Most insurance companies and mortgage lenders consider knob and tube wiring, and/or a 60 amp service, to be unsafe or a high risk.
When initial 60 amp service was installed, only 6 to 8 distribution fuse panels were used and with today’s demands with additional appliances, this is not sufficient. The potential home owner may not be able to obtain a mortgage for a house until the electrical upgrades have taken place. This may prove to be an inconvenience and/or a major financial setback for those with a preset budget.
Before 1950, knob and tube wiring was designed so that the black and white wires can run separately. Today’s wiring system would have a single plastic sheathing covering both wires as well as a grounding wire. When installing knob and tube wiring, ceramic tubes were placed in drilled holes for the wires to run through for protection of wear against the wood. Another difference is the securing of the electrical wire. Knob and tube used elaborate ceramic knobs to clamp the wire to the structure, compared to today where the wires are stapled to the joists.