We are full-timers in a 43' Sierra 5th wheel, and travel all over North America.
I had a somewhat similar problem even using a surge protector - a TRC SurgeGuard (50 amp pedestal and connection). The surge protector indicated that the voltage was ok at the pedestal. The next thing is that my wife comes out of our rig saying that 2 portable fans had just lost all their smoke. Checked the voltage at 1 120V outlet. Yikes - 240 volts. Disconnected the shore power to look things over. Lost the the 120 volt part of both fridges, the electric fireplace, and both microwaves. Razzle frazzle frizzel, etc. Fortunately, the 2 AC units were switched off. Disconnected the surge protector, and plugged shore cable into pedestal, but did not connect to the rig. Found both legs at rig end of shore cable providing correct voltage, therefore connected it to the rig - everything 120v worked except for the stuff mentioned above. Subsequently found that the output connector of the surge protector had a ground problem - thought everything was ok. Wrong.
So I developed a much better procedure to verify shore power.
- I plug in the new surge protector to the pedestal (but do not connect cable to the rig).
- Verify 120 volts output on each leg.
- Inside the rig, turn off all 120 v breakers except for external GFCI breaker.
- Connect shore cable to rig
- Using a multi-meter, check for 120V at outside 120v receptacle.
- If OK, turn all the 120V breakers on.
I purchased 2 inexpensive voltmeters that plug into the 120V receptacles (one inside in the kitchen area, and one outside). I use these to continuously monitor the 120V circuits (especially for low voltage).
On another related note, last summer we were in a relatively remote area of the Province of Quebec. On the first weekend when a number of 50 amp rigs checked in, the voltage at the pedestals was dropping to 103 to 105V - not enough for the surge protector to switch off (only does this at 102V). Lost both microwaves and fireplace (this proceeded the first problem above (that's where I learned how to say "razzle, frazzle, frizzel".
So after having the 240v shore power problem and replacing everything that had let smoke out, I also purchased a voltage booster (Hughes Autoformer). If I see low voltage in my connection procedure above, I then hook up the voltage booster.
Additionally, I purchased and installed fire extinguishers in the kitchen (plus a kitchen extinguisher), both bedrooms, and keep a spare in the truck.
All this may sound like overkill, and a bit expensive, however this is our home, and I have a strong aversion to fire. Also, I have have gained way more experience in fixing non-operating 120v appliances (fridge circuitry, microwaves, fireplaces, etc.). I do not need any more practice.
My $0.02, and worth every penny.