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leureste · Mar 3, 2011, 07:20 AM

I was told by an electrician that he'd run 8THHN from my garage... bury in PVC 100 ft and into my shed to a 100 amp 12/6 box. He said there will not be a voltage drop if you run two 50 amps and 8THHN wires from my main breaker to the subpanel in the shed... will this work?

tkrussell · Mar 3, 2011, 08:43 AM

Yes, assuming the actual load does not exceed 40 amps on the 50 Amp circuit.

leureste · Mar 3, 2011, 08:52 AM

Is keywords the answer?

leureste · Mar 3, 2011, 08:54 AM

Sorry, the answer didn't appear until I wrote my 2 question.

tkrussell · Mar 3, 2011, 08:54 AM

Excuse me?

Originally Posted by leureste

Is keywords the answer?

What do you mean by "keywords" ?

leureste · Mar 3, 2011, 08:56 AM

All I will be power from the shed will be lights and recepticles in my pavilion a couple lights around the yard. Recepticles in my pavilion may power a blender

tkrussell · Mar 3, 2011, 08:59 AM

You should be fine.

I do have to ask, if your electrician told you something, do you not trust his advice?

leureste · Mar 3, 2011, 10:18 AM

I think I really trust him but I only question it because I had trouble getting a hold of him and I went to Lowe's and Home Depot and talked to them an they both told me two different things. I'm an Aircraft Electrician in the Navy and I have a basic knowledge of residential wiring but not to this extent. The other guys were talking voltage drop with that much feet in wire but when he told me that we'd run out of my MAIN breaker 2 50 amps to the shed... had my head scratching.

tkrussell · Mar 3, 2011, 10:47 AM

Clerks in the big box stores are really nice people, I question their knowledge.

One of the most important values in calculating voltage drop is knowing or making a safe assumption of what the maximum ampere load will be.

Very simply, no load at the end of the circuit, no voltage drop, to illustrate the extreme.

As amps increase, voltage drop will increase, and affected by the fixed length and size of the wire.

Vd= 2 (conductors in the circuit) x Length (of circuit) x Amp load x Ohms per foot of conductor.

Max Vd for a feeder should not be more than 3% of the supply voltage.

leureste · Mar 3, 2011, 11:03 AM

Thanks, that was really deep but I'm assuming I'm good to go with the plan.

tkrussell · Mar 3, 2011, 12:56 PM

You had my blessings here:

Originally Posted by tkrussell

You should be fine.

leureste · Mar 17, 2011, 06:45 AM

I forgot to ask this question, If I do run 8 THHN through PVC with a run of 100 ft, do I need to run four 8 THHN wires... 2 hots, 1 nuetral and 1 ground or can neutral and ground be a different type wire... trying to save a little money... just asking.

tkrussell · Mar 17, 2011, 07:46 AM

The neutral needs to be a white #8.

You can use a #10 THHN/THWN green for the equipment ground.

tkrussell · Mar 17, 2011, 07:48 AM

And be sure the THHN wire you sue is dual rated as THHN/THWN.

THHN only cannot be used in wet location. Rare to find but it is out there.

Most THHN is dual rated as THHNand THWN.

The "W" denotes wet location rated.

Any raceway outdoors and in the ground is considered as a wet location.

leureste · Mar 17, 2011, 08:14 AM

Awesome... thanks for all the help!! I love the internet!!

leureste · Mar 17, 2011, 08:56 AM

You said the neutral needs to be a white #8, is that regular wire or THHN/THWN also.

tkrussell · Mar 17, 2011, 09:07 AM

Thhn/thwn

leureste · Mar 17, 2011, 11:51 AM

News flash, just found a sale of #6 THHN/THWN on sale, 500 ft roll for $100, can I use this instead of #8

tkrussell · Mar 17, 2011, 12:18 PM

OK, you have some sort of electrical knowledge, you should be able to answer the last question.

leureste · Mar 17, 2011, 01:20 PM

In the Navy as an elctrician I would say the bigger the wire the better, #6 can handle more AMPS which is better... I'm new at this residential gig.