I need HELP in preparing my back-up power system

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I'm in the final stages of setting up my backup power system and I'm trying to keep my costs as low as possible, so I haven't contacted any electricians. I have decided to connect my AC power supply DIRECTLY into the nearest electrical outlet (after disconnecting my main circuit breaker from the power company). Since my modest 120 volt system will allow 12.5 amps max, I don't see why a standard 15 amp receptical wouldn't allow power to be distributed throughout the house. Anyway, I tried this idea but my power supply could not reach all areas of the house presumably because each area is connected to separate 110 volt legs of the multi-phase voltage entering the house.

Question: Can I use an extension cord (fitted with male plugs on either end) to connect the leg that gets my power supply to the one(s) that don't simply by plugging into the appropriate wall recepticles?

-- Dr. Roger Altman (rogaltman@aol.com), December 01, 1999


In a word - NO!

Keeping costs low is important. But if cutting corners results in your house burning down from an elctrical short, it's kinda self-defeating.

The y2k prep forum had a thread a few weeks back about installing a do-it-yourself whole house generator connection correctly.

If I find he thread, I'll post the URL here. (Unless someone else beats me to it .... :-)

-- hiding in plain (sight@edge. of no-where), December 01, 1999.

Dr. Altman : This plan of yours sounds good . What I would do, is double check each circuit as to be able to open each breaker at the box. This way you wont get a back feed. Good Luck...

-- Capt Dennis (capden@hotmail.com), December 01, 1999.

here's one:

The Juice Page

-- hiding in plain (sight@edge. of no-where), December 01, 1999.

"Hiding in plain ..." Thanks for the heads-up. I checked your link but he didn't discuss my plan. He did mention that "back-feed" can put you and your house in harms way. I'm proceeding cautiously, and I won't test my idea until I'm certain it will work. It looks like using a back-feed tester ("Jesus Stick"?) would be the first step.

-- Dr. Roger Altman (rogaltman@aol.com), December 02, 1999.


Found the two links I was looking for ...

Popul ar Mechanics Article on installing a transfer switch

Link to a different chat BBS

BTW: what is your PhD / Doctorate in? just curious! There seems to be several of us on here at this level of education. I have a PhD in Comparative Theology, but also have MSEE (Electronics).

-- hiding in plain (sight@edge. of no-where), December 02, 1999.


Thanks again for your interest and help. I'll check the links now. BTW, wouldn't an ohmmeter be useful for determining which house circuits were connected (to a common neutral??) and which weren't?

Since my doctorate is in metallurgical engineering, I'm stretching my electrical engineering knowledge to the limit (maybe two "cookbook", i.e., "don't need to think" classes about 35 years ago -- could it have been that long?).

If I can understand the basics well enough, I usually can figure things out for myself. But, as you can tell, I'm not there yet, so any specific house circuit knowledge you could impart would be appreciated. (I'm also very bullheaded and don't give up easily. So I'm going to go down this road until I'm convinced that my idea WON'T work.)


-- Dr. Roger Altman (rogaltman@aol.com), December 02, 1999.

Just a thought...insurance!! When I contacted the insurance company to add our 40kw generator, they about cancelled us. I had to prove that #1. We pulled a permit from the county for installation and that the county then inspected and signed off the work. 2. I had to show that we actually had a qualified electrical company hook it up and provide a schematic. Sooooooooo, if you have a fire due to your "homemade" system, you might find that your house insurance is invalid. Taz

-- Taz (Tassie123@aol.com), December 02, 1999.


If it weren't for Y2k I wouldn't consider doing ANYTHING "out of spec" But if my idea is sound, read SAFE, Y2k will probably make the "insurance" question moot. However, I won't try this approach until I'm convinced it is both safe (what can go wrong as long as I remain off the grid?) and effective.


-- Dr. Roger Altman (rogaltman@aol.com), December 02, 1999.

Dr. Altman: What type of power supply are you using? You may be better off just to power one leg of your 220 service. You won't be able to run the whole house any way. Look at your main service panel; if there are two 'columns' of breakers, one column is on one leg, and the other column is on the second leg. Choose one, and plug into a circuit that is listed on that column. Make very sure any 220 devices are disconnected at the breaker.


-- Pinkrock (aphotonboy@aol.com), December 02, 1999.

Yes you can Dr Altman. This is exactly the way I hooked up during power outages last spring. It will only provide power to the circuit that is connected to the specific breaker, so using a couple of different extension cords will allow you to reach different areas of the house, but just not at the same time. I try to overcome the complexities of electricity by thinkin of it as water, and see the system as a series of faucets turning juice on\off. I run the genny outside and link to a GFI recepticle. This gives me one circuit for 110v plugs. Then using a power strip, I have easy access to an assortment of items ie; TV or radio or microwave etc. Just not all at the same time.

God speed, God bless, and end well Dr Altman



-- Michael (mikeymac@uswest.net), December 02, 1999.


I'm using a Trace 1.5 KW inverter. My circuit breaker box shows two columns, so I guess I have two 120 volt legs. However, there is essential equipment that I need to run from BOTH LEGS SIMULTANEOUSLY. The KW requirements are modest though, under the 1.5 KW limit of my inverter. Thus, I need to connect both 120 volt legs to my inverter at the same time. Assuming I won't be transferring input power back and forth between my home power system and the power company, can this goal be accomplished safely WITHOUT wiring a transfer switch to the circuit breaker box?

-- Dr. Roger Altman (rogaltman@aol.com), December 02, 1999.

As a minimum precaution to prevent feeding power back into the electrical distribution system pull out your electrical meter. Otherwise if your main breaker is inadvertently switched on you risk electrocuting a linem

-- Roy (bushwacker @ north woods . com), December 02, 1999.

please please please...

Do it right.

While your proposed method of feeding power to selected circuits in your house will certainly work, it is in no manner a safe way to do it. Electricians call double-male end power cables "suicide cords" for a reason.

You indicated you're using a Trace inverter in your emergency power setup. That clearly indicates to me that price is not a primary consideration (unless you picked it up at a garage sale for $50.00), and that you *know* how to do things right. Bottom line:


There are several alternatives when considering how / what transfer switch to consider. For goodness sakes, at least invest $50.00 in a double pole isolation switch and an appropriate male inline generator connection. It's really easy to install this stuff if you have even a little bit of handy man ability. There's a link above to a PM article, and there's an great companion article on the How Stuff Works website.

Lastly, GenTran 60amp transfer switches are so damn easy to install, my mother could do it. It takes about an hour, and you'll never have to worry about breaker alignments or anything. While GenTran's are a bit on the pricy side (around $300.00), there's none better or easier to work with. (And no, I'm not a shill for GenTran, just a very satisfied customer.)

PLEASE, Doctor, do it right, or just buy some extra blankets, candles and a kero heater.

-- Nom (nom@de.plume), December 02, 1999.

Home Depot (Lowes also, perhaps ?) has these type of quick connect generator/AC invertor panels for various sizes between 6 ckts and 15 ckts, including the double breakers you are referring to.

My local Home Depot has a free 9 minute video that makes it very clear, very easy to see what to do. Also, this kind of power transfer panel allows you to balance loads, to selectively power other circuits in the house without rewiring or running extension cords, and to absolutely prevent back-powering anybody "upstream" from your breaker.

Your main breaker can stay shut too - so if/when regular power comes back up, you can run a regulat automotive style battery charger from house power to refresh the batteries....gives you other options as well.

Figure a cost of 20.00 for the cord, and 150.00 - 200.00 - 275.00 (depending on the number of circuits) for the ease, safety and convenience of using these regular circuits and circuit breakers to isolate the generator power. It will save time too - but figure two hours (not one) to install.

-- Robert A. Cook, PE (Marietta, GA) (cook.r@csaatl.com), December 02, 1999.

Could you provide a list of the items you need to run simultaneously?

You mentioned that they are currently on seperate legs of the box.

You may end up with say, 4 essential circuits on one leg and 1 essential circuit on another. You could just move the single breaker over to the other leg and then ALL your essential circuits are on one leg.

BTW- we have 100amp service with 2 legs of 120vac. Normal usage is UNDER 10 amps, peaking to 25 amps. So when I hooked up the Trace 5548SW, I literally got rid of one of the legs and ran the single leg through the Inverter and then back to the board where I jumped both legs to provide power to the entire house, wherever needed. We have no 240vac circuits or appliances.

-- plonk! (realaddress@hotmail.com), December 02, 1999.

Roger: Nom makes some very good points above. Connecting the two legs together with a double-male cord is a dangerous maneuver. A transfer switch and a small sub-panel for your critical loads is the safe and approved method for your desired result. As we are not in an emergency situation yet, I would urge you to follow this course.

I assume that your inverter is a Trace 1512 model. I am not familiar with this particular model. But I am familiar with the 4024, which senses the presence of utility power, and will not attempt to power the entire grid upon failure of same. I suspect the 1512 does not have this feature. If this is true, and if it were allowed to look at the grid load, it would fail very rapidly and (for the 1512) catastrophically.

I am sure that installing the safety switch and critical-load sub-panel would be well within your technical abilities, and could be acomplished at a modest cost.


-- Pinkrock (aphotonboy@aol.com), December 02, 1999.

Dr. Altman,

There is some good advice presented here, take advantage of the safety warnings.

In re the suicide chord, all you have to do is turn your back and some child or other uninformed person could pull out the plug and be harmed. You may be too busy with other matters to monitor and supervise a quick and dirty job. It isn't worth it.


-- Tom Beckner (tbeckner@xout.erols.com), December 02, 1999.

I would like to thank everyone who has taken the time to express his/her views, particularly the emphasis on safety. Based on this advice, I called a local electrical contractor, to go over my options and preceed with providing a safe and dependable backup power system.

-- Dr. Roger Altman (rogaltman@aol.com), December 02, 1999.

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