# Indoor layout power



## Don T (Dec 28, 2014)

I'm looking at the MRC Throttlepack 9900 and I'd like to hear what any of you guys think about it.

Largest engine LGB 2019S Mogul, Lighted Caboose, Metal wheels on all cars, 5 to 6 electric 
switches, no other lights, Layout about 15ft X 11ft against the walls and 7ft X 5ft at the ends in a bit of an( L) shape, and all the track I can cram in. 

fThanks in advance for any input,

Don T


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## chuck n (Jan 2, 2008)

I looked it up on the MRC site. It has 80VA, that should handle what you have. If you have plans of double heading, or getting an engine with two motors, it might a be marginal.

Chuck


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## Greg Elmassian (Jan 3, 2008)

Is that VA rating inclusive of the accessories output as well as the track output?

(I remembered to bring this up because I learned to watch for that from you Chuck!)

Greg


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## chuck n (Jan 2, 2008)

Greg

All I know is what the website says. My guess is that it is the total output. As you have said VA is a poor indicator, but sometimes, that is all we have. 80 is better than 20, which may mean something.

Chuck


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## Don T (Dec 28, 2014)

Sooooo------- Does anything really equate to VA ?

Don T


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## Greg Elmassian (Jan 3, 2008)

Yeah, I thought you would chuckle at my remark Chuck (no pun intended)...

Pretty sad state of specifications, the MRC web site says 80 watts...

but the manual says 80 VA... and it does state that 80VA is a total of the fixed DC output and the variable DC output. The "G" scale setting goes to 18 volts.

Personally, since I run long trains and diesels and passenger trains I would be worried a bit at 18 volts, but it should be fine.

Greg


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## chuck n (Jan 2, 2008)

Greg

More often than not "VA" is all we get. Bridgewerks is a company that gives the amps, but they are a rare exception. Maybe it is meaningless as an electronic absolute, but it does help in comparing power supplies that don't list amps. 

What would be interesting, when amps are shown, would be to know if that is the real maximum, or just the rating on the circuit breaker.

Chuck


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## Greg Elmassian (Jan 3, 2008)

The MRC power G does spec 10 amps.

All typical power supplies do spec volts and amps

It's only the "transformer" combinations that seem to do VA, and it's deceptive in that the definition that there is SOME point where the volts times the amps equals the rating.

The important thing to take away is that it is not at EVERY combination of volts and amps, and MOST IMPORTANTLY it is rarely at the max output, where we are usually most concerned.

So let me pick something that is a multiple of 24 for an example:

Suppose you buy a system that is 24 volts max and rated at 48 VA.... most people would assume that then you have 2 amps at 24 volts output because 2 x 24 = 48.

Not true, normally in systems like this the transformer output voltage sags a lot as it approaches maximum load (amps)...

For many people a good solution USED to be a Crest PWM throttle, and then an inexpensive regulated power supply. I have the MRC Power G for running DC, but if I ran a lot of DC, I'd find some used Crest throttles, and use a $50 10 amp meanwell, and come out ahead.

Greg


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## Dan Pierce (Jan 2, 2008)

I think of watts as the input of a power supply rating and the VA the shared output rating. There is a power loss through the transformer or DC to DC converter and the input power is always higher than the output power available.
If there was no loss inside then there would be no heat from a power supply!!


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## Greg Elmassian (Jan 3, 2008)

True Dan, but VA ratings can hide the true operating specifications, i.e. what happens to the system as you reach maximum load. 

The reality is that you have an inexpensive system. With the price of switching supplies so low, it seems silly in this day and age to not have one, but it's all about cost.

VA is simply a technique to help make the transformer look "better" as opposed to a full load voltage and amperage rating.

Greg


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## Don T (Dec 28, 2014)

Well guys,after all that exhausting help, which I do appreciate very much, I went ahead and 
ordered the 9950 instead of the 9900.

Why?- I have no idea except it shows 125 Watts instead of the 80 Watts for the 9900 and 
has Volt and Amp output screens. 

Should get it on friday and I'll let you know what I think of it.


Thanks again for the help,

( Great Forum)

Don T


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## Greg Elmassian (Jan 3, 2008)

Great idea, the readout of volts and amps is very helpful in G.

We will be interested to see the actual voltage and how it performs for you.










Regards, Greg


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## Don T (Dec 28, 2014)

Well----- I received the MRC 9950 on Friday and hooked it up this morning. The train ran perfectly 
in forward and seemed to have good power. However, the LCD screen, direction, brake and momentum buttons did not work at all.

I just sent it back to Amazon for replacement and will get back to you later. 

Amazon is sure easy to work with!

Don T


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## chuck n (Jan 2, 2008)

Don

I don't know how the brake and momentum buttons function, but did you hold them down, or just push and let go. It is possibly the you might have to hold it down for slow change in voltage.

Chuck


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## Don T (Dec 28, 2014)

Chuck,

I tried everything and read the directions over and over. Held the buttons down,pushed them harder but to no avail.

Looks like I'll receive the replacement controller on Monday and will let you know then.

Thanks,

Don T


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## chuck n (Jan 2, 2008)

Thanks for the reply. It was just a thought.

Chuck


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## Don T (Dec 28, 2014)

Well I received the MRC 9950 and it seems to work very well so far. I've tested it on a 18 x 5 ft 
track and this what I got on the LED readout.

All at full throttle!

2019S Mogul-------------- 1.2 Amps

Plus 5 cars including lighted caboose--------1.6 Amps

Plus 2090 Switch engine--------2.6 Amps

Plus Starter Engine_______3.3 Amps 


Does that tell us anything at all?

Don T


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## Greg Elmassian (Jan 3, 2008)

Not really, it would be interesting to test it at higher loads.

Any measurement must have volts and amps measured at the same time, so you need to measure both.

So the system has the potential to source around 5 amps my guess, but most systems rated in VA do NOT have full VA at full load..

My first experience was an LGB track cleaning loco... I could not get it to run properly even on level track. The amp draw of the 2 motors caused my MRC 6200 to drop the output voltage too much. This is a real problem for this loco, since you need full voltage to make the cleaning wheels spin and break free.

This not only brought this VA thing into focus, and the sometimes overrated MRC power supplies, but also the fact that the top speed of electric motors is often achieved in the last few volts, i.e. big difference between 20 volts and 24 volts in motor speed.

These are 2 important concepts to remember, how VA really works and how motor speed is a nonlinear relationship with voltage.

Greg


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## Don T (Dec 28, 2014)

Thanks Greg

I just want to clarify one thing just in case you didn't understand my reply.

All three engines and 5 cars were running at the same time on the same track and
the voltage remained the same with in one tenth of a volt. I will only be using the AC
for switches.

Thanks again greg,
Don T


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## Greg Elmassian (Jan 3, 2008)

Great, and you did forget to mention the voltage 

What that tells you is that the system is really an adjustable, regulated power supply, and that is a good thing, you will have more consistent running results.

Greg

p.s. it's worth double checking the meters in the unit, with a known accurate meter, not a big deal but sometimes these are off. Being digital, I would assume they are probably within 10%. The old analog meters (in toy train transformers) were notorious for inaccuracy.


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## Don T (Dec 28, 2014)

Thanks Greg

Actually I did check the track with a voltage meter while they were running and it showed very very 
close to the same as the meter on the controller. Looks as if this unit will work very well for my needs.

Now, I just need to find something else that I don't know anything else about so I can do more
posting.


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## Greg Elmassian (Jan 3, 2008)

hah! good attitude!

Let us know how the unit performs every so often, there's not a lot of products in that space. I'll be particularly interested in max current.

And, what pray tell is the voltage? You have still not explicitly stated what you observed.

Greg


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## Don T (Dec 28, 2014)

Sorry Greg,

Voltage Is 18 on unit screen and 17.8 to 17.9 on volt meter while running trains.

Don


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