after losing power for 3 days twice in the last month, I'm looking at setting up a more permanent generator arrangement than I've been using.

I'm thinking of wiring in a separate system to run a few essential items. Never the twain shall meet. For various reasons it's impractical to do what most do and backfeed through a heavy duty outlet.

My questions are about grounding. I'm aware that you can use the existing ground buss but should you? Does it have a negative impact on the generator?

Secondly, I'll be installing a separate breaker box and obviously it's ground buss will connect to the ground on the generator. Should I also tie into the existing house ground or add a dedicated ground for the generator system (it wouldn't be a big deal to do a second ground rod)

Best way to do it is to run the generator through a transfer switch, the switch wires to selected breakers in your main panel and the switch is fed by a large single cord. Individual switches on the transfer switch select between your utility power and the generator power. The transfer switch wires to your ground buss and it's recommended to also ground the generator.

My installation has a 6-circuit transfer switch but you can get them with more circuits. I didn't ground the generator and that doesn't affect its operation.

One of the problems is connecting to the main panel. There's no easy way to access it from outside the house. Not to mention that getting the generator near the main would be impossible in the winter with snow on the ground.

That doesn't include the fact that the main is diagonally opposite the garage and most of the stuff I want to run. I keep the generator under the lean to for weather protection and ventilation, that puts it about 85 wire feet from the main breaker, and then the items to run are about 75 wire feet from the breaker.

Or, I add a dedicated system to run everything desired within a 20 foot distance.

That said, it looks like I'll be adding a ground rod, thanks.

It sounds like you're saying everything essential you want to power is 20 feet from the generator and to connect to the panel is 85 something feet away? If you're only hooking up a couple things then yeah it sounds like you might be better off with your idea of doing a separate system and changing where stuff is plugged in when it's needed. That also avoids the transfer switch part because you're not connecting to your electrical panel.

Yeah, that's pretty much it. It can be done of course but then it's a lot of heavy wire run from opposite corners of the house, hence a separate system.

Street power comes in to the SW corner of the house (meter andpanel location), the well pump, water heater and furnace are in the NE corner of the basement. The attached garage is the E end of the house and the lean to is on the N wall of that. I can literally touch the water heater and the door to the lean to at the same time.

Besides those items, we'll be setting up 1 outlet in the kitchen (next to the garage) and maybe 1 in each bedroom for a lamp. Basically just the essentials. I'm thinking twist lock cords for the basement items to connect to the 2 systems and putting the extra panel next to the man door for selecting which items are powered at any moment.

Just be careful that whatever you do doesn't create a back-feed hazard where you're pumping generator power into the utility line coming to your house. Linemen have been hurt and killed when they contact the back-fed line that was supposed to be dead.

This device from Home Depot is quick, simple, versatile, but $650

https://www.homedepot.com/p/GenerLink-30-Amp-Meter-Mounted-Transfer-Switch-MA23-N/301961623

This 5 minute “This Old House” episode details another type of unit

https://www.youtube.com/watch?v=d9V4RjzUXV8

I had an electrician install a panel & switch in the main house panel, got a HF 9000W generator, and put it to the test.
Works fine, runs my gas heat & appliances.
Oddly, my place runs the well and 1 shop from the main feed from the road, so if power goes out they don't work.
Not a big deal, I keep extra water: 5 gal for toilet, gallons for drinking & etc.
Even after building a screened enclosure, grounding & hook-up cord, I'm in the project under $1,000.
Sits on my back deck under a carport, only place it can avoid snow.
To know when power returns, I run a trouble light from the back shop & switch it on.

At the end of that video I wonder why he turns off the main breaker to use the transfer switch. The transfer switch will isolate the circuits and prevent any feedback.

If there isn't a disconnect between the incoming electricity from the meter to the transfer switch, the transfer switch needs to be Service Entrance rated, which has a built-in circuit breaker to interrupt the power coming in from the meter.

Not to mention it would destroy the generator. This is intended to be an isolated system.

Let me make sure everyone understands the danger there, when the home generator backs feeds the damaged utility lines at 120v?, when that power reaches the first utility transformer, it can get stepped up to from 5,000 to 22,000 Volts or higher, and that can sure hurt a lineman, or a kid playing in a water puddle with a nearby hanging powerline, that was "off" minutes earlier. Additionally, everyone wants the workers to get their power back on as quickly as possible after a storm, but it only takes one careless homeowner to energize a whole neighborhoods damaged power grid, and the workers have no idea who the jerk is, so don't be one.

The transfer switch used in the video has individual breakers for each circuit and the switches isolate the service.

I have installed a few of these or similar ones for customers. Very inexpensive and follows code. Just google and find one for your brand of load center.
http://m.eaton.com/Eaton/ProductsSe...s/TypeBRMechanicalInterlockKit/index.htm

Some jurisdictions may insist on seeing "air between the contacts" i.e. an open blade transfer switch...
Also the breaker manufacturers don't rate their breakers for back feeding (to avoid liability, mostly).

Otherwise, there's no reason not to use a mechanical interlock and back feed through an appropriately sized breaker.

Square D (Schneider), Eaton (Type BR) are the only two so far that I have used and both are UL listed and meet NEC article 702. I think Cutler Hammer also has one with a factory dead front cover preinstalled.

In the past, while I have been very careful, I have used the backfeed method to provide whole home backup power when needed. However I was never comfortable doing that.

When I recently replaced my 1981 main panel I incorporated something I also saw on "This Old House" or "Ask this Old House".

It is two interlocking breakers that prevent the generator circuit from being closed when the main breaker is closed. Said another way you need to open the main breaker before you can close the generator breaker.

However to use this solution you have to be comfortable with managing the loads unless you have a generator that will actually run your entire house.

This is probably the least expensive solution if your existing panel will accommodate the hardware.

Thank you for thinking of us! Sounds like the OP is wanting to build a system that would not do that. That being said, anyone who uses a generator when the power is out....please don't be surprised or upset if power company workers show up to investigate the situation with your generator if they hear it running when they get close by working to restore power.

Generator back feed is a major risk to lineman during power outages. A transformer works either way it doesn't care if you put 120 in to get 12,000 or 12,000 to get 120. We always install heavy ground cables to our system before working on them. Never know when someone is going to get home from the store with their new generator and try and kill ya. We might not see ya but our grounds will destroy your new purchase. Lol

Got lucky several years ago in an ice storm. A tree had taken down a service from both the house and pole. We were putting the service back on the house and co worker said he keep getting shocked even though no hot wires were energized or even hooked up. This was in a dump of a yard with trash everywhere we finally found and extension cord buried in trash going from the neighbors basement window going to his basement window. He hooked up his furnace to the cord backwards without removing the wire to the panel and had energized the bare neutral wire trying to kill us.

Mike

A little bit off topic, but a lot of years ago, we had an ice storm. The power was out for days. My kids were both under 5 years old and getting restless. I got the small 500 watt generator I took to the track out. Ran an extension cord inside and hooked up the TV, a lamp, and the VCR. You could put a tape in the VCR and it would bog the little generator down like crazy when the tape started. Then it would recover and Mickey Mouse was playing. Kids were tickled to death. Pretty soon, though, Cinergy was in the driveway wanting to see how I had lights on. They didn't want to get killed so I could watch cartoons.During the weekend, I borrowed a larger generator from work and connected it the furnace. Now we had heat AND Mickey Mouse. All was good.