Fuses

Well, a 10A thermal breaker will always lose to a 10A fast blow fuse, or even a 15A fast blow fuse.  If you look at the trip profile for most common inexpensive circuit breakers, you'll find that it takes a significant overload to trip them quickly.  Look at the chart on the left, that's probably as good as it gets.  A 10A breaker will have to see 30 amps for ten seconds to trip.  The peak currents with a real short greatly exceed that, which is why occasionally one will trip very quickly.  However, when you put a fuse in the mix, the fuse wins every time.

GRJ - Thanks for your input as usual.  Yes, the fuses are always going to win but can I make them win less without risking damaging the TIU's ?  What if I used 15 A slow blow fuses.  A lot of folks just have the 10 A circuit breakers with the 20 A fuses in the TIU's.  Seems like adding a 15 A slow blow fuse in series can't hurt except for the blown fuses trips.  The 15 A fuse in place of the 10 A fuse must be a nuisance trip improvement ?  Am I missing some important point regarding TIU damage other than a fuse 10 A in series provides more TIU protection than 15 A fuse ?   OR, is  a 15 A slow blow fuse a minimal risk given TIU's are designed to take 20 A as evidenced by the fuse size.

Attached is an old Bussman catalog with many fuse charts.

Well, two different people have told me that they repeatedly blow the 20A fuse in the TIU with the Z-1000 brick as input, it has, I believe, a 6A breaker!  The reason the TIU has that fuse it to protect against excessive current through the traces.  FWIW, the fuse in the TIU is a fast blowing fuse.

IMO, if you're blowing even a 10A slow-blow fuse, you need to address the reason why, not increase the size of the fuse.

gunrunnerjohn posted:

Well, two different people have told me that they repeatedly blow the 20A fuse in the TIU with the Z-1000 brick as input, it has, I believe, a 6A breaker!  The reason the TIU has that fuse it to protect against excessive current through the traces.  FWIW, the fuse in the TIU is a fast blowing fuse.

IMO, if you're blowing even a 10A slow-blow fuse, you need to address the reason why, not increase the size of the fuse.

I know why the fuses blow, derailments caused by Grandkids, my switching ability prowess or lack thereof and an issue I have with one of my NJ switch machine's leaf contacts.  I'd just like the easy to reset breakers to pop instead of the pita due to location fuses.   So, most fuse pops are dead short derailments.  Since this is a race condition, maybe at test is in order.  I could jumper out the TIU.  Start with a 10 A slow blow, short the track and see what happens.  If the fuse goes first, I could up the anti to 15 A slow blow and repeat the test.  If, the fuse still blows, I might as well stick with the 10 A fast blow.  Postwar ZW 's feed my TIU's.

I do have 5 A breakers in series with 10 A fast blow fuses fed by a Z1000 powering individual trolley lines.  The breaker pops first with derailment.

There is always the PSX-AC electronic breaker, available from Charles Ro and Tony's Train Exchange among many others. This would be my choice if I had electronics in my engines. 

Then there is this video about breakers for ZW's Lionel Trains ZW Transformer Overload Short Circuit Protection. This was posted before by someone else here on the forum, but I can't remember who it was? I thought it was interesting and it should apply to other transformers or power supplies as well.

There is also the Lionel PH-180 power supply that has an excellent breaker (and you would also get more power to the track). Also available at Charles Ro and many other forum sponsors. 

Along with GRJ above, I've also always been a little leery of those inexpensive breakers that can take quite some time to trip. I have never tried the method used in the video, but it seems like a better way to size the breakers to me? Maybe someone more knowledgeable will comment.

Personally, I like over kill, and have both PH-180s and PSX-ACs on my layout. Or as a good friend once told me, "anything worth doing is worth overdoing" 

rtr, I don't know that one can equate inexpensive and longer trip time.  Any thermal current breaking device, be it fuse or breaker, depends on a strip of wire overheating from current, which metlts (in a fuse) or causes a component such as a bimetallic strip to bend (in a breaker).  It takes time to heat. 

Now an electronic of electromagnetic breaker should pop fairly quickly at its rating.

Steve, you want the breaker to open fast, so the rule of thumb with a thermal breaker or a fuse is to use the lowest rated breaker that let's you run trains. 

RJR posted:

rtr, I don't know that one can equate inexpensive and longer trip time.  Any thermal current breaking device, be it fuse or breaker, depends on a strip of wire overheating from current, which metlts (in a fuse) or causes a component such as a bimetallic strip to bend (in a breaker).  It takes time to heat. 

Now an electronic of electromagnetic breaker should pop fairly quickly at its rating.

Steve, you want the breaker to open fast, so the rule of thumb with a thermal breaker or a fuse is to use the lowest rated breaker that let's you run trains. 

I was generalizing the less expensive breakers (costing only a few $$) that I've seen posted around here a few times. (I have some myself.) The few I have checked the specs on had trip times that can be quite long at the device rating (like GRJ has posted above). 

The PSX-ACs (electronic) do pop extremely fast, beating my PH-180s every time, but to be fair the PSX has only an 8 or 12 amp setting (nearest to the PH-180s rating) and I am using the 8 amp setting. For some reason (not sure why  )  I don't recall ever trying the 12 amp setting?  

The video link I posted is explaining and demonstrating exactly what you say here about sizing thermal breakers. Although I have not tried this method myself, it makes sense. And it also looks like a much better way to size the thermal breakers, rather than on power supply rating alone. Looks quite good in the video.

The one I forgot was the old #91 breakers from Lionel. I have had no experience with those either (don't have one), but have heard they are very fast (as well as adjustable, IIRC).

I use a 2A thermal breaker on my bench supply.  FWIW, it'll get up well past 4 amps before tripping unless I wait several seconds.

I use the old #91 breaker on my bench as well, it's very fast and has two posts, one for low current and one for high current.  I normally use the low current post, it'll run most engines, even smoke, but any surge above a couple of amps immediately trips it.  The 2A thermal breaker never trips when the #91 is in the circuit, that should tell you something.

Guys, I'm sorry if this is a dumb question but do the fuses go between the TIU and the track or do they go between the TIU and the power supply.  I have some 7.5 amp fuses that I bought to use in my hook up but I'm not sure where to put them.  This is totally new to me so I'm not sure about where to use the fuses.  Also is a 7.5 Amp ok or do I need to go up to a 10 amp fuse.

Best place is before the TIU, that way they cover everything.  For fast blowing fuses, I'd be using 10 or 12 amp fuses.

Thanks Gunrunnerjohn, I appreciate it.  I'll go ahead and set it up that way and change out the fuses to the 10 amp.

I also have both fuses and breakers between my ZWs and the TIU.  Initially I only had the 10A fuses, but I added Sensata magnetic hydraulic breakers because I got tired of replacing fuses.  Unfortunately, I got 10A breakers and they almost always lose to the fuses.  Currently I only use the breakers as ON/OFF switches when I want to deenergize a track.  I also have a good stock of 10A fuses.  I’m thinking about getting some Eaton FAZ Series breakers, but before I get any, I will get a clamp on ammeter and see what kind of current various locos and passenger cars draw.

With fast magnetic breakers, I'm curious why you feel the need for the fuses?

Belt and suspenders.

If I hadn’t gotten the wrong size magnetic hydraulics, I might have removed the fuses.

Hopefully I will do a better job at selecting the Eaton FAZ thermal magnetic size.

Breakers can fail, so if a fuse is slightly higher rated that, adding the fuse provides redundancy without any real operating expense.

Anything can fail, but at some point you have to have some faith.  I use the PH180 transformers, and I don't feel the need for extra fuses, breakers, etc.  I'm all for protection, but I'm not sure you have to double and triple it.

Let me put it this way, GRJ.  When I built the layout in the early 90's, I had 2 ZWs and a KW providing power.  I used thermal breakers, and for redundancy had higher-rated fuses in series with them.  I have no idea what the number of short circuit breaks it will take to damage the breaker points, so the redundancy was prudent.  Now I have one ZW, one Z4000, and one PH180, but there's no point in removing the fuses (still the originals).

I also have breakers without fuses in the accessory and switch power feeds.

RJR posted:

Let me put it this way, GRJ.  When I built the layout in the early 90's, I had 2 ZWs and a KW providing power.  I used thermal breakers, and for redundancy had higher-rated fuses in series with them.  I have no idea what the number of short circuit breaks it will take to damage the breaker points, so the redundancy was prudent.  Now I have one ZW, one Z4000, and one PH180, but there's no point in removing the fuses (still the originals).

I also have breakers without fuses in the accessory and switch power feeds.

RJR -  I'm similar.  I had the fuses first and then added thermal breakers years  later.  So I just left the 10 A fuses as added protection in series with the 10 A breakers.  Not a good solution.  I'm working on up-sizing the fuses in hopes of the breakers tripping first.  Any suggestions based on your experience ?  I'm thinking of some type of 12 or 15 A fast blow (AGC) or slow blow (MLD) combination.  My current overloads are mostly caused by derailments.

Steve:  I have 6 TIU circuits i use.  I never turn on smoke.  I want breakers to pop fairly quickly under overload, so I use the smallest which will not pop under normal operations. 

On one circuit I occasionally have 3 trains operating, 1 or 2 of which will include lighted passenger cars (most of which have LED lighting) and all of which have can motors.  On this I have a 7.5 amp thermal breaker.  Originally had a 5, but that would occasionally pop with 3 trains running including passenger cars.

On each of the other 5 circuits, I'd be hard pressed to have more than 2 locos moving at the same time, so I use 5 amp breakers.  All have 10-amp fuses as I recall.

Two of the circuits are now fed by a PH-180; they formerly had two levers of a KW.  Since I switched to a PH-180, the 5-amp breakers have never blown on these two circuits.

Note that the so-called fast-blow fuses really aren't.  Check the blow times on the Bussman web site.  I understand that there are some VERY quick blow fuses available, at higher price.

I would not use a slow-blow fuse on a RR layout.  They are designed to starting loads on circuits with large motors, which have a huge draw on start-up, until they reach operating RPM.

RJR posted:

Steve:  I have 6 TIU circuits i use.  I never turn on smoke.  I want breakers to pop fairly quickly under overload, so I use the smallest which will not pop under normal operations. 

On one circuit I occasionally have 3 trains operating, 1 or 2 of which will include lighted passenger cars (most of which have LED lighting) and all of which have can motors.  On this I have a 7.5 amp thermal breaker.  Originally had a 5, but that would occasionally pop with 3 trains running including passenger cars.

On each of the other 5 circuits, I'd be hard pressed to have more than 2 locos moving at the same time, so I use 5 amp breakers.  All have 10-amp fuses as I recall.

Two of the circuits are now fed by a PH-180; they formerly had two levers of a KW.  Since I switched to a PH-180, the 5-amp breakers have never blown on these two circuits.

Note that the so-called fast-blow fuses really aren't.  Check the blow times on the Bussman web site.  I understand that there are some VERY quick blow fuses available, at higher price.

I would not use a slow-blow fuse on a RR layout.  They are designed to starting loads on circuits with large motors, which have a huge draw on start-up, until they reach operating RPM.

RJR - Thanks for your input.  I have some 12 A fuses on order.  I'm going to try them first.   I could try lowering the circuit breaker value although I'm wary since my passenger cars are all incandescent.  I've popped the ZW breaker more than once after running 3 trains for an extended time although each  of the trains were on a separate TIU channel fed from the same ZW.

Shoreling, step down the breaker vs raising a fuse that hasn't blown.

Put two on a switch if you have a problem loco.

Ideally I'd use a fuse as last defense and breakers to lessen costs of fuses that blow often.  E.g. 7a breaker and a 10a fuse. Breakers are quick to reset, fuses are work and $$.  

Fast blow is best for protection, slow blow is more for sturdier cicuits with more overkill designed in and/or lots of short current peaks, like a motor alone.  

Like anything electrcal it's a balancing act, no one answer.

Adriatic posted:

Shoreling, step down the breaker vs raising a fuse that hasn't blown.

Put two on a switch if you have a problem loco.

Ideally I'd use a fuse as last defense and breakers to lessen costs of fuses that blow often.  E.g. 7a breaker and a 10a fuse. Breakers are quick to reset, fuses are work and $$.  

Fast blow is best for protection, slow blow is more for sturdier cicuits with more overkill designed in and/or lots of short current peaks, like a motor alone.  

Like anything electrcal it's a balancing act, no one answer.

Adriatic - Thanks for the advise.  I'm considering downsizing the breaker size from 10 A.  However running a post war F3 ABA with 7 passenger cars must be around 7 amps.  Adding a second consist and I"m breaking 10 A.  I'm going to have to do some testing in order to decide.

I agree with Adriatic, who is giving you good advice.

The Lionel postwar two-motored diesels drew a lot of power.  My recollection is that Model Railroading, the old Lionel manual, said they drew 55 watts.  It is possible to easily include a SPDT switch to change breakers if you have one power hungry train set.

Price also means I'd test with a similar speed (cheap) fuse before I buy a more pricy breaker that wouldn't be adjustable. Fuses need to blow to be more costly.  

One might choose a 6a sb and a 10a fb using charts and a crossover area as GRJ shows and get similar saftey and cost saving long term.  Again, You have to gamble on a balance point with a logical guess as you can with what you expect.

A meter with a 10-15amp read capability is real nice for knowing draw vs guessing

Fuzzy photo of fuses protecting power supply for twin shelf, 5 track, 14 x 32  operation when powered by 3 pw ZWs and removed when power replaced by five 180 PoHos which have very quick breakers.

.