To Sub-panel Or Not To Sub-panel.. (long Circuit Runs)

[Stan the Man]

Thanks in advance for taking my question.. First I will say, while I have done many wiring projects around the house, I am NOT an electrician.. I'm in the middle of putting two rooms in the back of my shop.. One above the other.. The shop is 70ft long,.. the breaker box is at the front, the rooms are in the back.. So I have a run of 60ft to the rooms.. Maybe a total longest circuit length of 90ft.. There will be six can lights and four outlets down stairs,.. three lights and four outlets upstairs.. A mini fridge being the only planned constant on the down stairs circuit.. I already have an empty 3/4 EMT running to the back, and have plenty of space in my main panel.. Should I use a sub-panel, or just run the circuits from the front and do my thing?? looking for suggestions..

Stan

 

[Standardairconditioner]

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[Sponsor]

 

[hj]

One larger wire feed and a sub-panel almost ALWAYS wins out over a bunch of long, smaller wires.

 

[Stan the Man]

Oh,.. I forgot to say,.. there will be a dedicated circuit,(220v) for a ductless HVAC system..

 

[Standardairconditioner]

Should I use a sub-panel

No.

or just run the circuits from the front and do my thing??

Yes.

Unless your home is a multi-building mansion, the distances you cite are VERY SHORT. I've done plenty of HVAC mini-split runs from the main panel to detached garages, guest houses, with lengths much greater.

Aside from the fact that mini-splits use very little current, when you respect the current amps and distance, 100% you can do everything from the main panel.

Your main panel can't see what you are doing. It simply thinks it is in a slightly bigger home now.

 

[Stan the Man]

This isn't to scale and the symbols aren't right , but you get the gist.. Yes this is a shop separate from the house.. service was run from the house (with updated socket) and has its own main panel..

 

[Stuff]

For only a couple of circuits it is not worth the effort. If you have extra money then maybe upsize the wires to reduce any voltage drop. Not really needed as most things don't care even at 90'.

 

[Standardairconditioner]

If you have extra money then maybe upsize the wires to reduce any voltage drop.

There will be none at all.

 

[Jadnashua]

One thing to consider, is how far do you want to walk in the dark should you trip one of the breakers. 15A, 120vac, 14g wire, 90', the voltage drop is minimal - calculated at about 0.25v. That's without any potential resistance through connections, i.e., a straight, continuous wire.

 

[Stuff]

How do you get .25v? NEC has 14 gauge solid copper as 3.19 ohms/kFoot. So 90' is .2871 ohms each for hot and neutral. E=IR=.2871*15=4.3 You double it so total of 8.6 volts at max load.

Online calculator - assumes 2.525 ohms/kFoot so comes up with a 6.82 volt drop.
http://www.calculator.net/voltage-d...nce=90&distanceunit=feet&amperes=15&x=86&y=16

 

[Reach4]

For 3 circuits, I would probably use just the main panel. For 5 or more I would put in the subpanel. I am not a pro.

 

[Cacher_Chick]

There is not much benefit to installing a subpanel. Size the wiring properly and run your individual circuits.

 

[Jadnashua]

How do you get .25v? NEC has 14 gauge solid copper as 3.19 ohms/kFoot. So 90' is .2871 ohms each for hot and neutral. E=IR=.2871*15=4.3 You double it so total of 8.6 volts at max load.

Online calculator - assumes 2.525 ohms/kFoot so comes up with a 6.82 volt drop.
http://www.calculator.net/voltage-d...nce=90&distanceunit=feet&amperes=15&x=86&y=16

Yep, I agree. The one I tried showed what I listed, so much for believing the first one I found.

 

[Stan the Man]

OK,.. so no sub-panel.. The electrician that wired the shop did everything to code.. used 12ga. in emt for all the quads(120v) and lighting.. He ran the 3/4 emt to the back for my rooms but I didn't know what he was planning.. Now that the rooms are ready to wire, he seems to be too busy to come back.. I'm tired of calling people that don't show up.. I'm moving on..
I want to keep this as neat as possible and avoid using more wire than I need.. Thinking about pulling two circuits of 12ga. to a box in the back corner and branch from there.. one circuit for each room.. There would be four outlets and two LED lights on one, and four outlets and six LEDs on the other.. Not sure what HVAC unit I'm going to use yet.. Questions?? Suggestions??