I would like to add 240V/50A infrastructure to support a portable generator for power outages. I’m planning to buy a Westinghouse WGen1200DF, 15000/13500 Peak Watts and 12000/10800 Rated Watts (Gas/Propane) due to its fuel flexibility and low THD. A permanent generator was overkill and outside my budget.
The garage contains the sub-panel powering 75% of circuits to my single-story house, although several key (at times) 120/240 branches are also fed from within the MBP. I considered installing an interlock at the sub-panel to facilitate back-feeding there, but can’t because there isn’t a main breaker inside the sub-panel (the 100A breaker for the sub-panel is in the Main Panel). I considered a Generac or Reliance manual transfer switch (with breakers) at the sub-panel, but I wasn’t happy with the limited number of circuits and also felt it wouldn’t be cost effective after buying appropriate GFCI/AFCI breakers for the transfer switch in order to meet NEC. In the end, I felt providing interlocked 240V/50A generator service directly to the MBP was my best course of action. It would cover the entire house and use existing breakers, although I would have to actively monitor the power demand.
My main concern is distance- the main breaker panel (MBP) is on the opposite side of the house from the driveway and garage (hindsight 20/20). I would like to keep the generator on the garage/driveway side of the house for security, ease-of-movement to/from the garage, and close access to my buried 500 gallon propane tank for fueling the dual-fuel generator. I considered using a very long 6/4 cable, but it would require about 120 feet to make it from where the generator would rest, not to mention lay on the ground in front of the house.
Given all that, I believe my best course of action may be to add a 50A Power inlet by the garage, and run the line through the attic (I have easy access, and it would essentially follow the same path of the existing sub-panel cable), out the soffit (in conduit) and down into the MBP mounted on the outside wall of the house. The overall distance from the power inlet through the attic to the MBP would be about 90 feet. Add a 20 ft 6/4 cable from the power inlet to the generator should make the maximum distance about 110 ft.
With all that said, I wanted to ask:
- Does my thought process and approach make sense and seem reasonable?
- Is a 110 ft distance from generator outlet to MBP ok? I want to want make sure I have maximum voltage/current available at the MBP.
- For the 90 ft run through the attic, will 6/3 suffice, or would I be any better off using 4/3 to overcome any increased impedance? My understanding is that 6/4 or 4/4 would not be required for the 90 ft run through the attic.