Help with Transformer Size Required

Depends on the locomotive and the cars he is going to run, and any other accessories.  Theoretically the total wattage of 80 watts will handle a 4.33 amp draw.  My locos (all- from postwar to Legacy)  draw about 2 amps running, probably more on startup, pulling 12- 15 cars on a level track.  And I have over 200 feet of track.

This application (as I read it) does not have any accessories to use up available power- just a circle of track and some cars behind a locomotive.

I might have him stay with just the CW80, complete the circle of track using a buss wire with booster connections every 10 feet or so, and start running.  You'll know pretty fast if the load is too much- the transformer circuit breaker will kick out. Or, the train will slow down as it gets separated from the power hookup.

The only SURE thing- if you do something else- is an expenditure of one to several hundred dollars on a new transformer.  I'm guessing it will work fine on the CW80.

@Charles Wojun posted:

I am helping friend who is installing a large ceiling mount oval for his polar express set. The oval will be between 88 and 120 feet of tubular track. he has the Lionel transformer that came with the set (80 watts I think) but is that sufficient?  My own layout uses a ZW and I have installed additional "boosters" of direct wire from the transformer to strategically placed lock ons, so I assume we would have to do that as well.

Will the 80 watt handle it? What about another one (or two) same size transformers feeding different sections. There was some discussion on the forum a while ago about connecting a couple of transformers to a single line (the question was polarity for the older transformers) but since the new 80 watt units have polarized plugs would the automatically work?

If he has to buy another transformer, how many watts?

The question is not how much power the transformer has -- if it's powerful enough on a small oval, it'll have enough power for any size loop -- but rather a matter of minimizing voltage drop between the transformer and the point you need that power, by reducing the resistance in the circuit.

In addition to making sure all the contact surfaces of your track sections are in good condition and making good contact with adjacent sections, the classic solution is either to create a high capacity, low resistance bus (typically 12-14 gauge wire) that follows the track around the layout with drops (connections to the track) every 6 feet or so, or a central terminal block from which smaller feed wires (16-18 gauge) run in a star configuration out to drops every 6 feet or so along the track. Since your friend is contemplating a ceiling mounted oval, ISTM a bus mounted under the oval and following the track around the room, with drops every 6 feet or so, would be the logical configuration. Good luck, in any event!

I just want to add to the importance of bus/drops as @Mike Wyatt and @Steve Tyler have already suggested. You can easily change out the CW80 for a more powerful transformer in the future with only connecting two wires to your bus system and plugging the new transformer into the wall. It would be very difficult to add bus/drops the large ceiling loop after it is built.

Recall that the track rails themselves are not our main problem for getting power around the layout, rather, it is the track to track connections that are our problem. The connections can be poor at the time of building the layout, and, overtime, can become a larger problem.

Though the prior suggestions didn't implicitly mention it, the bus/drops should consist of both the power and return wires.

How often to have drops can be debated all day long. My (and I emphasize My) rule of thumb is no more than three track to track connections between drops. If you use 10" track sections, means drop every 30". If you can use 40" track sections for straights, then you can see drop every 120" could be with this longer track section size.

If the room is subject to high humidity, I might actually consider the pain of adding to the bus/drops soldering a jumper across every center rail to center rail connection, and across every outer rail to outer rail connection (only one of the two outer rails, both are not required.

I have not seen this mentioned - though it certainly could have been commented upon in the huge library of this forum - is to use the no oxide paste on the track pins before mating. Unfortunately, I have a hard stop now, so I can't get the name of the paste that has been suggested in this forum and I have some by my layout. Again, hopefully another forum member will read this and give comment and paste name.

Thank you all for the quick response.  We will try this with the track on the floor before mounting and check the voltage along the rails to ensure that we have consistent power.  The train is a Polar Express with 3 or 4 cars and not accessories, and I am advising him to buy new track.  THANKS!

The trying it on the floor is a good idea.  However, each installation can be different. Regardless of your floor results you need drops every 8-10 feet or so in order to maintain uniform power on the tracks.  The connections between tracks will degraded over time and the drops will help compensate for this.  The idea of using new track is excellent. You want to start out with the best connections possible.  Also, each drop  needs to include both outside rails plus the center rail.