Determining Circuits

[Spudland_Dave]

So how do you guys determine what your gonna run for circuits. Heres my issue or question...
All along I was thinking I was going to seperate everything out individually..for example, Garage Door Openers on on its own, Exterior Recept on its own, various circuits for banks of recept's. Now that real world wiring has started, I'm starting to see my thought is going to be wasteful in terms of wire. For example, in one single stud bay I've got a recep. inside and one outside...using my old mentality, thats 2 circuits. factor in that run will go 6" away from the recep for the Liftmasters, and I could use that one circuit and one wire for 5 recepticles. Which IMO isnt out of line for a 20A circuit...and save me a bundle of wire in the long haul.

SO that being said..should I approach wiring the garage more like a house where everything in a room or area is a circuit vs its specific use within reason?

 

[ddawg16]

So, you think your the only one who struggled with that question? Actually....it's a very good question....and gets discussed a lot.

For the most part, you have to look at concurrent loads....what is the worse possible load you could have going at one time? Also helps you decide how much power to supply to the garage....no need for 100A if the biggest concurrent load you have is maybe 30A.....

So......worst case...air compressor, mig welder, AC or heat and lights running at the same time.

I put my opener on the same ckt as the lights.

Compressor needs it's own ckt...same for a welder....

Outlets....some differing opinions here....some say put outlets on alternate ckts....others do it by wall....mine are split by wall....the chances of my running two power tools at the same time are slim.....worst case, I will run my table saw and the shop vac at the same time....so the saw is on one ckt...shop vac on the other.

 

[kert]

I'm at a similar stage. I'm figuring if I have multiple circuits running around anyway, I might as well alternate. Thinking Maybe outside lights and openers on one circuit and a couple circuits for inside lights so I can still have light if I'm working on one. I'm probably looking at dedicated circuits for all my 220 items.

Another option would be 12-3 wire and alternate red and black. Not sure if this is up to code though. Also the last time I priced 12-3, it was more than 2x 12-2, so no cost savings.

 

[ddawg16]

I'm at a similar stage. I'm figuring if I have multiple circuits running around anyway, I might as well alternate. Thinking Maybe outside lights and openers on one circuit and a couple circuits for inside lights so I can still have light if I'm working on one. I'm probably looking at dedicated circuits for all my 220 items.

Another option would be 12-3 wire and alternate red and black. Not sure if this is up to code though. Also the last time I priced 12-3, it was more than 2x 12-2, so no cost savings.

That is called a MWBC and is ok...as long as you use a tandem ckt breaker...in other words, if you trip one side, the other has to trip as well....

At least, that is how I understand it....hopefully one of the experts will chime in...

 

[lakee911]

That is called a MWBC and is ok...as long as you use a tandem ckt breaker...in other words, if you trip one side, the other has to trip as well....

At least, that is how I understand it....hopefully one of the experts will chime in...

Close, but no cigar ... MWBC needs to have a common disconnect, not common trip. Common disconnect is achieved with a handle tie. You can also use a two-pole breaker to get common disconnect, but you'll also get common trip instead, which isn't always desired.

I don't think tandem is an industry standard term, but what it typically means is a special breaker unit with two breakers in the space of one. If it's a single pole breaker you'll be overloading your neutral by 2x if you wire it up 'like a MWBC.' They make units that are four breakers in the place of 2P and some of those can be made to properly work with MWBCs.

Certainly seperate out your lighting from receptacles and I personally like the GDO on it's own circuit. I believe these days the GDO needs to be on a GFCI circuit. To prevent having to climb up on the ladder for test and for reset, either use a GFCI breaker or daisy chain the GDO receptacle off another one that's mounted in a easily accesible location.

 

[Alchymist]

Run as many (2 or 3 perhaps) around the garage for outlets, GFCi in the first box on the circuit inside, and put any outside outlets on one of these circuits. Put another outlet where convenient with a GFCI and feed from that to the GDO outlet. Lights on a separate circuit, so they don't go out when/if a power tool trips a breaker or GFCI. 240v circuits usually dedicated runs to individual machines.

 

[Spudland_Dave]

Certainly seperate out your lighting from receptacles and I personally like the GDO on it's own circuit. I believe these days the GDO needs to be on a GFCI circuit. To prevent having to climb up on the ladder for test and for reset, either use a GFCI breaker or daisy chain the GDO receptacle off another one that's mounted in a easily accesible location.

No code, and I cant stand GFCI with certian tools...so I will not put any in, only GFCI I plan on is the one on the exterior of the garage.
Lighting circuit is already done, nothing but interior lights on one circuit, exterior on another. I WOULD have put the GDO Recept's on its own in the cieling, but going with the LM3800 puts them on the wall, right above a 20A Recep circuit. I've got my holes drilled, hopefully will run wire tonight depending on weather, but the GDO recpt is 6" above the hole for the recep feed...so wiring wise, I could wire it with scraps of 12-2, vs running 25' of new 14-2.

Big dedicated loads like my 50A for Welder, 30A for Compressor, and things like that become simple so to speak...it is what it is.

Why I started contemplating it was I just got lighting in on exterior and interior for the front half, and i'm burning thru the 14-2 at an alarming rate....AND I'm finding I'm drilling more holes then I thought I would to pass all the wiring.

 

[Gary S]

Wire is never wasted if it is in the wall working, so be generous with it.

I ran one circuit for my garage door openers on the ceiling. I ran 6 circuits around the wall. I ran 1 circuit for my 120v compressor, 1 for the outside receptacles and 1 more for my refrigerator. The lights are on 3 separate circuits.I have about 30 receptacles.
For 240, I ran two circuits for my electric heaters and one for my 240v compressor.

When the wiring is done, and you walk up to any wall in the garage, you should be able to reach a circuit without taking a step aside. If not, you cut yourself short.

 

[kert]

That is called a MWBC and is ok...as long as you use a tandem ckt breaker...in other words, if you trip one side, the other has to trip as well....

At least, that is how I understand it....hopefully one of the experts will chime in...

Actually the breaker should be double-pole, not tandem. I think that is what you meant. It is important that the hots be on opposite legs so that the neutral won't be overloaded.

 

[Falcon67]

I just eyeballed it work a while on paper. I tried to look at the sub spaces inside the big box and how I was most likely to use those smaller spaces.

I have two plug circuits in the general work area and two in the bench/machine area. Lights were split into two circuits with the outside lights going on the #2 run because of fewer internal bulbs on that run. I ran one 120v plug circuit to the spot where there would likely be a larger AC unit installed. The light circuits all have lots of switches so I can light just where I need.

220V runs are all separate - heater, compressor, mill, well pump. There are 5 spaces left, so a 20 slot box was adequate. There are several 3/4HP motors that can end up on the same general use outlet circuit, but I can only run one or two at a time. Most of those motors are metric 3/4 chinese HP anyway. I'll probably never put in a door opener, but if I do I'd just tie it into one of the plug runs because it use would be very intermittent. I'd just plumb a switch to shut it off.

I also came in with power on the wall closest to the house to minimize the power run. Duh-oh, most of the circuits were on the other end. Hindsight would have placed the breakers on the wall near the center of the shop. It would have still been reasonable on the voltage drop and would have saved at least 250' of 12-2. But the cost figures show that center location would have been a wash except for my labor. A subpanel with a 50 or 60A feed actually came in more expensive that running more 12-2 all the way from one end to the other.

 

[Stuart in MN]

No code, and I cant stand GFCI with certian tools...so I will not put any in, only GFCI I plan on is the one on the exterior of the garage.

You may not have local inspections, but the state of Maine does follow the 2011 revision of the National Electric Code.

 

[Falcon67]

No code, and I cant stand GFCI with certian tools...so I will not put any in, only GFCI I plan on is the one on the exterior of the garage.

Every run in my shop except the lights and dedicated machines starts with a GFCI. All plugs are protected. I have had zero issues with tools and GFCIs, including drill presses, lathes, the MIG, etc. Code, schmode - I don't want to get taken out by a shorted Chinese motor case and a spilled drink, thanks.

 

[48Classic]

Do not know how large your shop is. When I helped with my brothers 40 x 40 shop. We ran the lights on 2 different breakers. Also alternating the Load. Row 1 and 3 are on one breaker and row 2 and 4 are on the second breaker. We also did this if he just need to walk in and tinker or both when it is time to work. Wire the shop power every 4 feet with 3 outlets per breaker. Also took a sharpie to all the wall plates and wrote the breaker number on each wall plate. Don't know who many times you pop a breaker and can't remember which one. Good luck and remember code is your friend...

 

[pitterpat]

Another option would be 12-3 wire and alternate red and black. Not sure if this is up to code though. Also the last time I priced 12-3, it was more than 2x 12-2, so no cost savings.

Just bought some 12-3 and it was only about 65% more than 12-2....Menards is the same price as Lowes.

 

[Spudland_Dave]

Howd this thread turn into a safety rant on GFCI's?

IN terms of the MWBC, I had another post here a week ago and while it sounded good on paper, in the end, I didnt think it sounded like the hottest of ideas.