Depends on what 120v things you will be running. The latest RVs use those 15/20 receptacles with 12 gauge wire for any 20 amp things. 20 amp breakers to match.
Why a WFCO 8700?? Something you already have handy?
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.
