Any HVAC Gurus Out There?
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So you have to cool the fan, instead of the other way around? :)
Luc Pattyn [Forum Guidelines] [My Articles]
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Luc Pattyn wrote:
So you have to cool the fan, instead of the other way around?
...only in Soviet Russia...
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Yes; I have automatic updates enabled. And I did reboot. Twice.
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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Unless it's inacessible, changing the cap is going to be inexpensve both in $ and time, so I'd just do it anyway.
Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)
Why are you using VB6? Do you hate yourself? (Christian Graus)It certainly won't hurt. :-D
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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Can you not measure the SCALAR voltages with your DMM (Supply voltage, Capacitor voltage, Motor voltage) and infer - or at least get a good idea of - the phase angle from that? It might also be worth looking for the stupid fault - is everything free running or has something expanded in the heat and jammed?
Everything spins freely, but since the failure is intermittent (I only notice it when the sound is "wrong") I can't tell if the fan stops, or fails to start. If it stops, that would indicate that the built-in thermal protection of the motor is kicking in, and increase the likelihood that the motor is bad. If it fails to start I'd be more inclined to suspect the capacitor.
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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Pixa wrote:
Is it plugged in?
I can't tell. It's dark back there because the power is out. ;P
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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Yes; I have automatic updates enabled. And I did reboot. Twice.
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
Well, then it might be a BIOS problem. If you installed the latest drivers and also flashed your BIOS to the latest version, then this is a technical problem and you'll have to send your unit in for repairs. If you still have a warranty on it, the repairs are free. If not, you'll have to pay double the price of normal repairs. ;P Lastly, if your product's warranty period hasn't expired, we will offer you a replacement if we cannot fix it and return it to you in more than 16 days... A kind RTFM is also in order. Or, rather RTFW(arranty).
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Pixa wrote:
Is it plugged in?
I can't tell. It's dark back there because the power is out. ;P
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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Humid and 120. You need to get that thing fixed fast. I used to live a bit southwest of Death Valley. Evaporator was all you needed there.
I know the area - not far from here at all. But there are no farms under irrigation or large bodies of water there as we have, so our humidity can get a bit thick. X|
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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Well, then it might be a BIOS problem. If you installed the latest drivers and also flashed your BIOS to the latest version, then this is a technical problem and you'll have to send your unit in for repairs. If you still have a warranty on it, the repairs are free. If not, you'll have to pay double the price of normal repairs. ;P Lastly, if your product's warranty period hasn't expired, we will offer you a replacement if we cannot fix it and return it to you in more than 16 days... A kind RTFM is also in order. Or, rather RTFW(arranty).
I tried flashing the BIOS, but I couldn't find it. So I flashed the neighbors instead, and that just got plain ugly. I really don't think the police needed to be involved in what is, essentially, an appliance repair matter.
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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Everything spins freely, but since the failure is intermittent (I only notice it when the sound is "wrong") I can't tell if the fan stops, or fails to start. If it stops, that would indicate that the built-in thermal protection of the motor is kicking in, and increase the likelihood that the motor is bad. If it fails to start I'd be more inclined to suspect the capacitor.
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
I think you're probably right on both counts. Have you been able to measure all three voltages? If you can measure them in both 'good' and 'failed' states it should give you plenty of clues. If the problem does turn out to be the motor and its protection - and I'm guessing from what you say that there's a thermistor or two buried in the windings, would it be possible to replace it with a larger motor, because as it's a recurring problem and temperature-related, I'm inclined to think the motor size is marginal for the duty and/or environment. E.g. to cheapen the job, the manufacturer may have chosen a frame size that is just within its rating for a 25 or 30 deg C ambient, and if you are consistently seeing higher temperatures (I think 121 deg F comes in that category :() , you are probably into the operating range of the thermistors. And at the same time the insulation is being stressed that much more and the life will be dramatically shortened. I still wouldn't rule out a weird thermal-expansion-related break in the capacitor somewhere that's causing a (total?) loss of capacitance, but you'd be pretty unlucky. I've just checked the UK's largest supplier and their 5uF motor start capacitors are rated to 85degC - and they're self-healing, polypropylene film; so it's unlikely that temperature is the primary cause if the capacitor has failed. Stupid question: it's not a thermal overload tripping, is it?
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Shog9 should have become an HVAC guru by now:). I recently (2 weeks back) had a dead capacitor. The way to find out is if the capacitor is swollen or the size is abnormal. Once it was replaced everything worked fine. But my outside fan was not moving at all. Is it the same with you?
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You need to go low-tech and get a swamp cooler. I thought they were standard equipment out in the desert.
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Got a question... This weekend, when the temp hit 121°F, my a/c unit quit. The condenser fan motor stopped turning, the refrigerant vaporized, and the compressor was working its little iron heart out trying to work it all out. Without success, I might add. I shut down the system for an hour and hosed off the condenser coils to liquify the refrigerant, and it started working again. I've replaced this motor a few times over the years, a 10 minute surgery that the a/c guy charges $270 to do, and the motors used to cost $50. Now they've gone up to $180, so I'm not so quick to replace this one. It uses a 5μF run capacitor, and I've just read that the capacitor should be replaced every time the motor is changed out; I've never done that. Can anyone tell me whether this is a symptom of a dead capacitor? I really don't want to get out the oscilloscope and check the phase shift between the main and auxillary windings of the motor in this heat, but the a/c guys I've talked to are all idiots. They suggest checking continuity across the cap with a DMM. That's useless unless the thing has failed open, a rather rare failure mode for capacitors. Electrolytics usually fail shorted because of punch-throughs of the dielectric between foil layers, or loss of Q or capacity through electrolyte dehydration. Is there an easy way to check this?
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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I think you're probably right on both counts. Have you been able to measure all three voltages? If you can measure them in both 'good' and 'failed' states it should give you plenty of clues. If the problem does turn out to be the motor and its protection - and I'm guessing from what you say that there's a thermistor or two buried in the windings, would it be possible to replace it with a larger motor, because as it's a recurring problem and temperature-related, I'm inclined to think the motor size is marginal for the duty and/or environment. E.g. to cheapen the job, the manufacturer may have chosen a frame size that is just within its rating for a 25 or 30 deg C ambient, and if you are consistently seeing higher temperatures (I think 121 deg F comes in that category :() , you are probably into the operating range of the thermistors. And at the same time the insulation is being stressed that much more and the life will be dramatically shortened. I still wouldn't rule out a weird thermal-expansion-related break in the capacitor somewhere that's causing a (total?) loss of capacitance, but you'd be pretty unlucky. I've just checked the UK's largest supplier and their 5uF motor start capacitors are rated to 85degC - and they're self-healing, polypropylene film; so it's unlikely that temperature is the primary cause if the capacitor has failed. Stupid question: it's not a thermal overload tripping, is it?
BarrRobot wrote:
it's not a thermal overload tripping, is it?
It could be. In fact, that's highly likely, since it stopped after starting successfully, and started working again after I hosed off the condenser coils which surround it. This is a familiar pattern from past failures. It starts with an occasional failure, then gradually gets more frequent until it won't run at all. I do have a capacitor on hand - the right size but higher voltage - so I'll pop that in this weekend. If the existing cap is marginal it may be increasing the losses in the motor and causing self-heating great enough to trip the thermal overload protection. If that doesn't stop it in its tracks, then I'll have to invest in a motor. I know I can get a replacement locally, but I may also check into increasing the horsepower rating if I can find one that mounts the same. Good thoughts - Thanks!
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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:-D I agree, but with payday over a week away, bills to pay, and a cost of at least $150 for the motor, it's worth trying to diagnose the problem if it will save some cash. If a capacitor solves it, even just for now, next payday I'll invest in a spare motor, just to have available in a pinch.
"A Journey of a Thousand Rest Stops Begins with a Single Movement"