Sharing Neutrals

[eschlomach]

on a CTB16PC i was wondering if i could share the neutrals. Maybe 4 channels per neutral. Would that work or do i need a neutral for each channel. Running all LED lights so i dont think the load would be a problem.

[flogger7]

The neutrals are all on a common bus on the board anyway. So assuming you are talking about doing something like using a 5 wire cord for 4 hots + 1 neutral (and doing a breakout at the far end into 4 outlets) it should just be a question of load management and safe wiring practices...but nothing conceptually wrong with it I don't believe.

[Guest wbottomley]

on a CTB16PC i was wondering if i could share the neutrals. Maybe 4 channels per neutral. Would that work or do i need a neutral for each channel. Running all LED lights so i dont think the load would be a problem.

If you don't have a complete understanding about electricity and shared neutrals, revert back to SOP (standard operating procedure). Ignorance & stupidity don't mix with electricity.

But... if you do understand, shared neutrals will work. Remember, the total rating of the wire plays a huge role here.

[LOR Staff]

I'm on a tear tonight about electricity questions.....

You did NOT give enough information to answer your question.

• What are the loads on each of the hots?
  
• What AWG wire are you proposing on using for the hots?
  
• What AWG for the common ground?
  
• Is this a bundled cable? If so:
  
  • Is insulation rated to insulate the voltage in use?
    
  • Is the outer insulation rated for the voltage in use?
    
  • Have you properly de-rated the wire to correctly compensate for the bundling?
    

  [*]Are you using polarized plugs & sockets?

  [*]Are you 100% sure that you have wired the controller properly?

  [*]Are you 100% sure that the outlet you plan to use is wired correctly?

Here is the thing: If you have enough experience and knowledge to know the answers to those questions, you probably wouldn't be asking if you can share a neutral or not.

Be safe. Wire it the 'normal' way.

[eschlomach]

I forgot to use the search before i asked my question. I had the answer about 10 seconds after i posted it. I know it was a stupid question. Especially being as i am an electrician. i was just wondering if any one had tried it and if it caused any problems with the channels. Thanks for all the advice. I will remember to use the search next time

[Ken Benedict]

Shared neutrals will almost always trip a GFI or GFCI outlet, which is what you should be using for outdoor displays.

You can share neutrals upstream of the GFCIs.

[LOR Staff]

Shared neutrals will almost always trip a GFI or GFCI outlet, which is what you should be using for outdoor displays.

You can share neutrals upstream of the GFCIs.

This is NOT true.

You will trip a GFCI (outlet or otherwise) only if the current exiting the HOT doesn't equal the current coming back on the NEUTRAL. The only time this is an issue with your example would be if you are sharing a neutral AND that neutral is connected to 2 or more DIFFERENT neutral return paths: IE, you have a HOT from 1 GFCI circuit and are returning the electrons via 2 or more DIFFERENT circuits.

This is the exact thing a GFCI will be looking for: a load imbalance on the hot/neutral pair. It doesn't matter if the electrons are safely returning to the load center, or through your body to ground -- both correctly trip the GFCI.

Remember: Electrons OUT must equal Electrons IN. If they don't a GFCI will trip.

[cenote]

Next question: (I am NOT being a smart a## here), but fits this thread. Is a set of 50 old fashion incandescent lights really polarized? Meaning, does it really matter which side of the light bulb filament the neutral is on? I cut off a lot of my plugs, and pull off the extra wire and direct wire them into molexs and custom plugs. This would make me think even deeper that than it would matter when you pull the burned out bulbs and replace them. So if it does not matter, than why are 50% of the plugs polarized, or is it just encase you plug something in on the recp side if there is one?

[LOR Staff]

Do the lights themselves care? Nope. Does a standard string of lights plugged in need to be polarized? Nope.

In the case of cutting plugs and sockets off and then sharing neutrals? YOU BET.

Assume for a moment you have 3 conductor cable. 2 will be HOT, 1 is the neutral. You now have 2 plugs that share a common circuit element, and are therefore tied together.

Now let's examine some of the ways this can go bad->

• Plug one of those plugs into a live socket. Grab the other plug by the prongs. Are you dead? No? Congrats, you plugged it in the right way. Now flip the plug over and grab the other plug by the prongs again. Congratulations, you've created a 'dead man's cord' and you are now dead. Since you don't know which way to insert that plug, are you inserting it on the 'SHARED' side or the 'HOT' side?
  
• Plug one of those plugs into a live socket. Plug the OTHER end into a socket. Did your house burn down? No? Congrats, in a 50/50 chance you just happened to plug BOTH plugs in the same way - which may not be the RIGHT way. Now plug a device into the other end. Did it smoke a lot, and glow bright red? Congratulations! You've plugged both plugs in upside down and now have a 240V extension cord. Awesome! Now unplug one plug, flip it around, and plug it back in. Congratulations, your house has just burned down. Reason? You've created a DEAD SHORT between the hot on one plug and the neutral on the other.
  

Ok, so let's use polarized plugs.... Did you wire them correctly? Did you wire ALL of them correctly? Are you 100% sure? One flipped wire is going to cause one of the 2 problems above even if you are using polarized plugs/sockets.

OK, so you wired everything correctly. Are you sure your WALL SOCKETS are wired correctly? If the electrician flipped the hot and the neutral when it was installed, you have the EXACT same problem.

Ok, so the outlet is wired correctly. Are you sure everything else is?

There is ZERO margin for error when going outside the 'rules'. Can you do it? Yes. Should you do it if you don't know why you shouldn't? NOT ON YOUR LIFE.

[cenote]

Thanks Jeff and Mike, I'm sticking with Polarized plugs, I like my house

[steve synek]

Cenote..............I am just spewing here cause I am not 100% sure as I haven't worked with the old C9 and C7 strings for years. But the overall design of the old strings were polarized. The screw shell is the neutral and the point of the bulb base was the hot/ power connection. My understanding of things is if your were going to possibly touch a bare conductor, you would chose the neutral- but warning here- don't touch anything hot. Hence as you screw a bulb in or out, the shell or threaded part of the bulb should alway be connected to the neutral as you are more likely to touch it as you remove or install the bulb while it's still in contact with the neutral. A half turn or so of the bulb removes the connection at the base of the bulb from the hot conductor. I think, but can't say for sure, that the reason for the non polarized plugs on the typical mini light strings is that both contacts break at the same time when you remove the bulb.............

And that's my 2 cents............

Steve