Powering New Layout

Well, I think you're overestimating a few things:

- First, I think you're a bit high on the engine consumption. Most engines are more in the 1-3 amp range during operation IME, and I routinely run four engines or trolleys on one PW ZW, at a 275 watt rating, with no problems. You'd really have to run the engines flat out with an enormous consist to approach anything like that amperage, and if you did, I doubt the transformer would be the first to let go!

- Second, the lights in most Dept 56-type buildings I've encountered are powered directly from the house supply, using nightlight-type bulbs (typically 4 to 7 watts). If that's the case for yours, the power for them will not be running through the transformer, and can be disregarded for your calculations. If you *are* using accessory voltage incandescent bulbs, I strongly suggest you consider LED replacement bulbs, to reduce heat and your electric bill!

My other thought was to at least separate your operating power from your accessories. That way, you can change and upgrade (or further split) either at any time without having to change the overall system. On many layouts, powering accessories is the duty typically assigned to otherwise obsolete or underpowered transformers, saving money and extending the usefulness of what you already have. Good luck, in any event!

Thank you, Steve, your reply is very helpful.  And you're absolutely right about the D56 buildings running on 110v house power, so I can cut out all the watts for the lights.  It certainly sounds like a ZW-L is far more than enough, and that even just a GW-180 would be plenty.

What about the incandescent lights in the passenger cars?  (At least until I convert them all to LEDs)  How much power do they draw per car?

And re: your point about separating accessory power from operating power -- Do the inner throttles on the ZW ostensibly used for accessory power actually separate the operating power from accessory power?

Thanks again, and for your rapid reply,

@Bob W / cprail posted:

Thank you, Steve, your reply is very helpful.  And you're absolutely right about the D56 buildings running on 110v house power, so I can cut out all the watts for the lights.  It certainly sounds like a ZW-L is far more than enough, and that even just a GW-180 would be plenty.

What about the incandescent lights in the passenger cars?  (At least until I convert them all to LEDs)  How much power do they draw per car?

And re: your point about separating accessory power from operating power -- Do the inner throttles on the ZW ostensibly used for accessory power actually separate the operating power from accessory power?

Thanks again, and for your rapid reply,

I've never had occasion to measure the draw, but I'd be very surprised if it was much more than a watt or two each, and I believe some cars used more than one bulb per car. As a simple measure, you might see if there is a plug-in LED replacement for whatever size bulbs are in the car. That won't get you the flicker-free performance of the premium conversions (in fact, LEDs tend to be a bit more prone to flicker), but would probably be cheaper and easier to implement than installing LED strips and PCBs to fully upgrade the lighting.

No, just using separate taps on a single transformer will not reduce the overall draw through the transformer -- it all goes through the same windings and core. I was speaking of separating the source of the power -- IOW using a separate transformer for the accessories, independent of the transformer providing track power/control. It is easy enough to run both (or as many as you end up with) to a power strip with switch, in order to create a master on-off kill switch for your whole layout.

Steve,

Thank you again - it's great to have you as an electrical resource.  I really appreciate it.

Just curious - and forgive me for asking - has your expertise come from electrical/electronics engineering or your own experience in model railroading?  I'll certainly understand if you'd rather not have it public.

@Bob W / cprail posted:

Thank you again - it's great to have you as an electrical resource.  I really appreciate it.

Just curious - and forgive me for asking - has your expertise come from electrical/electronics engineering or your own experience in model railroading?  I'll certainly understand if you'd rather not have it public.

No problem, Bob -- always glad to add my 2 cents, and happy when it can help.

Well, I started down that path -- interest in science since elementary school, HAM radio license in high school, enrolled in electrical engineering at Hopkins before encountering integral calculus and switching majors! Most of my "expertise" has been picked up along the way, most recently in the most recent COVID-hobby renewal of my interest in toy trains (mostly Marx PW stuff, but have dabbled in modern electronics, Arduino control, and scratch building as it caught my interest). So, enough knowledge to let me get in over my head, but at least I've found resources (like this and other forums!) where I can send up distress flares at need!

I would recommend looking at the MTH Z-4000 for transformer power. It has two separate handles - one for each loop, if you want - 400 watts of power and is pretty much bullet-proof. It also has both 14 volt and 10 volt accessory terminals for powering lights, accessories, etc.

I think the GW-180 may be overkill for accessories. I recently picked up an NIB Lionel 1.8 amp 6-32923 accessory transformer with adjustable voltage output to 18 volts on the 'bay for $25.

I measured the power draw on my 140 foot main loop with a total of three diesel engines running pulling a total of 40 freight cars.  All three Legacy engines had the smoke running, and the total amp draw was varying between 6A and 7A, primarily due to the grades I expect.

If you run passenger cars with incandescent lighting, the picture can be quite different as a typical incandescent passenger car can consume from 300ma to 600ma, depending on the specific car, size, and configuration.  Any of my passenger cars that run regularly have been converted to LED lighting, so they're using about 25ma each.

Thanks for the Z4000 suggestion, Richie, I'll certainly take a look at it as I get near to the transformer decisions.

John -- thank you for the info and amps being drawn, both for the layout in operation overall and for passenger cars individually.  Does the 6-7A figure mean the total power used by the transformer would be 110v times 6.5A, or 715 watts?

The info on the passenger car lighting is great and I presume the per-car amperage is cumulative across the total number of cars -- so the max amps drawn would be (Total Number of Cars) x 600 mA?

Steve  -- Thanks, I'm always interested in hearing about the background of colleagues in the hobby.   I think the interest comes from my own experience -- at one time (the start of my college years at Michigan) I was planning on being an engineer.  They had an intro course in the first year that exposed students to all of the main areas of engineering -- mechanical, chemical, electrical, industrial at the time (1966) -- I found the EE section the most difficult.  I was undeterred since I'd always thought of being an aeronautical engineer, and pressed on into year 2.  The thing that changed my mind was the first aero E course - I sat in the back of a huge lecture hall and could barely see the board or hear the professor, whose heavily German-accented English ("zeese are ze wectors on the ving") made me realize this was probably not my cup of tea.  So I switched to psychology and loved it -- but to this day I always think I might have enjoyed engineering as a profession -- if I'd ever gotten there!

@Bob W / cprail posted:

  Does the 6-7A figure mean the total power used by the transformer would be 110v times 6.5A, or 715 watts?

We need @gunrunnerjohn to verify this but I don't think that rights. I assume John measured that amperage at track voltage. So with slide rule math it would be 7a X 20V = 140 watts. The line side or 110v side would be drawing a little more them 1 amp.

Thanks for the clarification, Pup. Could you please explain why the 110v side draws only 1 amp?

Am I correct in concluding that @gunrunnerjohn's transformer is consuming 140 watts of its own total output, and whatever is left is available to run the trains?

Bob, I don't want to go too deep into this because I could be wrong and don't want to send you down the wrong path. I'm figuring that if the transformer is drawing 140 watts then 140w/110v is a little over 1 amp. That assuming a 100% efficient transformer which we know is not possible.  I also agree with your second sentence but  to be sure I'd appreciate it if @gunrunner john would confirm or correct what I'm saying.

Thanks for spelling it out for me, Pup.  Yes, of course!  I know the w = v X a relationship, one of the few things I remember from intro EE, but somehow just it didn't register as I was reading your post.

We'll wait until @gunrunnerjohn weighs in.

Yes,

Bob, I just ran a postwar F3 with duel motors pulling 3 passenger cars with lights. It drew 4 amps at about 10volts

@Bob W / cprail posted:

Thanks for the clarification, Pup. Could you please explain why the 110v side draws only 1 amp?

Am I correct in concluding that @gunrunnerjohn's transformer is consuming 140 watts of its own total output, and whatever is left is available to run the trains?

The voltage ratio of the transformer input/output is the difference.

110V at 1 amp is 110 watts.  Assuming a transformer efficiency of around 85%, the total power to the secondary is 93 watts.  If it's an 18V output, that would be a bit over 5 amps.  It's a straight 3rd grade math problem of the voltage ratios.

Forget about the VA ratings for now, that's a topic for another day.

Thank you John

Thanks, John - I appreciate your simple, clear explanation.