Power line indicator

Lenny, try taking a plain NE-2 with no resistor and connecting about a foot of insulated #22 solid insulated wire to one lead and wrapping that around a piece of insulated wire the same size as your service entrance wire and connecting the other lamp lead to neutral. Energise the heavy wire with 120V and see if the NE-2 glows just from the capacitance of the large wire to small wire. That is about as simple as it gets and is adequately insulated from the service cable to not need any current protection.

Neil S.

Sure. You're describing a capacitive AC voltage sensor. Ground the end of the tick tracer that you would normally hold. You have to rig a mount that places the probe tip in proximity to the cable drop, and couples the barrel to ground. But you only need to mount it when you have a power outage, correct?

I have good luck with a battery operated AM radio. There is so much electical noise where I live that AM stations are covered by it. When the power goes out to the neighborhood it becomes clear.

I just turn on the radio and wait for the noise to come back and be stable.

Geoff.

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Geoffrey S. Mendelson,  N3OWJ/4X1GM
My high blood pressure medicine reduces my midichlorian count. :-(

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I really like the NE2 capacitive probe idea. I've actually seen this work around flyback transformers and fluorescent lamps but never thought of trying it in this application. I'm going to experiment. When you mentioned "neutral" Neil, connecting to ground on the service entrance should work as well shouldn't it? And to answer Spamtrap's question I would just as soon leave the probe in place all the time. NE2's are cheap and the breaker box is on the other side of the room. (You haven't seen my basement). The AM radio scheme sounds like an interesting possibility too however with all the CFL's, dimmers, switch mode power supplies, etc in use today I don't now how "Quiet " my house would be even without the utility. I'm assuming that you may live in an apartment building Geoffrey with many close by sources of noise. Our nearest neighbor is about 750 feet from us so I don't think their noise contribution would be very influential. I am going to listen to this noise though at several different frequencies next time power goes out and then compare it to the noise when power is restored. I'm going to try the capacitive approach first and I'll let everyone know how it works. Thanks, Lenny

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In addition to the insights by other posters, if you have standard U.S. 'split phase' service, please consider an indicator for each half - phase.

Consider using two 4 W 'night lights'. They won't be fooled by electrical noise on the line, as the neon lights might.

So L1 to neutral gets a lamp and L2 to neutral gets another lamp. The reason I mention this is that the last three 'brownouts' in my area were characterized by the total loss of L1 and very low voltage from L2 to neutral.

--Winston

Winston, one of the main concerns that Lenny rightly had was connecting to the entrance wires AHEAD of the main breakers. Your average modern branch breaker is rated for 20,000A interrupting and the main breaker for probably 50,000A. One cannot safely stick a 1/4A

3AG pigtail fuse off the mains to ptotect against a fault in your 'night lights'!

Some years ago I assisted in wiring a friends new house and for the electric heat in the crawl space, we installed a neon indicator in a box in the utility/laundry room to show when the crawl space heaters were powered. I ordered a neon panel indicator rated for 240V and double checked it's markings along with the carton information to be assured it was for 240V. It was connected across the 240V 30A supply to those heaters and the breaker switched on. Ka-boom !! Fortunately the breaker panel was not in that room since it was showered by shards of the Bakelite box cover and fragments of the neon bulb and holder plus there were nice black marks radiating on the wall around the box. A replacement indicator [same type] worked fine for years.

Neil S.

I do like the idea of monitoring each side of the 240 as you had suggested Winston. I have gotten equipment in here in the past for repair which had been severely damaged by a loss of the neutral, or some other imbalance as you had mentioned. However I have to agree with Neil about isolation. If there is a way to do this without physically connecting to the utility ahead of all circuit protection I would like to explore that option first. Lenny

I can see how it might be a difficulty WRT the NEC. I imagine they forbid *any* kind of load 'north' of the branch circuits.

But looked at from a sheer electrical engineering standpoint, I don't understand why fuses off of L1 and L2 should not be adequate protection for these indicators, even connected right to the input horn. Theoretically speaking, of course.

The power company uses inductive coupled sensors far 'north' of the consumer's branch circuits. Perhaps it is legal, moral and correct to use inductive sensing in a residential power situation as mentioned upthread?

That is weird!

--Winston

Except for the fact that the fuses and lamps would have to be "moused" into the panel before the main breaker in some sort of safe way, I guess from a theoretical point of view it would seem like a workable safe plan. However in looking at it from a strictly pragmatic point of view I guess that I must consider the litigious society we all unfortunately live in as well. There is always the possibility of an insurance inspector seeing that modification on a disconnect after a fire.

Even if the fire was caused by something totally unrelated to the modification everyone knows that the last thing most insurance companies will come across with is a check. And since this modification, however technically feasible and safe would be a violation of the NEC, subsequently a case could still be made for noncompliance and therefore, no money. I hate to have to think this way but I guess we all should. The inductive, or capacitive approach would totally eliminate that factor from the equation.

I do have one question though Neil about the experiment that you initially suggested. I can understand how wrapping the one foot length of #22 wire around the piece of cable which simulates my entrance cable would capacitively/inductively, or both couple the AC to the NE2 lamp, however in actual practice I won't be able to wrap just one conductor of the entrance cable outside of the panel as they're both together in a jacket. I would think if I were to wrap both, every time I'd cross the pair, the second wrap would be out of phase with the first and the net induction into my "probe" would be zero. I could get into the panel and without making a direct electrical connection wrap just one or both of the mains, (if I do an indicator for each phase), and perhaps that's what you had in mind? Or am I looking at this incorrectly? Lenny

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Neil When you say "you can probably use the circuit sensor probe on the outside of the sheath", what if I made the probe wire somewhat longer and just merely "laid" it up against one of the entrance conductors for a distance outside of the panel? I could tape it in place. (If this worked I'd use one on each phase). If I'm understanding this correctly when you "wrap" the probe wire around the conductor that would appear to be induction, (transformer of sorts), and if you were to just "lay" the probe wire against the cable then that would seem like capacitive coupling? I don't know what kind of field we're dealing with here however I would suspect that the magnitude of both induction and capacitive coupling would be directly proportional to the size, or rather the length of the probe, right? Lenny

I almost hate to say anything because there are so many variables. First of all in most places the insurance company can't get out of paying because of non-compliance unless that is the cause of the loss. In this case if the non-compliance still exists it was not the cause of the loss and if it is, it would be gone. The capacitive method is a nice idea but I think it would be too easily fooled by circumstances.

First of all take the case of if the power ison, here in the city there is always 60Hz SOMEWHERE and could be picked up capacitively even if power is not restored. If you connect a high impedance DVM or VTVM to the power lines when it's out it will likely read some voltage. That's why alot of electricians use what's called a Wiggy. This type of meter presents enough of a load to make sure that when it says a circuit is live, it is really live. It's a similar comcept to using a battery tester instead of a meter, to find out if there is any current behind it.

At 60 Hz of course you can't just put the bulb near and have it glow, so you wrap the wire(s). Getting enough area for the plates of this "capacitor" is the key of course. If you have Romex type entrance cable you would have to tape it along the sides, if it's in conduit you need to get inside the box.

If you are turning off the main breaker and backfeeding the panel, that's not quite the way to do it. There are setups available for this purpose at electrical supply places. First of all the first thing the mains must hit is a main breaker or disconnect. Unfortunately you need to be before this. Since this pain in the ass exists why not just get another box that will hold a relay to switch it automatically ? It's probably about a hundred bucks in components tops, and that should include the enclosure and whatever wire needed. A relay simply switches the source. It pulls the relay with line voltage, when it is gone it switches over. With some minor enhancements you can make it shut off the generator as soon as power is restored, and if you want to get fancy and the generator has electric start the whole thing can be automated.

There are products available that do just that, but you CAN DIY this if you mind the NEC and local codes. If you DIY, mount a dorrbell Xfmr in a box right on the side of the main panel. Hold a relay open with it for the ignition of whatever cutoff the generator has (can be a problem if it's deisel). To have it autostart the main problem is sensing when the engine is actually running to disengage the starter motor. There are several methods of doing this, and some generators are setup for it already. It all depends on exactly what you have.

However, if you look for example at Grainger, the proper enclosures are available. What makes it legal is the doorbell Xfmr, which must be installed a certain way. Then whatever you do with the 24 volts doesn't mtter because it is class two. Remember class one and two wiring must be separate, and even with class two you can't do just anything you want.

Tell ya what, since it's a lazy Sunday afternoon I'll have a look around, I bet what you need is available, and for less than a hundred bucks.

J

"If I'm understanding this correctly when you "wrap" the probe wire around the conductor that would appear to be induction, (transformer of sorts), "

That is correct if you provide a return path at the other end of the wire. Doing that will make it sense current inductively. If you leave it open it wil detect the voltage capacitively.

J

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Fantastic idea!!!

The neon lamp method works. You'll need one for each phase.

However, I smell a different problem. I couldn't see why you would need to monitor the voltage before the main breaker. If you had a proper transfer switch, it wouldn't be necessary:

If you're powering some appliances with an extension cord, you can tell if the power has returned when the house lights come back on.

My guess(tm) is that you're opening the main breaker when the power dies, and back feeding a wall outlet with a suicide cord (a power plug on each end of the cable). If you're really clever, you'll backfeed both phases with a 220VAC suicide cord.

The 220VAC version will work, but the single phase suicide cord has a problem. Under normal conditions, the current through the neutral wire is nearly zero. That's because the 180 degree phase difference between each phase cancels the current in the neutral wire. However, with only one phase powered, you're likely to see the full current through the neutral. If you're creative and parallel both phases, then the neutral current is even higher. Code compliant wiring can survive this, but I've seen a few blown neutrals. That's when the neutral wiring was rotten, and nobody noticed until the full current was applied.

Another problem is that when you back feed a single wall outlet with a suicide cord, you're going to be limited by the current limit of the connected circuit breaker. In the US, that's about 15A. That should be sufficient for most loads, but I suggest to disconnect the high current loads to prevent blowing the breaker.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

I think that what you may be talking about Jeff is an "automatic" transfer operation. This sounds like a system that will automatically start the generator on sensing a loss of power, and then activate a huge double pole contactor. Then when power is restored the generator is stopped, and the contactor switches state. This is a whole house system and you're correct in that you would not need to monitor the utility because the generator system would do it for you. However if you look at the first example of a transfer switch on the page you included with your post you'll notice that the example is a manual switch which controls six circuits. To utilize this switch you pull six loads out of your panel and wire them through this switch. The generator is manually operated and essentially the utility mains is on one side of a double pole switch, (if you will), the generator is on the other side, and the load, (house) is in the center. In any case and regardless of what system you use, there can't be any connection between your generator and the transformer on the pole. Therefore, and please correct me if I'm wrong but it would seem that with any manual system, whether you use one of these manual switches or you back feed a 240 volt circuit and manually kill the main, you would have no way of knowing when the utility is back in service. Lenny

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I suggest that Klem adopt this philosophy of life, instead of being Nick Negative:

"As you go through life, make this your goal: Keep your eye on the doughnut and not on the hole."

The manual transfer switches connect only certain house circuits to a portable generator -- presumably those powering appliances that the homeowner deems to be critical. The rest of the household circuits will be unenergized until the mains power is back on. So the owner will know to shut the generator off when all the lights and radios, etc. come on.

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Thank you for correcting me on that point. But in what way was I being negative? Doughnuts are no good for you. Lenny

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Jeff gave you your answer, but you rejected it instead of trying to understand how it met your needs.

But the "return path" coil will then detect current, not voltage. I think the capacitive idea is better, but you might need a bit of load on it to avoid false detection of noise on the line. Cheers. Roger