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Shed electrical questions.

8.3K views 43 replies 10 participants last post by  ibewjon  
#1 · (Edited by Moderator)
Hello,

I'm currently building a detached shed, so we can clean up our garage to use as a small workspace.

The other goal of the shed is to install dust collection and an air compressor.

I've been reading the portion of the NEC that covers MWBC's(210.4), and trying to make sense of it all.

Basically, I need 2×20a circuits. Since I can't run two separate circuits into the shed, I'll need to utilize a Multi Wire Branch Circuit.

I think I've got things figured out, but I just want to run things by some more knowledgeable resources.

Here's my breaker box:

Image


The cable run will need to come out the back of the box. I was thinking that unused mounting hole in the bottom left pic. Similar to the one on the lower right that was used when our AC was installed.

My shed is just behind the breaker box on a small slab we had poured last year. The cable run will be very short. Less than 15 feet away from the breaker box.

I've been trying to read as much as possible on MWBC's. I'm comfortable around electricity. I plan on doing the job myself, and saving roughly $3k.

I want to pull all the permits and do everything correctly, I'm just trying to get my ducks in a row first.

Here's a sketch I found that looks like exactly what I want to do:
Image


For those who are familiar with powering their own shop, does this look correct for what I'm looking to do?

I know I need to free up some space in the box. I've been looking at the use of tandem breakers to do so.

Any help would be awesome!
 

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#30 ·
I agree with the Captain above.

- bmerrill
Oh yeah. I don't disagree one bit.
I'm just trying to dumb it down to my level.

This portion specifically:
Replace the #1 location 2 pole breaker with 70-100A breaker, wired into a 125A sub-panel next to the original. Connect the one existing 240V circuit to new panel with wire nuts (tape wrapped/sealed to met code). Then wire new shed power from the new panel. I know this seems extreme, but it is minimalist approach to changing the old wiring - swapping one circuit for another. Plus the 1st locations on top of most panels have higher bus current rating, and special exceptions on bus bar current limit calculations.

I can visualize replacing the 30a for a 70-100 then running that to a sub panel. So then am I putting the 30a in the new sub panel via proper pigtails?

Also. Even with doing that, if I wanted to run 2 circuits to the shed, don't I still need utilize an MWBC? To my limited knowledge, I can't run 2 circuits into the shed and an MWBC counts as 1.

Or should the sub panel be in the shed? It would be weird to have our dyer circuit in a sub panel in the shed, but not a huge deal.
 
#32 ·
Image


Here's what I have. Just trying to figure out the tandem breaker situation.

- Derrick
Can't find the manual for the panel either? Best I can determine is you have older EQ III series panel.

This web page describes use of tandem breakers with pictures that might help you figure it out?
http://www.startribune.com/how-to-know-when-tandem-circuit-breakers-can-be-used-aka-cheater-breakers/140688183/

I can visualize replacing the 30a for a 70-100 then running that to a sub panel. So then am I putting the 30a in the new sub panel via proper pigtails?
- Derrick
Yes. Move the old breaker into new panel and pigtail the wires from old cabinet to new cabinet. Plus install the (2) new 20A bridged beakers for shed.

Even with doing that, if I wanted to run 2 circuits to the shed, don't I still need utilize an MWBC?
- Derrick
Yes. Still need to install same multi-wire circuit. The new panel is only there to remove the need to change (4) simplex to (2) tandem breakers and worry about the new code ramifications. If you cant use tandem breakers, this may be the only solution. lol
Technically speaking, if the shed is hard mounted to concrete pad, conduit is used between locations, and only outlets are installed in shed; you don't need the disconnect switch in the junction box to shed. Disconnect switch is only required on hard wired devices like HVAC or SPA; where you need to disconnect remote device from breaker for service work. With outlets in shed, you can unplug the compressor/DC for service.

should the sub panel be in the shed? It would be weird to have our dyer circuit in a sub panel in the shed, but not a huge deal.
- Derrick
I would put the new panel next to old one. Keeps the 30A jumper wire short and simple. No one should have to hunt for dryer breaker.

Cheers!
 

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#33 ·
Ok. That's not an obscene amount of work.

Is there a need for any new ground rods to be installed, or am I good to go with whatever is currently in place?

Also, if I don't need any sort of disco between the conduit and the liquidtight, would an exterior rated work box go in place?

I've seen videos where there is a service loop within the boxes when a transition is made. Does that make sense?
 
#34 ·
Is there a need for any new ground rods to be installed, or am I good to go with whatever is currently in place?

Also, if I don't need any sort of disco between the conduit and the liquidtight, would an exterior rated work box go in place?

I've seen videos where there is a service loop within the boxes when a transition is made. Does that make sense?

- Derrick
- No new ground rod.
Only need new ground rods when sub-panel installed in remote structure. I.E. Putting the sub-panel in shed would need new ground rods.

- yes, exterior rated, weatherproof box is used for conduit junctions in weather exposed locations.

- sorry, not following the last question?
 
#36 ·

This seems to be what I'm looking for. Hopefully I'm not breaking any rules by posting a video.

The video all made sense, but I saw one particular comment saying that he shouldn't have had exposed wire in the wall. It should have been conduit from the main panel to the J-box.

Obviously I need an inspector to verify what I need for my specific city, but for those in the know, does this install look up to snuff?
 
#38 ·
The wire type used in video needs to be totally enclosed in conduit when inside the structure. He could have used SER cable.

- WhyMe
Ok. That's not a huge change. Did you see any other issues?

In my garage the sub would need to be just as close. I'm trying to find a reference number for the NEC, that tells me all of the installation requirements, but I'm coming up empty. The only thing I've seen is that the top of the box can't be higher than 6'7" or something along those lines. I'm just looking for more info.

Thanks again for the help!
 
#39 ·
You will not find a single code article to cover your installation. Each detail is covered in a different article, section, subsection, note, and so on. Grounding, overcurrent protection, conduit. The book gets thicker every third year with new and changes to old. And many local areas have their own additions, as the NEC is the MINIMUM standard. Around northern Illinois, many areas of not allow Romex. Conduit only.
 
#40 ·
You will not find a single code article to cover your installation. Each detail is covered in a different article, section, subsection, note, and so on. Grounding, overcurrent protection, conduit. The book gets thicker every third year with new and changes to old. And many local areas have their own additions, as the NEC is the MINIMUM standard. Around northern Illinois, many areas of not allow Romex. Conduit only.

- ibewjon
Yep. I was starting to piece that together last night, as I got deeper into reading.

I'm looking at the permit application form right now for my area. I still don't think the job warrants the $3k I was quoted.
 
#41 · (Edited by Moderator)
I'm looking at the permit application form right now for my area. I still don't think the job warrants the $3k I was quoted.
- Derrick
Obviously this is new for you. Contracting electrical work is strange beast, especially if permits are required. There is wide range in what electrical contractors charge.
Cardinal Rule: If you don't like price quoted: get more quotes!

$3K for what work you are claiming is needed, seems too high from my desk chair?
But #IAMAKLUTZ, what do I know? :)

Not defending the price, but let share some info that might explain building contractor quotes:

- Creating permit documentation is not hard, but it takes ton of time. Most large electrical companies charge $750-$1500 for small project permitting process. Small private contractor is usually 25-40% less. Time costs money. Licensed/bonded electricians are worth a minimum of $25-35/hr, plus $5-$20/hr in benefits. Senior folks get even more.
Spend 8 hours filling out forums, documenting existing wiring, drawing a cad drawing; all to submit a simple permit package, and someone owes them $250-$750. If the package needs editing due refusal, double the cost. Permit work is such a PIA, large companies have desk jockey Sr. electricians who do nothing but permit paperwork and drawings to help guarantee better 1st time success and lower overhead costs.

- Permits requires several inspections. Each one can be huge time suck. The wasted time is exaggerated on small job where it's less than a days work. Ever called government office and tried to make an appointment? Some are wonderful, and others are nightmare. Then there is waiting an hour for inspector to show up. Every inspection cost 2-3 hours, and they are usually 2 visits on small jobs and 3 on large jobs. Multiply wasted 4-9 hours by labor+benefits and the cost for permit climbs higher.

- DIY always under estimates the parts cost, even after getting ripped off by retail stores. Lots of small bit required in new panels. Don't forget the 1-2 hours lost running across town to buy parts and deliver to site, or add $50-75 for commercial delivery.

- This is gross over simplification, but building contractors usually have 3 pricing levels:
First; Not working, need money for food anyway I can get it, or the cheapest rate. Also called friends and family rate.
Second; Need money but life is comfortable and not working for free.
Third; Way too busy to be bothered with projects where I can't earn a hefty profit.

When construction is booming and electricians are in high demand; small permit jobs are annoying waste of time and always priced higher. They spend nearly same amount of permit/inspection time on small or large job. Know a couple guys who openly admit they double the quoted price for jobs when the work backlog is more than a couple months. They don't really need or want more than a couple small non-permit jobs a month as filler.

Bottom line:
IME - Can usually find someone willing to install a sub-panel with (~$150-250 in parts) without permit process for $500-700, when work is slow. It costs me double if I ask them to submit the paperwork instead me doing it, and deal with inspectors. Costs 3-4 times more when they are really busy. YMMV

Cheers!
 
#42 · (Edited by Moderator)
Two points to consider.

1.I vote for a sub panel with individual breakers for lights, outlets, and any equipment for multiple reasons. It will give you max flexibility if you do anything else in the shed.

2. In our area, you have to be a certified electrician to pull a permit. But it is not the process described above at least not for my job. I was updating the main panel, and running a few lights and outlets. We didn't need drawings, and I think applying for the permit was about a 10 min job at city hall. When I remodeled a commercial building, I consulted a certified electrician who agreed to pull the permit and inspect my work. I paid him for his time to inspect my work and make the tie-in to the panel go live. I seem to recall he charged me $150 for everything. he had about 2 hours in the job. And he wanted to hire me at the end.
 
#43 ·
Cin2929, great you got someone to do that, put their license on the line for so cheap.
CaptainKllutz is correct on some of the pricing and what not, but a small job like this pulling a permit (depending on your local ordinance) shouldn't be a big deal. Yes the inspection is a pain/ waste of time if you have to be there at the same time, I had (retired 30 yrs. Master) great relationships with the inspectors in my area and didn't need to show when they did; got a phone call when they were at the job (including million dollar jobs) if they had questions.
Go with the sub-panel, remember this about price what do you pay a doctor, auto shop, plumber, lawyer, who is the only one that will probably never be back, the Electrician; so pay up.
 
#44 ·
As a retired electrician, even after over 40 years in the trade, the small jobs still take much longer than expected. A one day job, and if you find something unexpected, another trip to the truck or maybe the store. On a large job, there is tomorrow or the next day to finish the details. Doing a small job next door to big org, blue or green, and a quick trip into the store for a small part is still a half hour to an hour. Small jobs are tough, I did them for years, as well as multi million dollar electrical jobs. And don't forget the cost of insurance. Workman's comp, vehicle, and liability for anything that might happen in your house. Even if not related to the last job, that contractor was still on the property and will be dragged in. I will never do a "side job " or moonlight because of the insurance costs. I am not losing my home and savings for a little cash. Not even for friends.