Background:
<!—-><!—-> <!—->
I am trying to layout the wiring for my garage that I am converting to a work shop. I will need (2) 220v circuits. (1) for the Unisaw, band saw and jointer to share and (1) for the dust collector. I’m the only person working in the shop, so I don’t need to worry about the Unisaw, band saw and jointer all being run at the same time. I will probably need a couple 110v circuits for outlets around the perimeter of the garage and a circuit for additional overhead lighting.
<!—-> <!—->
I have a 200A service panel in the basement that is 40-50% full. Distance from the panel to the garage is about 15’. A home run from the farthest corner of the garage to the panel would measure 50’.
<!—-> <!—->
My Question:
<!—-> <!—->
Should I run a line to a sub panel in the garage, and then run all my wires from the sub panel? Or should I just run the circuits from the main panel in the basement to the locations in the garage? Is there any real benefit to using a sub panel, besides having easy access to be able to cut the power to the garage tools?
<!—-> <!—->
Thanks
<!—-> <!—->
Trevor
Replies
Trevor
While a 15 ft home run isn't a problem for running wires, you need to think about how much you can save on time and labor.
If you run one #6 or #8 wire to a sub-panal in the garage, then all the garage wiring is then a short hop to the new sub-panal.
In my experience, in the long run, you break even on the material cost but save alot of headaches in labor.
Plus any future changes are easier.
And, it's nice to have all the shop wiring in one easy place to get to.
Jeff
That makes sense.
<!----><!----> <!---->
Can you recommend a quality sub panel (80-100A)?
<!----> <!---->
Can the ground wire for the sub panel be attached to the ground bar on the main panel or do I need to install a separate ground rod for the sub panel?
<!----> <!---->
Thanks again.
<!----> <!---->
Trevor
Trevor
You don't need a seperate ground rod, and actually I think code says to tie it back to the main panal except in a seperate building.
A simple run of #6 will handle saws and accessories.
A Square D panal will do the job fine.
If you want to kill everything in the garage at once, a main breaker will do it, otherwise, you don't need a main breaker and just a sub-panal will do and save on money.
If only 2 circuits are needed, then you don't save any real money here.
2 220 circuits and a few 120 end up saving time and work, but pretty much cost a little more for material.
The sub-panal and wire shouldn't cost more then $100, so you won't have alot in this.
Jeff
Edited 1/23/2006 6:50 pm ET by Sardog
I would run the two circuits directly to the panel. You could run a sub panel, but why? the extra cost for the panel, with a breaker, would far out weigh the cost of the extra 15 feet of cable. I just did the same thing. My need was a little different. I wanted a single disconnect point that could kill all the power at once when I left the shop at night. I have kids and it is a safethy thing with me to not leave equipment energized. I added up the cost of the wire #6 for 50A sub panel, and it was cheaper to run individual circuits out of my main, and just cut them off individually. If moneys no object go for it. Of for that matter, if you just want to. Good luck.
Hay Bones
Yeah I agree 2 circuits doesn't really need its own panel.
I'm just a big believer in sub-panals for shops for ease of use.
Also, it's amazing how circuits in shops keep getting added on after the fact.
They kind of multiply like rabbits.
Everytime I install a sub-panal, I always oversize it for extra breakers as I know more will end up being added on.
Jeff
Great!
Thanks again for all the information and help!
Trevor
I have a 200 amp main panel (square d) at the house with a 100 at the garage & a100 at the shop
by having subs you save valuable time in case of a emergency or when you kick a breaker due to overload
you don't have to put all the breakers in at the start & by using Sq d anyone can tell which is the one that kicked out , handy if your holding a sheet on the ts and someone else is looking for the breaker
I also wired my motor plugs eg. bench saw ,planer ,chop saw ,edger for 20 amps because i found they were kicking the breaker to dam often when being pushed hard
I have had no more trouble since doing that ,works slicker than snot on a door knob
If you are going to run a sub panel, be sure you know what you are doing. It isn't hard to install, but it has a unique setup that is different from installing a main breaker box. Before I installed my sub I did a lot of reading and research on line to be sure I had the procedure down pat.
Agree 100%, will just add that if you decide to get a permit and get it inspected, your inspector might also be willing to review your plan prior to installation. Mine did, which saved me from a couple minor m8istakes and a reinspection. At least in my town, the inspectors are very helpful, mostly interested in making sure you don't burn your house down -- a good thing!My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
I had new service installed in the garage so I have a 200A panel there. However, if you don't want to do that, a subpanel for the garage is an excellent idea. Another idea I discovered is using three wire circuits that provide 120 and 240 volts on the same circuit which makes it much easier, faster and cheaper to wire your shop. Just make sure all loads and receptacles are the same amp rating such as 20A breaker 12/3 wiring and 20A receps. If you have any 30A tools and don't try to use them at the same time you can save time, money by sharing a circuit except put the dust collector on its own dedicated circuit. Use 20A circuits for all your plug-in hand powertools and make sure you provide for lots of lighting. Try to plan for future tools purchases in your wiring design. Double check your grounding system and follow the NEC rules for subpanels. I would also suggest that you use surface wiring in conduit so you can easily make changes if necessary. The best advice I could give is to get the book "Practical Electrical Wiring" ISBN: 0971977917. It is the best book on the subject and you should read it thoroughly. It has great info on motor circuits. If you read this book, make sure you never work on live wiring and use common sense, you can do your own shop wiring. Do get a building permit for the project and have it inspected. The permit in my town is only $20.
Something you might add is that if you use three wire conduit that the black and the red wires are hooked to different legs (240 volts apart). If they are on the same leg, it is possible to get up to forty amps through the neutral wire - not a safe thing. If you put them on opposite legs the amps could be zero - thus saving in line loss.
Tinkerer2:
Good point - in a three wire circuit there are really 4 wires: black-hot 1, red-hot 2, white-neutral, and green-ground. Connect the black, red, and white to a 240V receptacle of the correct amperage rating for the circuit for 240V power. Connect the black or red (but not both), the white and the green to a 120V recep. of the correct amperage rating for 120V power. Load balancing is important with the 120V outlets - try to have an equal number or receps. on each leg. You can even remove the connection between outlets on a 120V duplex recep. and wire the top outlet with the black wire and the bottom outlet with red wire (to the gold color screws) and the neutral to the silver screw so any load plugged into both outlets will automatically load balance. By the way, there is lots of confusion about the neutral vs. ground in 240V circuits. In 240V single phase circuits, the black and red are the current carrying conductors with the white wire acting as the ground (referred to the grounded conductor in techie books) because the white is connected to ground in the panel box. The green wire is the grounding conductor (also referred to as the equipment grounding conductor) and must be used for 120V circuits and must be used to bond all metal recep. boxes and conduit. Be careful not to overfill conduit because all circuits produce heat. Check NEC for this issue. Also if you are working in an unfinished space (garage or basement) you must use GFCI receps. to meet code and for your safety. Good luck!
Edited 2/1/2006 3:09 pm ET by CTWoodWkr
Good thread,I would just like to agree and clarify what Tinker and CT said,The only place the neutral (white) and ground (bare or green) wires are bonded (connected together) is at the main service (in residential, typically where the meter is.)All subpanels (ones w/o a meter) should have an "isolated neutral" meaning the neutral bus (the bar in the sub that all the whites connect to) is not bonded (touching) to the metal panel box or the ground bus. Many panels come with a 'jumper' that has to be disconnected if it's used as a sub-panel.Lastly, each neutral should only have one 'A' (black) and one 'B' (red) phase and no more. The colors (red/black) aren't important, but the phasing is.
A (single phase) 120/240 vac sub-panel has two 'hots' A and B (which together make 240) feeders and one neutral feed (and a ground(ing) conductor) and depending on the panel, it typically will be every other breaker (top to bottom) will be on the same 'phase' (red or black feeder) so only one 'A' breaker and one 'B' breaker (black and red) should share a neutral (not 2 'A's or verse-vicea)
Having more than one phase on a neutral can'overload' it beyond it's ampacity rating, leading to hot/smoking/burning <sniff, sniff> wires and potential fire hazards.Sorry this was so long, but I felt the need to be as clear as possible in non-electrical jargon as overloaded neutrals are a bigger fire hazard IMHO than arc-faults or ground faults and inspectors, typically never look or know about them.3-phase users disregard the above, you can use one A, B, and C hot per neut.hope this helped,Mark
licensed electrical and general contractor, in CA (not that passing some tests means a guy knows the trade(s), but it doesn't hurt. :)
A question about the GFCI receptacles:
<!----><!----> <!---->
Does each of the outlets have to be GCFI or could I just get a GFCI breaker and use regular 20A outlets?
<!----> <!---->
Thanks again for all the help.
<!----> <!---->
Trevor
Hi Trevor,You can do either. Another solution is to use a GFCI recepticle, and come out of the "Load" side to feed regular (cheaper) plugs. Anything off of the 'load' side downstream will be GFCI protected. I would still probably use more than one GFI plug, so as not to get 'nuisance tripping' but it would still be more cost effective than doing every outlet.
I'm not fond of the GFI breakers, because you can't have more than one hot (the protected circuit) on the neutral wire or it will trip the breaker, and you still have to limit the number of outlets to prevent nuisance tripping.hope this helped,
Mark
That helps and will save me some $$$.
Thanks for the info.
Trevor
I did what you describe. I have two GFCI outlets right by the breaker box, and five standard outlets per GFCI on the load side. This gave me ten GFCI-protected 110 outlets on two circuits at a very low cost.
I was going to do it another way. I'd heard of three-wire 110 circuits, in which you run two hots and a neutral (and a ground) down a length of 12/3 (+ground). As long as your two hots are off the two different legs (important!), your neutral works fine for both circuits. But these circuits were for a garage, and required GFCI. Easy, I thought, just use a 2-pole GFCI breaker. But (and this is a big but) this configuration is no good, because when the load changes on one leg or the other, the GFCI breaker thinks there's a ground fault and trips. So the inspector looking at my plans said to do exactly what you recommend -- it's per code, works, and will pass inspection. :)My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
Exactly John, it tricks the GFI.The AFCI's (arc fault circuit interrupters) which are now code for bedroom plug circuits, behave the same way and have taken some getting used to, because we used to take 14/3's (romex) and drop off bedroom plugs, but no-can-do anymore or they'll trip.RE: the GFI plugs, I'd stagger the plugs also. For example, if you have 4 plug circs. dump 2 in the first two gang box (a double duplex) and in the next one down the line dump the other two, then repeat. That way you can plug multiple loads in and lessed the chance of a GFI trip.I didn't say this, but if it's in my shop(garage/home), I wouldn't have nare 1 GFI. (which is against Ntnl.Elec.Code:NEC) because of motors loads and nuisance tripping. IMHO, the GFI/in the "garage" part of the code doesn't take into account home workshops.
My reasoning is because I've wired industrial woodshops/machine shops/plastic injection molding plants/aluminum foundries and all were on slabs (in CA) and passed inspection and not a one GFCI was ever used. I believe the thought is the employees are taught shop electrical safety. The only exceptions were in 'wet locations' which I completely agree with.
But I didn't say that so, you didn't hear it from me. :)hope this helped, now I'll go back to being 'edjumacated' in the ways of woodworking by all you helpful termites. :)Mark
I ran two independent breakered circuits in parallel. I pulled two 12/2 (+ground) everywhere, into every box. In each duplex box the pair of outlets on the left is on the "A" circuit, and the right pair of outlets is on the "B" circuit. So at any workstation I have 40A of available 110 (plus the 30A 220 I also ran in parallel).
I was worried about this configuration, because turning off the "A" circuit breaker leaves the "B" circuit hot, and I thought this would violate code, but I specifically ran that issue by the inspector prior to installation and he said it was fine.
The only trips I've had is when using the GFCI tester tool. I haven't had any nuisance trips, mostly I guess because I'm running way under capacity, and the only 110 machines are pretty small -- router, DC, etc. -- and I only run one machine per circuit.My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
John, it sounds like you have a nice set up there and if the GFI's aren't giving you grief, I wouldn't change a thing. I was giving the NEC some thought re: the GFI in residential garages and not in commercial. My guess it's a requirement in homes because someone is more apt to run an extension (with the ground prong cut off)cord out of his garage to power a weedwacker/hedge-trimmer, while standing in ankle deep water wearing metal golf spikes <wink> Half joking, but you get the point of what's possible with people who don't understand how ugly 120v can get when mixed with the wrong combinations and the code protects them from themselves. Which, is a 'good thing'.Your right about what is being plugged into them too. It's typically large saws and drills and portable compressors with big amp draws, used all day.Mark
Perhaps a little late, but here goes.
1. I like having a sub-panel, but I suggest you get the same brand as your main panel. That way you don't have to have different types of breakers. I like square-D QO myself, not the homeline version. 60 amp would be sufficient, but I'd probably do 100 amp anyway. If you have an old main panel, you can convert it to a subpanel by modifying the ground bar connection.
2. I'm pretty sure that you DO need a grounding rod at the sub-panel. It seems like most wiring installations are requiring two grounds now.
3. There may be a requirement for an outside shutoff. This may depend on how far from the door your sub-panel is. And it is a good idea anyway.
4. I like GFCI breakers over GFCI outlets, the reason being that if anything trips, there is only one place to look. I have an outdoor light that turns out to come off a GFCI outlet that is as far away as possible. I had a heck of time figuring out why the light worked sometimes and not others. Turns out that it was getting damp because of the motion detector I had installed, and tripping the GFCI outlet. This outlet had all the battery chargers on it, so I'd reset it whenever I'd notice it had tripped. Never dawned on me that the outside light could possibly be downstream of that outlet!
However, GFCI breakers are much more expensive than outlets.
5. If you wire for only 20 amp (including the lights) you may have a hard time finding 20 amp switches. Lighting legs are typically 15 amp, because 14 gauge wiring bends easier. So most switches are rated at 15 amp only.
6. If you have a bathroom out in the shop, it will have its own wiring requirements. This is also true of sinks, if you have a washup area.
You need two ground rods for a sub panel if it is in a separate building and you will need to isolate the neutral from the grounding conductor in that panel. 20 amp light switches are readily available at Home Depot.
I was using 3-way switches, and I couldn't easily find any 20 amp ones. I'm sure they are out there somewhere though.What does a seperate building do to necessitate 2 ground rods? That is why is a seperate building any different from a single building?
Is this the latest? I just had my place rewired this past summer. Two ground rods were put horizontally just below the surface of the ground and hooked to the incoming panel (three hundred amps) mounted to the outside of the garage and fed the garage (100 amps), the house (200 amps) and the barn (200 amps). None of the buildings had separate grounds. Didn't even bother hooking up to the copper water line.
I'm not trying to jerk anyone's chain or submit that what you have is wrong. Ag buildings do have some different rules that I'm not that familiar with and am too old and stupid to learn now. I was an electrician and electrical supervisor for more than 40 years but I don't know everything. Here's a nice summary I copied this from another website rather than type out what the code says:
http://www.imsasafety.org/journal/janfeb/article1.htm
Ground Rods at a Remote Building or StructureThe NEC requires a grounding electrode system for each building or structure [250.50], and for buildings or structures fed from one common service [240.32]. Ground rods are part of the grounding electrode system...
An exception to [250.32] does not require a grounding electrode (ground rod) if only one branch circuit feeds the building or structure, and the equipment grounding (green wire) conductor is run with the branch circuit. [225.30] states a multiwire branch circuit shall be considered a single branch circuit. For example, a “three wire” branch circuit (2 hots, neutral and equipment ground) could be run to a remote sign, and ground rods would not be required.
Ground rods.
Do you think that only set of ground rods like I have could possibly be unsafe? I always figured the more grounding the better and questioned it first but then got to thinking - What difference does it really matter whether there are a few wooden boards that run continuously from one building to another to make one or more buildings?
Hard question to answer. Under certain circumstances it would be safer to have the additional groundrods. I don't have airbags or anti-lock brakes in any of my rigs. I'm not losing any sleep over it. : )
For more on whether to ground or not to ground, see the article at:http://www.iaei.org/subscriber/magazine/03_f/03_f_threechiefs.htmPete
When you mentioned, "I have a 200A service panel in the basement that is 40-50% full. Distance from the panel to the garage is about 15’. A home run from the farthest corner of the garage to the panel would measure 50’." does that mean that the usable spaces for circuit breakers is not nearly full or that of the available amperage only 40-50% is used. If you add up the amperage of the circuit breakers you are limited to what you can use in that panel. It is not controlled by the number of spaces but by the amperage.
This forum post is now archived. Commenting has been disabled