AC compressor

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On Aug 24, 12:31pm, The Daring Dufas <the-daring-

Go ahead give us the science behind it then?
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On 8/24/2010 11:50 AM, jamesgangnc wrote:

You don't know how to use a library? I don't need to give you the science, I have directly observed the phenomenon. Direct observation makes up most science. I did find a document online that has some equations if that will help you understand but if you know anything about electricity, you can visualize that a length of wire has a magnetic field when energized. Take a look at page 3 of the PDF:
http://www.pppl.gov/eshis/ESHD_MANUAL/safety/es7.0.pdf
TDD
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wrote:

I know something about electricity. I know it takes a great very deal of current to make a strong magnetic field in a straight wire. Possible in a commercial setting with high pulsed current, yes. In a home ac compressor, I doubt it. Go ahead, hold your ferrous screwdriver blade near the 10 guage wire with the compressor running. Feel any pull?
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On 8/24/2010 1:21 PM, jamesgangnc wrote:

You obviously didn't understand, the wire movement happens when the compressor starts, not continuously. The compressor starts, you can hear the breaker buzz and the wires in a conduit jump, rattle for a split second, not during normal run operation. GEEZ!
TDD
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The Daring Dufas wrote:

There is a circular magnetic field around a conductor carrying current. With 2 wires carrying current both ways in a circuit, the magnetic field pushes the wires apart. The starting current for a motor is about 6x the running current. Seems to me you might hear wires moving in some cases.
--
bud--

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The starting current is typically 2 to 3 times run in hvac units.
The breaker is slow to respond to the startup current surge so it's rating can be closer to the unit run current.
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On 8/25/2010 10:40 AM, bud-- wrote:

Like I posted to someone else, the noise sounds like a steel fish tape rattling around in an otherwise empty conduit. It's a distinct sound. Sometimes it sounds like someone whacked the conduit once with the metal shaft of a screwdriver, the sharp noise seems to travel down the length of the conduit if you understand what I mean. It's unmistakable when you hear it, you may even hear the breaker buzz too.
TDD
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On 8/24/2010 10:50 AM, jamesgangnc wrote:

High current --> wires heat --> heat causes expansion --> expansion causes movement (not exactly "rattle" perhaps, but insulation sliding against insulation could probably approximate a squeak)
Am I missing something? What's so hard to understand?
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A piece of 10 guage wire is not going to heat up fast enough to move at a rate you could observe with the naked eye at these currents.
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On 8/24/2010 12:07 PM, jamesgangnc wrote:

First, you haven't quantified the surge current.
Second, he didn't see it, he heard it. Things that appear still can make noise -- consider a piezo speaker.
Third, the other poster has offered an alternative explanation.
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On 8/24/2010 1:46 PM, cjt wrote:

The inductive kick of a high current motor/compressor start can cause wire inside a metal conduit to make noise. I've heard the telltale racket a million times in many different settings. It sounds a lot like somebody shaking a metal fish tape inside an empty conduit.
TDD
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wrote:

Thats it, shaking a fishtape in conduit, and thats how I knew it was kicking on since 94, I wonder how long it will take to shake off some insulation.
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On 8/24/2010 7:07 PM, ransley wrote:

I wonder what will happen when one of the wire dancing deniers first hears that sound. Hummm, must be a big rat in here? 8-)
It's probably THHN insulated wire which has a clear Nylon outer jacket that is slippery making it easy to pull and chemical resistant. The slick jacket may keep it from abrading unless it's on a sharp metal edge somewhere.
TDD
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wrote:

You picked a good moniker.
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On 8/25/2010 7:03 AM, jamesgangnc wrote:

Oooooo the wire dancing denier is trying to insult me. Dufas is a proper name you less-on. *snicker*
TDD
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I missed the conclusion. Did Mr. Ransley get the AC repaired?
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Christopher A. Young
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On Aug 25, 10:26am, "Stormin Mormon"

It runs but is it fixed? He said it was out of freon and he bypassed the 5 minute timer circuit thats for my old Honeywell thermostat. But It was just filled 3 weeks ago by the same company but different tech fixed a leak, but there is nothing leaking where it was fixed. Here is where I get suspicious, last time it failed it took a few days to leak out and I noticed it and saw ice on the coils, this time it just stopped cooling and the handler had no ice. I know the tech has no motive to lie but having the timer and a leak??? But he didnt charge me when he found out they were out a few weeks ago, so, I will just see if it all leaks out again, the date on the compressor is 94 so it may have run its life but I cant afford a new one anyway, hey summers about over so im not worried. They want 300 for just a leak test and he thought I would say yes yes yes, but I said no. I see leak detectors for 29$ on ebay and 75 at HF so maybe I should get one for fun and saving a 300$ test.
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You can mix a big squirt of dish soap with a cup of warm water. Paint it on with a brush (on the copper tubing) and some where you might find where it blows bubbles.
And like you say, buy your own leak detector. I sense that HVAC company is expensive, and not very service minded.
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On Aug 25, 6:52pm, "Stormin Mormon"

You must have another leak or the first repair was flawed. The mormon is right, soapy water is not a bad leak detector. The cheap leak detectors are not much better than soapy water. Unless it's in the evaporator coil. Big leaks are usually pretty easy to find. I'd start where the first repair was made.
You paid once for them to find leaks. I'd be on the phone with the manager. When I had someone find a leak in my upstairs unit they went over the entire system even though they found one leak in the evaporator part way through the check. They used a leak detector but it was not a cheap one.
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.
It's also amazing that they would just refill it with refrigerant without doing the leak test. They repaired a leak and filled it a few weeks ago. Obviously the refrigerant went somewhere. You would think they would just do the leak test for free while they were there rather than screw around.
I guess the worse case is that it's leaking somewhere other than where they repaired it. If so, I guess you're out of luck because they're likely going to say they only guarantee the particular leak they fixed, not a new one. Of course if there is another leak, it could have been there all along too. I guess the question becomes, if there is another leak, is it worth continuing to try to fix this or time for a whole new unit. Also consider the tax credits available this year.
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