Hi all! Thank you in advance for your experience and time! OK, I have searched alot of places and have gathered some information, but, I am somewhat confused. I just built a workshop behind my house. I have a 200 amp panel in my house , and I want to feed my sub panel from the main house panel. I am going to run pvc conduit 18" below to the workshop. I know I have to isolate the equipment and bus bars. I plan on running 3 ,
15 amp circuts and 1 20amp circut. One lights, one dedicated for my coffee roaster (draws 7amps) , one for my computer , and the 20amp for general use. What I need to be sure of is , 1. the size of the breaker I should use in my main panel. 2. The size of the wire to the sub panel. And 3. the size of the sub panel I should install. I need a panel with a main breaker in it, not just lugs. Some of the forums I have searched with similar questions to mine, the expert tells the homeowner to use 4 wire. 2 hots , a neutral and a bare ground , and other experts tell the homeowner to use 3 wire with one hot. This is what is smoking my brain! What is the difference and which wire should I use? I have alot of room in my main panel, and I draw about 100 amps. I have a small rancher house. Any help will be awesome! Thanks, Brian

coffeetaxi

I do have a good overview, but I'm not familiar with alot of the lingo you use. I just want to be sure that I use the correct panel, wired the correct way, with safety in mind. Not being an electrician, I will never understand NEC recommendations , voltage drops and so on. What I want to do is "keep it simple stupid"!
What I am using this shop for is roasting coffee. The coffee roaster is a propane burner type that has two electric motors. One is for the roaster drum to turn. 3.5amps. One is for the cooling bin aggitator. 3.5amps. The factory wants this on a dedicated circut. This machine only draws 7amps. This will be my office also. So I want a dedicated computer circut as well. One lighting circut. And one general circut for my coffee grinders. Each (2)grinder draws about 11amps, but will never be run at the same time. A small scale .7amps and maybe a lamp. I will be installing a ceiling fan light combo , and an outside light (incadescent) on the light circut. That is all. It will never be anything other than what I built it for. It is a purpose built workshop for roasting coffee. It is 75' from my house. It's not a hard job. Pretty simple actually, but I want to understand the correct way to complete this task. I want to use your expertise to recommend proper technique. The two things that I really want to know, is proper sub panel and proper feeder guage and type from the main. To make it simple, I am going to return all 15amp recepticals and gfis, and buy the 20amp models. Thank you for your help!

KeepItSimpleStupid

Is direct burial an option?

Otherwise we'll assume copper in conduit.

You'll then go with 20 Amp GFCI breakers, correct?

The 75' is cable length, one way, correct?

The likely reason the manufacturer specifies a dedicated circuit is because of the motors.

I'll do the voltage drop calc's for 75' of copper at (0.8 * 60 A) and check the wire size required.

coffeetaxi

I have moles that tunnel around my property, so I would feel safer with conduit. Also, I have poor drainage.

Yes, 20 Amp breakers.

75' one way.

The reason for a dedicated circut is incase someone would plug in a heavy draw on the roaster circut, it could pop the breaker which, depending on the temperature of the roaster, could catch on fire. We are dealing with temperatures reaching almost 500 degrees.

Thanks again!

stanfortyman

I'm not sure what you are getting at KISS but this is a bit misleading.
A 60A FEEDER is a 120/240v circuit supplying the potential for 14,400 watts worth of power.
This is NOT equal to a 120a circuit of 120v. It's just simply NOT accurate and not how it's explained.
It's 60A @ 240v. In layman's terms this could be stated as 2X 60A @ 120v, but even this terminology is simply not used.

KeepItSimpleStupid

I agree with you. Tried to simplify or say that a 60 amp sub wired with 240 gives you the ability to have 120 amps of 120 available to you, but you cannot deliver that to one piece of equipment.

KeepItSimpleStupid

As for copper wire at 75' one way, 48A continuous on the panel:
#6 copper gives a 3.5 V drop at 2.9%; Load sees 120-3.5 volts
#4 copper gives a 2.2 V drop at 1.8%; Load sees 120-2.2 volts

Compare costs. #4 is obviously better.

stanfortyman

Better? In what way? You mean more expensive?

Do you seriously consider a 2.9% VD not acceptable???

KeepItSimpleStupid

Wow, this is cool, someone who is more detailed than I am.

2.9% is acceptable.

The #4, #6 argument is similar to the #14, #12 discussion. WHo knows? Maybe they are having a sale on #4 or they have it on ebay. Let's leave it as #6 minimum.

Here is #4 and #6 in 500 foot put'ups

Insulation Type - THHN Products

Taping the ends the proper colors.
4 lengts of 75' you'd have 200' left over.

Gives you the idea of relative prices.

mr500

Are you sayin the #6 is in the ground a few inches OR the ground electrode is in ground few inches. My understanding the electrode must be least 8 ft under. But Hey I may have read this wrong lol

coffeetaxi

mr500 this symbol (') after a number means feet.