ReplyNope. Increasing the load on a PSC motor reduces the voltage across the run capacitor. It's primarily the heat that's getting them, coupled with the capacitor being a PoS right out of the box.Originally Posted by Glennhvac
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Maybe you need a more accurate clamp meter.
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Nope. Increasing the load on a PSC motor reduces the voltage across the run capacitor. It's primarily the heat that's getting them, coupled with the capacitor being a PoS right out of the box.
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I think we're getting closer to the source of the problem - a combination of conditions - heat and higher voltages. Caps are rated for voltage. The higher the voltage rating of the cap, the more durable it should be. And IMO you can't trust the voltage ratings on the "POS" ones.
In my area, the line voltage is already pretty high to start with, i.e. in the 240-252V range. And it isn't unusual to measure over 370V across a new, tested cap. The question in my head is what happens when you start heating up the shell of the cap, i.e. does it make it less able to handle that rated voltage?
In short, what cap temperature is that voltage rating valid for?
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Here's a link to a technical article about the effect of high ambient on the life of electrolytic caps. It's primarily about DC voltage, but might also apply to AC.
http://www.newark.com/pdfs/techartic...ultipliers.pdf
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Quote:
Originally Posted by Glennhvac
I don't think it's the heat on the capacitor. I think it's voltage being dropped to keep up with load.
Nope. Increasing the load on a PSC motor reduces the voltage across the run capacitor. It's primarily the heat that's getting them, coupled with the capacitor being a PoS right out of the box.
Yep, starting to lean toward the cap shell temps as the problem but I still maintain that they also tend to blow when the power company starts jerking around as well. I have had a good number of calls that were blown caps the day after an evening storm when the power was dropping in and out. Could be coincidental.
Plus when you take into account how many of those ancient 10 pounder caps are still going strong....heck I had some 30's and 40's laying around for emergency that were like 4"x3"x10" bricks! Plenty of radiant surface area to be sure.
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Sounds like an innovation for the Binford 5000 capacitor add on cooling fins. LOL
Aircraft Mechanical Accessories Technician. The Air Force changed the job title to Air Craft Environmental Systems Technician. But I've decided I'll always be a Mech Acc.
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Or a heat exchanger system using the suction line
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Or to keep the heat out of the electrical panel to start with. The units that catch a good amount of sun seem to be the worst offenders. Some of those that have been off all day have caps that are almost too hot to handle when you open up the unit. Has to be IR causing that, plus the fact that there's very little openings in most electrical panels for the heat to dissipate via convection.
I'm wondering if a $4 can of spray foam around the outside part of the electrical panel might work.
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there you go!. Charge the unit so it sweats back to the compressor, tape the cap to the suction line at the compressor and in addition to the cool line it would be water cooled!
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And the water could also serve as a bleed resistor when it dribbles over the cap taps...there you go!. Charge the unit so it sweats back to the compressor, tape the cap to the suction line at the compressor and in addition to the cool line it would be water cooled!
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we're on to something. I can tell!
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Heck yes! Speaking of that what ever happened to that gadget I thought I heard of years ago to heat domestic water with the residential a/c unit.we're on to something. I can tell!
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dunno. But speaking of hot water: We're wacthing the end of a movie last night around 11:30 - both tired and ready for bed. The fire/burglar alarm starts chirping and then goes off blaring. The thing is loud and I have to get my firearms ear plugs I still keep in my night stand from when our kids were teenagers. I rip off the cover off the alarm as I can't stop the thing at the door interface and rip apart a red wire and stop it.
I was BQing earlier so I check the grill - nothing. I go down stairs to the main alarm panel in the utility room to discover the rust spot on the water heater expansion tank had ruptured and was spraying a fine mist all over the alarm panel.
Emergency service call at midnight in my own home. Valve to tank not functioning, shut off main, lucky to have 3/4 plug on truck. Temp fix done in 20 minutes - all the while the wife whinning "what are you doing - can we go to bed now...?"
As annoying as it was, I can't help but be grateful: As little as 18-24 months ago I would have been clueless as to what that barrell looking thing on the side of the water heater even was, and would have had to live without water until a plumber showed up so I could give him a bunch of money to fix it.
This trade comes in handy at times. Off to the Depot in a bit for a new tank.
I'm sure the wife will recognize my hero status shortly. If not I'm buying some tools with the money I saved her.
I know, I know
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And if it rubs a hole in the pipe when the unit vibrates, it would be gas cooled - for a while.
But if you flatten out the pipe, you'd get more heat transfer, and it wouldn't rub through it as bad.
OR you could turn it into a GROUND SOURCE capacitor by burying it in the ground. Just hope Fido don't dig it up lookin for his bone.
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We shouldn't talk like this. Being an open forum, some DIY might steal our ideas.
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If they did, we'd hear about it pretty quick,, on the news.We shouldn't talk like this. Being an open forum, some DIY might steal our ideas.
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china and mexico parts are ruining america
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That's why we have to STOP the EPA from making it virtually impossible to make things here.
[Avatar photo from a Florida training accident. Everyone walked away.]
2 Tim 3:16-17
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Are you saying that the EPA is driving up labor costs?
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I'm saying that the cost of compliance with the bureaucracy is one of several controllable elements that makes the production cost of many items in the US to be far above the cost that Americans are willing to pay for finished goods.
[Avatar photo from a Florida training accident. Everyone walked away.]
2 Tim 3:16-17
RSES CMS, HVAC Electrical Specialist
Member, IAEI
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