# Electricity usage, wiring, saftey, and YOU!

Discussion in 'Do It Yourself' started by 13ronin, Mar 3, 2009.

1. #1
Last edited by a moderator: Mar 3, 2009
Hello all my fellow blades here at GC! I’ve been a member here for a while and watched a lot of journals, asked a lot of questions, and read just about every sticky there is on growing, nutrients, lighting, seed banks; you name it. But I noticed one thing conspicuously missing. Electricity. Everything we use indoors needs it to function from lighting, to ventilation, and even our bubblers in some hydro setups. So why is it not covered? So many people come on here worried about the amount of power their op uses and that it might set off an alarm at the power companies. What about safety? Too much power through wiring that is old or through power cords and strips that is not made to handle the load can cause a lot of heat and quite possibly fires. So why has no one made a sticky on this yet? Ok, I guess I will. So, here goes my shot at GrassCity fame… in a sticky. Woot.

First off, let’s start with the simple formula for power usage calculation. I know math sucks, especially algebra (even simple stuff), but look at this way: remember in high school when you said “I’m never gonna use this shit?” Well, I’d say there is no more fitting or ironic a place to use those mostly useless skills than for growing cannabis.

Voltage x Amperes = Watts

Let’s assume a few constants for those of us in the U.S. Every house in the U.S. has a line voltage on any outlet of 120 Volts, as a rule of thumb. Some non-grounded devices only use 110, but that’s not for our discussion. Let’s just stick to 120 Volts. So let’s use this in a calculation for an example for say, a vacuum cleaner.

Mine, as do most, use 12 amperes, or amps for short. So, 120v x 12a = 1440 watts. Yup, 1440 watts is what a sweeper uses on average. But WTF is a watt?

A watt is a measure of the amount of energy used. For the power company, it is often rated as Kwh. This is a Kilowatt per hour, or 1000 watts per hour. Now this is where it gets a little weird. People often ask, so how many Kwh does a 60 watt light bulb use per hour? It uses 60 watts per hour. That’s it. So in this case, we just do another simple formula and move the decimal place back.

60w /1000 = .06 Kwh.

Why is this important? How much are your lights using? USED watts, for you HID people. For HID people, just because the bulb is, say, rated at 600 watts, you might actually be using 640 watts. Check your ballast for that info. So, if you are consuming 640 watts for you 600 watt HPS, you are using .64 Kwh. Now you can calculate how much your gear will run as every device you use that plugs into an outlet will have a power consumption rating on it. Fans, lights, etc. All of it. So, let’s say you are using the following as an example.

2 400w ventilation fans
1 1040 watt HPS (total use)

You are using 1.44 Kwh there. But what about your bubblers and things that don’t have a wattage rating?

Ah ha! Well, on the power source (the black box that plugs into the outlet), you will see a rating on there expressed this way.

INPUT 9v, 0.5a. This means it is 9 volts and .5 amps. So using our first formula;

9v x .5a = 4.5 watts. So, let’s say you have 4 of these little guys running. Let’s add that to the total!

2 400w ventilation fans =800w
1 1040 watt HPS (total use) =1040w
2 4.5 watt bubblers = 9w
--------------------------------------------
Total watts = 1849 watt or 1.849 Kwh.

Power companies charge by the Kwh, as I said above. Now, from looking at your bill, you can see how much you are charged per Kwh. The national average is 12 cents per Kwh. So, the hypothetic setup using 1.849 Kwh multiplied by \$.12 = \$.22 dollars (or 22 cents per hour) to run. If you run this ALL OF THIS 24 hrs a day for a 31 day month, you are paying \$ 165.08 a moth to run it all. Compare that to you bill of current usage and decide how paranoid you are. Also remember that cutting down how long you have stuff on with save a lot of power. If you only run the equipment 18 hrs a day, then instead of 1.849Kwh x 24hrs x 31days = total Kwh use, you would calculate 1.849Kwh x 18hrs x 31 days.

Now that we understand a few of these basics, let go to safety using it. Safety is VERY important. And I’m not talking about getting the shit shocked out of you if you touch a live wire (which is a bad idea too obviously) but rather about fire hazard. An extension cord not able to handle the load you are forcing it to can over heat. Once this happens, the insulation around the cord can melt or burn causing a short and a fire. Just because you have a breaker on the circuit doesn’t mean it will flip and protect you. What if the breaker is faulty? What if the amp rating on the breaker is large enough that it won’t flip because it was in a circuit that can also handle big power items like dishwashers or things? A lot of us in this country live in old home where wire has been installed, patched, modified, and reworked over the last fifty + years, sometime done by shitty electricians. In my place, which was built in the late 1800’s early 1900’s, there are still natural gas outlets built into the walls for old gas lighting! Now the place is in great shape and has been well maintained over the last 100 years. You’d never know it was that old if you went on a tour with me. But, it was converted from gas to electric prolly sometime in the 20’s. And there is a scary amount of original wiring in the place. It works, and it’s nothing to be afraid of, just something to keep in mind. Mine has been modernized over the years to modern breaker boxes and what not for safety, but some of those outlets are still original. Scary. As a rule of thumb there I figure if the outlet doesn’t have a ground, bad idea to use it for a show’s power. If it is grounded (the third round prong hole) and you are still not convinced, open up the outlet and see, JUST FLIP THE BREAKER ON THAT CIRCUIT OFF BEFORE YOU DO! If the leads are insulated with what looks like braided cloth, it’s old. But like I said, just because its old doesn’t mean it’s bad and automatically unsafe or half this countries’ homes would have gone up in flames already! Just bear it in mind.

So that takes care of the power supply. But now you got to get that power to your equipment. Power strips are ok, BUT READ THE LABELS! All extension cords, power strips, etc will have on the label the amount of power they can handle. It will often be expressed simply in amps. So what do you do? As mentioned above pretty much every home in the U.S. uses 120 Volts. So, if you see a cord that says 12 amps, then 120v x 12a =1440 watts MAXIMUM POWER. I would undercut this to stay on the safe side. I would get a more heavy duty line that can handle more juice than you will be putting through it. Just think your setup through. Plan every connection and read every label of every cord you buy. Do your math. And you should be fine.

On a final note, some setups will require wiring things directly in. In that case, use wire caps to connect wires, not electrical tape, and place all connections in junction boxed. I won’t delve into this too far as it is more advanced than most subsistence growers will need to do, but if anyone has any additional questions about wiring, ask away and I welcome other members to help answer these questions and to point out errors in my post. Just remember, do your math and be safe!

For more questions and to look up how much common household items use, go here. It is a great source of info!

2. I'm judging by the lack of views/replies this would have been better suited in the beginners section?

3. i think its fine where its at
i was considering buying a 250 hps for 12 hour periods
this thread will def help to figure out the money spent on it a month
thanks man rep to you

4. Good info......def. should be a sticky.

question I have is you assumed 400 watt ventilation fans....I know it was just an example but I thought fans and crap like that did not draw that much power. Am I wrong in that or am I using a lot more juice than I thought.

What about normal little box fans and crap like that....does that draw a signifigant amount of power?

Thanks.

5. Again...I am really curious to figure out my power usage now....I have a 240 cfm fan that is attached to a carbon filter....fan says 48 v and .42 amps.

Just so I know I am doing this right.....that would be around 20 watts per hour?
I am having trouble thinking straight today.

6. #6
Last edited by a moderator: Mar 3, 2009
nope your math is right on!

But some of these big inline fans and squirrel cage fans can use 100 watts or more, but then again they can also move like 600+ cubic feet per minute of air. But for big grows making a lot of heat, these fans aren't that uncommon. Thanks for checkin in !

If you're using a box fan, that's part of why it is so low in power use. Inline fans have to compress the air to push it through the ducting which is why they don't push as many cubic feet of air per minute... they have to use more power. What setup are you using for your fan?

7. Great post! Thanks!

8. p.s. can you please take photos of your natural gas outlets and post or pm them? sounds bad ass.

9. Sure man but they're just little nubs in the wall. lol. I'd be happy to take some pics for you tonight if I remember though. Peace!

10. that would be nice if you ever get the chance

11. Is each 3 prong outlet 750 watts? So if your running the two connections off the outlet you will have 1500?

12. Sorry, I don't know what you mean...

13. umm, you know how each outlet has two places to plug in cords too. If you plug in to many things into the one of the sockets, too many watts it will flip the breaker? each socket i thought could handle up to 750 watts of usage before you need to run another cord to your grow box

14. no you will still have 750, just split.

15. That is incorrect. Each outlet doesn't have a specific wattage rating that it is neccesarily capable of. As I stated in my post, a vacuum cleaner uses about 1440 watts. lol. Most sweepers don't even have the ground built into the plug! An outlet (generally) can handle an ass load of power. What you ARE limited by is how much the breaker on that circuit is made for. For example, if you were to look in your breaker box and see 20 breakers, you will see on each breaker is a number. most will say 15 or 20 with one or two being larger, much larger. Now, on the grey metal panel, you will see that each one of those breakers has an individual number. For this example, we'll say they are numbered 1-20. Now. On the inside of the panel door you will see (or should see if a good electrician installed the panel) what circuit each breaker handles. So if you are growing in the closet of the master bedroom, it will likely be on the master beadroom breaker, so you look to see what number says "master bedroom". It says 17. cool. So look at what number 17 says. Let's say breaker 17 says it is 20 amps. cool. 120volts x 20 amps = 2400 watts. that is how much wattage the ENTIRE circuit can do. Including other lights in the room, computers, etc.

To sum up, a 20 amp breaker IS capable of putting 2400 watts into one plug, and the outlet itself won't limit you, but I WOULD NOT want to test that out! lol. I have seen outlets cook before. I personally wouldn't want to try to put more than say 1800 watss through one outlet, and I wouldn't even be comfortable with that. And I do mean per outlet, not plug. the number of plugs in one outlet make no difference because you still have to bottleneck that power into one line coming into the outlet itself from the power supply. Always be cautious.

16. Great post!!

I can't stress enough the importance of proper wiring!!
Junction Boxes and wire caps people!

17. Amen. Keep it clean! Btw... love your handle and avatar man. Made me chuckle!

18. DO NOT MAX OUT YOUR BREAKER!!! Figure out the maximum wattage and only put 80% of the watts. 2400W x .80 = 1920W.

The 20 Amp mark is the "NON-CONTINUOUS LOAD" The CONTINUOUS load (ie lights on for more then 20-30 minutes) is only supposed to be 80% of the breakers rating. Going for long periods of time with more then 80% but less then 100% (between 1900-2400W) may NOT POP THE BREAKER... but slowely burn it up... resulting in everybody in the house dying.

find Exhibit 210.22 in the electricians national electrical code book to understand more.

(I'm a 2nd year electrical engineering student trying to build my own hps ballasts... and mounts/reflectors... from scratch. Can anybody give me direction>>>>>>>>>>>

19. can't help with your work, but that's great to know! Thanks for the info. Filed in my brain for permanent storage! + rep

20. so if my extension cord and power bar are rated for 15 amps. Thats 120 x 15. they can handle 1800 watts less 20% to be safe. Or is that 15 amps they advertise safe to run at 1800 watts.