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Power-User

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Generator Power and Clocks

01/17/2007 9:57 AM

Good morning all! Nature blessed many of us in the US with an ice storm this past weekend and some of us are without power still... I invested in a backup gas powered generator 4 years ago and it's the best home investment I think I've made.

My question is that it seems that the electric clocks in our house are gaining 15 to 20 minutes a day. What component of the generator power is different from the line power and causes this "speed up" of the clocks? Is this a potential problem for my other household electrical equipment?

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Guru
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#1

Re: Generator Power and Clocks

01/17/2007 10:03 AM

If they are motorized clocks, or electronic clocks that sync to the AC, it's the frequency of your AC voltage, nominally 60Hz, and very carefully controlled by the power company, but much less so in your gas generator.

If they're quartz crystal digital clocks, it can only be because your generator has ripped a whole in the space time continuum. Please turn it off.

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Guru

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#2

Re: Generator Power and Clocks

01/17/2007 1:00 PM

At not much more than a 1% speed up, I'd think it's nothing to worry about re other stuff in the house, such as motors. I suppose you could reduce the rpm of the generator a bit, while measuring output frequency with a good digital VOM (some of which, I think, can resolve to within +/-.1 hz.). I'd guess, however, that when the load is high, the rpm drops -- in other words, the governor is probably not perfect, so it might be better to just live with it as it is. At least you'll always get to your appointments on time.

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Power-User
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#3

Re: Generator Power and Clocks

01/17/2007 2:52 PM

Just a note on gas powered generators

I think we're moving toward a time when gas generators will need to be governed by sound ordinances. Several of my neighbors have generators, and when the power fails during the summer it becomes impossible to sleep because it sounds like jackhammers running outside my bedroom window all night. Closing the windows isn't an option because (obviously) my A/C isn't running.

I've been tempted to go pour sugar in the gas tanks!

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Guru
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#4
In reply to #3

Re: Generator Power and Clocks

01/17/2007 2:59 PM

I noticed that after the last hurricane. Those things are LOUD.

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Guru
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#8
In reply to #4

Re: Generator Power and Clocks

01/18/2007 4:08 AM

Bhankiii:

I bought a cheap new generator last year after my ancient one finally gave up the ghost. It's only a 3.5 KW model, but that's enough for all the essentials and lights plus a TV and computer, if I watch the toaster, microwave etc. The power rarely fails here for any length of time, and then gas storage is more of a problem with larger generators, and a diesel or natural gas unit just isn't a wise investment here, the need being only once every few years on average, and then only a day or so. It is insurance for the less frequent several day blackouts and they are only a few times per decade.

I was in awe how quiet it is! They've come a long way. I had added an additional large my muffler on my old unit, but it still made a racket.

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Anonymous Poster
#15
In reply to #8

Re: Generator Power and Clocks

01/18/2007 10:37 PM

After five years of non use a gas powered generator will likely have varnish in the carberator and the fuel will likely have gone bad. Diesel can gel at low temperatures. A normal gas generator can cheaply and easily be converted to run on natural gas or LP and these potential problems will be eliminated.

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Power-User

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#5

Re: Generator Power and Clocks

01/17/2007 3:18 PM

Update - - My wife just called to say that after running rough for a while, flames started coming out of the generator exhaust and she had to shut it down. Fortunately, the power had just come back on so we don't have to worry about freezing. (Till the next outage, that is) I don't know what to expect to find when I get home besides a slightly charred generator that won't start...

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#6
In reply to #5

Re: Generator Power and Clocks

01/17/2007 3:21 PM

I WARNED YOU - YOU WOULDN'T LISTEN!!

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Power-User

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#17
In reply to #5

Re: Generator Power and Clocks

01/24/2007 9:20 AM

Don't forget to put oil in the generator!! I almost burn one up. My father-in-law loan me his when we got hit by the October snow storm in 2006. (You may have heard about it in the news, I lost power for 9 days.) That was my first generator experience, and he forgot to mention about putting oil in the generator. So I ran that generator 24 hours a day for 2 days, and then on the third day it won't start. The motor sieged up on me. Lucky my father-in-law was able to free the motor by using oil and a wrench and working it back and fore to lube it. I learn my lesson that day.

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#7

Re: Generator Power and Clocks

01/18/2007 3:51 AM

Many years ago I built a digital clock which used the mains 50Hz frequency as the time base. At the end of the first days operation I was surprised to find that the clock was running several minutes slow. Next morning the time was spot on! After a couple of days of this I rang up the local power Company and they said that generators run slower during the day due to the loading, then at night they run faster so the frequency roughly evens out over 24 hours. They had an electric clock in their control room to check that the slow/fast swings were acceptable and I believe they are allowed 50Hz + or - 6% over 24 hours.

I eventually built a digital clock synchronised to the transmitted signal from an atomic clock but then found that they switched the transmitter off on the first Tuesday of every month for maintenance - gave up after that and bought a good Seiko!

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Power-User

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#9

Re: Generator Power and Clocks

01/18/2007 4:35 AM

Always throw off the main electrical circuit breaker when using a backup generator. Failure to do so could electrocute the utility workers that are reconnecting a lowned line.

Failure to do so will also "cook" the generator when the utility restores the power.

The clock speed is directly controlled by the frequency of the generator. No small generator will operate at precisely 60 Hz. The error in Hertz (cycles per second) is measured by the clock. A generator at +10% error will operate at 66 cycles per second rather than 60 cycles per second and gain 6 minutes each hour. If the power remains off for only a few minutes during a given work day, the power company has the option of running 3% fast to automatically reset all the clocks. All utilities tied to the same grid must be synchronized in generation frequency. A small generator will not be in sync and will "smoke", a term representing self destruction. Responsible for controlling generation frequency and thus clock accuracy, there is one designated utility in each of the three US grids. AEP controlls the frequency for all utilites in the eastern grid. Hopefully, the western grid frequency is NOT controlled by California Edison.

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#10

Re: Generator Power and Clocks

01/18/2007 8:19 AM

It is most likely caused by the frequency difference that the generator engine causes. The engine keeps the frequency and it is most likely off just a little, the revs in the engine move up and down through out the day. In my experence that amount of time seems a little high but is not out of the question. Computers are mostly effected by this frequecny change. Other than that it should cause no other problems to any other appliances.

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#11

Re: Generator Power and Clocks

01/18/2007 8:51 AM

It would appear that the generator is running at around 1 to 1.5% faster than the frequency of the normal mains supply.

Transformer-containing appliances connected to this supply might see a slightly lower voltage downstream of the transformer. This may or may not be anything to worry about, depending on the intended use of the appliance.

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Guru

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#12

Re: Generator Power and Clocks

01/18/2007 10:23 AM

OK . . . here we go. Just live with the error in your clocks and get a battery powered atomic clock, like I have (3 of them) and don't worry. How a generator works: The rotor that is turned by the engine develops a magnetic field just like a rotating magnet with a North and South pole. And as that field rotates, the North pole, let's call it (+), 'cuts' through the stationary windings just laying around in the case of your generator (the stater . . . . the wires that are connected eventually to your house to create power for you). As these magnetic fields 'enter' a stationary copper wire (the stater windings), a voltage builds to a peak (a + peak in this example of the North pole coming around), then falls away when the magnetic field leaves that stationary wire >>>> and then comes around the "South Pole" of your rotating magnet and it begins again, but on the negative side of zero (-). You then have a sine wave of "One Cycle". Zero, then up to a peak (+) then back to zero then down to a negative peak (-). If I made one rotation like this per second, I would have 1 cycle per second (1 Hz). But if I want more cycles per second, I must create a way to have this happen more frequently (frequency). So, if I spin my rotor faster, I can finally hit a speed where I make 60 of these cycles per second, or 60 Cycles (60 Hz) which is the USA (and a few other countries) standard frequency; and 50 Hz, or cycles, or frequency, in most countries. Now we come to the point of little engines. They have a very simple sloppy cheap speed governor (like cruise control on your car), so, they must begin at a speed of 63 - 65 Hz in order to arrive at 60 Hz under full load, and, these cheap little governors are only about 5% accurate on top of that. So if you are at 50% load, the frequency will be much higher than at full load, but in any case, I will guess you may never get precisely 60 (or 50) cycles. On large generators we use very sophisticated electronic governors that hold the frequency precisely. Your AC electric clocks have a motor (the backwards equivalent of a generator) so you can see that if we put 63 Hz into the windings of your clock motor (the stater), that the rotor (the shaft attached to the clock hands) will turn faster and be off time (gaining time).

For noise: Most of the noise you hear is engine noise, not exhaust noise. So with even the BEST muffler, you will still have 'engine' RPM noise. Turn it slower, and the noise drops tremendously. Typical small gasoline engines are 3600 RPM (60 Hz) and have a 2 pole rotor to equal 60 Hz while running at 3600 RPM with a single North Pole (+) and a single South Pole (-); just remember the speed is a multiple of 7200 for 60 Hz. If you had a 4 pole rotor (two North Poles and two South Poles) you can now have a 1800 RPM engine and still arrive at your multiple of 7200 = 60 Hz; or, even better, a 1200 RPM engine (very very quiet) with a 6 pole rotor (3 x (+) and 3 x (-); 8 pole = 900 RPM; 10 pole = 720 RPM , etc. etc. The problem is the power of the engine is related to the square root of the speed. So a 3600 RPM 60 Hz generator is MUCH cheaper than a 1800 RPM "Quiet" generator, because the quiet 1800 RPM version must have a much larger engine to produce the same power (watts) of the other machine. I don't know anybody that makes a 1200 RPM small unit like 3 kW (3000 watts) because the engine would be VERY large and nobody would buy it.

Now you have the full story . . . so go buy some battery powered atomic clocks.

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#13
In reply to #12

Re: Generator Power and Clocks

01/18/2007 11:45 AM

UPS (Battery Back-up) Is a much better and far more cost efficient method of voltage / frequency regulation and stand by power supplementation. Any load is better protected during outages, the vast majority of which are short duration variations in the utility power. Computers, modems, routers, TV and TV set top boxes along with other electronic devices suffer more form the periodic voltage variations. In the event of prolonged power outages, UPS systems provide ample time to power down any sensitive equipment. A generators will do nothing to protect connected loads. In addition to the poor power quality produced by the vast majority of small portable generators. So a clock running fast should be the least of your concerns. Stand-by generators provide a false sense of security. It better feeds the ego than the utility needs of the average consumer.

Additionally UPS systems are completely silent.

Now you have the real deal.......and you should have a good wrist watch to boot!

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#14
In reply to #13

Re: Generator Power and Clocks

01/18/2007 2:23 PM

At least in this area (Northeast US), people are less concerned with transiently protecting sensitive equipment than with keep basic home functions operating.

One of the primary causes of power outages during the winter is the weather. In such cases, power is often out for hours (at least) to days. In fact, about 18,000 homes in the area are still without power today (Thursday) from the ice storm that hit Monday.

In such cases, the only way to keep the heat running in your house is with a generator. Without heat, your water pipes will freeze and burst (the temperature yesterday hit a high of about 8o F or -13o C). Who cares about the TV and computer!

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Guru

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#16
In reply to #14

Re: Generator Power and Clocks

01/19/2007 3:32 PM

You got it Steve, although I appreciate our Guest's UPS comments a lot! Gen sets are the only long term solution where UPS systems are, as most know, for small short term loads. The battery size, storage area required for huge systems to keep you going for hours, and risks of those systems (we have them just igniting now in some installations, and are updating the batteries to types that don't spontaneously combust) is too much. And if they don't work, the average person cannot repair them (although very dependable). If a gen set doesn't start, you can normally get Uncle Phil to come over and bend something and get it going.

The perfect deal, which I have installed many a time in 3rd worlds where I work without power for days, is a UPS, sized for 2-3 hours maximum and only for critical loads such as communications and emergency lighting (gotta have your radio, email, lights and a phone when the bad guys come over the wall), an automatic transfer switch that disconnects utility and connects your gen set when the gen set reaches 80% voltage throttling up, and an automatic start gen set with a start time delay set for instant up to a few minutes (so it doesn't start during blips, unless you want it to so you can ride through the 3-4 more blips that will come in the next hour).

And maybe the power isn't perfect (5% voltage and 5% frequency regulation), but one might be surprised how even a seemingly stable utility varies 10% voltage at times. Frequency is normally guaranteed to 0.5% Normally, when you have a gen set running you are already inconvenienced by some major weather event or other disaster, so clocks may be the least of your worry. At least you will be early to events. If you overload your generator your clocks will run slow, but you will have a great reminder when the generator blows up from overload.

Also, to those buying gen sets after reading this, take care for altitude. The derate 3% per thousand feet above 500 feet. So a 5 kW running at 6500 feet is only good for 4.1 kW. And you cannot 'block load' these small guys with all 5 kW at once. The engine will fall on its face with more than about 40% load at a single blow.

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Guru
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#18

Re: Generator Power and Clocks

01/14/2025 7:20 AM

It sounds as though the incoming mains has fried the <...gas powered generator...> as a result of its having been connected to the incoming mains when the mains supply resumed. The only <...potential problem...> is its having been rendered unserviceable by this act, precipitating either its repair or its replacement. As a matter of safety to maintenance operatives restoring the power, the installation needs to be isolated from the incoming mains while running on the <...generator...>, and the <...generator...> needs to be isolated from the incoming mains prior to that service being reconnected. It's an expensive learning exercise in that respect.

One might hope that no-one got killed or injured by that oversight?

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Anonymous Poster (4); bhankiii (3); Blink (1); Cornstoves (1); Greg G (1); MidniteFighter (1); Paddy O'Flanigan (1); PetroPower (2); PWSlack (2); Steve (2)

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