Wiring for 4x8 storage shed

[jhankel]

I am building a shed behind my garage for the lawnmower and air compressor. Need to have 20 amp 240 v for the compressor. My plan is to use a 20 amp MWBC and a dual voltage outlet.

The main question I have is I think I need to have a GFCI breaker in my panel. Is this correct?

Second question is can I have an additional 120 outlet and light ran after the dual voltage outlet? I have not found any wiring information about the dual voltage outlets.

See my attached diagram for details. Thanks.

 

[G_P]

I believe you will need a disconnect in the shed. Probably easier to put in a small subpanel with a breaker for the 240 and a breaker for the 120 circuits.

Sent from my C5120 using Tapatalk 2

 

[pattenp]

The shed will need it's own disconnect switch. You may find it cheaper to have an individual 240V outlet and use 2 regular 120V outlets with the first 120V outlet being a GFCi. Thw 240V outlet is not required to be GFCI protected.

Edit: And I agree with the small sub-panel. That takes care of the disconnect.

 

[justsam]

What is current requirement for compressor? That Leviton 5844 is rated for 1 HP at 120V or 2HP at 240V.

In regard to need for GFCI breaker, I will defer to experts here. My notion would be no, but GFCI outlets in shed are required, which may negate the use of 5844.

Also looks like you are switching neutral for the light. Switch the hot lead instead.

 

[jhankel]

What is current requirement for compressor? That Leviton 5844 is rated for 1 HP at 120V or 2HP at 240V.

Not sure on the current, I will check tonight..

In regard to need for GFCI breaker, I will defer to experts here. My notion would be no, but GFCI outlets in shed are required, which may negate the use of 5844.

Thats why I use the $95 dollar GFCI, so they are all protected.

Also looks like you are switching neutral for the light. Switch the hot lead instead.

My bad, I will fix the drawing...

 

[jhankel]

The shed will need it's own disconnect switch. You may find it cheaper to have an individual 240V outlet and use 2 regular 120V outlets with the first 120V outlet being a GFCi. Thw 240V outlet is not required to be GFCI protected.

Edit: And I agree with the small sub-panel. That takes care of the disconnect.

I will use a double pole switch for my disconnect in the shed. I am not running a subpanel, then I need ground rods and more breakers.

For goodness sakes, this thing is 32 sq. ft. How many lights and equipment do you think I can stuff in this thing?

 

[Highbeam]

Most compressors that I've been looking at, full sized ones, are fed with 30 amp 240 breakers and have nameplate ratings of 23 amps. A HP is like 730 watts so 2hp ain't gonna cut it.

 

[justsam]

I hear you in regard to the 32 sq ft. These things can take on a life of their own and based on your original post, you know what you are doing, and can make it work.

The issue is more one of what is code compliant, even for 32 sq ft, pump house, etc. I'll leave that to the pros.

My question in regard to compressor current is not to exceed the 2 HP receptacle rating, which if my math is right is about 6.25 Amps at 240 V. Also I believe you can not exceed the nameplate data, so it can not be over 2 HP rated.

 

[jhankel]

The compressor has a 20 amp plug on it.. I already have it wired in my garage on a 20 amp 240 volt outlet.

Justsam, I will look tonight at the manual and the motor plate...

 

[jhankel]

Looked at the compressor tonight. It is labeled as 4 hp. I attached a picture of the plate on the motor. 13.1 amps. So I guess the outlet is not rated for this size of motor?

 

[jhankel]

Here is a picture of the compressor. It would not let me attach two pictures in the last post.

 

[BD1]

I will use a double pole switch for my disconnect in the shed. I am not running a subpanel, then I need ground rods and more breakers.

For goodness sakes, this thing is 32 sq. ft. How many lights and equipment do you think I can stuff in this thing?

You gonna put in a lift ? What about pallet racks ??

 

[tylernt]

Your "4HP" compressor is not really 4HP. Manufacturers these days are severely inflating the "HP" they claim their compressors to have.

According to the NEC, you size the circuit based on the true horsepower of a motor. But your numbers don't add up:

http://www.engineeringtoolbox.com/electrical-motor-hp-amps-d_1455.html

A 13A motor is closer to 2HP, not 4HP. I see no reason you can't run a 13A, 2HP motor on a 20A 240V circuit.

 

[pattenp]

That being a portable compressor it's factory wired with a cord and plug. If it's a 240V 20A plug then use the 240V 20A outlet on a 240V 20A circuit. Don't get all caught up in the back and forth about the so called 4 HP motor.

 

[VHF]

Have you found a source for a 20A double pole GFCI breaker designed for use with a MWBC as shown in your diagram? I'm thinking that will be hard to find!

Just using a GFCI recepticle for the 120V recepticle is probably more practical, especially as GFCI protection isn't required for 240V recepticle.

The only other ramification of this approach is direct burial cable would need to be 24" deep instead of 12" deep. (12" deep is only allowed when GFCI protected at the source.)

 

[tylernt]

Have you found a source for a 20A double pole GFCI breaker designed for use with a MWBC as shown in your diagram? I'm thinking that will be hard to find!

Square D makes them for about $100. I imagine other manufacturers are similar. Spendy, but available.

 

[wyliesdiesels]

Square D makes them for about $100. I imagine other manufacturers are similar. Spendy, but available.

Why bother? A 240v outlet is NOT required to be GFCI protected. Use GFCI breakers for the 120v circuits and be done with it!

 

[tylernt]

Why bother? A 240v outlet is NOT required to be GFCI protected. Use GFCI breakers for the 120v circuits and be done with it!

GFCI feeders only need to be buried 1ft deep. Non-GFCI, 2ft. Can save some digging.

 

[pattenp]

The 1ft depth for circuits that are GFCI protected is limited to a max of 120V. If over 120V the circuit needs to be 18" or 24" depending on if direct bury or in conduit and a few other factors will change the depth requirement.

GFCI feeders only need to be buried 1ft deep. Non-GFCI, 2ft. Can save some digging.

 

[theoldwizard1]

Use a fused AC disconnect inside the shed. You should be able to pick one up for under $20. You will need to buy some 20A cartridge fuses.

Run 12-3 to the 240V outlet. Mount it in an over sized box. You can split it into 2 separate 120V circuits from there, with a GFCI outlet first in the string.

 

[wyliesdiesels]

The 1ft depth for circuits that are GFCI protected is limited to a max of 120V. If over 120V the circuit needs to be 18" or 24" depending on if direct bury or in conduit and a few other factors will change the depth requirement.

I forgot to mention this. Good catch! Those 240v GFCIs are only useable for hot tubs!