I have (4) Z’s, (1) ZW and (1) KW. I have a grand total of 57 Amps drawn on all transformers and 690 watts total as well.
Z#1: 11 Amps, 180 watts
Z#2: 11 Amps, 60 watts
Z#3: 10 Amps, 50 watts
Z#4: 12 Amps, 170 watts
ZW: 9 Amps, 130 watts
KW: 4 Amps, 100 watts
As given a Z and ZW can handle 15 Amps and a KW can handle 10 Amps. I never run more than 4 throttles at one time. Usually have all my 022 switches powered up and one loco running at a time. And 1 accessory at a time as well. I have a total of 85 Amps available and 1,100 watts available as well. But, these amps and watts are never used to the max. I have 15 Amp service. And only trips when I have 2 transformers all 4 dials on full blast then fuse blows or I get dimming in transformers light blub. I calculated each bulb as 1/5 amps and 1 motor locos at about 3 Amps and 2 motor locos at 4 Amps. I hope I did my math right. I added up all bulbs and motor Amps, and assumed the transformers were on full blast to get those numbers on each transformer. Thanks.
How do you get 25 volts out of that KW? (100 watts / 4 amperes = 25 volts)
Note that your transformers are perhaps 75-percent efficient at full load, less efficient with lighter loads. So, when you’re getting 1100 watts out, you’re putting in around 1500 watts.
250 watts x 4 = 1,000 watts + 275 watts + 190 watts = 1,465 watts. But, the actual out put of the transformers is less then what it says on the transformers. I only get 18 volts out of my KW. The current draw on the KW is 4 amps or 100 watts of power used up out of the 190 watts and 120 watts its rated at. On my KW, I run just (17) #71 Lamp Posts. 17x5 watts = 85 watts or 17 light bulbs at 5 watts each. So really the KW only power 85 watts of bulbs or 1/5 amp per bulb = 3.5 amps. Thanks.
But, Isnt each blub on a #71 lamp post 5 watts or 1/5 amps?? You take 17x5=85 watts and 1/5x17=3.5 Amps. And the KW can handle 10 Amps, correct?? or 120 watts?? what it is rated at. Thanks.
A lamp that is drawing 200 milliamperes and dissipating 5 watts has 25 volts across it. I don’t know the rating of the 71 lamp post lamps, but if it is as you say, then it is not drawing 200 milliamperes nor dissipating 5 watts at 18 volts (or whatever your KW puts out). In fact, it is drawing 167 milliamperes and dissipating 3 watts.
I think what Bob is trying to say is that the math is slightly wrong. Your adding each bulb’s amps used with each motor’s amps used is the right way to figure out how much power (how large a transformer) is needed. But the numbers you’ve used are good estimates, not necessarily accurate numbers. For example a light bulb will “use” a slightly different amount of amps based on the voltage going to it.
Anyhow, the formula Bob is going with is: Watts = Amps x Volts. Plug some of the numbers from your list into this formula and see what the voltages you come up with are.
Ok, Got it! Bob has helped me in the past is always right. I understand what I did wrong. Well, I am not too worried about it though. Thank you very much.
What you did wasn’t wrong. The numbers you used were what a lot of people use to figure transformer size. It’s not as exact as hooking a meter up to the transformer and measuring the amperage and voltage under load, and then… you get the idea.