more but it can’t hurt to add more.  

if you only run in command why do you need a ZW?  Just as a off and on switch through you Legacy?  I only use two PSX one for each fixed output of the TIU, I don’t use the variable outputs.  Even running four trains at once, even with lighted passenger cars I never get close to 10 amps per channel so no reason to use the other channels.

If you just run the 180W bricks to the TIU and skip the ZWC controller, since all your locomotives are command, you should be good to go. The ZWC is unnecessary if you're running command control. I run TMCC/Legacy/DCS and just have the 180W bricks connected to the TIU fixed inputs. The breakers on the 180W bricks are plenty fast, and I haven't killed a board relying on the 180W brick's breaker. I do have TVS diodes on the TIU input side as extra backup, just in case.

Protection here is about protecting against excessive current, i.e. short circuits, as well as against excessive voltage, i.e high voltage spikes.

1.) For overcurrent protection

PSX-AC Power Shield breakers are not compatible with conventional operation because they need at least 10VAC at their inputs all times.

This means that they're meant for command control only, and at this they do very well.  They're quite fast.

Since you have no conventional operation they'll be perfect for you.

Having said this the PH-180 bricks that came with your ZW-C are no slouch either.  As has been suggested removing the ZW-C from the picture and connecting the PH-180's directly to the track, for TMCC/Legacy, and directly to the inputs of the fixed channels on the TIU, for MTH, is your best route if you don't use PSX-AC's.

2.) For over voltage spike protection

TVS diodes are important for clamping off voltage spikes.  Common practice has them placed across the power connection(s) at the track(s), although for best protection with locomotives they really should be inside the locomotive between pickup roller and frame (common).

Using too many will interfere with the DCS signal being carried through the track from your TIU to the locomotive.  Not a good situation.

Mike

I am going to piggy back onto this thread.  Like Robert, I have been pouring over several posts on this forum and others concerning overcurrent protection and over voltage spike protection.  I run mostly Command Control locos with a few (3) conventional locos.  I want the option to run conventional and Command.  My current setup for the test layout / layout for my son is two MTH Z-1000 transformers and Legacy.  Future layouts will run ZW-L (Delivered at first of this year, not used yet) and GW-180.  BASE 3 is also on order (Layouts in different areas of home (Ceiling loop in my office, Dad's (me) layout in train room and son's layout in trainroom, in additon to our HO DCC / DC layout).

Brief History / Background.
Started in this hobby in HO in 1978 until 1990.  Switched to N Scale in 1999 and DCC.  2009, switched back to HO Scale and DCC.  Hobby paused again in 2014 until 2020 after several cross country moves, again in HO DC and DCC.  Started in O gauge in 2021, built a 4x8 Conventionall / Legacy layout in late 2021 along with a Christmas Lion chief DC layout.  Larger around the walls shelf layout is in planning and equipment acquisition phase.

The Problem(s):
For the 4x8 O scale layout, I decided to use the new Lionel CW-80 transformers to allow the option to run conventional, LionChief, or Legacy/TMCC locos.  Also installed Legacy.  After about 4 months using the CW-80's we had a derailment (son was 4 at the time and is now 5, things are going to happen even with dad present).  I killed layout power and turned power back on and one CW-80 was dead and unresponsive.  Well ok, my concerns over the new CW-80's seem to be warranted based on what I read about the older ones.  I contacted Lionel and they issued a RMA no problem.  2 days later, another car jumped the track at a turnout and was a very short derailment (maybe 1 sec) and this too killed the remaining CW-80.  Contacted Lionel for another RMA.   I decided that these transformers would be regulated for test tracks and accessories duty if needed.  (currently using older HO transformers to power accessories).  I then decided to purchase two MTH Z-1000 transformers based on good reviews and the fact that these used power bricks with circuit breakers instead of internal fuses like the CW-80.

About three weeks ago one of our MTH Z-1000 controllers I purchased in October 2022 partially died due to a short.  This short was from the barrel connector being bent and making contact with itself.  I was lazy and used an adapter to go from the terminals to the barrel jack as this layout is planned to be decommissioned in a couple of years for a larger layout for my son (and dad for the less serious stuff).  The compromised Z-1000 output does not go below 10 volts.  I followed posts I have read here and ordered parts from Digikey and replaced the components in the controller with no success.  So, I ordered a replacement Z-1000 from TrainWorld.

Finally I get to the question (about time):
My Remediation plans include replacing the FastTrack lock-on's with soldered wire to the underside of the track at 4 drops per isolated loops (Going from transformers to Terminal blocks then tracks).  This will help in conventional mode because even on a small 4x8, I noticed voltage drops.  In Legacy, the voltage drops were not notable.  To prevent further carnage to these apparently delicate O gauge transformers / controllers (I say this because I have never fried a DC transformer or DCC base station, Power distribution, block, etc in HO or N scale (we will not discuss improperly installed decoders though lol))  I want to install a circuit breaker between the controllers and track to help mitigate the risk of killing yet another controller.

I tried a 5 amp thermal circuit breaker while using the compromised controller and performed a short test, the breaker on the brick tripped before the 5 amp thermal breaker (from Amazon).   So, now I have been on the quest looking for a fast acting over current protection solution.  Was planning on using the TMCC Direct Lockon but learned that it requires at least 10 volts to function like the PSX.  I have thought about using fuses but would rather use a fast acting breaker.  I would want the circuit open in 1 second or less preferably.

What is a good Breaker or Fuse solution that will provide FAST protection while allowing for conventional and Legacy loco operation?

And then I stumbled onto the conversations about using Diodes to protect on layout electronics.  I have also read that this may not be a good idea (Tinman3rail which I have read some posts here that brews skepticism on their protection product and comments on using diodes).

I have read that many people liked hi-rail for it's electrical simplify compared to DCC and smaller scales analog.  So far, my trek into O scale / Gauge starting in 2021 has been a BRUTAL learning curve lol and makes even large DCC layouts look easy lol (of course I work in IT Infrastructure and Digitrax DCC is basically Ethernet, so there is that).

Short Version of this Ramble:

1.  What is a fast reacting fuse or circuit breaker to protect overcurrent to prevent killing my transformers / controllers?

2.  Is using Diodes safe and are comments suggestion otherwise hogwash? (looking at these TP1.5KE36CA)

Thanks and sorry about the ramble......I don't get out much LOL.

Matthew

Here's another thread discussion on Airpax "instant" trip circuit breakers you might find interesting.  I have these breakers(7.5 Amp) on a reconditioned Lionel "Z" transformer; they work very well.  YMMV

airpax-snapac-hydraulic-magnet...-internal-mechanisms

The Airpax breaker mentioned by Ted is an excellent choice.  Also, the TVS diode protection is good, however for the best results the TVS diode should be right at the electronics being protected.  Also, some of the protection schemes will change if you are running MTH Protosound 2/3 locomotives.

Thank you Ted for that, very helpful.

Thank you John

@gunrunnerjohn posted:

The Airpax breaker mentioned by Ted is an excellent choice.  Also, the TVS diode protection is good, however for the best results the TVS diode should be right at the electronics being protected.  Also, some of the protection schemes will change if you are running MTH Protosound 2/3 locomotives.

Hey John,
One more question, is the TP1.5KE36CA diode Bi-directional?  If Uni-directional, I am assuming installation would go from hot to common. or does it not matter?

Yes, bi-directional.  So no polarity, this is AC.