I just read the post on wire sizing and have some questions concerning common grounds. My current layout is really 4 small to medium layout that do not connect using traditional lional track and switches. I use a seperate tranformer for each loop and one ( A 150 WATT V) for accessories for a total of 5 transformers.2 kws 1 rw and 1 1033 for the smallest loop. The Track transformers run only the trains no accessories.More power than I need. I have some insulated blocks that I use the KWs dual control for. I use 14 gauge wire and some 18 for short runs to accessories and switches… Each of the four loops is wired directly to its own transformer with a hot and ground (14 gauge). In addition, I phase and connect all transformers with a common ground (14 gauge) to make accessory hookup easy and the use of insulated sections easy. The only transformer that may be even close to max capacity is my V 150 watt that runs lights,switches and accessories. My question is that since I have multiple paths back to my transformers with 14 gauge wire via dedicated (directly to the transformer) and common ground , Is the amperage load destributed back through the multiple routes ?. In other words there has never been any sign of anything getting hot. I f the combined amperage of all the transformers went back to each transformer then the circuit breakers on the small transformers would pop. This does not happen even when a big KW shorts. The smallest transformer I just connected and forgot tomention above is a 50 watt for my horse corral and coal loader. It has never tripped a breaker. If I have a short on one loop It does not affect the other loops in any way even though they are connected and phased with a common ground Am I correct in assuming that the load (The total amperage) is distributed through the various ground returns I have? and finds its way back to its own transformer? The previous post would indicated you would need 6 or 8 gauge wire and tha
I would phase no more than two transformers together. If what I read on other posts about Lionel using the common terminal for the circuit breaker you might be asking for trouble when you have multiple derailments or derailments that overlap(the wheelsets touching two sets of tracks) onto two or more tracks. I recommend adding in 10 amp circuit breakers to the A B or C terminals to the tracks from Scott’s Odds and Ends.
To clarify a point, if you have a 5 amp circuit with a hot wire you must provide enuff return capacity with the return wire, basically you should have a separate return wire to the transformer for each track to keep down problems. For example posts A & U should have their own wires to each track, you can seperate after hooking up to the transformer or add a jumper or buss wire system for that track if you like.
14 AWG is good for two transformers phased together even for the return or common.
The wire gauge chart in the NEC(National Electric Code) is for 120 volts to 600 volts A.C. The most volts a Lionel or MTH or other transformer will put out(with whistle control thrown) is around 31.5 volts, normal high end voltage is 25.5 volts.
Like you mentioned needing 6 or 8 AWG is totally absurd! Is your input wiring(house wires) to the transformer that big?? I don’t think so!
The return wire needs to be big enough to carry the maximum current that flows through it. If you were to combine all your returns into one wire and run your transformers at their limits, that would be a big wire. (This has nothing to do with the wiring in your house or the low voltage that we run trains at, as Lee obviously thinks; and it is not absurd at all.) The reason you don’t need that big wire is indeed because you are using separate returns from your loops, as you suspected.
If you were to combine all your returns, you would be better off having your transformers out of phase, not in phase. That way the currents would cancel in the return wire. For example, if you had two loops powered by 10-ampere transformers in phase, the worst case total return current would be 20 amperes, calling for a 12 AWG wire, even though the individual circuits need only 16 AWG for their 10 ampere loads. But, if you put those two transformers out of phase, the return currents cancel and might even be zero. But the worst case would be 10 amperes, when one circuit draws 10 amperes and the other 0 amperes. So you would need only 16 AWG for that return. In building wiring, that kind of copper-saving return is called a neutral. (“Neutral” does not mean “grounded” or “common” as many seem to believe.)
Since your returns are all separate anyway, there is no benefit nor harm in having them in phase–except perhaps for your accessory transformer. Accessories activated by control rails, like turnouts, block signals, and crossing gates, by design do share a return with the track. So it would be a little better to have the accessory transformer out of phase with the track transformer, not so much to save on wire, but also to reduce the voltage drop in the track by reducing the current in the outside rails.
You mentioned using the KW for powering “insulated blocks”
I have one more small hint … I and do advise it go over at least one or 2 guages heavier than most specs call for . It may be a tiny bit more expensive now … but as items are added and newer components are designed … they usually will have higher demands on wattage and etc. You know the old saying … better safe than sorry later !
When your train’s pickups connects the two center rails together momentarily as it crosses the gap, it is effectively connecting the A and B terminals together. If the controls are set so that the carbon rollers are at different places on the secondary winding, you are placing a dead short across the segment of that winding between the rollers. The circuit breaker is not in that circuit; so the “fault” current that flows is limited only by the voltage and the impedance of the transformer and your wiring. It can be much greater than the current that your circuit breaker would allow if it were involved.
If you set the voltages close to each other and move quickly across the gap, there will probably be no harm done to your transformer nor wiring. However, if you forget to adjust the voltages or the train stalls over the gap, and you don’t shut things down quickly, you could damage the transformer and wiring, including any wire connecting multiple pickups inside the locomotive or lighted cars. You might have a fire to put out.
An additional risk is harm to any modern electronics-intensive locomotives that you might have. When the short circuit is cleared, the stray inductance of the transformer will make voltage spikes on the order of hundreds of volts.
There are fairly simple block-wiring techniques to avoid these problems.
One way to follow Bob’s suggestion to equalize voltage is to have one tranformer throttle[or one transformer if two are in use] temporarily control both power districts when engine pickup rollers are crossing the rail gap from one district to another.
One method—IC Controls, [now Lionel] developed the Block Power Controller[BPC] to solve the crossing problem among other things.
It seems to me with the post I am using that my circuit breakers should be in the circuit. People have used these power blocks with these transformers for years like that that or am I mistaken? I purchased an amp tester and will create the situation you describe with different voltages and measure the amperage going to the transformer from each output on the KW this weekend. Have you ever measured It? If the amperage is less than 10 amps there should be no problems unless modern electronics are involved. I measured the amperage in my common ground and found I was fine . the way i have each loop wired hot and ground to its own transformer and those transformers also common grounded to my accessory transformer allows me to use insulated track as a switch for my accesories. Additional current only flows to my mainline tranformers when the train is activating an accessory with an insulated section and that is the amperage that the accessory draws. I proved this with my ammeter.Everybody needs an ammeter so there is no speculation. I just had to reluctantly spend the money. I really appreciate all of everybodies helpand input. What are some other sources for power block wiring info to avoid that situation? How was it done 50 years ago?
The circuit is from the A terminal to one center rail, through the pickup to the other center rail, back to the B terminal, then through a segment of the secondary winding back to the A terminal. As Lionel admitted, this circuit does not include the circuit breaker.
People have done this for years. Some of them have gotten away with it and some have not. I suspect that many of the latter have no idea why their wire burned or their transformer failed.
I measured the current with a type Z some time ago. I forget what I measured (it may be posted somewhere here); but it was well over the 15 amperes that the transformer is built for. I have a damaged Z transformer that I bought for parts. It has a burned section in the middle third of the secondary winding. The only way that could have happened is by a fault between two of the output terminals.
A simple way to wire your layout to avoid running between problematic blocks is to use an SPDT switch for each block to allow it to be assigned to one or the other transformer output. Then you can assign both blocks to the same source to go over the gap. This technique also allows you to have as many blocks as you want, even though you have only two transformer controls. If you use center-off switches, you can also completly shut off a block to park a train.
Individual circuit breakers on the transformer outputs are a good idea. I have them on mine. Even if you intend not to run between differently powered blocks, you will occasionally do it by accident anyway. I use and recommend automotive automatically resetting breakers, which are the same type as originally used in the transformers and are readily available at automotive parts stores.