Testing Electrical Consumption

Dans Klimkowski

New member
Hi I’m putting together a home music/video studio and want to make sure that I am not creating any fire hazards with all of my devices. I purchased a P3 Killawatt ( P3 International P4460 Kill A Watt EZ Electricity Usage Monitor - - Amazon.com ) to test the amps drawn by all of my devices and plan to compare this with the amp rating of the outlets in the room where the studio is.

Can you please help answer a few basic questions?


1. I’m a bit uncertain because it seems like there might be discrepancy between the amps Kilowatt is showing and the expected amps of devices. Example: The kilowatt is showing that my iPhone charger (when charging iPhone) is only between .03 and .09 amps. However, I’ve seen many forums where people say that an iPhone charger will draw approximately 1 amp. I want to make sure that there Kilowatt isn’t underestimating the total amps being used by the iPhone, as well as other devices too. I called up the company that makes the Killawatt and they told me that it was accurate and there is no way that I could be using it incorrectly.

So I just want to make sure here: should I completely trust that the Kilowatt is giving me accurate readings and assume that the forums that I read had incorrect information? Or do you think that the low amp reading of the iPhone charger doesn’t make sense… and maybe I should test it with another kilowatt? or take some other actions?


2. I have heard that its likely that my house (in the USA) is rated to supply 15 amps to the outlets in my room. I’ve also heard that its possible that some outlets in the room could be on separate lines/breakers (not sure what the right terminology is) or they could be all on the same line/breaker, and/or they could be on the same line/breaker as other rooms in the house. I think that I need to verify how many amps the room can handle and what outlets are on what line/breaker.

What is the easiest way to find this information out? Can I do this (safely) if I have almost no electrical experience?


3. If I ever did accidentally go over the amp limit, what would happen? I’ve heard that modern houses (my house was built 20 years ago) have systems to cut off electrical surges before they make fires- is this true? Or is this something that I should be concerned about?


4. The Kilowatt also gives me a reading that all my outlets have about 123-124 V . Some of my devices and surge protectors say that they are rated to 120 V. The person from the company said that this should be no problem at all (and I have run the devices/surge protectors for several months without any issues). But I just want to make sure- Is this potential a electrical hazard to have a few more Volts than the devices and surge protectors say they are made for?



Thanks, Dan
 
Your meter should be fine. Everything else is under control. But you should know what is going on in your fuse/breaker box
 
The rated draw on device labels is typically the maximum they will use, and many devices use a lot less most of the time. You could add up the numbers on all the device labels and consider that the upper limit to what the total draw will be.

All modern professionally built houses have circuit breakers which will cut power if something draws too much wattage.

Small voltage differences like that should be fine. That's less than 4% difference from nominal.
 
I’ve seen many forums where people say that an iPhone charger will draw approximately 1 amp.

:eek:
I doubt a phone charger draws that much. :)

TBH...if you just gave the list of equipment...most people here could eyeball it and tell you if your 15 amp outlets will handle it...no meter needed.

I doubt you will get anywhere near 15 amps draw.
When I'm running my 28-channal analog console, my 24-channel analog tape deck, my studio monitors, a couple of guitar amps, a bunch of outboard rack gear...etc...I'm hitting about 12 amps.
Most home studio setups aren't even close to that.
 
I'll have you know that I have a (Gardner-Bender?) meter that measures the same as the top unit and a Fluke that measures the same as the bottom. Both units are Monster and are connected to the same 20A circuit.

IMG_3279.JPG
 
That should be fine so long as you don't hoover and record at the same time.

hhah I'm just saying 10-15 amps was back in the penny fuse days, wasn't it. I really don't know what might have been installed in 1997, but 15 amps seems small.

I kinda doubt it pulls 17 amps unless I roll over a cat, or, something : )

MM; I think that is why jd simo runs his marshall on a variac
 
I assume you just moved into this house. If you've got someone to help you, plug a lamp into each outlet, go to the breaker box, and shut off one breaker at a time to see which lamps go out with which breaker. IF you've got to do it by yourself, its a bit more work - plug a radio into an outlet, turn it up, go to the breaker box and start flipping breakers until the sound goes out. Move the radio to another outlet, keep doing the same thing.
 
...but 15 amps seems small.

Considering the type of equipment in the typical home rec studio for the majority of guys here...it really is more than enough.

A big electric motor is going to pull more amps...but a computer, a preamp and maybe a couple of other pieces of outboard...with a guitar amp thrown into the mix...I doubt you would come close to even 10 amps.

Like I said...when I run my 2" tape deck, which has massive motors and all, plus my rather large console and a bunch of other gear at the same time...I pull about 12 amps on the moderate side.
I've tested things out by turning on just about all my rack gear (which I never do in real use situations) and even with a couple of guitar amps...I got close to 18 amps (my circuits are 20 amp in the studio).
My voltage regulator shows both incoming voltage and amps being drawn...so I always have view of that.

Back when I first set up the studio...I went through every piece of gear, and wrote down the power consumption requirements, did some math, and came to the conclusion that if I totally maxed out everything, including all my guitar amps, I would exceed the 20 amps easily...so I ran a pair of 20 amp lines...but in real world use, I never have all the gear on, so I can get buy fine even on heavy load days with just the single 20 amp circuit.
 
The draw is normal, but I would think they were installing 20-amp breakers back then. The appliances are drawing less now, but you still got a motorized workout room, shopsmith in the garage, microwaves on three floors, etc..

"I went through every piece of gear, and wrote down the power consumption requirements"

Ya I was doing that early on - like index carding ones books. Now studio gear is on index cards. quick access to tube layouts and operational notes

I cut the cards.

Fujiya EX dash 311 has 1-watt out at 8-ohm
Ser# 10338
2)12ay6
1)30a5
1)35w4

Under that one is the TEAC 808 (TD-108) ser# 363
model 505 in USA
The tubes and layout are on the first one acquired

My studio should be 105-110 degree by Saturday, so minimal watts
 
My studio should be 105-110 degree by Saturday, so minimal watts

There's this thing call air conditioning...works great.
I couldn't fire up all my gear in the summer without the A/C...the console and the tape deck alone would heat up the room in no time. Of course, in the wintertime, I can back off on the heat. :)
 
Hi Dan. I am in UK so all the currents are halved and the volts doubled. As folks have said you are very unlikely to get close to a 10 (5A for me) current pull leave alone 15A. I would also guess US 'code' is as conservative as our 'regs' and so you would have to exceed the line current by quite a margin for some minutes to cause a fire. NOT likely!

The voltage thing? Surge suppressors (don't like'em!) are 'one shot' devices. They use a small Voltage Dependant Resistor which conduct very heavily for higher than normal line voltages but this is MUCH higher, 1 kV or so I believe but once tripped (and the breaker will flip) they are buggered and you have to buy a new power strip! Unless you KNOW big spikes are likely, I would not bother. IF you do get spikes the only real solution is an expensive conditioner such as Furman.

I am surprised the makers of the meter did not tell you how to 'calibrate' it? Buy a 100W incandescent lamp and plug that into it. 100W at 124V is 0.8A . You might like to Google 'Ohm's Law' hiss easy math!

Dave.
 
You'll always find that some devices hardly tickle a meter - despite what their labels say. My studio is on 24/7, and apart from the racks full of gear, two computers, 4 monitors, a pile of keys, the power consumption is quite modest. Having just put a 400W power supply into one computer because the old one died, I note it is actually drawing less than 200W. A 2.5KW amplifier should (on our UK voltage) need 10A, but even working damn loud, I can run 3 of them on a 16A outlet, or at a push even a standard UK 13A one. Things with motors, heaters and filaments have constant ratings. Audio kit draws in proportion to the level. Chargers and many power supplies are switch mode devices nowadays and have a higher demand for only a percentage of the time - so current demand can be lower than the labels suggest.

It does work the other way too, though. My example of the amps in the racks - the running demand is low, but transformer designs saturate when switched on and for a brief moment take more current than the label suggests - so having a pile of them in a rack, running happily isn't going to happen if you power up by switching on the outlet - they all try to kick off at the same time, and can (in my example) easily draw more than 32A for a short brief moment, and trip the breaker. The circuitry for current meters is very established, so I doubt they are reading wrong - they can be fooled by devices that only draw current for part of the mains cycle - but that doesn't apply to much you're likely to have in a normal home or studio. The biggest constant current culprit in my studio is the tungsten lighting - 800W if both rooms are lit. With them out, the rest of the studio (no HVAC) runs around 300-400W.
 
garww,

One thing that I would definitely suggest --- DO NOT TURN EVERYTHING ON AT ONCE.

Most equipment draws its maximum current when it is first switched on and is in the booting stage. If you put a current meter on the line and switch everything on simultaneously, you will see the meter jumps to a peak current then comes down to a somewhat lower running current.

It is generally at this switch-on phase that you will blow a circuit breaker, not once the equipment has settled down.

If you can obtain a power board (or two !!!) that has individual switches, connect you gear to this and mark each switch numerically then connect the gear such that the biggest items (eg amps, computers, recorders, etc) go from No. 1 upwards (see comment below re the amps) and then turn on each switch from No. 1 upwards allowing (say) 5 - 6 secs + between each switching.

I have recently built a Control Room for a local community musical organisation and there was only one 20A power circuit available. This circuit runs a large console, 2 x powered mid-field speakers, a hefty powered sub, a full equipment rack (24-TK recorder, 2-trk recorder and about 8 x DSP units, etc) and an extra 100W amp for studio playback. All is controlled by a couple of switched power boards.

Only time I blew a fuse was during the testing phase when I deliberately turned everything on at the same time.

By the way, always turn on the speaker amplifier/s last and off first to avoid any power thump when everything turns on/off --- I have seen large PA speaker blow their cone by not doing this.

Hope this helps a bit.
 
+ 1 to 'progressive' turn on. WRT Monitors, you can put them on wireless mains switches. These default to 'off' so you don't even have to think about turning them on last. Also a bit of a safety feature since in the event of a power failure when you are not home, gear will not come back on.

Dave.
 
Ya, I've put in my own extra mains breaker to have extra juice. Luckily there was a extra slot in the box : ) I also installed a rear panel breaker on a old Rotel amp for that momentary surge. My mother's observation in my baby book upon surviving a baby for one year, was that my favorite Toy was electrical wires. Never any Wardenclyffe Tower aspirations, just the ho hum stuff
 
I've always followed the old studio adage - "first on, last off".

The electrical power-on follows the audio signal path. So like...I would first turn on my outboard preamp, and then the console it's feeding, and then the monitors that the console is feeding...etc...and then for power-down, it's in reverse.

In that sequence, I also start with the gear that has the big draw...like I would turn on my 2" tape deck first, since it can really pull amps in that initial moment, and then it settles down...and then I would go for the smaller rack gear.

That way, my main power distribution units have a chance to gently adjust.

One of the things that always bugged me was what happens during a storm power flicker...where you instantly lose all power, and then a second later it all surges back on, and all you gear gets slammed and powers on simultaneously, and your monitors pop...etc.
I installed a special relay just in front of my main power units that will keep the power off upon initial loss of power. That way I can go to all the gear's switches, turn them off...reset the relay to ON...and then do my normal power-up sequence.
 
"I installed a special relay just in front of my main power units that will keep the power off upon initial loss of power. That way I can go to all the gear's switches, turn them off...reset the relay to ON...and then do my normal power-up sequence. "

We call them 'Contactors" over here. Basically a shaded pole AC energized relay with 32A (or better) rated contacts in a tin. As I said, the cheap wireless switches do the same job, power drops out, the switch does NOT reset.

Mind you, our power rarely goes out even in storms (of which we get very few) because 99% of the juice runs in armour in the road and comes from big local subs, 11kV to 315 3ph traffs and they are all in steel cases. Rural areas have 'pole pigs' and I understand they trip out for a VERY close strike and a man with a very long GF pole has to go out and re set them!

Dave.
 
It's not the going out that's a problem (though it's been awhile that we've had any power outage even for a short time)...
...it's that with the big electrical storms, you get that flicker sometimes.
Two years ago they did a lot of upgrading...following a couple of years where hurricane storms and winter storm knocked out the power for days, even weeks in some areas.
It's actually been pretty good...but I am out in a more treed/rural/hilly area...and except for my street, the rest have lines/tranny's on poles...so more chance of strikes.

The storms roll in over the big hills and I'm on the the downward slope on the other side where it then heads into the big valley.

I've got my 15kW permanent generator...longer outages are not an issue. I also have a sat dish, and my internet is DSL, over basic phone lines...so I'm usually running when my neighbors are burning candles. I installed that monster about 12 years ago (all by myself)...and it's been a worthwhile nice-to-have, even for that once-twice a year need. I leave it on manual, but it has an automatic transfer switch too...and it runs on propane (or natural), and I've got 3 tanks, for 300 gallons...:D...so I could last a couple of months or more with judicious use.

I'm not a doomsday prepper...:p
I got it when my father was still alive, and he needed to use a powered nebulizer every day, plus was kinda panicked a couple of times when the power was out for a whole day...so I put the generator in for his peach of mind.
 
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