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Author Topic: A/C frequency?  (Read 11367 times)

280plus

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A/C frequency?
« on: August 29, 2011, 04:00:45 PM »
Do any of you computer people know if there is a way to monitor the A/C frequency coming into my windows based clone here? I got a boiler here telling me it doesn't want to run because the frequency is not right so I'm curious as to what it is coming off this generator. As it is the 240V outlet is pushing 260 V but I don't know if it's because generators do that or it's effed up somehow or bercause it had no load on it. 125V each leg to neutral. frequency issue doesn't seem to bother the computer.
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Nick1911

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Re: A/C frequency?
« Reply #1 on: August 29, 2011, 04:07:38 PM »
Computers don't have any real provision to monitor incoming line power.  The powersupply deals with it and provides DC to the actual computery parts.
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dogmush

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Re: A/C frequency?
« Reply #2 on: August 29, 2011, 04:24:13 PM »
My DMM measures freq.  Short of that I don't know of many handy things that could do that.

Do you have a digital timing light, or portable tach that you could measure Genset RPM with?  You could get find freq pretty easy with that.
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Brad Johnson

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Re: A/C frequency?
« Reply #3 on: August 29, 2011, 05:20:34 PM »
Quote from: 280plus on August 29, 2011, 04:00:45 PM
Do any of you computer people know if there is a way to monitor the A/C frequency coming into my windows based clone here? I got a boiler here telling me it doesn't want to run because the frequency is not right so I'm curious as to what it is coming off this generator. As it is the 240V outlet is pushing 260 V but I don't know if it's because generators do that or it's effed up somehow or bercause it had no load on it. 125V each leg to neutral. frequency issue doesn't seem to bother the computer.

Make sure the generator is set to 60 hz and not 50.  Some generators made for the global market are switchable.  If it's set for 240 I could see someone having dorked up the frequency setting by simply not knowing.

Brad
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zahc

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Re: A/C frequency?
« Reply #4 on: August 29, 2011, 08:50:46 PM »
Any decent DMM can read frequency. Also, very few things actually care about incoming frequency anymore. What is this "boiler" device that you have?
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RocketMan

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Re: A/C frequency?
« Reply #5 on: August 29, 2011, 08:53:05 PM »
Ask Kenneth?
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zxcvbob

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Re: A/C frequency?
« Reply #6 on: August 29, 2011, 09:05:01 PM »
Quote from: RocketMan on August 29, 2011, 08:53:05 PM
Ask Kenneth?

Dammit!  You beat me to the punchline.  (I guess one has to be quick around here)
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Jim147

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Re: A/C frequency?
« Reply #7 on: August 29, 2011, 09:15:17 PM »
I'm going to guess you've tried restarting the boiler. Some boards read the freq when you power them up. Sometimes killing power and restarting will get it back to reading right.

jim
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280plus

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Re: A/C frequency?
« Reply #8 on: August 30, 2011, 06:51:10 AM »
Paspifically it's a Triangle Tube "Excellence". I did retry. My thought is to disconnect everything else from the gen and see if it works then. Maybe a frideg motor or something is effing it up. No way to adjust frequency on the gen that I can see.
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280plus

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Re: A/C frequency?
« Reply #9 on: August 30, 2011, 02:42:26 PM »
Turns out TT boilers won't run on a generator unless you get a magic TT box and put it between the gen and the boiler.  :facepalm:

 :laugh:
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230RN

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Re: A/C frequency?
« Reply #10 on: August 30, 2011, 03:52:46 PM »
Does the generator deliver a sine wave?  I guess most of them nowadays are square-waves generated by a converter. If may be sensing all the harmonics of square waves and deciding it isn't 60 Hz.

I think (I'd have to think about it) if your meter measures frequency, it may also measure duty cycle, and I think (again, I'd have to think about it) the duty cycle can tell you whether it's close to sine or close to square.

Just guessin'.
« Last Edit: August 30, 2011, 03:57:55 PM by 230RN »
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AJ Dual

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Re: A/C frequency?
« Reply #11 on: August 30, 2011, 03:53:08 PM »
Wire a speaker directly into an outlet (add a resistor...) and then record the noise the speaker makes with a microphone attached to your computer's sound card. You can then evaluate the frequency with any number of freeware audio programs.

 =)
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230RN

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Re: A/C frequency?
« Reply #12 on: August 30, 2011, 04:00:57 PM »
(add a resistor...)

A low wattage light bulb might work well there for a resistor.  I've used one of those 7 1/2 watt night light bulbs to drop voltage.  Their hot resistance is around 1600 ohms.  Which would be about 70 ma, thinking DC.  That's less than one watt for a 16 ohm speaker in series with the bulb, which any speaker ought to be able to handle.

If my 'rithmetic is right.
« Last Edit: August 30, 2011, 04:14:49 PM by 230RN »
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Nick1911

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Re: A/C frequency?
« Reply #13 on: August 30, 2011, 04:03:44 PM »
Quote from: AJ Dual on August 30, 2011, 03:53:08 PM
Wire a speaker directly into an outlet (add a resistor...) and then record the noise the speaker makes with a microphone attached to your computer's sound card. You can then evaluate the frequency with any number of freeware audio programs.

 =)

Short of using a piezoelectric speaker, I don't think this will work.  I'd expect that the physical inertia and magnetic capacitance to smooth out a square wave.  

...Might have to try it tonight with an oscilloscope and function generator.
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AJ Dual

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Re: A/C frequency?
« Reply #14 on: August 30, 2011, 04:51:00 PM »
Yeah, I wasn't thinking about the speaker's own inertia and physical dwell time removing  the square wave information.

I just am well acquainted with what 60Hz sounds like, from my misspent youth and lots of ill conceived electrical experiments.

I just know you can use a sound card and a little math for damn most anything, even as a chronograph for ballistics, if your target is noisy enough.  =D
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280plus

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Re: A/C frequency?
« Reply #15 on: August 30, 2011, 05:00:04 PM »
yes, my kingdom for an oscilloscope right about now.
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Nick1911

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Re: A/C frequency?
« Reply #16 on: August 30, 2011, 05:06:15 PM »
Quote from: 280plus on August 30, 2011, 05:00:04 PM
yes, my kingdom for an oscilloscope right about now.

Too bad you're not closer to me, I'd lend you my bk precision 2520.
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AJ Dual

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Re: A/C frequency?
« Reply #17 on: August 30, 2011, 06:04:54 PM »
Sticking your finger in the socket with a pedometer enclosed in your other hand so you shake it for a minute, and count the "steps" is out of the question, huh?
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birdman

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Re: A/C frequency?
« Reply #18 on: August 30, 2011, 08:05:08 PM »
Just a thought, variation on the speaker idea, speaker on the line (with resistor as suggested, but easier would be a cheap 120/12 step-down transformer you can get from a wide variety of places) would give you a power line frequency tone, then just play a 59hz (or 61hz) tone from your computer speaker and snap yo' fingers to the beat...you get a 1hz beat for both, it's a 60hz line frequency.
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280plus

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Re: A/C frequency?
« Reply #19 on: August 30, 2011, 08:54:33 PM »
Quote from: Nick1911 on August 30, 2011, 05:06:15 PM
Too bad you're not closer to me, I'd lend you my bk precision 2520.
Where are you again?  =D

 
The square wave theory sounds pretty plausible. I could always call them. Should have done it today.

What I DID do is tie 3 separate loops of twisted steel cable from the generator to the garage door frame inside to make it a little more difficult to steal the thing. Everybody else seems to be getting their power back so we're hoping it won't be much longer. Still no cable.  I'm stressin' man. :'(

:laugh:


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zxcvbob

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Re: A/C frequency?
« Reply #20 on: August 30, 2011, 09:14:19 PM »
If it's a waveform problem, wouldn't an isolation transformer smooth it out?  (by attenuating the high frequency harmonics)
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Nick1911

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Re: A/C frequency?
« Reply #21 on: August 30, 2011, 10:06:13 PM »
Quote from: zxcvbob on August 30, 2011, 09:14:19 PM
If it's a waveform problem, wouldn't an isolation transformer smooth it out?  (by attenuating the high frequency harmonics)

This, or actually any induction load.

Got a 1/2 hp PSC motor sitting around?  Tie it in to the circuit, in parallel with the boiler.
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zxcvbob

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Re: A/C frequency?
« Reply #22 on: August 30, 2011, 10:22:25 PM »
I think an inductive load in parallel would make it worse.  You'd need a choke (inductor) in series or a capacitor in parallel.  A resistive load, like a waffle iron, in parallel might help.

I also wonder if the problem has nothing to do with frequency and it's really a floating ground?  Is the frame of the generator bonded to earth ground?
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Jim147

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Re: A/C frequency?
« Reply #23 on: August 30, 2011, 10:49:02 PM »
Put a UPS between the gen and the unit. This should clean up the wave and let it run.

jim
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Nick1911

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Re: A/C frequency?
« Reply #24 on: August 30, 2011, 11:01:37 PM »
Quote from: Jim147 on August 30, 2011, 10:49:02 PM
Put a UPS between the gen and the unit. This should clean up the wave and let it run.

jim

Eh?  All the consumer grade UPS's I've run across just pass the current through metal oxide varistors when not in battery mode.  Line conditioners, yes, but those are expensive, uncommon, and heavy!   Have you run across some UPS equipment that has some provision for frequency correction?
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