Calculating amp draw

[Mach7]

Sort of hijacking another post...however I need some help calculating...or at least ensuring, i am within the amperage envelope of my simulator.

My simulator room has 6 wall outlets, three are powered off one 15 amp breaker and the other off another 15 amp breaker...however the second set of 3 outlets also are on the same line as the room lights.

So basically I am realising that I have too much stuff plugged into these outlets....so I am trying to do the math on my devices in order to bring me under the 30 or so amps I have to play with....

Having said this, I have not had a breaker trip off as of yet.

so....my question is how do I calculate the amp draw of a computer....i thought it might be as simple as taking the power supply wattage and dividing it by the household voltage of 120...but in searching the internet it does not seem to be that simple.

What do you, the simmers, use in your calculations for your gaming computer, and possibly other devices you have plugged in?

My current set up has 7 client computers to run the visuals, and one master computer as the main.

The client computers are small Dell slimline 280 watt units...so I am figuring around 2.5 amps per computer, with the gaming computer around 5 amps (?).

I have 10 22 inch lcd monitors, 7 for the visuals and 2 for the captains and fo's panels, then a third for the instructors panel.

Not too sure on the amperage draw of these units....

I have a number of 12 and 5 volt omron power supplies for other items as well.

any info would be appreciated!

Jim

[KyleH]

Jim,

Safety standards require that power supply's and devices have a rating label. Usually this must include the worst case current draw for the device. Use this number for calculating the total current drawn from your sim.

Some ratings for different voltage inputs will look like this:

Input 120-240V 2.2-1.1A

This label indicates that with 120V input it draws 2.2A, and with 240V input it draws 1.1A.

When using wattage rating to determine current draw you have to be careful as to if its an input or an output ratting of the power supply.

If it's an output rating (or if it's not specified best to assume it is) you need to take into account the efficiency of the power supply and the power factor. Good quality power supplies should be in the 90% efficiency range with better than 0.95 power factor with 120V input. To be safe use 85% efficiency and 0.95 power factor.

So lets say you have a 1000kW output rated power supply.
Calculation would be:

1000W x 1.15 = 1150  --> calculation for efficiency
1150 x 1.05 = 1208W  --> Total power on input at maximum load including power factor
1208/120 = 10.1A --> max input current

Then add all the current draw up for your devices.
Don't run breakers near their rating. Keep the load at less than 80% of the breakers rating or better. So for 15A circuit, don't draw more than 12A max.


Room lights, assuming incandescent bulbs is simply wattage/voltage. Use the fixtures rating for calculation though, not the bulb's.

[blueskydriver]

Hi Jim,

I just posted this over on Jack's thread, but I copied it below:

I think you'll be okay, but is there anything else on the circuits that you're unaware of? My suggestion is shutoff the breaker and see what else goes off...you might be surprised as to the circuit branching.

As for your computers, with the values you listed, roughly the slime lines are 250watts on the power supplies and the main computer is around 500watt for its power supply? How many 22" LCD's are you using (I forgot)?

You could plug everything into one circuit based on the AMP amounts, but I wouldn't because this is what I was talking about heat build up. With high load devices they draw a lot power and produce a lot of heat, even though you'd be under the threshold for tripping the breaker. So, all that power going to a few high load devices will heat up the whole circuit line (meaning the actual wire in the wall) and anything else plugged into it at other outlets on that same circuit. A good way to check, is feel another outlet that is not used, but is on the same circuit. If it feels a little warm there is no need to worry, but if it feels hot you need to split up where the devices are plugged in. Of course if it feels really hot to touch, you need to turn everything off right now and then split it up. If you do split it up and the same unused outlet is still to hot, you have something else wrong and that could be another circuit right next to the one or two for your simulator.

In other words, let's say for example, you have a circuit that has a 120volt deep freezer plugged into it and the continuous draw is 11.8AMPS when the motor is running (it turns on and off automatically). Next to it is your Sim circuit(s)...let's say two circuits and one circuit is using 10AMPS and the other 5AMPS when the sim is all fired up. So, the deep freezer is causing some serious heat down the circuit it is on, and due to the way breaker boxes are made, the hot wire bus is all the same, meaning all circuits breakers snap onto this hot bus. With your two circuits being next to that deep freezer they're going to get some of that heat because the hot bus is producing the most heat in that location.

Anyway, you have three circuits and they're all running hot, so anything else that cannot take that heat will slowly fade the plastic on the plug brown/black or even melt it. However, it only happens when the sim is running full and the deep freezer motor is on, so you most likely would never notice this because everything is working normally. Once you do discover this and let's say your sim is running, the deep freezer motor is running and you step away from the sim for whatever reason, it will be then the heat finally melted something too the point of starting a fire! You come back to a smoke filled room and/or a small fire (hopefully small), putting it out with your fire extinguisher and never knowing what caused it. Many house fires start like this and it gets called a "a faulty circuit was the blame", but most likely it was due to overloaded circuits without tripping the breaker(s).

I don't want to sound to alarming, but household wiring setups are not designed to maintain non-stop high loads. The only circuits in the house that get setup for high loads is the stove, the fridge, the HVAC, the hot water heater, the washer and dryer units. Anything else that might be a high load like a hair dryer, microwave and etc usually has a GFCI outlet (bathroom or kitchen) with it's own breaker on the outlet that will trip with an overload and thereby, preventing the actual circuit wire from the heat or overload.

Finally, there are so many things that only electricians understand and I am not one, but I do know that a simulator with multiple computers, monitors and so on need more then the standard 15AMP "shared" household circuits. You need a dedicated circuit(s) or at least a household one or two that has nothing else on it, plus knowing what else is on the nearby circuits in the breaker box...

John

[blueskydriver]

Hey Kyle,

Great post! That is where I was heading for my next post, you explained it much better. So Jim, does all this help?

However, do write everything down and figure out the totals for all the devices. Once you get the numbers just place things on the outlets where you're under the 80% or 12AMPS per circuit.

Also, look at the neighboring circuits/breakers just so you know what is next to your sim ones. Most likely you will not have any issues, but like I said in the post above, heat on circuits can carry over to other ones. It's all due to the electricity will use the path of least resistance or was it don't fly a kite in a storm with a key at the end of the string...lol.

John

[Mach7]

Hello Guys, this helps a lot!

It's slowly starting to sink in

Anyway, here are some of my numbers;

The sim room has 12 overhead 48 inch flourescent lights rated at 34 watts each. Each lamp panel has two tubes so this would equate to 24 lamp units.

By my calculations the total amperage draw of these lights would equal 6.8 amps, (34 x 24 / 120 = 6.

These lamps are on the same circuit as 3 of the room outlets, all protected by the same 15 amp breaker, therefore with the lights on I am now limited (i think) to around 7 amps from this outlet line.

The other 3 outlets in the room are stand alone and also have a 15 amp breaker protection.

I have a Jetline Systems gaming computer, which has a 600 watt power supply, so I am assuming, for the time being, that this unit might have  a 5 amp draw at its max output (?).

I have 10 (ten) 22 inch LCD monitors and the rating on the back says 19volts and 1.3 amps. So I am assuming that each monitor has a max amp draw of 1.3 amps therefore I would have 13 amps in monitors alone.

I have 7 HP compaq computers, each with a 300 watt power supply, so my assumption is each unit can draw up to 2.5 amps, therefore the numbers on these units run up to 17.5 amps.

My CanBus engine gauge arrangement uses a 24volt power supply...on the supply it says "DC 24 5A...100-240V 1.6 amp input"..so...would one assume that the supply can deliver up to 5 amps, however the input from the wall outlet would only be 1.6?

I also have three 12 volt omron power supplies and two 5 volt power supplies to operate certain LED's etc.

Also a number of USB hubs, but I believe these only draw milliamps.

So by my calculations I am already over budget in my power demand, at somewhere over 43 amps!! (not sure why nothing tripped...and I tried feeling the outlets and they were as cold as cucumbers)

As long as these numbers are correct....my solution would be to reduce the visuals by eliminating 3 computers, this would bring me down to 31 amps or so.

Then...maybe look at running an extension cord from the next room from a different outlet for some other items.

This is of course assuming my math is correct on these units.

Am I still on the right track here? or do my values look suspect?

I am also assuming that these are max amp values...i would think that, with the exception of the room lights) the monitors or computers would operate at somewhat less than there rated values??

[KyleH]

... So, all that power going to a few high load devices will heat up the whole circuit line (meaning the actual wire in the wall) and anything else plugged into it at other outlets on that same circuit. A good way to check, is feel another outlet that is not used, but is on the same circuit. If it feels a little warm there is no need to worry, but if it feels hot you need to split up where the devices are plugged in. Of course if it feels really hot to touch, you need to turn everything off right now and then split it up. If you do split it up and the same unused outlet is still to hot, you have something else wrong and that could be another circuit right next to the one or two for your simulator.


Anyway, you have three circuits and they're all running hot, so anything else that cannot take that heat will slowly fade the plastic on the plug brown/black or even melt it. ...

I'm not sure if your just not explaining clearly John, but this is factually incorrect. Please don't trouble shoot this way.
High loads will heat up the conductor from the load to the source, but not devices down stream.

[KyleH]

...

The sim room has 12 overhead 48 inch flourescent lights rated at 34 watts each. Each lamp panel has two tubes so this would equate to 24 lamp units.

By my calculations the total amperage draw of these lights would equal 6.8 amps, (34 x 24 / 120 = 6.

Fluorescent lights have a ballast in them that converts the power. You'd have to add an efficiency factor for them. I'm guessing you'd have 2 bulbs per ballast

These lamps are on the same circuit as 3 of the room outlets, all protected by the same 15 amp breaker, therefore with the lights on I am now limited (i think) to around 7 amps from this outlet line.

The other 3 outlets in the room are stand alone and also have a 15 amp breaker protection.

I have a Jetline Systems gaming computer, which has a 600 watt power supply, so I am assuming, for the time being, that this unit might have  a 5 amp draw at its max output (?).

The line would probably see closer to 6

I have 10 (ten) 22 inch LCD monitors and the rating on the back says 19volts and 1.3 amps. So I am assuming that each monitor has a max amp draw of 1.3 amps therefore I would have 13 amps in monitors alone.

19V? do they have external power supplies? If so, you need the input rating from the power supply.

I have 7 HP compaq computers, each with a 300 watt power supply, so my assumption is each unit can draw up to 2.5 amps, therefore the numbers on these units run up to 17.5 amps.

I'd call it 3A each

My CanBus engine gauge arrangement uses a 24volt power supply...on the supply it says "DC 24 5A...100-240V 1.6 amp input"..so...would one assume that the supply can deliver up to 5 amps, however the input from the wall outlet would only be 1.6?

This is correct

I also have three 12 volt omron power supplies and two 5 volt power supplies to operate certain LED's etc.

Also a number of USB hubs, but I believe these only draw milliamps.

USB ports can be supplied with up to 500mA (0.5) each, so it can't be just dismissed. It's a factor of what's plugged into it. Use the rating on the USB hub.

So by my calculations I am already over budget in my power demand, at somewhere over 43 amps!!

......

I am also assuming that these are max amp values...i would think that, with the exception of the room lights) the monitors or computers would operate at somewhat less than there rated values??

Keep in mind that these are maximum values. Always design for worst case.
Your computers are not all drawing their maximum power. Your main sim machine would come the closest.


Also re-visit your monitors numbers, 19V at 1.3 would translate to something like 0.3A at 120. Don't assume that I'm right, the difference is significant, check it.

(...and I tried feeling the outlets and they were as cold as cucumbers)

This doesn't really mean anything. You're only really checking the load on that one outlet that way and when did you last have your hand calibrated

[blueskydriver]

Hey Guys,

Sorry about that, what I was trying to say with the heated outlets is more of a way to determine things about heat and not a way to choose from that. I meant that if you feel an outlet with everything (sim) on and it's not really warm, nor hot, at that moment then I don't think the wires or at least that outlet is overheating. Of course it could get hotter based on other factors, but I do know this can happen because it actually happened to me; the closest non-used outlets did heat up to the point of being to hot to touch and the browning/melting occurred on the simulator power supplies and power strips. The problem was all because of too many items and/or overloading without tripping the circuits. It really derived from the deep freezer in my case, but not like in the example in the above/previous post. I only used the deep freezer portion for explaining about motors kicking on and off, yet you might not be aware of it.

Maybe, this will make more sense...I had my entire sim in the garage using three 20amp circuits and I had 12 computers, 3 LCD screens behind the MIP, 3 Projectors, the MIP and Overhead with FDS cards, several USB Hubs, 5 volt and 12 volt lights here and there, a laptop, a power supply for an iPad, a power amp for the sub woofers, two sets of computer speakers with their power supplies, 3 more LCD monitors on the desk outside the sim, an audio mixer with another 100watt amplifier, plus a few other smaller power supplies for things I cannot remember. So, even with all of these items the circuit breakers never tripped; unless, I turned a laser printer on, which would draw a lot more power causing one circuit to trip.

Anyway, what I didn't know at the time or think about was the deep freezer which was on one of these three circuits, along with a window air conditioner unit and a portable air conditioner unit being on another, so by all thoughts nothing should have worked or it at least should've tripped the breakers. Yet, it kept running until the day a MIP LCD monitor starting sparking and smoking big time, luckily it did trip the breaker. However, the melting around the PCB internal power connection looked like it was ongoing for a long while before it eventually sparked. To add insult to injury, I went to the restroom and it happened right as I got back to the sim, so I few minutes sooner and I would've missed it... It was this day I discovered the browning/melting on all the other items and it was then I decided to have a 100AMP sub-panel with 12 20AMP circuits installed into the garage, along with each circuit having hardwired power strips, no more plug in types.

Now, based on what you're saying Jim, I believe you're really overloading your 15AMP circuits big time. And, if it were me, I would have a sub-panel added with some dedicated circuits for your simulator. As for using extension cords, you could (personally, I would not), assuming it is a thick gauge cable, but I mean really thick like a 10 gauge. However, where would it be plugged into and what else is on that circuit?

Here is a quick story: I have an air compressor that can be rolled around, so if I plug it in directly to any outlet it runs fine, but if I use an 25' 14 gauge extension cord it might run really slow for about 3 seconds and then the circuit breaker trips. Why? Because the extension cannot supply enough power to the air compressor, yet it overloads which trips the breaker. Now, if I use my 100' 10 gauge extension cord the air compressor works just fine. The reason this is possible is because the cord is of course thicker and able to supply the power needs even though it is longer. My point is a 25' 14 gauge would not work and even though I was thinking a shorter length would work over the longer length...

Therefore, I am just trying to say in a long or round about way that you must match things when regarding power needs; although, it might sometimes seem illogical when it comes to this size or that size, this many amps to that many and so on. And, at this point, I would suggest you have an electrician come out and evaluate your sim area/room...that is what I did for the shed/hangar.

John

Ps here is a link to the cord I purchased for the air compressor:

https://www.menards.com/main/electrical/electrical-cords-cord-management/extension-cords/flexzilla-trade-pro-10-3-outdoor-premium-extension-cord/p-1483082284223.htm

[blueskydriver]

Hey Guys,

I forgot to add this link, please read about unused outlets on the same circuit overheating due to another device plugged into a different outlet on that same circuit. It's all because with home electric wiring you loop through the outlets.

As for circuit breakers next to each other and causing crossover heat ups, that can be due to one breaker being faulty and not tripping; thus, the overload or heat build up would carry over to the breakers next to it on the same bus. Of course there are different types of circuit breaker boxes with different bus configurations. And, without knowing the age of the home or the circuit breaker panel itself, things like this can and do happen...

Here is the link:

https://www.google.com/amp/s/homeownerbob.wordpress.com/2011/09/17/wall-outlets-feel-warm/amp/

John

Edit: Jim your codes, Canada Electrical Codes (CEC), are similar to the US National Electrical Codes (NEC), but are not exactly the same, so that is another reason to check with an electrician and/or purchase the CEC codebook...here:

http://shop.csa.ca/en/canada/landing-pages/2015-canadian-electrical-code-part-i-/page/cecode2015

[Mach7]

Thanks KyleH and Blueskydriver,

Your information is getting me closer to my solution. Thanks for the amp values KyleH! This will at least bring me into the ballpark for now

-Jim

[Mach7]

@KyleH

Hello...I did some additional checking and with respect to my LCD monitor power supplies, then plug right into the outlet (power bar) and then connect into the back of the monitor.

The supplies themselves say;

INPUT 100-240 V 50/60HZ 1.0 AMP MAX
OUTPUT 19 V 1.7 AMPS

With respect to the remainder of my power supplies that power various items in the simulator (like LED's etc). They are high quality OMRON brand and here are some of the values;

Here are some examples;

for the 5 volt supply

INPUT 100-240v 50/60hz 1.4 amps
OUTPUT 5 V 10 AMPS

for the 12 volt supply

INPUT 100-240v 50/60hz 1.4 amps
OUTPUT 12 V 4.2 AMPS

for the 24 volt supply

INPUT 100-240v 50/60hz 1.6 amps
OUTPUT 24 V 5 AMPS

My question may be academic, but I do not understand how you can get more output amperage from the smaller input amperage.

Regardless....for my calculations, would I use the INPUT amps for my budget calculations or the OUTPUT amps?

Also...ran some household circuit breaker testing and I think I am in pretty good shape as I have around 39 available amps from 3 different outlet sources.

As long as I leave the simulator room lights off, then the available amps from one set of outlet(s) increases by 6 amps...of course I will ensure i only come to 80 percent of the maximum rating(s).

Another question I have is....can I connect a power bar up to one outlet and run a number of devices to 80 percent of the 15 amp rating?

Thanks again

-Jim

[mickc]

My question may be academic, but I do not understand how you can get more output amperage from the smaller input amperage.

Regardless....for my calculations, would I use the INPUT amps for my budget calculations or the OUTPUT amps?

You get more current out as you are reducing the voltage (and rectifying it to DC)  The same works in reverse if you invert DC to AC.  A small camping inverter may provide 10 Amp AC output, but could draw 50 A from the 12v Battery.

The input amps are the ones you need to cater for.

Another question I have is....can I connect a power bar up to one outlet and run a number of devices to 80 percent of the 15 amp rating?

Theoretically you could, although most power-boards will have an internal breaker to prevent overloading.  In Australia at least all power-boards have a 10A breaker or tripping mechanism. We use 240v so that equates to 2400w per board.    Sure you could plug in 4 2000w fan heaters and have them all running on low and they will work, but as soon as the total draw through the board is 2400w (10A) the board will trip its breaker. 

Also in AU, our power circuits are 16A, but each power outlet is only rated for 10A.   anything that draws over 10A needs a dedicated 15A circuit, where that outlet is the only one on the circuit. Anything over 15A needs to be hardwired onto its own circuit. (single phase. anyway)

Probably made things worse with that info, but if you want know how much your sim uses, you can buy cheap energy meters that go between your wall socket and the plug, with a little display that shows how many watts, amps, volts etc are being used by whatever is plugged into it.  like this one http://www.ecosavers.nl/?page_id=117

Very handy to see how much is being used for either the whole sim or individual components.    I was surprised that my MIP drew so little.  It has 4 separate power supplies, 6 LCD Screens, 2 micro PCs, a heap of OEM gear, and also a test PC & screen.  When running with full backlighting and under lights test, the whole thing pulls no more than 4 amps.

[KyleH]

@KyleH

Hello...I did some additional checking and with respect to my LCD monitor power supplies, then plug right into the outlet (power bar) and then connect into the back of the monitor.

The supplies themselves say;

INPUT 100-240 V 50/60HZ 1.0 AMP MAX
OUTPUT 19 V 1.7 AMPS

With respect to the remainder of my power supplies that power various items in the simulator (like LED's etc). They are high quality OMRON brand and here are some of the values;

Here are some examples;

for the 5 volt supply

INPUT 100-240v 50/60hz 1.4 amps
OUTPUT 5 V 10 AMPS

for the 12 volt supply

INPUT 100-240v 50/60hz 1.4 amps
OUTPUT 12 V 4.2 AMPS

for the 24 volt supply

INPUT 100-240v 50/60hz 1.6 amps
OUTPUT 24 V 5 AMPS

My question may be academic, but I do not understand how you can get more output amperage from the smaller input amperage.

It's the relationship between current, voltage and power.

Power = Voltage x Current

If you keep power constant then reducing the voltage or current will increase the other.

A power supply is rated at a certain power level. Lets say you have a perfectly 100% efficient power supply rated at 100W, with a 5V output. This would calculate to 5V at 20A. On the input side with 120V input, it would be drawing 0.833A from the line.

Look at your 24 volt supply: 100V at 1.6A is 160W. On the output side its 120W. That means that with maximum power being drawn and 100V on the input the power supply itself is burning 40W, making it 75% efficient.


Yes, if you have the input ratings, always use those as that is what that power supply will attempt to deliver before tripping it's own internal protection.

Another question I have is....can I connect a power bar up to one outlet and run a number of devices to 80 percent of the 15 amp rating?

Can you? Well that depends on the power bar and it's rating. It's not the best practice as now all that current is being drawn from 1 outlet.

[Mach7]

Thanks for the info guys.

@KyleH, your electrical knowledge is impressive, thanks for taking the time to explain the details.

I am also going to try and purchase some outlet devices so that I can see the true amp draw from my plugged in units.

So just to confirm with KyleH....I am going to use the rated INPUT amp rating for my calculations...correct?...if that is the case then my numbers would look something like this;

22 inch monitors have a rated input amperage rating of 1.0 amps, therefore I am going to budget 1 amp per monitor

The 12 volt omron power supply has an input rating of 1.4 amps, so that will be calculated at 1.4

The 5 volt omron supply is also 1.4

The 24 volt omron supply has a rated input of 1.6 amps, so 1.6 will be used for calculations

The main gaming computer will be estimated at 6 amps, and the smaller client computers at 3amps each

I have 2 USB hubs, so I will round up and budget .5 amps for each

Hopefully my numbers are safe!

Thanks again guys

Jim

[Mach7]

Hello everyone,

I just received my P3 "kill-a-watt" meters..the ones you plug into the wall and can select amps, watts, volts etc for whatever device you have plugged in.

So....maybe I am not reading this right but it shows my main Jetline Systems, liquid cooled computer drawing only .59 amps with everything up and running.

I tested the P3 units with my hair dryer...and it shows them drawing between 8 and 12 amps.

Could this low amp draw be accurate on such a large computer?? I was thinking somewhere around 6 amps.

confused....

[mickc]

Probably quite correct.  It should be slightly higher during boot up, then settle down once its running.  That equates to 150 watts @ 240v or 65 w @ 110v
Is you are using SSDs etc then they use less power as they are solid state, but the power supply will only draw what it needs at the time, where a hair dryer will have a constant power draw

Try loading the PC up with a benchmarking program and see how much it ramps up

[Mach7]

@mickc and anyone else...

Tested out the entire system today and was more concerned with the 7 client (visual) computers I am running...so what I did was I separated the monitors and the computers....the monitors connected to one power bar and the 7 computers to another, each power bar was then plugged into an outlet  protected by separate 15 amp household breakers.

I found that, once the power bar with the 7 computers was selected "ON", my draw from the outlet was approximately .28 amps.

Each computer, when selected ON, would boot to .85 to .92 amps, then stabilize to .59 amps, increasing to approx .75 amps each with Fs9 booted up.

This showed me an approximate draw of 5.28 amps with all 7 computers up and running in FS9 visual mode, and about 3.60 amps with only the windows start page viewed, (Fs9 shutdown).

The Monitors drew .29 amps each in fS9 mode, for a total amp draw of approx 2.03 amps.

I have attached some pics of my setup test...the visual monitors are a bit out of alignment as I am doing some electrical upgrades to the master warning panel and overhead panels.

So, unless anyone can see something terribly wrong with my calculations....I think I am in pretty good shape budget wise when it comes to staying within 80 percent of my maximum household breaker limit of 15...

Any comments are welcome....

-Jim