Suggested AMPS for Circuit Breakers

I agree with Dale on 10-amp max.  Put one in each output On the ZW, on A,B,C,&D.  For full protection, I suggest a fifth, on the U circuit.  A ZW secondary coil can handle about 10 amps.  With just the first 4 breakers, you could conceivably have 40 amps flowing (not for long) wihout any breaker protection.  You may ask why not just put the breaker in the U circuit?  The reason is that you can have shorts between any pair of A,B,C, & D posts, and may not realize it.

I think Dale and RJR have given you good advice.

With proper protection the ZW and KW will give you good service.

Recall that when we were kids we knew nothing about circuit breakers, and maybe had a vague idea about what a fuse does.

We ran our ZW's and KW's to death and somehow we managed to live through it without burning anything up. I do recall a few hot wires however.......

Rod

7.5 amps is my maximum fused track circuit.

I depend on the very good 10A breakers on the Lionel PowerHouse 180 transformers.

Call me old fashioned but I am still leery of reliance on breakers for protection on my layout.  I go with 10 amp fast blow fuses from each post on the ZW or KW. 

I learned something here though about protecting the U post.  Thanks for that tidbit.

MichRail.  Breakers can & do fail.  Fuses can malfunction.  In the long run, fuses are more expensive.  I use both, a breaker and a fuse in line, with the fuse a higher rating than the breaker.  I have never blown a fuse, but the in-line breaker pops often.

All: check the www.bussman.com web site for some interesting tables on how long it takes a "so-called" fast-blow fuse to activate.

"I agree with Dale on 10-amp max.  Put one in each output On the ZW, on A,B,C,&D.  For full protection, I suggest a fifth, on the U circuit"

I understand how to wire the CB on the output on A,B,C,D. but where or how do you wire for the "U' side?

Greg

Put it near the transformer U terminal, feed all ground lines--TIU black inputs---to the breaker, and connect the breaker to the U terminal on the transformer.

I am concerned about the advice given about putting a fuse in the U return circuit.

Remember that the return breaker or fuse needs to be able to handle the total current of all the individual supply posts, A B C & D.  Therefore, I would say a 12 Amp breaker or even a slightly larger one, like a 15 Amp, would be required.  The ZW, whose input wattage is 275, can probably deliver 200 Watts continuously at 20 Volts.  That would equate to 10 amps. (200 W / 20 V = 10 A)

Arthur, you are correct.  I would use a 10-amp max in the ground circuit.  I don't catch what is your concern.

My calc was that Lionel, back in the 1950's, published a Bantam paperback on Model Railroading, which said to limit continuous drain to about 70 or 75% (I forget which, and my copies of the book are in shambles), Let's say this is 200 watts (as you do); to me, as to you, this means 10 amp is the continuous carrying capacity of the secondary winding.  So we are in fill agreement.  Since these transformers could be on for long periods, for safety I'd limit the current to 10.  One consideration is that I don't recall any provision for cooling the core, unlike the Z4000 which has a blower.  12 amps would give 240 watts, which has me uncomfortable.

Having said that, I also have an old Type R, 100 watts.  There was a time when I used it to run 2 Lionel steamers, a #97 coal elevator, and a pair of 022 switches.  Obviously, I was pushing the envelope.  But I still have it and use it on the workbench

The problem is your assumption.  ZW breakers are notoriously unreliable.

You are correct regarding normal practive in 120 and up circuits.

I use 7.5 fast acting fuse which have worked very well for me.  However RJR makes a point about the unreliable and very slow action internal breaker on the ZW.  I was wondering then if there is a suitable replacement breaker for the ZW that is more reliable and faster acting.  I would still keep my external fast blow fuses in place.

Thanks,

Ed

I've used the automotive cartridge type breakers in the KW, and I suspect they'd work as well in the ZW.  I personally would put the internal breaker at 12-15 amps in the ZW.

Strongly disagree, GRJ, about 15 amp.  Too many amps for the secondary winding.  Will generate too much heat in wire at point where that amperage is flowing.

What you're saying is you want to limit the ZW to 10 amps?  That's your call.  I know the stock breaker is at least 15 amps.

There is no need for a breaker/fuse on the ground side (the "U" terminal) of the circuit.

If you have all the hot lines (A, B, C and D) protected, that's all you need. 

GRJ,

Can I and Should I install this 10amp breaker on my TW175 ?

I use this on my test track and I would like that protected as well.

You're wrong, Rich.  10 amp breakers on each output theoretically means up to 40 amps flowing through at least part of the secondary, which is dangerously too much.  I say theoretically because with dead shorts on the outputs, internal resistance would probably limit current tondome extent.

Doesn't it depend on the loads you run at?  I started with 10 amp marine breakers on the outputs of my ZW, reduced them to 7 and then finally to 5. They blow quick now, but I don't get unnecessary cut-outs. For my layout and the loads I run, 5 amps has been perfect.

Roger

Roger, I actually use 5's on my layout for 5 of thr 6 circuits, and 7.5 on that.  Since I leave smoke off, I have enough power for operating.  The 7.5 is for an area on which I often have3 trains running, one with 8 lighted cars.  5's open quickly on minor derailments.

The TW is an odd duck, and has two separate windings.  It actually has two circuit breakers, and if I were to replace them, I'd use no more than 5A maximum for the values.

"...Bantam paperback on Model Railroading, ...my copies of the book are in shambles."

HAH!  I feel your pain. When I discovered that book in 1950-something, I thought I'd died and gone to heaven.  Mine turned to shambles within a month, from the workout I gave it, to the exclusion of all other activities.  It took a lot of whining to get my mom to buy me a newer edition, a few years later.  That one fell apart, too, in short order.

At a 10A draw, I've never seen a ZW that can get anywhere close to 20 volts output, it's normally down closer to 16-17 at that current draw.

GRJ, using your figures, with which I agree, that means 40 watts is being dissipated in the secondary windings.  That's a lot of heat.

Arthur.  I have the separate pages in a box, but I think some are missing.  I had both the first and second editions, and pages may be intermingled. It was certainly one of the best books ever printed on model railroading.

Well, the way to determine the actual power loss and efficiency is to measure the primary and secondary voltage and current.  Then you can figure what is being "lost" in the transformer, all of that would be converted to heat.

True, GRJ, but would you not agree that if the voltage drop within a transformer is 4 volts, per your example, and you're pulling 10 amps, that that is 40 watts?

Not really.  Open circuit voltage is 20 volts, I don't think that translates directly.  I think I'd want to see the measurements before making a judgment.

Watts is amps times volts.  If voltage is dropping 4 volts inside the transformer, and you're passing 10 amps, that is 40 watts being dissipated inside the transformer.  When you have open circuit, there is 0 amps and therefore 0 watts being dissipated in the windings.

Not really, the efficiency of the transformer isn't being considered.  Also, the efficiency may change as the core gets saturated. 

No doubt efficiency does change with core saturation, and some wattage is lost in the core, which is why a transformer isn't 100% efficient.  But that would be loss in addition to the 40 watts per our example.

How did we get off on this tangent anyway?

thanks for a whole lot of information, I'm going with 4- 8 amp CB's  on the output of my PW ZW I did replace the internal breaker with a 15 amp. 

Does anyone have a recommendation for a CB?  I have a Lionel 135W PH-1 and probably need to add a CB.  Lionel recommends their 7.5Amp 6-22914 Powerhouse Lockon, which looks good because of the auto reset.  I'm feeding a DCS TIU channel, so I can put the lockon on the output side of the TIU as the wire goes out to the track.  Any thoughts?

Do NOT put the TMCC Direct Lockon on the output side of the TIU, it stomps on the DCS signal.  I've seen three locations where the same thing happened with them in the picture, including here.

I get mine from Defender Marine.  Check at

http://search.defender.com/?ex...rs&x=10&y=10

# 201683 has slip-on connectors; # 201684has screw-on connectors.  $5.79 each for either style.  Come in 3, 5, 7, 10, & 15 amp.  For some reason, further down that page they may be a little cheaper.