capacitor

[rundawg]

I recall that we had a rather spirited discussion about the validity of the test illustrated in that pdf.

Perhaps someone will find it and link it to this thread.

Here is one of them.........

http://hvac-talk.com/vbb/showthread....acitor+testing

[Cool_Air]

[QUOTE=hvacrmedic;14977841]

The multiplier is derived from

1,000,000/(2 x pi x hz)

In this case hz is 60, so plugging into a calculator we get

2652.5823848649222628147293895419...

Rounding off to the nearest digit gives us

2653 (but 2650 is close enough)

For those on 50 hz systems the factor works out to

3183

haacrmedic thanks for this information

[Robertjn2000]

Double post.

[Robertjn2000]

this may help you.

Unfortunately, some capacitor checkers we use in the field are ineffective at testing for a bleeding/leaking capacitor because there is no load on the capacitor at the time that it’s being tested.
The good news is that there is a fairly reliable way to test a capacitor under load.
While the compressor is running, measure the ac voltage across the run capacitor. You will be reading the voltage that the compressor is generating. The term for this is “back electromotive force.” Measure the amperage being drawn through the start wire between the capacitor and the compressor start terminal.
Be sure to keep your amp meter away from the components in the control box - that could distort your reading. Use the voltage and amperage readings you’ve obtained in the following formula:
Amps X 2,650 ÷ Voltage = Actual microfarads.

If the solution to your test gives you a microfarad rating that is 5% below the capacitor’s labeled rating, be suspicious. If the results of your test show the capacitor to be 10% or more below the labeled rating on the capacitor, replace it.


The most important amp draw reading to take is of the start winding (the wire that is connected to the run cap). If it is approx. half of the run winding then the run cap is good. For example if the run winding is 14 and the start winding is 3 then we have a problem. This is one of the biggest call back producers in our industry. Techs think that the run caps are either bad or good (not true) many many are just weak.
See if no current is going thru the start winding (run cap weak/bad) then all the current will go thru the run winding and the amps will show much higher than normal. This is the reason you will find melted/loose connection on the common or run terminal of a compressor. You will never see it on the start terminal

[Robertjn2000]

Double post

[Core_d]

Thank you robert

[54regcab]

Another handy tool is an ESR tester. It sends a high frequency signal through the capcitor and measures internal AC resistance. Test can be done in circuit, no disconnecting required. Since the signal is high frequency very little passes through the motor windings. As capacitors dry out thier ESR increases. As ESR goes up capacitors run hotter. Eventually the capacitor overheats an the top bubbles up.

http://en.wikipedia.org/wiki/ESR_meter

[timebuilder]

There is a low price kit for "blue ESR capacitor tester meter" on eBay.

I believe this is the same technology used in battery conductance testers, which gives a better picture of battery condition than a simple load test.

[54regcab]

There is a low price kit for "blue ESR capacitor tester meter" on eBay.

I believe this is the same technology used in battery conductance testers, which gives a better picture of battery condition than a simple load test.

The ebay kit is the one I have if it's the one I think you are talking about. Translucent plastic.

[timebuilder]

How do you like it?

[54regcab]

Works well, but I would choose removable leads if I was to design one of my own. The only caps it has a problem detecting bad are those that break down under load.