Should I Use My Heavy-Duty 15Amp Extension Cord or 30Amp RV Cord for Multiple Appliances?

I purchased an adapter that allows me to convert an RV 30A (TT-30) connector to a standard 15A, 3-prong extension cord (Example). Then I attach a standard 15A extension cord to reach my RV. Can I use a standard 15A extension cord to run the air conditioner or the microwave for extended periods of time, or should I use my 30A cord?


You really have to know what your appliances draw before using a 30A to 15A adapter such as this one. Your 30A cord is capable of running a large air conditioner, and a few small appliances at the same time, but the adapter cord will not.

If you want to run a small microwave, and heating element (hairdryer, etc.) you could probably use your 15A Adapter cord+Extension cord combo. Anything more, you should bust out the clunky 30A cord.

If you choose the adapter route, you have to watch how much power is being drawn and have the right size cords! Here are some things to consider:

#1 Your extension cord Gauge should be the same as the adapter (or larger)

The adapter example listed is a 12/3AWG cord which is very capable of running 15 to 20AMPS. This size is very common for heavy-duty 15A extension cords. If you had to attach another cord to get to your RV we recommend matching the adapter’s gauge size (or larger if possible)

You will want to get at least a 12/3AWG extension cord. (Like this one) This set-up will allow you to run a medium sized air conditioner and another small appliance.

Why it’s important…

The big problem with using a 30 to 15AMP adapter is that you essentially lose the protection of the circuit breaker at the camp site pedestal. You end up with a 30AMP circuit breaker protecting a 15AMP cord. You could pull 20 or 25AMPS through the 15AMP cord and the camp site pedestal circuit breaker would not trip. This will heat an under-rated cord and can cause a fire!


Conntek LogoYou really have to know what your appliances draw before using a 30A to 15A adapter such as this one. We can help you make that choice as well. Just contact us anytime and we can work out a good plan for your power needs.

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Posted in FAQ, RV
4 comments on “Should I Use My Heavy-Duty 15Amp Extension Cord or 30Amp RV Cord for Multiple Appliances?
  1. Howard Armstrng says:

    I have bought a 240V 30 amp Dimplex 4800 modle number EMC4240

    This is a portable heater, I want to make an extension cord for it to plug into other work shops. The cord plugs into a 240V straight blade 2 pole with a ground. If you go you can see the a picture of the plug I will mount in two different locations to match the plug end coming on the heater:

    I can’t seem to find the correct plug ends to make a 30A 240V extension cord? I do find these plugs :

    But these are 15Amp rated? Can I make a 20 ft extension cord using these types of cord ends?

    If not what is a better solution?

    • Admin says:

      Hi Howard,
      Which receptacle, specifically, were you interested in? There was a page of results in the Leviton link.
      We will also need to know the NEMA configuration for the plug on the heater.
      If you are unsure about the configurations, we might be able to help if you send us pictures. The email address you can contact us at is

  2. Howard Armstrng says:

    This is the receptacle I”m going to use because its the same as the heater calls for ;

    I wan’t to make an extension cord with the below type connectors, can I use this connector and its receptacle to run the 30amp heater?

    The plug above is only 15amp, do I have to use a 30amp plug/connector?

    If not, can you tell me where I can get such connectors?

  3. Admin says:

    Hi Howard,

    Unfortunately, we do not sell an extension cord that would match that configuration. I would recommend checking with your local hardware store to see if they have the parts you need to make one.

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