Terminating #4 conductors onto receptacles

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sparky 134

Senior Member
Location
Joliet, IL
I walked thru a landscape lighting project today and the landscape contractor specified where he needed 120volt 20amp circuits located. The longest run is ~375' from the panel and according to my voltage drop calculator I need to install #4 conductors to supply 15amps and limit the VD to 3%.

So my question is, how do I terminate a #4 conductor onto a 20amp GFCI receptacle in a bell box ?
 
infinity

infinity

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sparky 134 said:
Why #4 ? I would have sized it according to 250.66 which calls for a #8.
Click to expand...


For an EGC the correct Table is 250.122. Take a look at 250.122(B). The ECG needs to be the same size as the ungrounded conductors for a 20 amp circuit.
 
augie47

augie47

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State Electrical Inspector (Retired)
Hopefully you do not plan on routing your #4s to a bell box.
With #4, 314.28 comes into play.
It might be time to consider a "Quazite" box with #12's extended to your receptacle box.
 
iwire

iwire

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Staff member
Location
Massachusetts
My experience servicing site lighting tells me the rule should stay in place as smaller AWG sizes are much more prone to psychical damage either directly or via corrosion.

I do not think it makes sense in underground / wet conditions to have the EGC be the most fragile conductor of a circuit.
 
bob

bob

Senior Member
Location
Alabama
You have a good point. Do you think that in this case the EGC really needs to be #4? I still
think the table should be changed.
 
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danickstr

Senior Member
for outdoor lighting 3% VD seems a bit overkill. I would consider pulling an 8 all around. is the 15 amp load a group of lights? If so, it will not dim much, til the end :)

Also, I have recently purchased 2 gang PVC bell boxes, I would recommend them. I special ordered ones with two 3/4" holes on the bottom, since no one in the entire city of Seattle seems to carry them stock. I am not even sure if you can satisfy your cubic inch requirements without an extension ring on a two gang box, since #4 must be like 6 cu in. per conductor or something really high like that.
 
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sparky 134

Senior Member
Location
Joliet, IL
I don't know what the full load will be so I'm engineering this for a 15amp load. Since I had to upgrade to the #4's I decided to route the conductors into a 8x8x6 3R junction box and I'll attach two single gang bell boxes to opposite sides of the 3R.

I would prefer to pull #8's but I want to design the system properly. How would excessive VD affect the GFCI receptacles ?

I'll be pulling four #4's to the 3R as the customer wants one GFCI to be switched via a time clock and the other GFCI is to be hot at all times. I suggested using an astronomic time clock that will auto adjust for sunrise/sunset and daylight savings time.

The next phase of the project will be upgrading to a 400amp service, adding a second 200amp panel and running about 400' of underground to supply a 100amp sub panel in the new garage. BTW, the new garage will be located next to the new helicopter landing pad being installed. The customer wants to be able to land his helicopter at home......
 
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Jlarson

Member
Location
AZ
sparky 134 said:
I'll be pulling four #4's to the 3R as the customer wants one GFCI to be switched via a time clock and the other GFCI is to be hot at all times.
Click to expand...

Any reason you can't or don't want to set the time clock at the jbox and just run 3 conductors instead of 4?
 
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dbuckley

Senior Member
Location
Canterbury, New Zealand
Or indeed have a big relay or small contactor out there for the remote switched outlet, and run a fourth conductor that is adequate for just the relay power?

Of course, switching power to the GFCI requires a GFCI that doesn't open when the power to it is removed.
 
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