Any electricians want to help me out with a question?

pcloadletter

I currently have a dedicated 20A line with an Intermatic T101 timer feeding a single outdoor 20A duplex outlet. My Christmas lights are about to exceed the 20A capacity of the circuit.



Suppose I want to use the full 40A capacity of the timer - how would I wire two 20A duplex outlets for this purpose? Assuming I upgraded the line from the panel to the timer to 40A with 8g wire. Would I need to use a mini load center?



Jeff

Ironman

Christmas Lights Exceeding 20 Amps

Wow, that must be some display you have.



Is the timer 1 pole or 2 pole? If it's 2 pole, then you could split the load between the poles. If it's one pole, then a 2 pole 20 amp contactor could be added with its coil energized by the timer.



Then I would use a 12/3 underground cable (type UF) that could carry up to 16 amps on each hot leg. Use a 10/3 cable if more ampacity is needed.



Then connect the cable to a 2 pole circuit breaker and the white wire to the neutral buss. You MUST use a full size 2 pole breaker to assure the the hots originate from opposite phases in the panel. The neutral is shared and only carries the IMBALANCE between the OPPOSITE phases.



Example: phase "A" is carrying 10 amps and phase "B" is carrying 15 amps. The neutral then is only carrying the IMBALANCE of 5 amps. If the hots were connected to the SAME phase, then the neutral would carry the SUM of both phases and would be overloaded ( 10 amps + 15 amps = 35 amps).



I used 16 amps for 12 gauge wire because a circuit is only supposed to be loaded to 80% of its rating, but the ampacity of #12 is actually higher and carrying 20 amps is generally okay. Use a 25 amp breaker if you need that many amps.

Zman

Not an electrician

To do it the way you describe you would need a load center. Why not just install another timer on another circuit? If you absolutely have to have the one timer you could install a double pole relay off the existing timer and control 2 separate circuits.I think 2 small circuits are going to be easier than 1 large. 

Timco

As stated above...

You want the timer to run a 2-pole, 20A contactor so two normal circuits are switched together. you really wouldn't run #8 out there and use a 8-3 and a single pole 40. Then you have two 20A circuits switched. Use a PVC J box and lid. Paint it green.

pcloadletter

I think for this year...

Most of of my Christmas lights are old-school C9 and C7 strings that draw a ton of power. I'm all about tradition and I don't care about energy efficiency for this stuff. I will just plug the second half of the lights into a 20A basement circuit I installed a few years ago with a plug-in timer or two that can handle the load. I totally understand the the twin 20A loads sharing the DPST timer with a common neutral, but my timer is a SPST so I would need to upgrade it. I'd rather do that instead of rigging up the contactor and such. There's always next year.