Help me wire my new shop

[EarlyBroncoGuy]

Almost done erecting a 2400 sg ft shop, now I need to start planning how to wire it. First off, I'm no electrican - I understand and work on automotive 12v DC circuits with no problems, but once things start getting into AC and multiple phases, I admit my limitations. The basics I get - voltage, amperage, resistance, inductance - but I've never bent conduit or installed a panel.

The shop is new construction, metal building on concrete slab with fiberglass insulation on walls and roof. We're out in the country, have a pole on our property that serves the house, it's about 300 feet away from the shop. Would it make more sense to have the power company run another cable from that pole to the shop, or should I dig a trench between and run underground? Here in central Texas, frost isn't a problem.

The shop will be mainly used as a storage garage for my stuff, but I do plan to install a 2 post lift and do repairs, maintenance, and some light fabrication/restoration work out there. No heavy equipment or tools, just the basic drill press/bench grinder/welder/comprssor power tools. Shop will have 3 large doors which I'll open for light and ventilation most of the time, and skylight panels in the roof for some additional light, but I'm open to suggestions for additional lighting. Ceiling is 16' at the peak.

I'll probably never use all of it, but it's been suggested that I go with 200 amp service, since it's new construction and might as well go bigger than I think I need and be able to grow into it. Mainly I'm looking for advice and ideas on the most efficient way to run conduit inside to the various outlets once I decide on where they're needed.

 

[pattenp]

What size service is to the house and how far is the house from the shop? Would a feeder from the house work?

 

[theoldwizard1]

Some power companies will not run a second line off of the same meter. Having a second service can be expensive.

An alternative maybe to mount your own disconnect box on the pole to feed the house and shop. You need to verify if this is "legal" with both the power company and your local building inspector. Of course then you own all of the wire coming out of it.

300' is going to be expensive no mater what you do.

 

[Aceman]

Call the power company first and see what the cost would be to set some more poles for a second service at your shop.

 

[brownbagg]

its easy. Think of Mr T with all the gold chains around his neck, and that vanilla ice dude

just remember the black wire always goes on the gold(brass) screw and the white dude always get the silver

never forget that and you can wire anything

 

[laser3kw]

what you can do depends on what country your in and your location.

 

[2ManyProjects]

Almost done erecting a 2400 sg ft shop, now I need to start planning how to wire it. First off, I'm no electrican - I understand and work on automotive 12v DC circuits with no problems, but once things start getting into AC and multiple phases, I admit my limitations.

For standard residential 120V/240V AC, it's easy enough if you simply equate "phase" to "polarity". Your "Neutral" (white) wire ALWAYS represents 0-volts; think of it as "Chassis Ground" (even tho' it really isn't). The voltage on the Hot (black, and sometimes red) wires "swings" around that Neutral, following a sinusoidal wave form:

...first going positive, hitting its peak, then returning to zero, then going negative, hitting that peak, then returning to zero again to finally finish the cycle. Lather, rinse, repeat, 60 times per second (for the USA, anyway).

Voila! We've just described a 120V branch circuit.

Now IF the circuit in question is 240V (such as for an oven, big air conditioner, etc.), then we have TWO "Hot" wires (one black, one red); and the voltage on each of these wires is exactly 180-degrees out of phase with the other one. So...

Because the two voltages are out-of-phase with each other, they "add up to" twice the total voltage as either "leg" by itself.

(And yes, if you've gathered from all this that a 120V branch circuit is effectively "half" of a 240V branch circuit, you've been paying attention! )

The basics I get - voltage, amperage, resistance, inductance - but I've never bent conduit or installed a panel.

All that is essentially the same. Thus endeth your "AC Electricity 101" lesson for the day.

The shop is new construction, metal building on concrete slab with fiberglass insulation on walls and roof. We're out in the country, have a pole on our property that serves the house, it's about 300 feet away from the shop.

Ouch!

That distance is going to kill you, no matter how you slice it.

Would it make more sense to have the power company run another cable from that pole to the shop, or should I dig a trench between and run underground? Here in central Texas, frost isn't a problem.

This depends almost completely on the vagarities of your local PoCo, and their policies. But I can tell you this much: IF you can get them to set a new (second) meter MUCH closer to the shop, it will very probably save you a ton of money (not to mention work).

The shop will be mainly used as a storage garage for my stuff, but I do plan to install a 2 post lift and do repairs, maintenance, and some light fabrication/restoration work out there. No heavy equipment or tools, just the basic drill press/bench grinder/welder/comprssor power tools.

Don't kid yourself. Many of the items you just mentioned ARE (or at least very easily could be) "heavy equipment", at least from an electrical load standpoint.

Shop will have 3 large doors which I'll open for light and ventilation most of the time, and skylight panels in the roof for some additional light, but I'm open to suggestions for additional lighting. Ceiling is 16' at the peak.

Lighting a space like that is a discussion unto itself. And much of it will depend greatly on EXACTLY what you plan to do where, within the space. While there are various online "lighting calculators" around which can be used to genn up a simplistic "rank & file" lighting plan based on the whole thing being one big undifferentiated open space, you would be FAR better off to first come up with a layout of how you intend to furnish & use the interior space, then tailor the lighting to that.

I'll probably never use all of it, but it's been suggested that I go with 200 amp service, since it's new construction and might as well go bigger than I think I need and be able to grow into it.

If, and ONLY "if", the PoCo does set a new meter relatively close to the shop, then that is a reasonable approach. But if you have to run the shop off a subpanel-feeder cable coming from either that distant pole or the house itself, then you absolutely DO need to "budget" your amperage requirements much more tightly than this. Have you priced 250 MCM feeder cables lately? Here's a hint:

http://www.wireandcabletogo.com/250-MCM-XLP-USE-2-RHH-RHW-2-Building-Wire.html

(And note that you will need THREE runs of this stuff, plus a somewhat smaller fourth run for the EGC.)

Mainly I'm looking for advice and ideas on the most efficient way to run conduit inside to the various outlets once I decide on where they're needed.

I'm sure many folks will have suggestions on this; but the "Bottom Line" is, you just aren't "there" yet.

What size service is to the house and how far is the house from the shop?

Those are indeed two of the more critical questions.

Some power companies will not run a second line off of the same meter. Having a second service can be expensive.

"Can be", yes. But not necessarily. I've seen plenty of anecdotal evidence that, at least in SOME places, they'll (sometimes) set the new meter for free and charge maybe $10-15 for the second monthly reading and account maintenance. OTOH, in other places, they automatically assume that any customer who needs two meter drops MUST be a commercial entity, and uses that assumption as an excuse to jack up the rates obscenely.

The OP really needs to talk to his power company.

300' is going to be expensive no mater what you do.

Very probably, yes.

Call the power company first and see what the cost would be to set some more poles for a second service at your shop.

Agreed. That should be his FIRST call, before he even breaks ground.

its easy. Think of Mr T with all the gold chains around his neck, and that vanilla ice dude

just remember the black wire always goes on the gold(brass) screw and the white dude always get the silver

never forget that and you can wire anything

Oh, Dear.

Note to OP: PLEASE don't take this literally!

what you can do depends on what country your in and your location.

He DID say, "Here in central Texas...".

 

[sberry]

Good job on the post above. For a common garage with a few tools you need a service north of 60A and ideal is 90 or 100. You are going a long way but you have a pole, there is some trade off here. You don't need 200A service but need a 200A wire.

Look on the breaker at the pole, we assume it can accept a 100A, just as a guess you can wire 2/0 to 100 and a 100A main breaker panel will take 2/0 I believe. , direct bury 3 of those and 2manyprojects can probably calculate the ground wire size for you at that distance etc.

Personally would buy a 1000 ft roll from a jobber and cut it in 3

 

[ishiboo]

IMO the best way to do these is to have the PoCo bury a cable and then mount a small pad transformer next to the building. The cost difference then between 100A and 200A at the distance from the transformer to your building as well as the main panel is quite small, and you should go with 200A right away.

 

[sberry]

Home Depot sells a heavy underground wire. I believe its 4/0 with reduced neutral, I use it on a couple wells about that distance. Looking back would downsize it for economy, all the load we predicted from looking at charts never materialized. This wire takes 200A lugs etc, wasn't all a real problem for us.

The modern small mig welder has taken peak loads off of small services. With a modest air comp of 5 hp,,, not including electric heaters or hot tub added but using tools will never trip a 60A breaker. I had buds with 60A service, we just didn't weld while the air comp was running, other than that would never know you are underpowered.

I got a bud who runs a welding shop on 100A service, he don't know any better, been doing it for 30 yrs. Runs only 1 50A process at a time and not likely to be using continuous air at the same time. He welds more than a hobby restore guy ever would. Routinely uses a 250 mig for most of what its worth.

 

[MikeYC]

its easy. Think of Mr T with all the gold chains around his neck, and that vanilla ice dude

just remember the black wire always goes on the gold(brass) screw and the white dude always get the silver

never forget that and you can wire anything

Black to brass or Ill kick your a$$, Brass is hot and Silver is not!

 

[sberry]

Want to see a hot service try a bar on Friday night fish fry in August smoking summer time heat. I have seen panels draw their rated capacity but never from Joe Hobby part time garage, in fact most of it is so low they barely include it in demand factors provided its not oven, heat or cooling beyond what you would plug in to a general use circuit.

With all gas appliances you can live on 30A service, given the opportunity and enough users it would be likely to overload one of the entrance conductors though without monitor of balance for lack of better wording.

The bigger the wire the less it matters with smaller more even distributed loads. I did how ever help a situation at a festival where someone had buried 200 ft of 6 copper and 60A, to a main lug panel and they add a beer cooler of a full 20A maybe and the band,,, all of a sudden out it goes, well had on amp on one leg and 49 on the other, swapped one breaker and pick the whole things up about 10V, moved one circuit from the band over too as I recall. but at 25 down each and not more than 1 or 2 on the N it works and still works to this day, never loaded it again so out of balance. It happens but with 20 spaces and one or 2 users not such a deal, many times I have found an opposite that didn't dim the lights when we kicked on a chop saw.

 

[jomobco]

IMO the best way to do these is to have the PoCo bury a cable and then mount a small pad transformer next to the building. The cost difference then between 100A and 200A at the distance from the transformer to your building as well as the main panel is quite small, and you should go with 200A right away.

^^^
What he said

 

[jwvess00]

Hi there!

Definitely talk to your electrician or the PoCo. Dad built his 32x40 shop fairly close to their house. His original intention was to have the new building fed on the same meter base as the old one since he didn't want two bills or a separate charge for service.

It turned out that it was much more expensive to do that than to install a separate service at the new shop. The difference in price meant it would take many, many years to pay off the little extra a month charge for a second meter.

 

[sberry]

I agree with looking at the options,,, but why ever bother with any realistic load calculations when its so much easier to spit out 200 amps as an answer to every question, no need to figure any margin factor of 30 to 50 % or so when we can just come up with a load 3X as big as likely to be applied?

 

[Falcon67]

Hi there!

Definitely talk to your electrician or the PoCo. Dad built his 32x40 shop fairly close to their house. His original intention was to have the new building fed on the same meter base as the old one since he didn't want two bills or a separate charge for service.

It turned out that it was much more expensive to do that than to install a separate service at the new shop. The difference in price meant it would take many, many years to pay off the little extra a month charge for a second meter.

It will depend on the POCO and the tarriff. Here's it's just the opposite. It's $40/mth minimum for a meter -any meter- on our POCO. So the payback was almost instant compared to buying the $150 of 2-2-2-4 to run back to the house. YMMV as they say. Texas also used to allow a utility to charge commercial rates for a second meter located at a residence but I have heard the PUC changed that.

 

[EarlyBroncoGuy]

Had an electric co-op rep come out today and give me some options, but even they suggested I get with an electrician and get some hard numbers.

I measured from the primary pole on the property line to the shop, it's 275 feet. They can run overhead wire to another pole nearer the shop, then underground into building. Or, I can trench the distance and go underground all the way. But, that would mean an additional meter and monthly charge for it.

Since my house disconnect panel (200 amp) and meter are on a pole in the front yard, I can't run an overhead from there to the shop because the house is in the way. However, I could upgrade to 400 amp service there, and split off after the meter and send 200 to the house and 200 to the shop, underground. That would mean upgrading the transformer on the pole, but it's only a few hundred to do that (according to the co-op rep).

There are 2 sub panels in the house, one is the heavy duty feed with 30, 50, and 60 amp breakers for the water heaters, furnace, A/C, oven, etc - and two 125 amp breakers that feed the other sub panel, which has all the other house circuits. The heavy duty panel does have 4 unused spaces, it might be possible to put in four 50 amp breakers and run the feeder to the shop off of those, but not sure if that's needed if I can just go from the disconnect panel on the existing meter pole.

 

[2ManyProjects]

Had an electric co-op rep come out today and give me some options, but even they suggested I get with an electrician and get some hard numbers.

I don't necessarily disagree with that advice; but for it to be meaningful, you'll ALSO need some hard & fast numbers from the PoCo for the various options.

I measured from the primary pole on the property line to the shop, it's 275 feet. They can run overhead wire to another pole nearer the shop, then underground into building. Or, I can trench the distance and go underground all the way. But, that would mean an additional meter and monthly charge for it.

Did he quote exactly what that monthly charge would be? And would it also affect the "per kWH" rate you pay for your electricity? FWIW, for comparable (ongoing) costs, I would surely go underground the whole way -- much neater & tidier installation, no ugly overhead wires, no additional poles to mow around, etc.

However, I could upgrade to 400 amp service there, and split off after the meter and send 200 to the house and 200 to the shop, underground. That would mean upgrading the transformer on the pole, but it's only a few hundred to do that (according to the co-op rep).

Just how many "few" hundred? Again, you need real numbers to make real comparisons.

And who would pay for the cable between the meter/pole and the shop, in this scenario? If it's you, that brings us right back to needing ca. 1,000 feet (well, 900 feet, anyway) of this stuff:

http://www.wireandcabletogo.com/400-MCM-XLP-USE-2-RHH-RHW-2-Building-Wire.html

(And, probably, about 300 feet of http://www.wireandcabletogo.com/4-0-AWG-XLP-USE-2-RHH-RHW-2-Building-Wire.html; but I might be off an AWG or so either way on this, pending exactly what the code requirements are for EGCs run with upsized main conductors, of which I am unsure.)

There are 2 sub panels in the house, one is the heavy duty feed with 30, 50, and 60 amp breakers for the water heaters, furnace, A/C, oven, etc - and two 125 amp breakers that feed the other sub panel, which has all the other house circuits. The heavy duty panel does have 4 unused spaces, it might be possible to put in four 50 amp breakers and run the feeder to the shop off of those, but not sure if that's needed if I can just go from the disconnect panel on the existing meter pole.

Well first, it would NOT be "four 50 amp breakers" (to make a single 200A service feed) -- and if your PoCo rep suggested that, you desperately need to talk to a different PoCo rep who actually understands how this stuff works.

Beyond that... Perhaps I misunderstand the situation; but at the moment, I don't see what this would gain you. Is that sub-panel in the house sufficiently closer to the proposed shop location (as compared to coming off the pole) that it would SIGNIFICANTLY cut down the run-length of the feeder cable? At the end of the day, that cable is the big cost issue; and mostly because, being so long, it ALSO needs to be much heavier (read: $$$-er) than would otherwise be required.

 

[Mustang51js]

Call an electrician and let them give you advice, a 400 amp meter pan is prob $200 for that alone. Your looking around $4 a foot for 200 amp aluminum sub panel wire and that's if it's not derated for distance. That's not including pipe and panel in shop.

 

[2Big2Ride]

You have to get quotes for new service and from your existing service to make a decision. We were able to get a new 200a service for the shop rather than run a 100a sub-panel from the house. House would have been a 175' run, new service was about 25'. In our case, install for the new service was half the overall cost to trench and install a sub. Meter monthly charge is about $7.00 a month and the rate is the same residential plan and rate as the house. Since it is an additional service to the property we have a separate electrice service account and monthly bill for the shop.

 

[FordsnFishin]

just the basic drill press/bench grinder/welder/comprssor power tools. Shop will have 3 large doors which I'll open for light and ventilation

If thats the majority of what you are planning on running i don't see why a 100 amp main would be any problem for you. Say you are running your welder, compressor, a table saw, lights, and a fridge all at the same time. You'd more than likely only be seeing around 60 amps drawn. As long as your circuits are separated properly there would be no trouble at all.

As for getting power to the garage, thats where you will need to talk to the electrical company and figure out what can be done and what will be the cheapest route. An underground sub feed from the house is a good possibility id say. If you go with a 100 amp panel you should only need #2 feeder wires with a #4 ground, 200 amp service would be #2/0 feeders with a #2 ground. This is aluminum wire sizes. You can buy it from a electrical supply house by the foot, will come in a intertwined triplex. Make sure your connects are tight, and using a product called no-ox is a good practice.

 

[2ManyProjects]

As for getting power to the garage, thats where you will need to talk to the electrical company and figure out what can be done and what will be the cheapest route. An underground sub feed from the house is a good possibility id say. If you go with a 100 amp panel you should only need #2 feeder wires with a #4 ground,

No.

Given the ~300-foot run to the sub-panel, that's not nearly enough. Even presuming copper all the way (read: big $$$), that would produce almost 5% voltage drop over the run. Aluminum is even worse. It would be limited by code to 90A; but even at that reduced figure, voltage drop would exceed 7%.

Neither of those figures is acceptable.

200 amp service would be #2/0 feeders with a #2 ground. This is aluminum wire sizes.

Again, no.

In this case, voltage drop would be about 19.13V at full load, or nearly 8%. No good.

To run 200A over a 300-foot run, while holding voltage drop to no more than 3% (which is the MAXIMUM possibly acceptable figure; the NEC recommends 2% for such feeder circuits) would require an aluminum cable of at least 353,333 CM -- IOW, 400kcmil, such as I previously cited. If we really want to stick to 2% max. voltage drop, even 500kcmil isn't good enough.

 

[Bib Overalls]

I wish I had gone 200 amps when I built my 1,200 sq ft shop. I started out with the basics; air compressor, grinder, drill press, and lights. Today I also have a 3.5 ton heat pump, a 7.5 hp three phase converter driving 4 machines (only one at a time), and another grinder. I have just about maxed out my 100 amp service. Your shop is twice the size of mine and there is no telling where you interests will take you in the future. And if you sell, having 200 amps at the shop may make the deal. And finally, if you or a future owner want to run a business out of the place having a separate meter is quite useful when you want to document your expenses for tax purposes.

 

[FordsnFishin]

No.

Given the ~300-foot run to the sub-panel, that's not nearly enough. Even presuming copper all the way (read: big $$$), that would produce almost 5% voltage drop over the run. Aluminum is even worse. It would be limited by code to 90A; but even at that reduced figure, voltage drop would exceed 7%.

Neither of those figures is acceptable.



Again, no.

In this case, voltage drop would be about 19.13V at full load, or nearly 8%. No good.

To run 200A over a 300-foot run, while holding voltage drop to no more than 3% (which is the MAXIMUM possibly acceptable figure; the NEC recommends 2% for such feeder circuits) would require an aluminum cable of at least 353,333 CM -- IOW, 400kcmil, such as I previously cited. If we really want to stick to 2% max. voltage drop, even 500kcmil isn't good enough.

Should have read more, didn't know he had a 300' distance from the house to garage. My fault. Thanks!