Temporary back feed

[Always-interested]

Hello - I have a some questions regarding a friends 1900 Sq' farmhouse that we are remodeling/rewiring. The existing house has the old style 60 amp service panel containing one "main" double cartridge fuse pullout with two 60 amp cartridges, plus another pullout with two 35 amp fuses which are marked for a stove. Four screw in style fuses are located at bottom of panel. (Two additional 15 amp and two 20 amp circuits.) It was determined that a new panel rated for 200 amps was required to satisfy the new load calculation. All old k/t wiring was removed and the entire house has been wired to code down to the new panel, except terminating the wires to the breakers. The old 60 amp panel currently serves a subpanel located in basement 20' away. This sub-panel is feeding a one ton central A/C unit, furnace, well and one general use outlet. The problem is, cash ran out just before utility company hooked up the mains to the new service... Now, next spring is the anticipated install time. My first question: We would like to run 6/3 +grnd from the old panels stove contacts to the new panel. My thought was to protect the 6/3 with a backfed 40 amp breaker in the new panel. Then connect only a few necessary lighting circuits, clothes washer, dryer, stove and a few outlets while using the old subpanel in its current configuration. This friend lives alone. (No multiple power users.) I informed him that (if) we did this, he would only be able to run one major appliance and a few lights at one time or he might chance tripping the 40 amp breaker. My last question is regarding proper grounding of the panel(s) The old panel is grounded via its ridgid metal conduit outside of the house, no internal water pipe connection. Is it acceptable to connect the 6/3 neutral together (with its ground wire) at the old panels neutral, then seperate the ground and neutral in the new panel and remove the bonding screw? Any additional suggestions? A thousand thank yous in advance for your help!

[Wgoodrich]

What you are doing is installing this new 200 amp panel as a sub panel through the winter until spring. This would make this new 200 amp panel a subpanel is you are supposed to separate the neutrals and grounding bars same as any other sub panel would be wired.

The 50 amp cartridge fuses in the range fuse block of the old panel would be fine but you could also use the heater lugs found between the screw in fuses. These heater lugs are 60 amp fused by the main fuses in that old 60 amp panel. You 6/3wGrnd is allowed to serve 60 amp fuses.

Then when you have the utility company connect to the meter at the new 200 amp panel you will then change the neutral and grounding bars to be a main service rated panel with the neutral and grounding bar married together as one entity as required for a main service rated panel. Then you would also have to have the main bonding jumper [most commonly a green screw] to bond the metal casing of that main service rated panel to the grounding bar of that main service rated panel.

The grounding electrode system must be any metal water pipe that is in direct contact with the earth for a minimum of 10 feet with the grounding electrode conductor connected within 5 feet of where the metal water pipe enters the dwelling from earth contact. Then you must install a ground rod also as a secondary grounding electrode in case the metal pipe is removed.

If you have no metal pipes in contact with earth but do have mostly metal piping in the home then you must bond those metal pipes to the main service rated panel to make them one with the equipment grounding conductor. Then also you must install that ground rod as you grounding electrode system to serve that home.

Hope this helps

Wg