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Generator questions

Posted by squishyball (My Page) on
Wed, Mar 13, 13 at 15:06

Hi all,
The other threads here have me thinking I should finally get the generator I keep putting off. I was looking at something portable. i.e. put it away, only use it on the rare occasion where power is out and we need to keep our fridge and sump going. 3000W would suffice for that.

The Powermate 3000 has a 120/240 twist lock plug...

In my garage, I ran a 120/240/20A twist-lock dedicated circuit for my table saw.

Can I throw the main breaker in the panel, then backfeed the panel thru this line? (I would have to whip up a 4-prong twist-lock to 4-prong twist lock cable, which would be easy enough)

It would sure beat extension cords, and allow me to then throw all the other breakers but the sump and fridge ones to ensure I'm only powering those.

Also... is the power from these little generators considered pure enough to power sensitive electronic equipment? i.e. in any emergency situation, a computer and internet access would be key elements of communication to keep online.

Thank you!
-mike


Follow-Up Postings:

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RE: Generator questions

With out some sort of mechanical or electrical interlock to keep both the backfeed and the mains from closing at the same time, it is ILLEGAL to do this.

Further, using a suicide cord (one where the plug is energized) is dangerous.

Note, while you didn't say it, you do NOT want to run the generator in the garage (even with the door open).

There are other ways. Where is the panel and the loads in location to where you might want to run the generator?


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RE: Generator questions

Hi Ron,
Panel is in the basement. Underground feed. Sumps in the basement, fridge on the main floor. Installing a transfer switch is doable... but would be a big project and cost more than a small generator.

Does a breaker even function this way? In theory, if you were to feed power backwards thru the breaker and pull over 20A, would it trip? A fuse would work that way, but I don't know if a breaker has more advanced ciruitry to prevent the backflow of energy thru it.

If they don't, and they shouldn't be used this way, then obviously they should be built to immediately trip if the terminal side is ever energized...

Oh, and (Edit) the only place I'd envision the generator would be the garage. Presumably in a chicago power outage / emergency situation there's either going to be a major storm or a blizzard, so putting a generator outside is not going to be realistic... Thoughts?

This post was edited by squishyball on Thu, Mar 14, 13 at 11:05


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RE: Generator questions

Running the generator in the garage is an invitation to carbon monoxide poisoning.


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RE: Generator questions

Chicago has it's own version of electrical code. Where it starts with the NEC it gets even stricter. I'm not versed in it. I can tell you what you want to do is illegal under the NEC and is illegal under the Chicago code.

The upside is you can get at the Chicago Municipal code online (which includes the electrical code).


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RE: Generator questions

I can't believe someone would risk:
1. Killing a lineman (backfeeding a panel without a proper transfer switch or interlock kit)
2. Killing themselves (using a male to male suicide cord)
3. Killing their whole family (running an internal combustion engine inside the garage of a house)
Just to save a few $$$ on having a professional come out and do it right. That means safe and legal. Sure, it is not free, not even cheap, but what is someones life really worth? Oh well, keep pinchin' them pennies!


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RE: Generator questions

...or do it right himself. We're willing to tell him how to do it right but he doesn't want to listen.


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RE: Generator questions

Um...
This is a forum. I'm asking how to do it right, and the responses thus far are "I can't believe you'd do that". Nobody has done anything. Yet. Except I've asked questions, and from the pros, gotten very little useful information.

So pls keep the snide comments to yourself, and if you have useful information on what TO do in such an emergency situation -- which most people are ill prepared to really handle -- and aren't just going to make ridiculous allegations about ones desire to kill linemen then feel free to help by sharing your knowledge.

This is a real-world crisis situation that myself or anyone could face. i.e. power out for extended time. Reading about it and listening to the pros now might lead to me or someone knowing just a little bit more when and if that situation ever does come up...

I've asked "does a breaker work in reverse". This is not to "do it anyways" like you are assuming, but to better understand the circuitry in a breaker. I like to understand things. I have breakers in my house, I want to know how they work, what their limitations are. I don't do things cuz someone said to, I do them cuz I've researched, understand the risks, and make decisions. It affects everything. I couldn't cook the other day w/o looking up why double-acting baking powder acts twice. I just wanted to know.

It's not a cost issue. I've replaced entire service feeds to code. But doing it might take me a year cuz I'm on another project at the moment.

It's not a quality issue. I've been told by inspectors that I do nicer work than most pros they inspect. But I do so by getting all the information first, which is what I'm trying to do here.

Thus far we've learned from the pro's.

"don't use a double plug cord". Yes I know they're dangerous. One could walk around w energized prongs sticking out of a cord and bump into someone or something (a car, machine, whatever) and instant zap. Well you know what? Driving a care is more dangerous than using such a cord. More ppl die in cars every day but the answer is not to not use them, it's to use them safely. How does one safely, practically, and necessarily in an emergency situation where transfer power from a generator to various parts of their house, possibly leveraging the existing wiring and given the urgency of the situation, knowing that installing a transfer switch is not feasible...

"don't run a generator in the garage". Ok, fine that's where not to run it but it gives no real help as to where TO run it. Where would you run it? A) don't run it at all. B) in the basement. C) in the garage. D) wheel heavy grounded machinery into an active lightning storm outside. Pick the LEAST harmful. None of them are completely safe. And then even once the storm passes... if you have an extended outage, are you going to leave your generator on your porch overnight when the city has been out of power? That is a recipe for getting your generator stolen, cuz there will be thousands of other ppl w/o power who would see it there and steal it in an instant. So again. Where do you (seriously) run it?

These are real questions ppl.
-mike


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RE: Generator questions

Yes this is a forum, but many of us are professionals and the law and are professional ethics bar us from telling you to do blatantly unsafe or illegal things.

I told you that you couldn't run it in the garage. You refused to consider other locations. With that level of impasse, I can't go further.

If you are willing to tell me you are willing to do otherwise, then we can help.

We can't tell you any situation that will result in the possibility of backfeeding the mains.

We can't tell you of a situation that involves suicide cords.

Your only options are temporary installations outside the code such as non-permanently installed extension cords, or putting in a transfer switch OR ...

My suggestion is to install (or reroute) the circuit for the freezer and the furnace to a place where it is convenient to switch these over to the generator feed.

Normally, this isn't a big thing but in Chicago you're not allowed NM cabling it's a bit harder.

The problem is that yes, portable stuff can get stolen. Frankly, the GARAGE is no panacea either. My cousin had his generator stolen from his garage while it was running as well. I'd suggest sinking some anchors and fixing it down with some cables or chains that are tougher than the average thief is going to waste time trying to defeat. Of course this is NOT an electrical issue.


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RE: Generator questions

Gens have a hard time starting motors. At motor turn on, in that first moment when the motor is not spinning, it's almost a short circuit. That's why the motor nameplate has Locked Rotor Amps (LRA) listed. The genset needs to be powerful enough to supply the LRA in addition to any other loads on at the same time or the motor won't start. It gets worse if the motor is 120V. Your 3000W gen only supplies 1500W per leg (120V receptacle). That'll start a motor with a LRA of 12.5A or less.

After experiencing hurricanes in Florida, and Sandy at my parents house, Deisel and gas are not the answer. Go natural gas if you have it. Propane is next best.


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RE: Generator questions

I've got a 80KVA propane (no natural gas in my neighborhood) on my house. The power goes out, six seconds later I'm up on the generator.


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RE: Generator questions

Of the four choices, I would say 'D'.

In your thunderstorm scenario, I would wait for it to pass, then move the genny outside the garage. I would chain it to the nearest substantial item. For me, I have both a large tree and/or vehicle, and heavy chain and lock.

The fact that you're asking up front implies you are thinking about this before you need to do it. With that, I would suggest that attempting to feed your panel with a 3kw generator in order to power most of the things in your home would be frustrating. You will be dealing with overloading the genny pretty much all the time.

You would be better off planning up front as to what circuits are critical to you and putting them on a subpanel designed for this purpose. Reliance makes panels like this with included manual transfer switch, breakers, generator outlet plug and even meters. They make 120v as well as 240v panels with different number of circuits in case your needs grow.


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RE: Generator questions

Good point on overloading, I'm doing some calculations now...

In fact I went to HD today, and they actually sell a small 6-switch transfer kit for $279. Neat part is it does not require moving the 6 circuits, it has a whip you connect to your main, then take the 6 circuits right off the breakers... they go thru the transfer switch, then back thru the same whip and hook up to the lead going to the devices. This makes installing such a device painless. The slowest part would be running the conduit to the remote plug-in... which is included for the $279. This remote plug in has an inverted plug, so you don't need to have a suicide cord. Cool.

So on to sizing... from what I can tell, the powermate 3000 is popular, and reviews on youtube and such seem to indicate it powers what ppl need. i.e. it can handle a saw and a compressor for construction, or furnace, sump, fridge, and a few lights at home.

Note it would be impossible to power your whole house, since you're gonna be limited to the 6 circuits anyways. I envision they'd be... Sump, Fridge, Furnace, Computer, Lights, Oven (starters only -- gas otherwise).

Energy guides say a 1/2 HP sump is 800W running and an additional 2200W starting (3000W total at start). If this is the case, and 3000/120 = 25A, why does this not trip a 20A breaker every time it starts?

Regarding Nat Gas... yes that's ideal... You've got the gas line already so it's indefinite run-time. If there was any requirement for this power other than the one-off chance of actually needing backup power in a storm, I'd consider the expense... but the goal is simply to have minimal cost while preventing major disaster (flooded basement) in a crisis -- not to create a comfortable living environment.

Ppl also say the 5000W is significantly heavier than the 3000W.


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RE: Generator questions

You can find those Reliance units on line in different sizes in case you need more that 6 circuits. I think they make up to 10. You can also do 220v if you want to hook up a water heater or something else. This would probably take up all the power of your 3k genny depending on how many elements you have in your heater. But you don't power anything else for the 30 minutes it takes to heat the water. Or 10 minutes.


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