I am hooking up the above ceiling mounted heater on my covered patio using 6-2 wire because of the unusually long run from my breaker panel to the switch controlling the heater outlet. The run from the switch to the heater is 15 feet. I am using a 20A breaker. The problem I have now is the wire is too heavy to fit into the 20A switch or the 20Amp-250V outlet. What do I do? Is there a connector I can use or do I install a junction box near the outlet and use lighter gauge wire to go from the junction box to the heater. If the second option, what gauge wire? The primary goal here is to not burn down my house.

 

Are you saying your patio is 700+ feet from the breaker box? If you use a 4x4 box for the receptacle there should be enough room to splice smaller wire in the receptacle box. Same at the panel you can splice on smaller wires to fit the breaker. Ground should fit the ground bar without size reduction.

 

In addition, you can use 12-2 cable for the last 15 feet from the switch to the heater location

 

Pull out that #6 wire and use #12. As Ray posted #6 is good for 730' away for voltage drop.

#6 is WAAAAAAAAAAAAAAAYYYYYYYYY overkill.

 

The run is about 120 feet, which seemed long to a novice like me. The nice man in orange insisted I needed 6-2 wire for that. Maybe he got a commission. Thanks for the responses!

 

Take the cable back. They may insist they don't take back cut cable but be pleasant but insistent it was their mistake. Wonder what other bad advice he gave you. Is it NM-b (AKA Romex)? If NM-b will any portion of it be run other than in a wall?

 

I agree with Ray, they gave you wrong advice. If they give you a hard time talk to the manager.

Based on the calculator here: Voltage Drop Calculator I used the following info:

Wire Material: Copper
Wire Size: 12
Voltage: 240
Phase: 1
Number of conductors: Single set
Distance: 120 feet
Load current: 12.5 Amps

Results:
Voltage drop: 4.76
Voltage drop percentage: 1.98%
Voltage at the end: 235.24

As you can see #12 is under the 3% voltage drop recommended by the NEC.

 

The run is in the wall and attic.

 

Then NM-b will be okay. Be sure to use a in use cover on the receptacle and a weather proof switch or switch cover if they will be exposed to moisture.

 

It's sad, but the men in both orange and red are not always qualified to give advice on electrical installations. Some of them are, but this one in orange for sure isn't.