Thor Forums

[Porkchop]

25 amp breakers are readily available, but that is not the answer to your problem.
1. Switching the breakers around is stupid. Now you have a 20a breaker for your main. It will not allow more than 20a so the 30 on the a/c will never see more than 20a anyway.
2. The wire to the a/c is rated for 20a, not 30. The breaker is sized to protect the wire AMONG THINGS. The bi-metal breaker can operate at 165% of it's rated capacity for 8 minutes before it trips, and this is from the heat generated by current flow according to design standards set by the NFPA and NEMA. It will trip immediately on a short circuit. This is all by design and testing. These breakers are inverse time trip, not instantaneous trip-which you cannot afford.
3. The comment about 125% is somewhat correct but it is limited to wire sizing and over current protection. The actual correct answer is the name plate on your unit. It will have a comment such as 'max. over current protection allowed'. That will account for everything allowed, plain and simple. NEC allows for NO deviation. As stated earlier 25 a breakers are easy to come by. Use the same brand as the rest of the breakers in your panel. They have been tested and labeled for use in that particular panel. Bad practice to mix brands or styles among brands. Your panel will have a label listing what is allowed.
4. The last place you want electrical advice from is an rv tech. If you need electrical advice ask an electrician.
Remember that your rv was not wired by a professional electrician but some guy on an assembly line to start with. I don't mean to run him down, but facts are facts. This is allowed by fed and Indiana state law because of the assembly line process. Is allowed in most all manufacturing processes. Still is supposed to be designed and installed to the relevant part of the NEC, but very little oversight as to workmanship, such as proper splices which cause a lot of electrical problems, especially fires.

The comment about we should not see fires due to bad connections is totally wrong. I'm amazed we don't see more. It happens in the 'outside world' every day. And to professionals. Humans make mistakes, especially untrained people.We should see more of it in rv's in my opinion.
Why take a chance of a fire and a death in the family over advice from a rv tech that tells you the way to fix your problem is to put a smaller main breaker in? FIND AND FIX THE PROBLEM CORRECTLY!!

Bill= retired EE with 40 yrs expereince