Adding circuit breakers

Amps is amps. Doesn't hurt to have both in series. Position doesn't matter. When it (fuse or breaker) trips, it trips.

I understand, but i want the breaker to trip first, since it will be at a much easier location to reset.  Not under the table.

I don’t think you can get a definitive answer without knowing exactly what fuse and what breaker you have. All things being equal, the one nearer the power supply will trip first, but these may be far from equal. I would just bypass the fuse or put in a bigger one. 

fuses almost always blow first beakers take longer to trip. actually a fuse blowing is much cheaper then a new train board! personally Fuses are much cheaper then a $200.00 electronic board.

Alan

If you really want protection, you want the DCC Specialties ~  PSX1-AC 3 & 2 Rail Power Shield Circuit Breaker (available on eBay). Get rid of your breaker and fuse and install this. It can be setup for automatic or manual reset. If you have multiple blocks on your loop, it can be wired for coordinated shutdown. Trip amperage is set by jumpers on the board. Not cheap, but IMHO worth every penny. Wire it between the TIU and the track. Wire a TVSS on the output of your transformer for extra protection.

I TRIED to trip a PH-180 breaker by shorting the rails with my pocket knife. This breaker tripped before the PH-180.

What magnetic breakers are they? I use Airpax 10 amp that trip before a regular 5amp resettable. They also trip when shorted with a 26 awg wire, while the 5amp just melts the wire. The PSXs are definitely good, but he mentioned “TIUs”. That could mean 8 circuits, and the PSX only covers one. That does make it “not cheap”. 

@Gilly@N&W posted:

Amps is amps. Doesn't hurt to have both in series. Position doesn't matter. When it (fuse or breaker) trips, it trips.

There are slow blow version of fuses and fast blow versions of fuses, so that could make a difference relative to a breaker. 

@John H posted:

What magnetic breakers are they? I use Airpax 10 amp that trip before a regular 5amp resettable. They also trip when shorted with a 26 awg wire, while the 5amp just melts the wire. The PSXs are definitely good, but he mentioned “TIUs”. That could mean 8 circuits, and the PSX only covers one. That does make it “not cheap”. 

I bought the Airpax 10 amp as well.  I bought 8 since I have 8 individual power feeds from the two TIUs.  The fuses that I have currently are the quick blow 10 amp glass fuses.

Based on the above, I will put the breakers between the fuses and the transformers.  I will see if the fuses trip first, if they do, I might move them up to 12 amp, so the breakers trip first.

The Airpax magnetic breakers are consistent and reliable.  The batch of 10A breakers I have trip instantly at 10.1 amps.

Where are you guys getting the Airpax breakers and what are you paying?

I bought my Airpax  breakers (PP11-0-10.0A-OB-V) about two years ago from onlinecomponents.com for $11.46 + shipping and tax when purchasing four. 

In my experience, they are very quick.  For example, I have one section of track that has a little dip, and one of our engines has a low drawbar that will barely nick the center rail.  The Airpax trips every time.

@gunrunnerjohn posted:

Where are you guys getting the Airpax breakers and what are you paying?

I just got mine at online components.com.  I paid $11.20 each plus shipping.  They sell them in increments of 3.  I needed 8, but ordered 9.  I did not fine anyone else that had them in stock.

I got mine from an aircraft supply house in LA.

Digikey seems to have them coming in, that's probably where I'll go.

I started out with 10 amp automotive mini fuses between my ZWs and the TIU.  I added Airpax/Sensata PP11-2-10.0A-XX-V magnetic hydraulic breakers because I got tired of replacing fuses.  Unfortunately, I got 10A breakers and they almost always lost to the fuses. I replaced the Airpax/Sensata breakers with 3, 4 and 5 amp Eaton FAZ magnetic hydraulic breakers (from automation direct).  The Eaton breakers almost always beat the fuses and rarely trip due to load.

@Lehigh74 posted:

I started out with 10 amp automotive mini fuses between my ZWs and the TIU.  I added Airpax/Sensata PP11-2-10.0A-XX-V magnetic hydraulic breakers because I got tired of replacing fuses.  Unfortunately, I got 10A breakers and they almost always lost to the fuses. I replaced the Airpax/Sensata breakers with 3, 4 and 5 amp Eaton FAZ magnetic hydraulic breakers (from automation direct).  The Eaton breakers almost always beat the fuses and rarely trip due to load.

How did you mount these?

I have to wonder why bother with fuses and the magnetic breakers?  Of course, a 3 amp magnetic breaker is going to trip faster than a 10 amp, that's not a surprise.

Tommy – The breakers are mounted on a DIN rail inside a plastic box.  I cut the lid of the box with a sabre saw.  The fuses are mounted in holders I got at the auto store.

John – It’s a belt and suspenders thing.  The fuses seldom blow, but when they do, I’m glad I kept them.

This is how I will mount them. This shows toggle switches, but the breakers fit right in.  I get these from Front Panel Express.  You can design them to your own size.  I have one ordered with 8 holes.

So if you're using a modern transformer (i.e. Z4000, ZW-L, PH180) are the external fuses/breakers redundant?

I used to use a Postwar ZW to power my layout's track with fast blow ATO fuses between the ZW and TIU. I recently replaced the ZW with two PH180s and removed the fuses, relying on the fast PH180 breakers, as I assume the fuses would be redundant. I have TVS diodes between the PH180 and the TIU and also had TVS diodes between the ZW and TIU, so that didn't change.

I just use the PH180 and TVS on the track feeds.  I see no reason for multiple levels of circuit protection with the excellent PH180 electronic breaker.

@gunrunnerjohn posted:

I just use the PH180 and TVS on the track feeds.  I see no reason for multiple levels of circuit protection with the excellent PH180 electronic breaker.

Neither do I. I can see the external protection with postwar transformers but people above were talking about adding external protection to PH180s, which I thought seemed redundant. 

@Tracker John posted:

The Airpax magnetic breakers are consistent and reliable.  The batch of 10A breakers I have trip instantly at 10.1 amps.

I ended up putting the breakers between the transformers and the quick blow fuses that i already had and the breakers have tripped before the fast blow fuses.  Both are 10 amp.  I only kept the fuses since i did not want to do more re-wiring under the layout.