I am revamping my back yard and installing a patio(now) and spa later. As part of this I will have an electrican upgrade my panel service to 200A. (the panel upgrade will be later during the spa installation, I don’t have an electrican yet.)
As part of the general upgrade I want to get rid of the overhead wires that supply power to my garage. I want to run the wires underground under the patio I am installing NOW. I have spoken to several people and from what I understand the conduit needs to be at least 18" deep and steel when it comes out of the ground. Being a take no chances kind of guy I will put it about 24" down under grade.
Now in the garage I have a chance to get a free air compessor (Whoo Hoo) it runs on 220 and draws 7.5A. I have a freezer that draws 5A, flourcent lights (6 eight foot 40W?) and a security light.
Plus the usual assortment of electrical outlets.
My plan is to run a 220 circuit (30A if I can or 20 otherwise) put a sub panel in the garage hardwire the compressor, split the lights and freezer onto 1 circuit, and the security light and plugs on the other 110 circuit.
I have gotten conflicting information about wire size and what amount of power I can get through a particular size wire.
It is 100 feet from my panel to where the compressor will sit. This includes bends, up down turns and all that.
So my question is can I run 4 #10 wires for either a 20A or 30A circuit? If the answer is no, what size wire do I need to run.
Is there a website I can refer to for this type of info? I have been having zero luck so far.
In case I did not make myself clear (not uncommon with me) the garage only has a 15A 110 circuit now. As this circuit is shared with stuff int he house, I will terminate the overhead run.
12 AWG is rated for 20 amps, while 10 AWG is rated for 30 amps. However, that’s a safety rating, not a performance rating. When making long runs, you should increase the gage of the wire.
As an example, I recently installed a 220 VAC / 40 A air conditioner. Normally a person would use 8 AWG wire for 40 amps, but I used 6 AWG due to the long run (130 feet).
Why increase the size of wire for long runs? Because wire resistance is proportional to wire length. More length = more resistance = more voltage drop = less power. To overcome this problem on long runs, conductors with larger cross-sectional area are used, which lowers the linear resistance. This is especially important for devices with high start-up currents, such as motors.
At what length should you increase the wire gage? I don’t know; you’ll have to check the NEC and/or your local codes. But 100 feet sounds like a pretty long run, and I would feel more comfortable using a larger wire gage. Hell, I’d probably just go ahead and use the next size larger even if it were not a long run, just for insurance. Besides, it won’t really cost you that much more $$.
No, Rick, I didn’t miss the line. My only point is that if you are going to have a licensed electrician do the job he will want you to tell him exactly what you want, including possible future expansion or extension, and he will then configure the system in accordance with local electrical code requirements and for good performance.
He, and he alone, will be held responsible for the safety and performance of the system and if he has any smarts, he will want it done the way he knows it should be. And I suspect he won’t be thrilled to be told, "Well, someone on the internet, whose qualifications I don’t know anything about, said this was the way to do it.
When you decide to install an underground conduit, use the pvc water pipe rather than the proper electrical conduit.
It costs around the same but is far tougher, do not put any fixed bends in it or the cable will not pull through easily.
I know this means you will have upward bends of a large radius but its not unmanageable.
When you install your pipe make sure you feed a length of drawline through it first, whilst the pipe is straight and, leave this inside your pipe with the ends out side of it.
Pick a goodly sized pipe, at least 32mm, that’s about 1"and 3/8ths.
If you are going to do this then you might as well install a water supply as well, if there isn’t one there already.
Doing this will allow you to pull the cable out if necessary too.
If I were you I’d also run some telephone cable down there and some intruder alarm cable, even if you are not going to use it just yet, it may well come in useful at a later date.
If you use a power breaker, RCD in the UK but you Americans have differant names for them, these trip very fast and it means you can use a slightly thinner wire(but I guess there is little point if you are doing it yourself)
If you plan on doing any welding then power breakers have a habit of tripping out, so you may not want to use one in such a case.
I you are going to carry out welding then your earth will need to be very good, and you might either wish to try one gauge thicker wire(the earth wires are generally thinner than the main conductors) .
The other option would be to install an earthing rod nearby and conect to both the earth wire from your house and also to this.
Upgrading to 8 AWG (from 10 AWG) will give you a 0.9% increase in voltage and 1.9% increase in power (assuming an 8 ohm load at 240 VAC). So I agree; it’s not that much of an improvement. However, if it were me, I would upgrade to 8 AWG anyway, just in case I wanted to change the service to 40 A in the future…
No! There’s a color code in the U.S. that must be followed for plastic pipes: Gray PVC is used for electrical cables, white is used for water, and yellow is used for gas. This is (obviously) for identification; you don’t want a plumber cutting into (what he believes is) a water pipe and have it turn out to be 220 VAC.
I just started researching spas. If you’re going to be connecting one up to this circuit at a later time, I’d recomment at least a 40 amp, two-phase (i.e 220V) circuit. That’s just for the spa itself (some of them require this much power, some less). Adding on other appliances (like that compressor) will require more power. A 50A circuit will probably be enough, although you run the risk of blowing a breaker if the freezer and compressor start up at the same time while the hot tub’s heating elements are on. It’s up to you to determine how likely that occurence is.
You should also call your local power/gas/etc. company to check your yard for buried nasties. Most states have just one number you call, and they come out and paint your grass and plant little flags. Don’t just assume that because it is your back yard, there will be no buried dangers lurking below the grass.
I installed central AC last year, and decided to locate the compressor unit 70 feet from the house. I (obviously) needed to dig a trench, so I rented one of those big, gas engine-operated “trencher” tools. I started up the engine, and just before digging, I thought, “Hmmm, I better evaluate this situation… I wonder if there are any utility lines buried down there?”
I surveyed the situation, and realized the trench would intersect four things:
The 220 VAC mains
The gas line (from propane tank)
Telephone line
Water line (from well)
“Better not use the trencher!” I said. So I returned the trencher (which they charged me for anyway) and ended up digging the entire length of the trench w/ a hand shovel. I ran into everything except the water line, which is not surprising since it was buried below the frost line. Thankfully I didn’t break anything.
