Dave make sure the old converter is turned off, unplugged etc..
So only one charge source is drawing power
From the control panel you should be able set the available shore power connection input amps
In this case you want it at something less than 20
You want to know how to change this so you can increase it when you have campground hook ups or a good size generator, and decrease it when back at home
Maybe Piano Tuna will pop in and post the exact instructions
That 100 amp charge should still work, with out hearing up the cord
If
You have the fridge on l.p. The old converter disconnected/unplugged
And no other 120v loads like the A/C
You can't run a big charger , A/C etc. On a 20 amp circuit