Electrical Questions - Wire to the workshop

[manfre]

I have a good plan about what I'm going to do with wiring inside of the workshop and the only real hurdle is getting the wires from the house to the workshop sub-panel. I just got an estimate back for completely wiring the shop from the main panel and it's almost $1000 more than I was expecting. I'm shifting back toward doing it myself, even though this means my limited free time will be spent wiring the shop instead of using it.

Basic Info

Main service is 150amp. The workshop panel will be 100-125amp and is ~20' (line of sight) from the main panel (~40' of cable needed).

One plan is to put in an outdoor panel at junction (yellow circle) and replace the wire and conduit (orange line) with 125 amp. The junction panel would have a 60 amp breaker for the air handler that is currently in the conduit, and a 100 (or 125) amp breaker for the workshop.

Is 125 amp feeding in to the junction panel enough to support the 60 amp air handler plus either 100 or 125 amp for the workshop? Does the junction panel need a main shutoff and grounding rods like the workshop's panel?


The workshop will need GFCI outlets or breakers. If a GFCI breaker is put in the junction panel, would that cover the entire workshop or does the GFCI protection not work that way?

 

[gator]

When I built my shop, I did all of the internal wiring myself, outlets, panel box, switches, lights, etc. I hired an electrician to run from the main panel in the house to the sub-panel in the shop and do the main hook-up. I also had him check all my wiring so it would pass inspection. He had to trench from the house to the shop for the wire so I laid down a 3" conduit beside the wire for telephone, tv, etc pulls to the shop.

I have basically two 110V outlet only runs in my shop, a GFCI outlet at the first station will cover the rest of the run so I only had to install two.

George

 

[Rhythm House Drums]

I'm in the process of wiring my shed now... 100 amps from the house to the shed on a 200amp main.

I think you'll need either individual gfci breakers or gfci outlets. 240 outlets don't have to be GFCI. and if you are running more than one outlet on the same circuit, only the first one has to be GFCI.. the others will be protected by that one since they all share a neutral. Most my outlets are dedicated 20amp (I only ran 15amp for the lights) so I had to pony up the cash for the GFCI on all of them.

You might want to think about upgrading your main service to 200amp. Running a workshop/house/and 60 amp air handler (not sure what that is) is going to be pushing it... assuming you've got a 15 amp table saw, a 14 amp DC maybe a small fridge 4 amps and lights 5 amps and a radio... 4 amps.. that's I don't know... 50 amps you'd be pulling, then if the air handler pulls 60, and you're wife turns on the oven or dryer... hut oh!


BTW I have some 100 amp SER (2 sections of about 25 feet) that can be run in conduit above ground.. if you need some...

 

[HMH]

I agree w/ Kevin, that drawing a 125A subpanel off of a 150A main is probably pushing it a bit. In an ideal situation, I would suggest an upgrade to a 200A main, although that can get expensive, and there are a few ways to work around it.

Do I understand from your diagram that you will be running your air handler off of the 125A "available shop power"?

If I recall from your posts about you workshop, it is a relatively compact space - not a pole barn ala Scott Smith. That will be a good thing here.

One key suggestion I would make, is that 220V power draws half of the amps of 110V power, therefore, I would suggest you convert what you can, (TS, Dust Collector, DP, BS, etc) to run off of 220V to conserve amps. Other tools, (sanders, routers, drills, etc.) that must stay on 110V power, will have a relatively low amp draw anyway - plus I imagine it would be rare that these tools would be run simultaneously. Probably wost case scenario is TS, DC, and an ambient air filter running in the shop, (8A* + 8A* + 3A = 19A) not too bad - garage dwellers like myself do that all the time with no problem.

*Assuming 220V input

I would suggest running the wiring inside the shop yourself - it takes time, but it's fairly simple , and will save you, (and your tool budget), a good bit of cash - Remember, if you spend it ON the shop, you may have a hard time convincing your wife to let you spend it IN the shop.

I would suggest you hire a pro to run power from the main to your subpanel in the shop, this will help alleviate any headaches w/ permitting, code compliance as it relates to re-sale, inspections, etc.

Good luck!

 

[manfre]

Air handler

Only overloaded circuits will draw a non-peak load of more than ~80% of what the breaker can handle. For example, you shouldn't plug a 13 amp TS in a 15 amp outlet.

Upgrading the main service would be a very costly and unnecessary expense at this point. I plan on upgrading the service a few years down the line, as part of an addition project. 150 amp is plenty for my house because most of the high amp items will not be used at the same time. I'm expecting to draw at most ~60 amp from the workshop. Putting in 100-125 amp is mostly room to grow to allow for future use without needing to rewire. I only need a 75 amp line to the workshop to handle everything I have planned.

3 HP TS - 13 amp
DC - 11 amp
Air filter - 3 amp
lights - 5 amp
air compressor - 13 amp
heat or A/C - 15 amp
Worst Case Total: 60 amp

 

[Bas]

Where exactly is the main panel located? Is it next to the door? I'm not sure that putting in a panel just to serve as a junction point is cost efficient. You might be better off leaving the existing line to the air handler intact and just add a second line (60A or so) for the workshop. If going that route, I'd simply go with larger conduit and run both lines in one tube, with a junction/ Tee at the spot marked with the circle. But I don't know how far the existing air handler line runs, disconnecting it and running it through the new conduit may be a headache. Easiest would be to use separate conduit for the new line. If neatly installed, having two conduits run parallel wouldn't look all that bad.

I agree that there is nothing wrong with using a 100A sub panel even if you never plan to actually draw that much power. Extra room for individual circuits is a nice thing to have. I have a 100A panel (with feeder wire to match), but I have it throttled at the main panel using an 80A breaker.

 

[manfre]

The main panel is to the left of the door where the orange line ends. I'll need to double check with an inspector about whether or not a junction panel is actually needed. The electrician said the inspectors will want the panel because it should be possible to disengage all wires in a conduit/junction with a single disconnect. I'm not sure if that is an actual requirement or just demanded by some inspectors.

A second conduit would be the ideal, but there is no more room under the door. I don't want to run conduit along the fence because I would like to put a gate from the patio to the front yard with a little sitting area. Sitting area benches will be made in the shop! I probably cannot trench around the patio because of the giant crepe myrtle's roots. I might do some exploratory digging. My wife would probably divorce me if I killed the tree. I'm trying to convince her to let me cut down the giant crotch that overhangs fence about 4.5' off the ground. It would make a really good carving mallet and make the future project of replacing the fence a little bit easier.

I did have the idea of trenching as far as possible behind the patio and then tunneling under it to avoid the roots. That would be a lot of effort and probably require a junction panel worth of tool rentals/purchases.

 

[junquecol]

I have a 60 amp feed into my 100 amp panel in the shop. Needed the100 amp to have enough spaces. I have all the ususal suspects; air compressor, TS, RAS (2), band saw (three), dust collector (1.0 HP), 15" and 13" planer, 6" jointer, 2 lunch box planers, metal cutting band saw, mig welder, and stick welder along with the usual line up of hand tools. Never, not once, have I tripped the main. Remember that a 60 amp 220 service is actually 120 amps at 110. Where did you come up with that 80% rule? If it were so, then most 110 volt contractor's saws couldn't be sold, along with jointers, RAS's, and band saws. The Delta contractor's saw is rated for 1.5 HP on 110, and 2.0 HP on 220. They down rated the HP so it could be used on a 15 amp circuit. My TS has a 2.0 HP motor on it, and it runs on a 20 amp circuit, along with a couple of lights. Only when doing a bunch of ripping will I ever trip the breaker. You can get around the GFCI rule by "hard wiring" your machines. You will find that a couple 220V 20 amp circuits, and a couple of 110V 20 amp circuits will serve your needs.

 

[manfre]

The 80% deals with continuous load, not short bursts. When you trip the circuit while ripping, it is due to the circuit not being big enough to properly handle it. The 80% load is stated in the NEC.

 

[JimmyC]

I have a 60 amp feed into my 100 amp panel in the shop. Needed the100 amp to have enough spaces. I have all the ususal suspects; air compressor, TS, RAS (2), band saw (three), dust collector (1.0 HP), 15" and 13" planer, 6" jointer, 2 lunch box planers, metal cutting band saw, mig welder, and stick welder along with the usual line up of hand tools. Never, not once, have I tripped the main. Remember that a 60 amp 220 service is actually 120 amps at 110. Where did you come up with that 80% rule? If it were so, then most 110 volt contractor's saws couldn't be sold, along with jointers, RAS's, and band saws. The Delta contractor's saw is rated for 1.5 HP on 110, and 2.0 HP on 220. They down rated the HP so it could be used on a 15 amp circuit. My TS has a 2.0 HP motor on it, and it runs on a 20 amp circuit, along with a couple of lights. Only when doing a bunch of ripping will I ever trip the breaker. You can get around the GFCI rule by "hard wiring" your machines. You will find that a couple 220V 20 amp circuits, and a couple of 110V 20 amp circuits will serve your needs.

I completely agree with Bruce's assessment of needing "only" a 60amp/220v feed into your garage . In the past I also ran a 60amp main breaker to a 100amp panel to get extra breakers, and I never tripped anything even when running a 3hp Jet TS w/ a 2hp Grizzly dc, a 3.5hp a/c, a full bank of lights with an air conditioner running. I'm not sure that one person in a normal shop will have more than that running at one time. More power is better , but only if available.

Good luck,

 

[Phil S]

I also agree that a 60 amp feed to a 100 amp panel will be more than enough power and circuits. If you choose this route you will need to run three #6 gauge conductors plus a #10 ground. Just as shown in your drawing, I would mount a plastic pull box (not junction box) where you want to breakout to the shop and upsize the conduit from the house panel to the pull box. You will probably need to move up to 1 1/4 conduit for the combined run. The pull box to the shop run could be 3/4 as three #6s and a 10 will fit in 3/4, you will need to pull them with a strong pull string. You should use copper #6 thhn wire not 6/3 cable use that will not fit in the conduit and is meant for direct burial.
This wire should be continuous from your house panel to your shop with out a splice or junction - that is why I called it a pull box rather than a junction box. You really want to avoid extra connections that can fail because when they fail the get very hot and cause fires, not a good thing when mounted to your house. The existing wire that feeds your HVAC unit will need to be pulled out and then repulled thru the new conduit - again no splices please.
The panel that you install in your shop will need a slight modification. The neutral bar will need to be debonded from the metal cabinet - you just need to remove the bonding screw.

I think you will find this quite easy to do and you can save some tool coins

 

[DaveD]

I'm not an electrician but have always been comfortable doing my own wiring (to code of course).

Tell us what is in the box that is under the meter head. I'm going to assume its a box with several breakers in it. One feeds the main distribution panel in the house and another breaker goes to the outside, 60A 'air handler'. Hopefully it has a spare slot in it for a shop breaker.

Here is what I would do and why. Increase the conduit size from the box under the meter head to the end of the patio so it can hold the wires for both the air handler and the workshop. This assumes you can put another breaker in the box under the meter head for the shop.

The breaker for the shop can be whatever you want it to be as long as the downstream wiring is sufficiently sized (or larger).Put this breaker in that existing panel under the meter head.

At the end of the resized conduit a the end of the patio put a 'T' style waterproof 'LB' (I don't know what they are technically called). From this 'LB' run the smaller (current size conduit you have) conduit to the air handler. Run a 2nd conduit off the 'LB' to the shop.

Your current idea of breakers in the new junction panel are going to require the panel to be mounted high enough on the wall (5'?) to meet code. it is also going to have to be weather tight (more money). That box back by the meter (if I assume correctly) is already a weather tight distribution panel (hopefully with room for one more breaker (for the shop)).

Now that you got all the conduits in (and I believe they can't be plastic down that low unless its maybe schedule 80 and can be exposed to sunlight), you can pull wires. You got wires for the shop and different wires for the air handler. Start at the 'LB' and pull all of them back to the box below the meter. Then take the other ends of the wire for the air handler and pull them toward the air handler. Do the same for the shop wires. Use lots of wire pulling lubricant. You can't use too much. Wires should pull real easy. Put the cover on the 'LB' and that part is done.

The conduit to the shop has to be buried a certain minimum depth (18"?). Whatever the code says.

As far as breaker size, my money says you will be limited to 60A or so for the shop from a practical standpoint. Particularly if you have a electric range or dryer.You can still run wire sized for 125A though so when you upgrade the service you don't have to change wire. Just the breaker.

 

[erasmussen]

I had about the same kind of problem.
I went the cheap and easy route, and just put in a new service, and now I have all the power I could ever want.
It wasnt as hard as I thought it would be to install.

 

[manfre]

After many months of hanging extension cords out of the door and then plugging various power strips to whenever I wanted to power anything in the shop, I've finally made some progress on the electrical!

The lighting is now wired. Each corner of the workshop has a duplex outlet installed in the ceiling with another above the door. It's all powered via a modified extension cord, plugged in to an external outlet in an in-work box. The external outlet goes through a switch by the door and then on to the other outlets. If/when I ever wire a panel, the external outlet will be rewired.

 

[mkepke]

Hi Manfre - if you decide you want to install permanent power and want help, let me (us) know. I have wired a couple workshops and panels. The digging is easier in the cool months

I think DaveD earlier in this thread had a very sound plan.

Lastly, my experience in both Raleigh and Wake Co. is that electrical inspectors are happy to look over your plans and answer questions.

-Mark