Help with wireing

[rambler]

*(See below....)

There is an ag building exception that allows 3-wire runs to seperate services, but I suspect for your needs, 90% of the time the answer is 'no'. You would need 4 wires.

The nuetral and the ground wire are not ever the same, and over the last few decades they have discovered bad things can possibly happen if you don't keep these 2 seperate all the time except in the very first service box you have where they both join together & right to earth ground.

So, they don't typically allow you to skip the ground wire any more between locations. To know for sure, you could ask a local inspector or electrician.

Sorry.

--->Paul


* - Rereading your qestion, yes you can run 240 out to your carrage house with just 3 wires! You would not need the _nuetral_ wire then, and would only have 240, you would not ever have 120v. I assume that is not what you want; you want a full 240/120v service out there? Driving the ground rod instead of running the 4th wire is mostly not allowed these days...

 

[rambler]

If you split a 240v connection into 2 120v ones, you have to have a separate return (e.g. normally the green-coated wire) in addition to the bare ground wire. Be aware that the return line and/or ground have to be big enough to handle the full current that the 240v circuit breaker is rated for. The outgoing dual 120v lines would be carrying only half the juice, but it all has to come back on the green or bare lines. You could conceivably do a 240v supply somewhere in the system (I'd probably run the lines to a 240v breaker), but be aware that the supply lines and main circuit breaker supplying them have to be good for the electrical current load by all the circuits that the lines are feeding.

It's all common sense. A little bit of electrical knowledge is useful and necessary if you're doing it for someone else or for hire.

I've reread this several times, and you know, I think I understand what you were trying to say. But I think you made it very confusing, and not very common sense?

On the first or second reading, it sounds like you are interchanging the ground & neutral wires at any old time, or just forgetting one & using the other for both jobs. That would be bad!

It is the number one thing folks have to fight in explaining electrical wiring on the internet. Ground wire & neutral wire are two different things and don't ever connect them but only one time in the main box, or bad things can happen.

When you say, "Be aware that the return line and/or ground have to be ..." I just scream no no no!!! Don't ever phrase it like that! There is never an 'and/or' situation!!!!!!! And nothing is called a 'return line', it is either a neutral, or a ground wire. Which one were you trying to talk about? It's just to hard to follow what you were saying.

Don't confuse a rather confusing thing.

--->Paul

 

[WVBill]

If you are going to have to get this inspected by your jurisdiction's building or electrical inspector, the only sure way to have it pass is to ask the inspector in advance.

When I ran the electrical out to my wife's studio building, I studiously researched the subject of grounding, grounded, bonding, neutral etc. etc. in books and multiple internet sources all of which said NOT to bond (connect) the neutral (white wire) bus and the grounding (bare wire) bus in the panel out in the studio building. So I didn't. But I kept the screw that goes in the panel to make the bond sitting on the window sill next to the box in the studio.

When the inspector came he looked in the box and said "good work". Then he picked up the screw and said "if you'll put this in you'll pass". So I did.

WVBill

 

[PILOON]

You will notice that the neutral and grounds are always a guage smaller than the 'hot' lines.
Being AC the electricity cycles or alternates from 120-0-120 or kinda pulsates up and down, all this at 60 times per second.
That means that the neutral never actually carries the full load at all times, hence they use a smaller guage wire for neutral and ground.
In large (usually commercial) installations the differance of guage sizes adds up to big $$ especially at today's prices of copper.
While in theory you get power between either 'hot' line and both neutral and ground it is not the same and therein lies danger as soil conductivity comes into play.(and grounding rods etc)
Sure in old installations they only used hot and neutral and it worked but soon they discovered that you could get cooked due to the conductivity differances so they added grounding as well.
Electricity will take the shortest and easiest path to ground and that extra bare wire 'ground line' will be it rather than you.
I'm not an electrician, but that how I understand the system.

 

[tommu56]

You will notice that the neutral and grounds are always a Gage smaller than the 'hot' lines.
Being AC the electricity cycles or alternates from 120-0-120 or kinda pulsates up and down, all this at 60 times per second.
That means that the neutral never actually carries the full load at all times, hence they use a smaller guage wire for neutral and ground.
In large (usually commercial) installations the difference of Gage sizes adds up to big $$ especially at today's prices of copper.
While in theory you get power between either 'hot' line and both neutral and ground it is not the same and therein lies danger as soil conductivity comes into play.(and grounding rods etc)
Sure in old installations they only used hot and neutral and it worked but soon they discovered that you could get cooked due to the conductivity differences so they added grounding as well.
Electricity will take the shortest and easiest path to ground and that extra bare wire 'ground line' will be it rather than you.
I'm not an electrician, but that how I understand the system.

the 120v thing is peak to peak 60v+ 60V-
When switching power supplies (computers and ups'es etc) came on the market it puts a strain on the neutral so it is suppose to be full size neutral now.
You can down size the ground and neutral but thats only for 3 phase and the Neut. still has to carry any imbalance in the system.

tom

 

[Danno1]

the 120v thing is peak to peak 60v+ 60V-

tom

No, it's not. 120 is the RMS (root, mean, square) of 169.xxx volts. One cycle of the sine wave goes from zero up to almost +170 volts back through zero to almost -170 volts then back to zero. This happens 60 times per second (60 Hz).

.

 

[tommu56]

No, it's not. 120 is the RMS (root, mean, square) of 169.xxx volts. One cycle of the sine wave goes from zero up to almost +170 volts back through zero to almost -170 volts then back to zero. This happens 60 times per second (60 Hz).

.

Yes you are correct. I was noting that it wasn't 120v -0- 120 as PILOON
had suggested.

tom

 

[DTCOOPER]

With the new codes that were changed between the 2005 and 2008 codes, this has gotten lots of people in trouble. Especially if your municipality has in fact adopted the 2008 Code. As of 2005 code, you could have just run the 3 wires (2 hots and a neutral) to a subpanel (in a DETACHED STRUCTURE), so long as it's not bonded in any form or fashion (metal conduit, telephone line, etc) to the main panel. Then you would treat the new panel as a completely new service, with a grounding electrode driven at the new location.. Well that's all changed now !!

I'll touch on the important points between '05 code and '08 code:

#2 aluminum used to be allowed for 100A subpanels under an interpreted wording of a code article. They have now explicitly changed the wording so that #2 aluminum is good for 90A to a subpanel.

Three-wire feeds (no ground) used to be allowed to an outbuilding provided that no other metal pathways like a water line or phone line were present. Now, four-wire feeds are mandatory, no exceptions.

The ground rods are required in either case, and they should be connected to the subpanel ground bar with #6 copper wire.

If you don't have to worry about inspections, code compliance, etc: When a three-wire feed is used, the neutral and ground bar must be bonded; when a four-wire feed is used, the neutral and ground bars must not be bonded. In this instance, you are treating the subpanel as just another circuit..

The purpose of the neutral is to carry unbalanced load.. That's why you can run a 240v compressor with no neutral.. Just two hots and a ground. But when you add 120v load to the equation, you are sure to have unbalanced load, therefore you must have a neutral to carry that unbalanced load back to the main panel and then to ground.

What we have to remember is that the code is written as an idiot-proof set of instructions.. I could tell you shortcuts all day long that are perfectly safe... Just not legal. LOL

 

[Aquaele]

I have been an industrial/commercial electrician for 40 years, now a Nuclear electrician, Listen to the Inspector (507) he know of what he talks. I agree with him on two circuits. and on the 10 gage wire. and you should know most building wire, (single strand) are rated THHN/ THWN so they are ok for wet locations. and 24" depth is required unless you put a concrete pad on top, so go for the 24".

 

[2manyrocks]

Thank you all and especially DTCooper. It clears up a lot to know that the code changed.

In pre2005 code installations, are you saying that the neutral and the ground bar must be connected together? Was it considered safe when done this way or did the 2008 code go to 4 wires just to make it more foolproof or should all these 3 wire installations be changed even if they were previously permitted?