Ok.
In the old days...
..that was when I was as young as most of the members here...
the superior oil used in oil filled capacitors and transformers was "PCB" oil.
That stands for PolyChlorinated Biphenyl.
http://en.wikipedia.org/wiki/Polychlorinated_biphenyl
It had very good dielectric properties.
Now, the oil is a more "environmentally friendly" substance that is not anywhere near as good for the purpose.
Secondly, the coatings used on the plates as the primary dielectric are not as good, mostly due to cost of production.
Mind you, you can still buy a pretty good cap, but it costs a LOT more money. Dry caps used in military electronics, for example, cost a bundle.
Finally, the Chinese are happy to build a cap to the specifications they are given. The specs they are given will often include a mandate to produce the product at a lower cost, and they will use ONLY the amount of chemicals and materials that are needed in order to accomplish their mission. Longevity of the part is usually NOT a part of their mandate.
Does that help?
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2 Tim 3:16-17
RSES CMS, HVAC Electrical Specialist
Member, IAEI
AOP Forum Rules:
Nope, doesn't help. I still go to the supply house and ask for a cap and its garbage. The good news is atleast things last longer now than they will in ten more years!
You could find a supply house that carries Amrad, or even a supply house that carries mexican made caps. They are better than the Chinese caps sold under the Beacon name.
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2 Tim 3:16-17
RSES CMS, HVAC Electrical Specialist
Member, IAEI
AOP Forum Rules:
ON the same subject. I have installed 50 or more universal run capacitors. You can adjust the size of capacitance. Most of them have failed, some blew up and caught on fire. I thought they would replace the 30 differnent run caps. I am back to stocking lots of different ones again.
I been gone so long I don't know what that fancy writing with the houses and boxes mean. Something about Q= something over something.
"Here in Carolina We Get-R-Done"
every thing is getting cheaper only thing you can do is buy the best you and your customer can or will afford and hope for the best.
After this summer i have concluded that a bad run cap is the best thing that ever happened to a dishonest company. Bad run cap=bad compressor. Its unfortunate but happens all the time im sure. We had a big problem with Packard brand this year (they wouldnt even swell up) and Global years ago (lost many customers). I wish they made them the same way as the old days, big and heavy!
My motor supplier say he has seen more bad caps in the last 5 years than the 30 years prior. Blames it on China.
Officially, Down for the count
YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET
I know enough to know, I don't know enough
Why is it that those who complain the most contribute the least?
MONEY CAN'T BUY HAPPINESS. POVERTY CAN'T BUY ANYTHING
I think a lot of power is wasted because of poor capacitors. My heat pump went from drawing 21.7 amps to 14.1 with a new run cap.
Let me tell you a technical secret.
If your run cap is the wrong uf value for the motor with which it is associated, it will draw more current compared to a cap of the correct uf value. It is possible that the new cap is correct, and the old cap was either not correct, or its uf value had changed significantly.
Unfortunately, no one has developed a replacement for PCB oil that has the same properties.
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2 Tim 3:16-17
RSES CMS, HVAC Electrical Specialist
Member, IAEI
AOP Forum Rules:
Explain PCB oil. The run cap was labeled right that does not mean it could have wrong printing on it.
I wasn't talking about labelling. I think I was giving you credit for more technical understanding than you might have.
PCB oil was discontinued in the 1970s due to hazard concerns. That said, there has been no good replacement for it.
This is a tech to tech forum. Are you an HVAC technician?
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2 Tim 3:16-17
RSES CMS, HVAC Electrical Specialist
Member, IAEI
AOP Forum Rules:
I had high failure rates with capacitors until I changed to Genteq brand. No failures in a year.
What kind of shelf life do modern run capacitors have?
Yes, I am own a small heating and cooling business in Michigan.
[Avatar photo from a Florida training accident. Everyone walked away.]
2 Tim 3:16-17
RSES CMS, HVAC Electrical Specialist
Member, IAEI
AOP Forum Rules:
[Avatar photo from a Florida training accident. Everyone walked away.]
2 Tim 3:16-17
RSES CMS, HVAC Electrical Specialist
Member, IAEI
AOP Forum Rules:
I have some that were in service for 20 years and on the shelf for 5 still test fine. Modern being the key word, those spend a short time on the shelf a little longer in service and a long time in the garbage.
I don't think shelf life is important. Idon't think age hurts them. Dual run capacitors I think last about 7 to 10 years. Run caps on furnace blowers like the 5 to 12.5 seem to last the life of the motor 15+ years on average. The universal capacitor that you wire the size you like. 1/2 fail in a year.