Please look at my garage electrical feed plans......

[gpalmer77]

New detached garage build about to begin, just thinking about electrical up front in case I need to do any prep work along the way.

• Garage is ~12 feet off the back of the house, to get to where I want the panel, I have about an 18 foot run underground.
• House main panel is in the opposite corner, so I have a 15 ft run across the house, then 35 feet to the back wall.
• Thinking 80 feet of wire total.
• My house has a 100 amp breaker in the main panel, I'm planning a 60 amp breaker to feed the sub panel.
• Typical homeowner/vehicle enthusiast usage, with a 110v lift, small air compressor etc. Just a 22x24 garage with one high lift bay, and an attic workshop above the low bay. Window unit A/C. Gas heat.
• #6 wire for the two hot legs and the common, #8 ground. This allows for small load 220V later if I need it.
• 1" conduit, metal inside the house, buried PVC outside the house (18" deep?)
• Separate 2" conduit for low voltage, cable, catv etc with a pull string. This may also get a 1/2" Pex water supply stuffed down it later, after the village signs off.

Some questions I still have.....

• Can I get a 60 amp panel with lots of breaker space for separating circuits? If not, will #6 wire tie into a 100A panel okay?
• Should I upsize my wire to #4 for the future? Cost is about double I believe.
• Will the 1" conduit be big enough? Conduit fill charts say yes, what does experience say?
• Can I run a #12 wire back from the garage in the same conduit for tying in smoke alarms to make the whole house go off if there is an alarm in the garage, or do I need a separate conduit run?
• Should I bring my PVC conduit(s) up through the foundation wall (install these sections during the pour next week) or wait and bring them in through the wall? Pros and cons here?

Thanks.

 

[wyliesdiesels]

Some initial things for u:

*You could actually use #10 for your EGC. #8 is for 100amps.
*You will need 2 ground rods @ the garage.
*Make sure the neutral bar is isolated from the panel enclosure and remove any bonding strap that connects the neutral bar to the ground bar or enclosure
*If you will have more than 6 disconnects, then you will have to have a main breaker panel instead of a main lug.
*18" depth will be fine
*I would never put a water line in the same conduit as communication wiring because if the water line ever sweated, it could cause the low voltage wiring to corrode. Yes, I have seen corroded multi-pair phone wiring, underground in conduit, that caused cross talk in a hotel phone system!

Your questions:

1) Yes
2) #4cu will only give u 20 more amps. If you are gonna have large 220v equipment running @ the same time like a welder, compressor, etc., I would consider going to a 100a feed. U would need #3cu. However, with that being said, u mentioned your main service is only 100a, so u may be limited depending on what your connected load is. Have u done load calcs for everything? Do u have any large electric appliances- dryer, hot water heater, baseboard heat, A/C, hot tub, etc.?
3) Yes, 3 #6 and a #10 will fit fine in 1" pvc.
4) Yes, but I believe code says u have to run 3 #12(hot, neutral and ground/a complete circuit) instead of just 1 wire
5) I would bring it up through the slab wall so it's in the concrete. Put a sweeping elbow @ the bottom. This will be way easier to pull than LBs plus it looks cleaner this way. If you choose to instead bring it through the wall u would have to deal with LBs.

 

[VHF]

Use 1 1/2" conduit for your power feed. Makes the pull easier and you are good if you ever need to upgrade to 100A in the future.

A 100A subpannel is the least expensive way to get room for lots of breakers. Need to check to see what the manufacturer says is the minimum wire size for the incoming feed.

#3 CU would give you a full 100A service (but at a higher cost.) #2 AL would allow you 90A to a detached garage at a lower cost, but need to work with heavier gauge AL wire.

Even if you don't need the full 90/100A, the larger wire would reduce voltage drop for your lift, compressor, etc.

Doing a 60A service as you proposed with #6 wire would certainly be easier as well as limit costs. But definatley use a 1 1/2" conduit (unless you are absolutely sure you will NEVER need more than 60A out there... thing is, "never" is a very long time!) Would be good to do a voltage drop calculation to make sure you are OK with #6 wire for your current intended use.

Stubbing the electrical feed up through the slab is a nice touch, the trick is exact positioning so it comes up through the center of the sill plate. I did this on my detached garage with 2 courses of block and 2x6 walls. Turned out pretty well. I put in 1 1/2" for power, 1" for communications, 3/4" for power out to my garden shed, and 1/2" for wire to ground rods. All come up through the slab, through the center of the concrete blocks, through the sill plate and into the stud cavity under the breaker pannel. Only thing I might change is upsize the communications conduit to 1 1/2" and move it 16" away from the incoming power so it comes up in a different stud bay.

If you don't stub up through the foundation, then you would typically run exposed conduit up the outside wall and then use an LB to make the turn into the building.

You might want to add a separate 3/4" conduit for your smoke detector wires. While they would be allowed to share the large conduit with the main feeder, it is nice to keep them separate to avoid physical damage or tangling with the larger wires.

One more thing to consider at this point is do you want a 3-way switch between the house and garage to control stoop lights from either location? (i.e. be able to switch on/off the garage stoop light from the house.) Those wires could share a 3/4" conduit along with your smoke alarm circuit.

 

[gpalmer77]

4) So essentially I would need to extend the smoke detector circuit out into the garage from the house? Has anyone else done this where the conduit feeding the garage has the 60A breakered feed coming in, together with a single circuit fed from the house that goes right through the subpanel without terminating? Wonder if there might be any clever systems out there to accomplish the same thing..... an alarm in the house when the smokes go off in the garage.

 

[gpalmer77]

Use 1 1/2" conduit for your power feed. Makes the pull easier and you are good if you ever need to upgrade to 100A in the future.

A 100A subpannel is the least expensive way to get room for lots of breakers. Need to check to see what the manufacturer says is the minimum wire size for the incoming feed.

#3 CU would give you a full 100A service (but at a higher cost.) #2 AL would allow you 90A to a detached garage at a lower cost, but need to work with heavier gauge AL wire.

Even if you don't need the full 90/100A, the larger wire would reduce voltage drop for your lift, compressor, etc.

Doing a 60A service as you proposed with #6 wire would certainly be easier as well as limit costs. But definatley use a 1 1/2" conduit. Would be good to do a voltage drop calculation to make sure you are OK for your intended use.

Stubbing the electrical feed up through the slab is a nice touch, the trick is exact positioning so it comes up through the center of the sill plate. I did this on my detached garage with 2 courses of block. Turned out pretty well. I put in 1 1/2" for power, 1" for communications, 3/4" for power out to my garden shed, and 1/2" for wire to ground rods. All come up through the slab, through the center of the concrete blocks, through the sill plate and into the stud cavity under the breaker pannel. Only thing I might change is upsize the communications conduit to 1 1/2" and move it 16" away from the incoming power so it comes up in a different stud bay.

If you don't stub up through the foundation, then you would typically run exposed conduit up the outside wall and then use an LB to make the turn into the building.

You might want to add a separate 3/4" conduit for your smoke detector wires. While they would be allowed to share the large conduit with the main feeder, it is nice to keep them separate to avoid physical damage or tangling with the larger wires.

One more thing to consider at this point is do you want a 3-way switch between the house and garage to control stoop lights from either location? (i.e. be able to switch on/off the garage stoop light from the house.) Those wires could share a 3/4" conduit along with your smoke alarm circuit.

Some great points in here..... thanks. It would be nice to control the outside lights from the house. So a separate conduit might be the answer.

Forgot about the grounding rods..... so the 1/2" conduit just runs open ended into the ground? Are the entire lengths of the grounding rods and the connecting wires completely buried? I guess I pictured the top of the rods sticking up, but I've never dine that before.

I'm also looking at conduit for gas line (radiant floor heat), at least just an elbow through the footing, for threading the end of direct burial gas line through later. Guessing 1 1/2" PVC is okay for this.

I'm having a separate footing poured, 10" wide with a 6 1/2" gas curb (for a 6" wall with 1/2" OSB and 1/2" drywall to sit flush on), so centering the stub-ins through the slab should be easy once they do all the form work.

I need to figure all this out by the weekend, should be pouring next week. Goal is to just put in the vertical stubs, a sweep 90 in the right direction and enough horizontal to get away from the footing. Cap both ends, dig it out later when it is time to run everything from the house. I'd like to have everything concealed where it enters the garage, avoiding as many LBs as possible.

Thanks for the advice.

 

[VHF]

There are smokealarms that form their own wireless network. You can combine hardwired and wireless units and they will all go off together. But I'm not sure if the range is good enough to reach out to the garage.

#14 wire should be sufficent for smoke alarms as long as it is on a 15A circuit. It it prefereable that all the smoke alarms are on the same circuit, thus the need to run hot, neutral, and a trigger wire (as well as ground.)

There are probably ways to acomplish this with relays and a dry-contact trigger for the garage smoke detectors, but this starts to get into more commercial/custom territory instead of the low cost residential 120VAC hard-wired detectors.

Note that normally the NEC requires there only be a single power feed to a detached structure with an appropriate single point of disconnect to kill all power in the detached structure. However, an exception allows separate circuits for special applications that need to be controlled separately, such a 3-way light switch between buildings. I think a circuit to power interconnected smoke detectors would also fall under the exception.

If the wires shared a conduit with your main feeders then yes, they would need to pass through your garage pannel. If they were in their own conduit then they wouldn't nescessarly have to pass through the garage pannel.

 

[VHF]

Forgot about the grounding rods..... so the 1/2" conduit just runs open ended into the ground? Are the entire lengths of the grounding rods and the connecting wires completely buried? I guess I pictured the top of the rods sticking up, but I've never dine that before.

Yes, all buried, clamps and all. Top of the rods about 6" below the surface. Second rod 6' away from the first, continous #6 bare CU wire connecting both rods to the ground bus in the panel.

I need to figure all this out by the weekend, should be pouring next week. Goal is to just put in the vertical stubs, a sweep 90 in the right direction and enough horizontal to get away from the footing. Cap both ends, dig it out later when it is time to run everything from the house. I'd like to have everything concealed where it enters the garage, avoiding as many LBs as possible.

Sounds like you're on the right track... Duct tape makes a good temporary conduit cap!

You might put in an extra sweep for future seasonal water line, air line, or some other application. Just label "future" and don't say what for if you are concerned about inspection. All kinds of things that might need a conduit in the future--landscape lighting, electronic dog fence, security system etc.