Receptacles sharing a neutral

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Jpflex

Jpflex

Electrician big leagues
Location
Victorville
Occupation
Electrician commercial and residential
In a sub-panel, our company originally had one branch circuit from one phase powering 4 parallel receptacles. Since this is outdoors, the first receptacle connected to line was a GFCI. The load side of the GFCI fed all other single gang receptacles as normal.

However, soon after company diesels were plugged in for heating motors over night, and soon increasing the number of vehicles, the standard GFCI overheated and blackened.

In order to increase total ampacity of 4 receptacles, another coworker, while I was off work fed a separate red wire from the other phase from the same panel to split receptacle into two groups. Which is ok.

What he did not do was run a separate neutral for the two pair of receptacles nor a separate equipment ground conductor

As a result two separate circuits shared a neutral which I believe defeats the purpose of having another line wire added since double amps from 4 receptacles return on one neutral as it did in original setup.

Also is NEC 200.4 which took me a while to find. Co worker said installing a separate neutral and ground was not necessary? What do you all think?
 

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Jpflex said:
In a sub-panel, our company originally had one branch circuit from one phase powering 4 parallel receptacles. Since this is outdoors, the first receptacle connected to line was a GFCI. The load side of the GFCI fed all other single gang receptacles as normal.

However, soon after company diesels were plugged in for heating motors over night, and soon increasing the number of vehicles, the standard GFCI overheated and blackened.

In order to increase total ampacity of 4 receptacles, another coworker, while I was off work fed a separate red wire from the other phase from the same panel to split receptacle into two groups. Which is ok.

What he did not do was run a separate neutral for the two pair of receptacles nor a separate equipment ground conductor

As a result two separate circuits shared a neutral which I believe defeats the purpose of having another line wire added since double amps from 4 receptacles return on one neutral as it did in original setup.

Also is NEC 200.4 which took me a while to find. Co worker said installing a separate neutral and ground was not necessary? What do you all think?
Click to expand...
You would not need a separate equipment grounding conductor or separate neutral. You would need to split the two circuits at the first box and have a G.F.C.I. At the first receptacle on each circuit.
 
Jpflex said:
As a result two separate circuits shared a neutral which I believe defeats the purpose of having another line wire added since double amps from 4 receptacles return on one neutral as it did in original setup.
Click to expand...
This will actually reduce total load on the shared neutral, as well as total losses and voltage drop.

The load-side of the GFCIs must be separate and unshared. One EGC for everything is Kosher, too.
 
Jpflex said:
In order to increase total ampacity of 4 receptacles, another coworker, while I was off work fed a separate red wire from the other phase from the same panel to split receptacle into two groups. Which is ok.
Click to expand...
 
Jpflex said:
As a result two separate circuits shared a neutral which I believe defeats the purpose of having another line wire added since double amps from 4 receptacles return on one neutral as it did in original setup.

Also is NEC 200.4 which took me a while to find. Co worker said installing a separate neutral and ground was not necessary? What do you all think?
Click to expand...
What the coworker did is fine as long as the two circuits breakers were tied together with a handle tie or a 2-pole CB was used. The neutral will only see the unbalanced current so it would actually be zero when the two circuits are fully or equally loaded.
 
Speaking from experience, a little time down the road and you will find that a GFCI at each receptacle is the best way to go. Only one truck down instead of multiple. One circuit per duplex is suggested as well.

What size breaker was ahead of these receptacles? The breaker should have tripped long before damage to a device became apparent. unless installation or device was PP.
 
ptonsparky said:
Speaking from experience, a little time down the road and you will find that a GFCI at each receptacle is the best way to go. Only one truck down instead of multiple. One circuit per duplex is suggested as well.

What size breaker was ahead of these receptacles? The breaker should have tripped long before damage to a device became apparent. unless installation or device was PP.
Click to expand...
I believe a 20 ampere circuit for 20 ampere branch circuit, with 12 AWG (supposed to be TW OR THHW) 60degree rated insulation wire but all company has is THHN for outside.

Someone also mentioned here that adding a neutral would lower the load for two circuits on opposing phases. If true would this have to do with current traveling on both phases and balance only on neutral?

Was I correct on adding a neutral? Thanks
 
I'm surprised you can power multiple block heaters on one circuit. All the ones I've ever had were 1500 watt. I have 18 receptacles on the side of my building for powering block heaters and they are all on their own breaker. Each one of those block heaters draw 12.5 amps on 120 volts. Duplex receptacles seem to be a bad idea too, the bone head drivers for some reason like to plug 2 trucks into the same circuit and you end up with 2 trucks that don't start
 
Jpflex said:
I believe a 20 ampere circuit for 20 ampere branch circuit, with 12 AWG (supposed to be TW OR THHW) 60degree rated insulation wire but all company has is THHN for outside.

Someone also mentioned here that adding a neutral would lower the load for two circuits on opposing phases. If true would this have to do with current traveling on both phases and balance only on neutral?

Was I correct on adding a neutral? Thanks
Click to expand...
It only lowers the neutral current of a MWBC. Adding a neutral hurts nothing and would allow separate breakers.
 
Joethemechanic said:
I'm surprised you can power multiple block heaters on one circuit. All the ones I've ever had were 1500 watt. I have 18 receptacles on the side of my building for powering block heaters and they are all on their own breaker. Each one of those block heaters draw 12.5 amps on 120 volts. Duplex receptacles seem to be a bad idea too, the bone head drivers for some reason like to plug 2 trucks into the same circuit and you end up with 2 trucks that don't start
Click to expand...
Why not split the duplex and feed it with two circuits?
 
Jpflex said:
I believe a 20 ampere circuit for 20 ampere branch circuit, with 12 AWG (supposed to be TW OR THHW) 60degree rated insulation wire but all company has is THHN for outside.
Click to expand...
How old is that wire? AFAIK all THHN has been dual rated THHN/THWN for more than thirty years I think
 
Jpflex said:
Someone also mentioned here that adding a neutral would lower the load for two circuits on opposing phases. If true would this have to do with current traveling on both phases and balance only on neutral?
Click to expand...

As ptonsparky said, it only lowers the current on the neutral, it does not change the circuit capacity.

1680786292815.png
 
As others have mentioned, with the handle tie this setup is allowed by code, and per Roger's post, it can actually reduce the current on the neutral.

But it's also important for you to be aware of the down side: If the neutral became disconnected somewhere, then you basically have 2 receptacles in series from Line to Line. The voltage across each receptacle will depend on load connected to each receptacle. Worst case is you could have 240 volts across one receptacle, and applied to a truck heater.

So whatever you do, don't disconnect the neutral wire while the power is on and something is plugged in.

That possibility might be enough justification to add a separate neutral.
 
roger said:
Why not split the duplex and feed it with two circuits?
Click to expand...

Actually that is what I have on my building. Not sure you can see them that well in this picture.


FB_IMG_1680786263313[1].jpg

There are 9 duplex receptacles on the side, All of them are split and on a 20 amp GFCI, for a total of 18 circuits. There is a big contactor controlled by a timer before the subpanel for all those receptacles. It saves a lot of money having them only come on a couple hours before they need to be started.


But I've done work in other plants and truck terminals where they used GFCI receptacles and it became a problem with drivers plugging 2 trucks into one GFCI and tripping the breaker
 
Joethemechanic said:
Actually that is what I have on my building. Not sure you can see them that well in this picture.


View attachment 2564760

There are 9 duplex receptacles on the side, All of them are split and on a 20 amp GFCI, for a total of 18 circuits. There is a big contactor controlled by a timer before the subpanel for all those receptacles. It saves a lot of money having them only come on a couple hours before they need to be started.


But I've done work in other plants and truck terminals where they used GFCI receptacles and it became a problem with drivers plugging 2 trucks into one GFCI and tripping the breaker
Click to expand...
You have two GFCI breakers feeding each split duplex receptacle?

Guessing installed before the common tie requirement.
 
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