You are here:

Electrical Wiring in the Home/240 Volt Portable Heater wire requirements



I am installing a NPH4A Portable Heavy Duty Workshop heater made by Farenheat in my garage. I have a separate 100 amp sub panel in my garage that only carries lights and a few receptacles.

The portable heater is 240 volts / 20 amps with a NEMA 6-20P plug
Watts HI = 4000  16.7 amps
     Low 2660   11.1 amps

The electrical store from where I purchased the heater supplied me with 12-2 wire, 20 amp double pole breaker and a 20 amp 250v  2 pole 3 wire grounding receptacle.

Is the 12-2 wire sufficient to carry the maximum watts/amps or should I jump up to a 10-2 wire?

It appears the manufacturer is pushing the limits with the 80% rule for the plug/amp configuration or am I over thinking this installation????

Thank You,

Tony from NE Pa.

I don't like plug in portable heater. If you can get a direct wire heater you will be better off. The wire size of your heater can be #10 or #12. I'm more concerned with the connection quality then the wire size. #10 is better for the run but more difficult for making tight connrctions. Unless you are a skilled wire worker I think #12 wire would actually be safer.  
About Electrical Wiring in the Home
This site answers questions related to home electrical wiring, home wiring, general electrical help,and other electrical questions related to aleternating current (AC). You can find help on the National Electical Code, home electrical issues, wiring electrical outlets, installing lighting, electrical grounding, and general electrical help for do-it-yourself projects not require an electrician. If you do not see your home electrical wiring question answered in this area then please ask your electrical wiring question here

Electrical Wiring in the Home

All Answers

Answers by Expert:

Ask Experts


Bill Lutz


Any questions about being an electrician or doing electrical work. I can help advise people on their wiring needs, what kind of outlets and switcher to use, explain what an electrical service is and how their breakers work. I can also help them with their lighting needs. . I CAN HELP YOU UNDERSTAND WHAT YOUR LOOKING AT.


My Father apprenticed to his Father-and I apprenticed to mine, repeating an invaluable tradition of child labor and a great place to learn a trade. Beginning at the age of 13, I worked with my dad every weekend and summer vacation in homes throughout Philadelphia repairing and rewiring all levels of residential electrical systems. Studying electrical engineering and earning a degree in architecture has given me a solid advantage in solving the myriad of residential electrical problems. Generation 3 Electrical, Inc. takes pride in every job - building confidence by how we do things - by being prompt, thorough and leaving every job site finished and clean.

©2016 All rights reserved.