Q:Do I need special wiring in my house for a growlight?
A: Usually (not everytime but usually) for one light nothing special will ever need to be done even for a 1000 Watt growlight.
Most of this tutorial is based on standard US electricity. Local differences may happen. Check on it before starting.
The maximum amount of electricity which can flow through house wiring is based on a unit of measure called "amperes"--most often called amps. The number of amps that can be pulled through a wire safely is based on the thickness (or gauge) of the wire and what the wire is made of. Most wire nowadays is made of copper. Some houses, however, were wired with aluminum wiring to save costs on construction. Many places in the USA do not allow new aluminum wiring anymore. This is probably a very, very good thing. On average, aluminum wiring uses 10% more electricity than copper wiring--in other words, your electric bill can be 10% higher every month with aluminum wiring. Some people will try and scare you about the safety concerns of aluminum wiring; often these people are trying to sell you a rewiring job on your house. Aluminum wiring does carry extra safety concerns about fire, but the important things to pay attention to are first, that any circuit breakers, light switches, outlets, etc. are marked something like "approved for cu and al wiring" (the abbreviation for Copper is Cu and for Aluminum is Al); and second, any time you make a connection with aluminum wiring use the special jelly at the connection point (the jelly is available at many hardware stores and home centers).
The most common thickness (or gauge) for house wiring is called 14 gauge. Nowadays, a type of wire which originally came from a factory way out in New York near Canada at the City of Rome, which features double insulated wires, is by far the most common wiring used throughout America. This wire, called "Romex" (whether it is manufactured in Rome anymore or not) is named by both the thickness gauge of the wire and by number of insulated wires inside the other insulated outer coating. There is always one bare metal grounding wire to pick up any stray electricity and channel it back to a safety ground. Got that? So a "14-2 Romex" uses 14 gauge wire and has two insulated wires and one bare ground wire. Don't believe it? Go to a hardware store or home center and check it out.
Alright now, 14-2 Romex is probably what you have your house wired with.
(If you have a somewhat older house or don't have 14-2 Romex, you have to read later on sections. The rest of you guys get to skip them.)
Now, the circuit breaker for 14 gauge wire is 15 amps. Please, do not screw around with this and put in a 20 amp breaker when the wire is only 14 gauge. Fine, fine, your friend told you he has done it lots of times and has never had a problem. Your friend is an idiot.
A 20 amp breaker is for 12 gauge wire.
Q:Wait just a minute, 12 is a lower number than 14.
A: When they started naming the gauge of wires, they based it on the number of wires that would fit inside a one inch pipe.
So, because it is thinner, you can fit 14 separate wires through the pipe.
The thicker wire can only squeeze in 12 strands.
The thicker the wire, the lower the gauge number.
On most new construction, the majority of the circuits are 15 amp circuits wired up with 14-2 Romex. Often, 20 amp circuits are required for the kitchen and the bathroom. These circuits are usually wired with a 12-2 Romex and protected by a "Ground Fault Circuit Interrupter" safety switch. These GFCI or GFI circuits are often required within 3 or 6 feet of a sink, bathtub,etc. THIS IS IMPORTANT: most of the time it does not cost any more to do wiring safely; sometimes it costs $3.00 or $9.50 or $20.00 more to do it right. Learn what you are doing, shop around, then do it right and sleep at night. OK?
If you are adding a new circuit from the breaker box, consider using 12-2 wire, a 20 amp breaker, and a 20 amp outlet. Make it all match, and you will be fine.
Q: I thought you said I didn't need any special wiring?
A: If we didn't go through all that stuff, would you have believed we were telling you the truth?
OK, here's your numbers for 115 Volts:
1000 Watt lights pull about 9 amps.
400 Watt lights pull about 4 amps.
250 Watt lights pull about 2 1/2 amps.
100 Watt lights pull about 1 amp.
Q: So, I can run 15 separate 100 Watt growlights on one 15 amp circuit?
A: Well, probably not.
The circuit breaker on a 15 amp circuit usually pops at about a 12 amp draw.
The breaker on a 20 amp circuit usually pops at about 15 amps.
It is not exact, and every time the breaker pops, it lowers the number it will pop at next time just slightly.
Over years, this slight lowering may make a difference, maybe not. Slightly means slightly, don't freak if the breaker has popped a few times.
Q: Why do they call it a 15 amp breaker if it pops at 12 amps?
A: Circuit breakers are electrical and not electronic devices.
Because they are mechanical devices "close enough" has been just fine for a hundred years or so first with disposable fuses then with the reusable circuit breaker. Nowadays that we 21st century folks have precise electronic devices, we tend to expect more precision. Circuit breakers pop lower than 15 amps to allow a good margin of safety.
Sometimes just replacing an old breaker with a new store bought breaker will keep it from popping.
A 20 amp breaker usually pops in the neigborhood of 15 amps, this is why your idiot friend has been able to get away with his trick at least nine out ten times. Your insurance agent, the fire department, and the fire marshall who come to your house after the fire may not blame your friend--they will blame you.
This can be especially important after you sell the house because you may be legally and financially liable for creating a situation which could be called "a reckless disregard for safety" by the insurance company's team of lawyers.
Q: So I could run 12 separate 100 Watt lights on a 15 amp circuit?
A: In theory, if everything is perfect in the circuit and there are NO other appliances or electrical devices pugged in or wired into the circuit, yes.
Q: That is not an unqualified "yes"?
A: In just about every circuit in the house, there is something else plugged into the circuit--whether the outlet is in the same room or not--it can still be on the same circuit. You can identify a circuit's outlets by turning off the breakers one at a time and plugging a small lamp into the outlets to see if they are live. Sometimes someone has already identified the circuits and written IN PENCIL on the list pasted on the breaker box. If you are identifying the circuits, please use pencil and identify rooms like "Front BR" or "NE BR" instead of "Mary's bedroom". Don't forget the ceiling lights or fans, the outside lights, and the doorbell.
The rule of thumb is that if the breaker pops, there are too many things drawing on the circuit.
Q: If I wire up at 230 Volts instead of 115 Volts, can I save money on my electric bill?
A: Here's a case where some people's arithmetic won't hold up in reality--the problem is that some of these folks will never acknowledge reality over their belief.
The electric company charges are based on the kiloWatt hours you have used.
Don't believe it? Just pull out your electric bill and read it.
Q: It does say kilowatt-hours right here on my bill!
A: "Kilo" is a prefix, which comes from Greek, it means a thousand. So a kilowatt is one thousand Watts.
A Watt is a measurement of Power. A Watt-hour is power as it is measured over time. So, put it all together and a kilowatt-hour is a thousand watts (a unit of power) measured over time. It costs in the neighborhood of a nickel--sometimes a dime for each kilowatt-hour.
Now then, here's one formula for figuring out Wattages: Watts=Amps times Volts (W=VA)
So, let's take a 1000 Watt HID light:
According to the chart above on this page it pulls about 9 Amps at 115 Volts.
Let's test that out to see if its right:
Take 1000 Watts and divide it by 115 Volts.
1000 divided by 115 is 8.6956521--easier to say about 9 Amps.
Now, let's double the voltage and try it again:
We are going to start with the Watts and work our way down to the Amps, again.
Take the same 1000 Watts, and divide it by 230 Volts.
1000 divided by 230 is 4.347826--or exactly half.
In other words, the Volts double and the Amps are cut in half.
Q: Wait, if the Volts double and the Amps are cut in half, then the Kilowatt-hours I get charged for are in the exact same place. I won't save any money on electricity.
A: Right, you will not save any money on your electric bill by doubling the voltage on your electricity. The electric company charges you based on Wattage not on Amperage.
