Portable Generator Temporary Connection

Question

I have a 150 amp switch by the meter at my house. My meter is too far from my service panel that's why I have a switch outside. There is a 50 amp service panel in my detached garage fed by a 50 amp breaker in my house service panel.

I was thinking about putting a 50 amp generator inlet socket in my garage and putting a lock on the outside 150 amp switch with the key to the generator in the switch box. Then if I need to use the generator I would unlock the 150 amp switch box and turn off the breaker get the key to the generator re-lock the box then go into the house turn off all my service panel breakers. Then go out side and plug in the generator start it go into the house and turn on the 50 amp breaker to the garage and then select which breakers I need in the house.

I have had one electrician to my house to quote a inlet to my house and a interlock on my service panel. He didn't seem too interested but said he would email my a quote. I have contacted another contractor but he hasn't call back yet. I want to eventually have it done right but want a temporary solution, if needed.

Answer 1

Heck No. Checklists of switches to throw in sequence are absolutely unacceptable. I know this is "new to you", but this is well-hashed territory to safety investigators and most people familiar with electrical. It falls in the "facepalm, what were you thinking" category.

This may seem counterintuitive, but for a temporary fix, you permanently modify the wire. You de-energize the entire system, then run around with flashlights physically severing the mains connections, and physically splicing in the generator connection. Like you'll never use it again, but leaving it intact for potential future use.

For instance I would physically remove the main breaker from the main panel and replace it with a (listed) blanking cover, and/or remove and insulation-wrap the mains feeds. Then hard-splice the wires to the garage so they go to the generator instead of the garage panel.

Walk that whole thing, double/triple check it, have the inspector visit if that's a requirement, then light 'er up. That's what I do for temporary work.

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For permanent work, obviously, I'd put in a proper interlock. This is not as big a deal as it sounds. I would start by installing a small** sub-panel right next to the main panel. This would have two "main breakers" in positions 1-4, with an interlock between them (rather simple affair). One would feed from the main panel, the other from the genny. Then I would decide which circuits I would ever want to light from the generator, and move those circuits to the subpanel. The original main panel stays mains-only.

src

I gather you want to use the wiring to the garage subpanel in a bidirectional manner, feeding the garage from mains, or feeding the house from genny. This has come up on this forum before, and there's just no way to do that even remotely safely. Bite the bullet and lay parallel cable.

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** by my definition, "small" is 42-space. Panel space is dirt cheap and often comes with free bonus breakers, so a net win. Whereas, running out of panel space is a catastrophe.

Answer 2

The only way to connect a generator permanent or temporary to a service is with a transfer switch. There are automatic types (expensive) and there are manual types (basically a double pole double throw disconnect and it must be service rated). Most generators are used as emergency generators, meaning they only are powered up to serve certain emergency circuits not the entire house. That means you have to install an emergency panel and split the load between emergency power and standard power.

What is important to remember is that there should be no way your generator could possibly "head up" into utility power under any condition. The lock out you are proposing does not meet that requirement, which may be one reason no legitimate electrical contractor wants to do it.

Answer 3

The only inexpensive way to connect a generator to a homes wiring in an emergent situation were it must be done now is called double block and break. To execute that you find 2 adjacent points that the current can be readily blocked by separating the Service Entry Conductors from their terminals or opening breakers or removing something that is required for the continuity of the conductors such as the meter socket enclosure and the Service disconnect. You get trained in how to safely remove a meter from its mounting socket and do it in exactly the order you were taught using a check list. Then you disconnect the Service Entry Conductors between the meter and the service disconnecting means. The easiest place to do that is at the service disconnect by removing the energized conductors from their terminals on the main breaker or switch and connecting a plug and cord pigtail in their place. With the Service entry conductors opened in two places and then disconnected in between you are assured that the return of utility power will do no harm and that power from the generator has no way to get on to the utility distribution conductors. The plug pigtail is then inserted into the female connector of the extension cord at least 30 feet in length that is connected to the appropriate generator receptacle outlet. The generator can then be started and once running well the service disconnect can be closed to connect power to the building's wiring system.