any electricians in the house? cabin generator transfer switch question

[sbishop]

Hi Everyone,

I've got a couple of deep cycle battery, 185w solar panel and 1500w inverter. I only watch satellite TV and recharge cell phones. i'm usually on there 2-3 days at a time but once or twice a year i'm there for a few weeks. The batteries usually go dead on my by the 4th day and I have to use my Briggs and Stratton P2200 inverter generator with an extension cord thru the window for the TV and receiver and charger for batteries. i'm like to be able to run the generator from my shed and have a plug on the outside of the cabin to plug into the generator when needed. Could I hook up a transfer switch (TF151 Furnance transfer switch) to switch between my inverter and generator? I keep reading about floating and bonded neutral. i'm looking for a simple setup, be able to watch TV and charge the batteries. any help is much appreciated.

Thanks
Sbishop

[Den-Den]

That should work fine.

[sbishop]

do I have to do anything with the ground wire? can I just hook everything up to the generator? Thanks 

[Bandmill Bandit]

Yea that will work BUT I would do either a 12"x12" ground plate buried at least 4 Feet deep or a good 3/4" 10 foot ground rod with #6 stranded ground cable attached to the rod with 2 ground clamps at least a foot apart on the rod.

You can NEVER have too MUCH grounding in any system that is electrical!

I have 4 x 3/4" rods 6 feet apart at the bottom of footings with #6 stranded copper wire back to panel and transfer switch location. Switch not installed yet) but it on the list for this summer.   

[sbishop]

since i'm not hooked up to utility power, is a grounding rod needed? what is the difference right now that i'm using battery/inverter and generator with extension cord? I don't have a panel or I don't think I will need a panel, just a transfer switch for one plug.

thanks for any information. I want to make sure I do it right..

Sbishop

[Gary_C]

If you want to do it right, you should have an inverter/charger that contains an automatic change over relay for when the generator is connected. 

[Al_Smith]

If you're just running things from an extension cord it is grounded back to the source which is the generator .It wouldn't be effectively any different than a generator to a tent .As for solar panels and what not it just depends on how they work I suppose which is impossible to see from a computer screen in Ohio .If in the future  it becomes hard wired then it might not be a bad idea to drive a rod and carry the ground up to the point of usage which could be a panel .You'll never know the true great feelings of having ground rods until you've driven a few with a sledge hammer trying not to fall off of a step ladder . A 90 pound jack hammer works a lot better but then you still have that ladder to climb .I've got a TE 80 Hilti impact hammer that will drive them but it's not a 5 minute job .

[Don P]

 :D Yup a cup on a Hilti is the most fun way, a fencepost pounder will work in a pinch. Swinging a sledge on a ladder will get you referred to forum flight rules :D

I think the portable generator is bonded at the generator and if hard wired later to a panel on mains power that is an issue. I did read articles online some time ago on it but have forgotten everything.

[btulloh]

Yeah - bonding and grounding for generators has it's own set of requirements. There are plenty of references you can find. 

As far as driving ground rods, all the above is true, however someone showed me a neat trick that makes it easy. 

[YellowHammer]

Every piece of standalone equipment including the generator should have an independent ground.  I believe that is a Code requirement.  We almost killed a couple guys running a machine at work that malfunctioned and wasn't properly earth grounded.  Nobody knew there was anything wrong that it was floating.  But with no truly functioning internal ground, it was trying to ground through a piece of metal piping that was about an inch above the grass and when the employee tried to place the machine with a forklift the metal tubing touched the ground, turned red hot, and melted.  If the employee had touched it, he would have melted, also.  Luckily, nobody was hurt, and all we had was a little grass fire.  

Earth grounds are for protection, and like seat belts, you don't need them until you need them.  

[beav]

3 ground rods will do for now: one next to the generator connected to the ground terminal on it.
One near the batt bank/inverter connected to the neg terminal on the batt or the ground lug on the inverter.
One connected to the aluminum frames on the solar panels.
Then they should all be connected together to eliminate differential potential.
That will keep the magic smoke inside your electronics during a thunderstorm and keep your synapses firing normally.
Get an inverter with a built in battery charger and forget the transfer switch

[beav]

Also you can keep running the phone and tv off the inverter while charging the batt.

[Al_Smith]

Of course I can tell stories after nearly 50 active years as a union electrician .One concerns two gigantic  Electromotive  diesels 5,000 HP 4160 volts running through two large transformers raised to 13,800 volts .Using a back hoe and a 90 pound jack hammer myself and my buddy drove over 100 rods the first day of the job which we started on a Saturday .By Thursday of that week I was general foreman over 40 men involved in the project .

BTW that  ground grid work was all "cad welded " (thermite )with 4/ 0 copper. .  

[Sedgehammer]

My electrician just said that'll work. You don't need a 3/4" ground rod with #6 wire. That's good for 100 amp service. He said 5/8" 6' is just fine, but going bigger won't hurt. 

[Al_Smith]

Old trick that works every time .Rod gets jammed with about 6 feet in the ground. Hack saw it off and beat the dickens out of it with a sledge hammer .They'll never know the difference .  Another is to pound a nut on the end going in the ground which punches a bigger hole allowing it to slide right in .It time the earth will fill in around it .I know,dirty little tricks but trust me it's done on a regular bassis .

[Raider Bill]

I just put a ground rod in at a rental. It's so sandy I was able to push it down about 5 feet by hand.

[Sedgehammer]

My electrician 1 ground rod was fine. 

[Al_Smith]

If this is not just idle conversation look up article 250-6 of the national electrical code .That will take the guess work out of it .--There ya go--- 8) 

[beav]

Does that cover canadian off grid solar electric systems?

[Al_Smith]

Canada has it's own code,can't answer that .

[Ljohnsaw]

This is timely.  So my layout will have a few hundred watts of solar, perhaps as much as 1,500 depending on the prices.  I will have a large battery bank, an inverter capable of running a large fire pump ~ 2hp (sprinklers required) and an auto-start generator to take over if the batteries are too low to run the pump.  My building will all be 12v dc lighting with maybe a smaller inverter for a convenience outlet or two (for a vacuum, maybe a standard refrigerator).  My building inspector had me put in some ties to the rebar in my concrete filled walls.  There is about 2,000' of all tied (not bonded or welded) together rebar in the walls and footings with two pieces sticking out of the wall about 24" apart.

From the above description (and what I just read in section 250 of the NEC), I should tie battery ground, solar frames and racking, generator ground, pump ground and inverter ground all together to the rebar.  Likewise, anything metal should be bonded (tied) together.  This would include my black pipe propane, any metal conduit and service panels.  I am envisioning two panels - a 120vAC panel with breakers for power coming from the generator and inverter and power going to 120vAC convenience outlets and a 12vDC panel with breakers for lighting and 12vDC convenience outlets for cell phone, computer, CPAP, etc.

Q1, do there need to be separate wires from each item mentioned above to each rebar ground bar (or just bond them together)?
Q2, for the solar racking and panels, I'm assuming this will all be bolted metal-to-metal together, is that bonded enough that only one ground lead is necessary rather than one to each piece of metal?
Q3, does this sound complete or am I missing something?

As a separate item, I have a Onan generator that the old owner installed a breaker panel to it's cage.  When I look inside, it has 240 across the panel with the generator frame ground attached (bonded?) to the box via the lug strip.  The negative terminal of the 12v starter battery is also bonded to the frame.  All the 120v outlets on the box have both the neutral and the ground going to that lug strip.  A 240vac welding plug has the neutral going to that lug strip.  Does that sound right?  If this were to be used as a backup supply for the cabin, I'm I correct in assuming that the frame would need to be bonded (grounded?) to the rebar and then "plugged" into the 120vac panel, potentially through a breaker?

This is all off-grid so I don't see the need for a transfer switch.

[Al_Smith]

Ground is ground the world around .Article 250 is pretty much straight forward and has not changed much over the years .Fact I cited from a 1978 edition although I have newer editions . I assume it can be  found on the internet though but I've never tried it ..Specific seldom used things like swimming pools impedance grounded neutrals ( zig zag auto  transformer ) etc  might take some research to find but it's on there some place .--Google is your friend ---