how to safely deenergize capacitor

Never had a problem using the screw driver method never destroyed one doing it. A lot have bleed resistors a lot don't. Lots of disinformation in this post. Rather arch out a screw driver than take a charge.Running around with a pocket full of bleed resistors is not practical. Even if a cap has a bleed resistor I don't trust them and will still short with a screw driver.

Some of you folks will get some one killed by telling some one that run caps don't hold A charger.

NEVER ASSUME A CAPACITOR DOES NOT HAVE A CHARGE

Capacitor self charging is real. It can be deadly when using high voltage capacitors!

A few sources of info:

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

http://blog.shuningbian.net/2005/04/self-charging-behaviour-of-electrolyte.php

And this one lots of you engineers will read with fond memories by Bob Pease -- What's all this soakage stuff, anyhow?

http://electronicdesign.com/analog/whats-all-soakage-stuff-anyhow

Bob Landry wrote:
Two pages of bad information has certainly made for an interesting read. The capacitors in an AC unit, start, run, and fan, are non-polarized and are not going to hold a charge. These are not power supply filter capacitors. It is also impossible for a capacitor to "recharge" itself if it is not connected to anything.

Speaking of bad information, just because it is non-polarized does not mean it can't retain a charge. Absolutely wrong! More bad information, capacitors CAN accumulate charge, though internal leakage usually keeps it in check. Ever hear of static electricity? As someone who is not only an electrical engineer but once shocked myself off the same television high voltage power supply which was discharged and safely handled before I started working on it, I can vouch for that. It certainly wasn't discharged when I was putting the high voltage rectifier tube socket back in.

Run capacitors *should* discharge themselves through the run windings and secondary windings because they are all in series, so if the power is removed they will be discharged. Start capacitors *should* be discharged in the same way if the centrifugal switch is working properly. Still, Westend's idea of using a light bulb to make sure they are discharged is safer than using a screwdriver. Oh sure, everyone's got an anecdote that it's okay, but exceeding the current rating in that instant still isn't good for it.

Thanks for the info guys

Bob Landry wrote:
Two pages of bad information has certainly made for an interesting read. The capacitors in an AC unit, start, run, and fan, are non-polarized and are not going to hold a charge. These are not power supply filter capacitors. It is also impossible for a capacitor to "recharge" itself if it is not connected to anything.

You obviously have never worked with one then. Mine sure did have a charge in it . The screw driver suggestion is dangerous, best bet is a resistor, next best is a modern voltmeter. Mine drained the charge in about 30 seconds and it was nice to watch the progress. After the drain you can go an extra step and tape off the terminals.

Two pages of bad information has certainly made for an interesting read. The capacitors in an AC unit, start, run, and fan, are non-polarized and are not going to hold a charge. These are not power supply filter capacitors. It is also impossible for a capacitor to "recharge" itself if it is not connected to anything.

FWIW- here is the latest from Dometic on the subject- http://bryantrv.com/docs2/docs/misc/Discharging%20Start%20and%20Run%20Capacitors.pdf

As an "ole" Navy tech, we shorted the terminals together. Never had one fail.

WESTEND has it right. Shorting the + and - together on a charged up cap can very easily destroy the cap. Discharging it thru a resistor or light bulb as above will be safer for both the cap and you.

You can safely discharge the capacitor by using a light bulb in series with the capacitors (+), (-) terminals. The bulb will dissipate the charge without arcing from (+) to Ground.