RV shore power question

Punchdrunk Monkey

Punchdrunk Monkey

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I was looking at a Tiffin Allegro Open Road (32sa) yesterday. The coach was plugged into shore power with a regular extension cord. We looked around and then tried the electric fire place. It didn't go on. Then the guy starts the generator, transfer switch kicks in and the fire place starts. I also noticed that the convection microwave turned on. I turned on the AC and everything was working. 

Then when I got home I started thinking about it. Shouldn't all of that worked off of the shore power, without the genny running? It might not of run good or even tripped the breaker but it all should of gone on?? I texted the seller to confirm that the motorhome was plugged in (I questioned why the items didn't work). He said they had to be plugged into a 30 or 50 amp plug for them to work. The regular house plug (15a?) will run the lights and charge the batteries but not the big stuff.  Doesn't seem right to me. 

I can run my motorhome stull off a regular plug but it will trip if the AC is turned on. But it will try to run it. 

 
The seller was correct. Most coaches have a power relay box to protect surges and regulate power. We have a Country Coach and the AC's, Microwave, washer and dryer will only power up when plugged into 30 or 50 amp or with the Gen Set running. When plugged into the 110v 15 amp like in storage only the lights and refer will operate. Hope this helps.

 
I think it’s because there are two legs of 120 volt. If you only have an adapter to a 20 amp outlet they wire the critical items to that leg the genny  or the 30 amp plug powers up the other leg

 
Thats a pretty nice feature actually that reduces the chance of human error. Not many people own 10awg electrical cords in the 15a size. It sounds like that coach must have a separate 15a and 50a hookup. Im more familiar with toyhaulers that have a single 30a or 50a hookup. People use adapters to get shore power at home. Maybe relatives stay in the rig. Running the microwave or A/Cs off a 15a electrical cord can result in damage. I think ive seen 108 volts being the number people mention about how much voltage drop you can have before problems occur. 

 
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