I am not telling you to get a generator big enough to power everything in your house at once. I am saying that having all that load connected to the generator and relying on someone (which might not be you) to turn breakers off to control the load is not good engineering design. Good design is putting your emergency circuits in a transfer switch, in some reasonable relation to the size of the generator. Just as a note, compressor starts on your refrigerator/freezer are quite taxing on a generator.
It would be best there, but you might want a safety switch before that... You're going to make me go get my copy of NEC aren't you? The new one has a whole section on transfer switches and generator connections - and I didn't memorize the darned thing.
But with your luck, your local codes are locally written and totally different. They really aren't standardized that well.
Make it easy on yourself - Call your local city/county building inspector, make an appointment for a pow-wow and talk it over, ask him/her what he wants to see. You can over-engineer it and make it "perfect" - but why? KISS.
You could stick it to one side of the meter socket, and put a big nipple or fitting between the boxes - but it's not the preferred method. You would have to send the 'Utility In' and 'Switch Out' power going through the same conduit and through the same meter socket can, and it would be too easy to get an accidental backfeed out onto the utility lines. ESPECIALLY if someone else gets in there and isn't clear on the concept.
I'd put the transfer switch off to one side of the main, and abandon the wires going out the back of the meter socket can directly to the house breaker panel. Make a new house feed out the back of the transfer switch going inside to the house breaker panel. And at the bottom of the transfer switch you put a landing-lug box where the leads from the portable generator tie down.
Try to lay it out so the wires inside the transfer switch can do not physically cross inside the can - so if the wires get all hot and melty (technical term, I know...) they can't make an unintentional cross connection.
I've always seen them in commercial situations with the Utility Main Breaker placed ahead of the transfer switch, so they can open that breaker as a drop-dead "No Way In HELL it can backfeed" safety. The extra safety step makes the utility linemen working on the snapped lines much happier when they hear a generator running way off in the distance.
That way you still have the separate Fire Alarm disconnect in parallel with the Main Breaker as a place to monitor whether the Utility Power has come back up. (For a business they might turn off and lock the Main and kill the lights for non-payment, but they have to leave the Fire Alarm feed on or the insurance coverage goes away. And it's also a Life Safety issue.)
In a residential situation, if you want to change over the entire house on the transfer switch you'd need a separate fused switch or enclosed breaker to power the monitor light. And get the concept cleared by the local inspector. Otherwise, how do you know for sure when they've got the utility power back on?
If it's a safe place to make a hole, you can get a pilot drill and a knockout punch and blast a hole through the side of the can in about two minutes. They can't put knockouts everywhere anyone could possibly need them, or the can would fall apart...
"Perfect" is an unreachable goal unless you are Bill Gates and have a ton o' money to spend on "Perfect" - Lets see here... A 40KW or
60KW genset with a ton of excess motor- starting oomph and automatic transfer switch, a large fuel tank, and a big UPS inverter running all the critical systems in the house as hold-over - That'll only cost you
25 grand or so to set up...
The lights go out partially, you hear a very muted engine cranking and starting outside, and 15 seconds later all the lights pop back on like nothing happened, and will stay that way for days. And the genset is big enough that no power budgeting is needed, you can be working in the shop on the lathe with the AC up full blast while the Mrs. is baking in the electric oven, no worries.
Remember that there is a breaker right on the generator. So nothing terrible would happen if it became overloaded. It would just turn off.
I looked at available transfer switches that switch several circuits only, they do not do what I want. I have no interest in continuing this discussion.
You come here begging for help, knowing nothing at all. The when you get advice you complain because you know better.
It's pretty tiring and lame.
You're such a pro, just connect the generator as you wish and be done with it. Why do you need to keep coming back here to talk about it? You've already decided what approach you will take.
My meter has been without a seal for several years now . Called the power company when I first broke the seal to work on my breaker box , they never came out to replace it . My panel was replaced recently too - after I looked inside and saw the AC breaker arcing on the tab . Got a buncha poles not being used - yet . Also got the capacity to wire my shed/shop properly now , with it's own box . Which is where I'll feed the main panel from next time I need to use the generator . Betcha if my power usage goes down significantly they'll be out with a seal . And a warrant . Only ones that get to steal from the utility company here are the people in charge ...
On Mon, 21 Aug 2006 21:06:47 GMT, with neither quill nor qualm, Ignoramus4235 quickly quoth:
No, I meant limiting only the high-current-draw circuits to one at a time, ORing the stove and a/c. The rest would remain live (but mostly unused, right?) That would limit the total current the genset sees.
Why can't it run the A/C?!?
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On Mon, 21 Aug 2006 22:01:49 GMT, with neither quill nor qualm, Bruce L. Bergman quickly quoth:
An old 40th edition copy of Richter's _Wiring Simplified_ came today. I haven't had a chance to open it yet. It's based on the 2002 NEC (close enough for my own use, eh?) Have you heard of it/what do you think?
I'll have to see the new NEC at the library for the transfer switch info, I guess. I've been curious.
Does a genset feed back through the transformers and step up to 7KV?
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Iggy has been on alt.energy.homepower for over a year that I recollect. He asks for opinions, not "help". He is excellent on feedback to those whose opinions he absorbs. What he did, what worked, what didn't.
Personally, I enjoy reading his posts... And I just looked through all the images he has on his website, so he is giving GOOD feedback. One could read his discussions, wait until he has his bugs worked out, then copy what he has done for themselves.
Because hermetic compressors have a nasty start surge, and if the generator is already partially loaded that surge will stall it. If there's nothing else running you might get away with starting it.
The AC Compressor (3 ton) might only draw 10 to 15 amps at 240V once it's running, but it takes a healthy 10X to 12X running amps spike (100A to 150A) for a half-second or so to get it moving, and then the load tapers down to the normal running amps over about another second, second and a half as it comes up to speed.
Small generator sets like Igor's Onan 7KW two-cylinder Diesel don't have either the rotating flywheel mass or the instant throttle response to handle big starting surges like that. They just stall out, like your car would if you dumped the clutch at a green light - too much load applied too fast. This is why you have to size generators way big if you plan to start these types of loads reliably.
That's my thinking exactly. Plus, who knows what will be the additional damage from the voltage and frequency drop that my generator would experience.
mine is 4 ton, 26 amps rated.
Yep. I can start little motors, I reckon, but not the A/C. I have a little window A/C unit, 15 a 125 volts, and maybe I could use it in case of some very terrible heat (in one small room).
Absolutely it will! Transformers will gladly run in reverse. They might not be as efficient in reverse, but they'll work well enough.
Of course, you need the "Perfect Storm" situation where there are no other loads on the distribution lead except that one step-down distribution transformer feeding your house, the lines are both open somewhere on the path back to town. If so, and you backfeed the
120/240V from your panel, there will be that nice 4,800V, 7,200V,
9,600V, 14,400V sitting there all stepped-up and ready to hurt or kill an unsuspecting lineman that gets between the "dead" lines.
Most of the time there are other transformers and other houses on that distribution lead, and their light and appliance loads will be too much for your generator. And the service personnel are always supposed to place a protective ground lead on the lines they are working on (in both directions) to shunt any sneak currents or accidental line re-energizings away.
The accidental backfeed will hit that ground shunt or the other loads on the lead, and either trip the output breaker or stall your generator. You hope.
Yes. Or even higher, depending on precisely what xformers are between the genny and the lineman. A step-down xformer being "driven backwards" is just as functional as a step-up transformer.
Backfeed can and has killed linemen (note deliberate use of the plural) and it doesn't take a monster genny to make it happen - Just the right (or wrong, if you prefer) combination of transformers. To make things worse, it's sneaky - the zap could happen literally miles away from the genny that's the source of the juice. Sane linemen fear the backfeed. And I damn sure ain't gonna call one of 'em "chicken" for it!
Nor will I , having been bitten by a mere 450 volts . . Last time we had a major outage they made me shut my generator down while they worked on the downed line next door . I showed them how turning on the main breaker would stall my little unit , but ... Biggest problem here is jealous neighbors ! They either want a share of the juice , or threaten to shoot you/your generator . I'm better armed than most of them ...
Nobody needs hot meals and air conditioning. I do kust fine without either and am healthy as I need to be. I sleep with a small fan running and a window open. I eat mostly cold food, drink cold beverages, don't have or wish to have a hot tub. I can barbeque with charcoal or bottled propane and fire up some logs in the fireplace to take the chill off. sleeping bags or an extra blanket if it gets cold enough. Most people could get by like this for many weeks if they really tried. My utility bill is usually under $25 a month.
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