Electrical Help

sonar · Jul 30, 2011

jgould said:
600 watts is 600 watts no matter how u look at it. Is your 20 amp line gonna be 120 volt or 240 volt? You can use Ohm's law for the value needed. Watts= volts x amps. So on a 20 amp circuit that you ran it would be 120 volts x 20 amps = 2400 watts, code says that you can only load a breaker to 80% , but thats code and not reality.

This is correct, at least in the USA. I've noticed the electrical code is far for lenient in the UK.

Just keep in mind a 600w hps lamp, and I would imagine 600w of cfl draw a little more power than what they are rated at. But yeah, a 600w even with fans at what not should be ok on a 20amp circuit with no less than 12 gauge wire.

zvuv · Jul 30, 2011

sonar said:
This is correct, at least in the USA. I've noticed the electrical code is far for lenient in the UK.

Just keep in mind a 600w hps lamp, and I would imagine 600w of cfl draw a little more power than what they are rated at. But yeah, a 600w even with fans at what not should be ok on a 20amp circuit with no less than 12 gauge wire.

When running steady, a 600W appliance is pretty much equivalent to any other 600W load (inductive loads like motors cause a phase shift between the voltage and current and computers introduce noisy currents into the line voltage but this usually doesn't make a difference to the user and I just mentioned it in case anyone wants to quibble

)

However, on startup, inductive loads (pretty much anything with windings eg motors and transformers) need to draw very large currents to get going. It takes energy to build up the magnetic fields in the winding and to get the rotor spinning if it's a motor. While this is happening, the appliance draws a much higher current than it's wattage rating implies. This is sometimes called the 'surge current'. You can see this when your fridge motor kicks in and the lights dim momentarily. Resistive loads, like incandescent light bulbs don't do this.

This has practical consequences for breaker size. An appliance that should run on a 15A breaker may trip the breaker on startup. I have a metal chopsaw that does this. It's rated 15A but it will trip a 20A breaker unless I spin the blade by hand before hitting the switch. I don't do this. I plug it into a 50A breaker.

The small magnetic ballasts in flourescents are not usually a problem, even if you have a lot of them because they dont start up at exactly the same time, but the big transformer in a magnetic HID might trip a breaker if the total load is too close to it's maximum.

doser · Jul 30, 2011

Wow!
two hot wires exchanging power?
on what planet?

zvuv · Jul 30, 2011

doser said:
Wow!
two hot wires exchanging power?
on what planet?

Yes that's right. Current will flow between two hot wires if there is any difference in their voltages. For example if you had a hot wire at +110V DC and another at -100V DC the voltage between the two will be 220V.

In the US, in domestic electrical service, there are usually two hot wires each being 110v with respect to ground but they are 180 degrees out of phase with each other so when one hot line goes positive the other goes negative.

This diagram is from wikipedia http://en.wikipedia.org/wiki/Split-phase_electric_power

This is a diagram of split phase 220V showing the polarity of each line

from http://idobartana.com/hakb/modifying_heavy.htm

doser · Jul 30, 2011

OK, but in the world I live in it flows from hot to nuetral
guess we're on different planets
just sayin!

zvuv · Jul 30, 2011

Neutral is not used in 220V except sometimes in cases where 110V is also needed, like a dryer - the heating element is 220V but the motor is 110V so the dryer plug has a neutral which also serves as ground.

In 110v circuits the current flows from one hot wire into neutral which is at ground potential. Your dryer, your electric range , the 220V motors in your shop all run the current from the one hot wire to the other in their 220V circuits. ( The wiring diagrams on some of these may show this explicitly.).

With a 220V electric motor there is no need of neutral at all although some might require it for the starting circuit which is 110V.

Here is a nice diagram

If you look at p49 in this old DIY manual
http://igor.chudov.com/manuals/ElectricMotors.pdf

You will see that in the 220V diagram the current runs from one hot to the other through the run windings. The starter wimding is jumpered into the center of the run winding. A trick to get 110v without a neutral.

doser · Jul 31, 2011

zvuv said:
Right. The current flows from the one hot to the other. {QUOTE]

And that is called a short circuit

We're all up into electrical theory here in my own private Idaho

I won't be a party to hijacking this thread any more than I have already
Ya can't fix stupid

mrmadcow · Jul 31, 2011

sorry doser but zvuv is correct about 220 circiuts, the only thing he has said in this thread that I don't agree w/ is

zvuv said:
....Spend some time managing your wiring so it doesn't become a tangle. Wind up any surplus on power cords and tape the loop.....

winding an extension cord into small loops is a no no. I have seen a 100 foot 12 gauge cord w/ 80 feet wrapped neatly trip a breaker w/ a 5 amp load. it causes an induction simular to the windings in a motor. neat is good but winding a cord into loops is not.

zvuv · Jul 31, 2011

mrmadcow said:
... winding an extension cord into small loops is a no no. I have seen a 100 foot 12 gauge cord w/ 80 feet wrapped neatly trip a breaker w/ a 5 amp load. it causes an induction simular to the windings in a motor. neat is good but winding a cord into loops is not.

I hadn't thought of that. I have that problem with my welding cables and I know to wind them up in a figure 8 to kill the field. I was actualy referring to winding up excess power cords which are comparatively short and only make a couple three loops. But now that you have mentioned it, I am going to rewind them in figure 8's.

One time at work there was a long power cord running across the floor, under and around various obstructions. At one point it was touching a large shallow pool of water. One guy stepped in the puddle and got zapped (no injury). There was a micro crack or puncture in the cord and the puddle was hot.

That set my opinion of ext cords. I really don't like them and only use them for temporary setups. They are a shock hazard, a trip hazard and they will snag on anything you want to move.

And that is called a short circuit

Yes if you connect them together directly. I was talking about connecting them through a load.

doser · Jul 31, 2011

OK, I've got an electrical contractor that wired the last house for me. He became an inspector. I totally trust him. If he agrees with you guys then I will admit I am wrong without any problem. I still am not convinced. when I put one leg of 220 on my meter I get 110.............never mind, I'll find out and get back to yas.
either way, no hard feelings. Just very strong ones on my part. but I was wrong one other time so anything is possible. Odds are against it but hey.........

zvuv · Jul 31, 2011

Excellent idea doser. Check with an authoritative source rather than listening to some guy's opinion on the internet. I'm sure I'm right, you are sure you are right. It's not important. What matters is the truth

Whichever way your electrician answers, I like to hear what he says.

Thanks

doser · Jul 31, 2011

yeah, He's not like Johnny on the spot with getting back to me but when he does I'll contact you. I'm kinda resolved to being wrong at this point
I hate it when that happens. Juice is one of my weak areas of expertise but I do wire most of my own houses so I'm not a complete ditz either.
This guy's panel looked like a catalog cut sheet on wiring though. a work of art. Hard as fuck to understand though being eastern europeon.
I don't usually take anything I read on the internt as fact without backup.

Electrical Help

sonar

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zvuv

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doser

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zvuv

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doser

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zvuv

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doser

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mrmadcow

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zvuv

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doser

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zvuv

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doser

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