Hi All
Need some feelings from the Electricians out there.
When I built my shop, I put in a 2″ Schedule 40 underground pipe.
I have a #6 50amp feed to my panal.
Between my new 5hp saw and dust collector, I’m pushing the limit.
I plan to upgrade the service this summer.
I can do one of the following:
1) Pull another set of wires thru with the current set to give me
another 50 amps on a second panal.
2) Pull another set of wires thru with a larger feed (up to #2).
3) Pull old wires and replace with #1 for 100 amp service.
Which idea (or maybe another I didn’t think of) would you suggest?
I know I need to do something and haven’t made up my mind which is
the best way to go.
I usually do all the work myself (obviously, with a helper feeding)
and am very good with electric, tho not licensed.
Any thoughts to help me make up my mind.
Oh, and yes, I realize I might not be able to pull the extra wire if
things don’t go right when I try. I might have to remove old wires
to make room.
Jeff
Replies
Yoo can use the 75 degree rating of the wire and up the size of your breaker.
If possible build a seperate service on your garage. Then you don't have to worry about tapping into the house anymore. If your present electric in the garage is up to code then it's pretty simple.
Who Dares Wins.
Jeff,
Good planning, laying 2" pipe.
Go with door #3.
And FYI, it's bad practice to pull conductors into conduit that already has wires in it. There's the chance that pulling in additional conductors will damage the insulation (either of existing or new). If you want to add, pull out the old and repull them with the new.
If you're considering the suggestion of having a separate service to the shop, check with the power co. In many places, it's more expensive to have two services, what with service charges and taxes, than to buy the same number of kW/hrs through a single meter.
The only advantage to another service would be if the poco could give you three-phase (120/208). You'd have to replace the motors in your big equipment, of course.
Good luck--
Cliff
Cliff
No service is available from the Power Company to the Garage.
I can omly feed from the main house panal.
Also, 3 phase is unavailable here.
I usually pull each wire seperatly. Is it better to always pull
the wires together as a bundle?
Of course, I don't usually pull big wires, mostly small stuff.
This 2" conduit already has a set of #10 and a set of #6 (and a pull
rope I left in there).
I had simply planned to remove the #10 and replace it,
You fell I should completely remove all the cables and just pull ####set of #1 for 100 amps. Am I correct?
Seems Harder, but then, I don't usually do this sort of thing.
Jeff
Jeff,
O.K., so you're going to feed the garage subpanel from the house (main) panel. That's fine.
And yes, it is better to pull all the conductors in at once. Less likely to damage the insulation or get hung up at an elbow that way (all at once). This becomes critical as you approach the capacity of the pipe.
You might look at my article in issue 154 (apr/may this year) to get an idea of what the "head" of the conductors looks like for pulling them in the pipe. Here it is in a nutshell. This is for a pull of three #1 Al and #6 Al equipment grounding conductor, for a moderately long pull (50-200 feet) with two (or three, the max allowed) sweep elbows.
1. strip the insulation off of each conductor--12", 18", 24", for the #1 and 24" for the #6.
2. untwist & spread out the strands of the conductors, clip off the inner strands (about half of the strands) of each conductor. Reform the strands to form a wire that's less bulky than the original.
3. tie a bowline in the end of your pull rope to form a loop with about a 12" diameter . Place each conductor through the loop, staggering them so that the insulation shoulders are 4" -6" apart. Bend each wire back on itself, and compress the bend with pliers. Use pliers to mash the strands together along the length of the bundle to compact it.
4. tape up with cheap electrical tape. Don't skimp--two or three layers, use about a whole roll. Keep the bundle as compact as possible. I've found that it's better to not tape the very end of the wire loops where they go through the pull rope loop.
You ought to have a "head" on the wires about 2 feet long, and not a lot bigger than the combined diameter of the individual wires.
5. then the fun begins...pull them in, with one person pushing the wires into the pipe, another smearing pulling lube all over them and squirting the lube into the pipe, and a third pulling on the pull rope.
This may seem like a lot of effort to simply get some wires into a conduit. If the pull is very short and only has a single 90 bend, it's a lot less critical to make up the head this way. But with a longer pull, especially using a power puller, it's essential to do it properly.
A few other thoughts:
--use copper wire instead of aluminum. Copper will be easier pull because the gauge is smaller, and also the terminations of the copper will stay trouble-free forever if you do it right. With aluminum, even if you use anti-oxidant paste, and carefully torque the terminal to spec (as given on the panel or the breaker), eventually the connections will have to be re-made. Aluminum is more likely to loosen up, and things go downhill real fast after that. Copper costs a little more now, but if you're planning to stay in the place for a long time and the feeder will see heavy currents, go with copper.
--try to get THWN-2 conductors (either Cu or Al). The "-2" signifies that the conductor is "compact", i.e., has been squished to reduce its diameter a little (a normal heavy gauge wire has a lot of air space between the strands). And THWN insulation is enen thinner than THHW. Some guys prefer to use RHW insulation underground; they think the rubber is more waterproof than the thermoplastic (nylon). But RHW is hard to find. I don't care, THWN is listed for wet.
--identify the neutral with tape before you pull it. For my money, it's just easier doing that than having to ring it out with a continuity tester later.
--don't forget that you need a grounding electrode system at the subpanel, as it's in a separate structure. Two ground rods, and a properly sized grounding electrode conductor. I strongly recommend pulling an equipment grounding conductor from the main panel to the sub, even if there are no metallic pathways between the buildings.
Good luck.
Cliff Popejoy
Sacramento, California.
Cliff
Read your article when it came out.
Thought it was pretty good.
I always use copper wire, never aluminum.
Planned on using a pull lube.
What's your feeling:
Just put in one run of #1 and not bother with the old #6, or put it back in (or new).
I can't see needing over 100 amps, but then I never figured I would
need over 50 amps years ago.
I heat with propane, so that's no problem.
Also, is the price much higher with THWN-2, I never heard of it before.
Also, is that the best there is? I want as little trouble in the future.
Oh, and thanks for all the help.
Jeff
Jeff,
Run just the #1. Why have any other circuit feeding the garage? In fact, a building can normally have only one supply (for safety--if a firefighter has to cut power to the building).
I don't know off the top what the price differential is for the various types of wire. You couldn't go wrong with either THWN or RHW. For that insulation on copper, I wouldn't be suprised if you have to go to Graybar, and have them bring it in from a regional supply depot. Measure carefully! (But then, you sound like the kind of guy who does things right the first time...are you a surgeon?)
Da nada...
Cliff
Cliff,
I would do a pull in/ pull out with the old wire as my pull line. We make the tie as you have decribed for each wire, staggering them enough so that only one knot is going through a ninety at a time.
Dave
Hey Jeff,
Cliff's giving you some good advice.While he's in a typing mood,have him tell you how to serve an eye in the rope too.A bowline takes up more room in the pipe and as long as you're getting the straight dope on wire pulling,you might as well learn it all.
Barry
Cliff
No, just a jack of all trades, master of none.
My father tought me something years ago, and that was to buy the best
and do the best. I try to follow that rule.
A few things have been suggested and would like your opinion:
From George: says a #3 would be ok for 100 amp at 75 Degree rating.
Sounds too small for me, but not sure.
From Dave: pull each wire out, with new wire attached and joints
staggered. I think he means all at once.
Sounds ok.
From Barry: Asked if you would explain how to "serve an eye" on the
rope, to attach wires to.
I've heard that before, not sure what it is. I usually
just tie a figure of 8 in the rope to pull with.
Oh well, that's the current crop of thoughts.
Jeff
You can pull two of your three wires out and use the third wire as your pull line. Either way it takes two people. If you pull out two wire, the second person has to hold back on the wire you leave in, or it will come along with the ones you are pulling.
Another caution, if you did not use schedule eighty pipe at the nineties, you can seperate or break schd. forty with too much pull pressure. Use plenty of wire lube and coordinate your pulls with your helpers push from the feef end.
Dave
About the wire size, I looked back quickly and did not see if you mentioned the length run. Voltage drop is also a limiting factor.
Not to be picky, did you ask the same questions about pulling new wires or adding to the existing wires in the conduit about 1-2 months ago.
Jeff,
I'll second the other advice you've gotten.
If you want to provide 100A, I think AWG 3 copper would be fine. It's rated for 100 amps for THWN, 3 current-carrying conductors in conduit.
When you look at the actual loads, 28 amps for the saw (5 hp @ 240V) and 17A @240V for a 3 hp blower motor, and some incidental lighting load (say 5 amps--if you've got a BIG shop), you're not going to be anywhere near 100 amps. Given a max continuous 50 amp demand, a #3 Cu feeder would cover it, even with the distance. Ditto for the a 1.25 factor for the motors. If you run a 100A-rated feeder, I think you'll have all the headroom you're reasonably gonna need. That is, unless there's someone else working in the shop at the same time, sandblasting, so your 5hp air compressor is running balls to the wall. Only you know what evil lurks in the heart of your shop....oh, wait, that's the old "The Shadow" radio show intro...
But it's funny, I did the same thing when I saw the initial post, calculated what the estimated actual load would be; and then I figured that you hadn't asked for an opinion on that, so why get into it? I don't care if you want to run 2/0 conductors. It's your money and your shop.
Using the wire in place to pull in the new conductors is a good idea. I just didn't think to suggest it, probably because I'd use the existing wire to pull in a pull rope. But then, I'd be using a power puller. And the comment about the possibility of the wires cutting through the PVC elbows is right on, if you're using a power puller. I use steel sweeps and let 'er rip...
"Serving an eye" on the pull rope means splicing the rope into a loop. Easy with a kernmantle (sheath over core) type rope, a real art with a laid rope (three-strand). Haven't served an eye since Pioneering merit badge in Scouts! Barry just wants to foul me up--rope splicing isn't something you can talk someone through. You gotta see it done and work with it, hands-on.
Decision time, Jeff. Pull the damn wires, terminate 'em, fire it up, and go play in your shop!
Cliff
Most wire has more than one rating. THHN, THWN, and the -2s appear on all the wire we can buy around here.
You might check the wire size you NEED. I think #3 copper for 100amps is about right. Use the 75 degree rating on the wire.
CAP, IBEW Barry, Bill Hartmann, or any other Knowledgeable Person, if he already has #6 in conduit, and the insulation and lugs are good for 75C, isn't the ampacity 65A (per Table 310-16), and isn't he allowed to use the next larger standard size CB, which would be 70A (per 240-6(a)) for an instant and inexpensive upgrade? This assumes the voltage drop isn't an issue, as BH mentioned above.
Even using the conservative FLA values of Table 430-148 for 3 hp DC and 5 hp saw (which will rarely draw FLA, I presume), that leaves 25A at 240V or 50A at 120V available at the same time (without derating). In reality, more would be available since the motor OC devices would almost certainly be set at lower values. I'd have a tough time using 50A worth of 120V power, while the saw is cutting at full-load and the DC is humming.
If this isn't the case, I'd sure like to know.Be seeing you...
I mentioned the 75 degree issue earlier in hopes he would realize he could use a larger breaker. Depending on the local interpretaion of the code 70amps might be allowed. Certainly 60amps is.
You are right about the power usage. He is not close to using even 50amps (even including his lights and radio and starting all of his machinery at once).
I suspect he will do what he wants.
T Tom, George and Bill
I remember something from a few months ago, but apologize if I have
repeated myself, so much has been going on here.
When I did the original work, I picked the worst case scenerio
from the electric book I had handy.
Yes, I probably could upgrade the breaker safely, just wasn't sure
and used the old 1 grade of wire larger, one grade of breaker larger.
I think my old question was only answered in part, which was why I
probably started it again.
As for length, I have about 125 ft from main panal to sub.
As for what I plan to do, it depends on the great advice that I have
received here on Breaktime.
If anyone wants to chime in on the 125 ft, voltage drop, and temp
rating. please do.
I want to do this one time, the right way.
Thanks all for bearing with me.
Jeff
Cliff, I'd never try to foul you up.Honest.I just wanted Jeff to see the best method for attaching wires to a rope.Knot tying is something we try to teach early to our apprentices who weren't lucky enough to serve in the Navy. Barry
Barry,
Great site! What say we just head to Vermont and do the job for Jeff?
Cliff
Cliff
All great advice, can't thank you enough, really.
I know a bit about ropes, and know what you mean about "serving a.."
I just never heard that term before (and also never did one.)
I priced the differance between #3 and #2 copper and it's small
enough to go with the #2 (if you think that's a better choice.)
When I did the original pull, I didn't pull a seperate ground from
the main panal (installed a seperate ground), so if you think so,
I'll pull one with this upgrade.
SO, when are you guys coming!!! I'll serve all the beer and food
you want (after we're done.)
Jeff
I'm actually in the midst of doing a similar thing with my place. I've got a three-car garage about 100 feet or so back from my house where I'm installing a 100-amp subpanel (as soon as I upgrade the house service to 200 amps).
I figure with additional length added to the ends for getting in and out of both buildings, I'll be looking at 125 feet of wire, so after consulting the Taunton "Wiring a House" book (the last ed., not the new one), I came up with the following numbers:
#2 copper has a resistance at 75C of 0.194 ohms/1K ft., so for the 250 ft. round trip, the voltage drop would be about 4.85 V at 100 amps, or about 4% of 120 V, which should be acceptable. #3 would drop about 6.125 V, or a little over 5%, so you probably shouldn't use that.
Also, in FHB #154, the article on subpanels suggests that #2 or better is required by the NEC for a subpanel of 100 amps (if your using NMC), so #3 is out anyway. #3 is ok for individual conductors. If you feel like spending the money, #1 will decrease the voltage drop to about 3.84 V or about 3.2%, and #1/0 will be about 3.05 V, which is only about 2.5% of 120 V.
So, for the expensive machinery and electronics I'm going to be running out there, I'd like to go with #1/0, but the cost may be prohibitive for 500 feet (125 x 4 conductors...yes, I'm going for a full-size ground).
I'd go compare pricing for #2 versus the heavier gauges, then buy as fat a wire as I could afford, assuming it will still fit in a 2 in. conduit. I haven't laid my conduit yet, so I can still put any size pipe I want in the ground. I'll also be running some fiber-optic lines for the computers, so the power lines don't cause any crosstalk in the data lines.
Unfortunately for me, there's only aerial service in my neighborhood. If I could get the utility to run an underground separate service, I'd be in better shape as far as accounting for my business is concerned.
Granted, all these figures are based on full load draw, which will probably never really happen, but it's my house, and I can afford to be overly-cautious about it.
Amper
Yeah, looked at all the numbers last winter.
That's why I was wondering about keeping the old wires in and having
2 feeds.
But, Cliff and everyone have given me great advice, and will follow
their suggestions.
I settled on #2 copper for the pull, good balance with price and
future need.
I never did get the temperature rating figured out, so always used
the worst case. Now I know what is going on, thanks to everyone.
I'll let you know how it goes.
Hope to do it in the next week or two (if the guys don't come and do
it) if the rain will ever stop.
Jeff
Jeff,
You're welcome, it's good to help someone who's done his homework and wants info and guidance on the fine points.
Running AWG 2 copper is very good.
About the equipment grounding conductor (EGC), if there are any metallic pathways between the house & garage other than the feeders (i.e., a metallic water pipe, tel or CATV cable, etc), then you must have an EGC. Otherwise, if the neutral is conpromised at some point and there's a ground fault at the garage, the fault return current will travel on the phone or CATV wire. Big, big trouble. And it happens.
Size the EGC per the Code. For a 100A circuit (feeder), an AWG 8 copper EGC is the Code minimum. I recommend pulling an insulated conductor, and if you want to impress the inspector, buy green insulated wire (Code says you can't re-identify insulated feeder wires with tape unless they're #4 or larger...but that's very commonly ignored).
I suggest running the EGC even if there aren't currently any metallic paths.
Take care,
Cliff
Cliff
Thanks for all the help.
No other conductors running between garage, so I'll pull a ground at the same time.
Now if it will stop raining long enough...
Talk to you again.
Jeff
I have a question in the same vein.
My house currently has 60A overhead service and the old Garage/carriage House is fed from the panel in the house. I am planning to rewire the house and upgrade to 200A service.
The thing is, I will have a 5hp compressor, welders, etc. in the garage as well as an apartment on the second floor with air conditioning.
I haven't done any load calculations but what I was thinking of was bringing in 400A service and splitting it, with 200A to the house and 200 to the garage. If I added a second meter to the garage I would have to pay commercial rates.
My question is, does this make sense? The alternative would be to run 400A to the house, then backtrack to the garage. The electric service is literally within 5 feet of the overhead power lines so it seems obvious to me. Am I missing something?
Also, there is 3 phase service available, what would that do for me? I am buying a new 5 or 7 hp compressor this Fall and can buy a single phase or 3 phase.
You need a disconnect on that line that goes to the garage. And you can't afford a 400 amp pannel anway.
So having a 200 amp disconnect and then feed the garage is the way to go.
I'm not sure what you're saying. Why would I need a 400A panel? My plan was to bring the service in and split it - sending 200 to the house and 200 to the panel in the garage.
"My question is, does this make sense? The alternative would be to run 400A to the house, then backtrack to the garage. The electric service is literally within 5 feet of the overhead power lines so it seems obvious to me. Am I missing something?"
That is your orginal question.
If you "run 400 amps" to the house and then split it off 200 amps for the garage then you need a 400 amp pannel.
Your other thought was much better a 200 amp disconnect for the garage and a 200 amp pannel (or 200 amp disconnect and then a sub-pannel) for the house. And probably a 320 amp meter. Because you probably don't have near a 200 amp demand on either pannel.
About th 3 phase service.
Check with the power company to see what there service charges are for that service. Often there is a demand charges and commercial rates that might put it out of the reasonable range. But in some area there the larger homes are going to 3 phase.
7 hp compressor would be nice on 3 phase, but you have to way the other cost.
Also need to check on your other equipment to see if it can run on 208 volts.
Thanks, that's what I thought. I realize I probably won't need it all, but I guess I would rather be sure and not have to worry. I live in the house I grew up in and some of the wiring my stepfather did makes me cringe. Like I said, the house has old 60A service and we had two big central air units hooked up as well as electric oven, stove etc, the garage with a crappy Sanborn vompressor, MIG welder, etc attached. Don't ask about the Romex/K&T connections I have found and the amount of black tape covering them up.
I don't want to have the situation I see at my neighbors house. When he engages his table saw or when the central air starts the lights dim significantly.
At least around here (Minneapolis area) three phase service to a residential property is pretty hard to do...unless you live along a main street or highway, chances are three phase power simply isn't available. Even if the utility does have a three phase line running right past your house, they really don't want to provide three phase service to houses, and will charge you an arm and both legs for it. In most cases, it isn't really necessary unless you're trying to run some seriously big industrial equipment.
It would be a good idea to contact your local utility to see just what kinds of rules and regulations apply, as it seems there's always subtle differences from one to the next (I regularly deal with four or five different utilities, and it can be a pain remembering what one company allows and the other one doesn't.) More and more often these days, this information is available on their websites.
Remember when determining how big a feed to install to a garage or workshop (as well as calculating voltage drops), it's not likely that you'll have every single power tool running at full load at the same time, every light turned on, every outlet plugged in with 15 or 20 amps of load, particularly if you work by yourself.
I know what you mean.
I live in a small residential lake community (about 350 homes) that is wedged into a fair size subburban city and surrounded by other developement.
About 1 mile away is a major sub-station on a US hiway and one entrance to our coummity is off that hiway. The other enterance is off a collector road that also goes to the US hiway. There are main feeders lines from the sub-station going down both roads. And the lake can be feed from either road via disconnects. And the lake is circled with 3 phase feeders.
And I have a transformer on pole at the corner of lot (actually it is 15 ft from the corner, but that is a whole other issue).
They could set another transform and give me open detla service is 1-2 hours. But I am sure that I would not be "happy" to get the bill.
I think so people put in a 350amp meter and connect 2 200amp panels to it.
You might be best off installing your service at the garage and running 200amp back to the house.