1) At the Park Model electrical panel, you will need a 50 amp double pole circuit breaker
for the 50 amp feeder circuit.
2) All sub-panels require a 4 wire feeder circuit comprised of 2 hots, 1 neutral and 1 equipment grounding conductor.
3) National Electrical Code recommends that the voltage drop be 3% or less.
Using a 50 amp load @ 240 volts on a 30 foot run results in using 6 AWG Copper conductors, type THWN insulated for the 2 hots and 1 neutral. This results in a voltage drop % of .6% (point six %) or a loss of 1.4 volts. Therefore, 6 AWG Copper meets the code recommendation.
4) The equipment grounding conductor needs to be a 10 AWG copper, type THWN insulated (green).
5) I recommend to use Schedule 80 Gray electrical PVC conduit
for the 4 wires. You can use Underground Feeder cable, but conduit is always recommended since you only want to trench and dig the feeder run one time. Using Underground cable, there is always a chance that the cable can get punctured from shifting soil conditions and then you will need to dig the trench to locate the problem, etc. Thus conduit is the preferred installation. Minimum conduit diameter size = 1" (one inch). I recommend to increase the PVC conduit size to the next trade diameter of 1 1/4" as this will make the wire pull easier. Minimal buried depth on the conduit = 18" below final grade. I also suggest installing a Warning Ribbon tape approximately 6" below final grade over the 3o foot run. This will provide a warning that an electrical line exists below if any future digging or trenching in that area occurs.
6) Since the shed is a detached building, you will need a quantity of (2) two 8 foot ground rods spaced a minimum of 6 feet apart. You will need an 8 AWG copper wire as the grounding electrode conductor from the 2 rods to the sub-panel equipment grounding bar. No splices allowed on the grounding electrode conductor as the 8 AWG copper ground wire will be a contiguous run from the 2 rods to the sub-panel equipment grounding bar.
7) At the sub-panel, DO NOT install the green main bonding screw or a main bonding strap on the neutral bus bar. The neutral must always remain isolated from the sub-panel metal enclosure. Only white neutrals will land on the neutral bus bar and never any bare copper or green ground wires.
8) At the sub-panel, you will need a separate equipment grounding bar to land the 10 AWG copper equipment ground wire as well as the 8 AWG grounding electrode wire and any bare copper grounds if using Romex cable inside the shed. DO NOT land any white neutrals onto the separate equipment ground bar.
9) The 120V shed receptacles need to be GFCI protected.
10) At the shed, you will need (1) one 30 amp double pole breaker for the electric dryer. The dryer circuit needs to be a 4 wire circuit using 2 hots, 1 neutral and 1 equipment ground. You may need to swap out the cord if it is a 3 prong cord as you will now need a 4 prong cord and a 4 prong dryer receptacle.
11) For the general lighting and receptacle circuit inside the shed, install one 20 amp single pole breaker.
12) The shed can either be a 50 amp main lug or a 50 amp main breaker panel. I always prefer using a main breaker panel as this provides a "means-of-disconnect" if you need to shut down the panel for any future maintenance.
13) Tape your 3 wire feeders using black and red for the 2 respective hot conductors and white for the neutral. Tape at both ends using electrical tape.
Hope this helps………If you have any additional questions, let me know and I’ll be glad to answer them for you.
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The next time you have an electrical question, you can also request for me at: http://www.justanswer.com/home-improvement/expert-your-electrician ……….Thanks…………..Kevin!