How to safely discharge a HVAC start/run capacitor?

[dmccarty]

To be honest with you, I think the danger is not all that great. If concerned, measure for voltage with your VOM. I doubt there is any, but it won't hurt to find out.. If you do find several hundred volts. Then take a resistor with a good set of insulated pliers and put it across the terminals. It will fall in in hurry. I have just used a screwdriver too. Might not be as good for the cap, but I can't say that I have ruined any by using that method.. I have repaired and worked on electronics for around 50 years.. Including many lethal circuits. but a cap disconnected from a circuit never worried me all that much.

Not sure the cap is your problem ,but ,I'll answer the question about the cap... I discharge mine with a screwdriver,etc, To test,,, set the volt meter to ohms scale. connect to the C and to fan terminal.. then move to the herm terminal Your meter will also discharge the cap.. It will charge it and discharge it.. To read what the cap is putting out, you need a cap tester

There can be quite a high charge left on a capacitor if you happen to disconnect at the peak of the mains cycle.
It's often enough to give quite a loud crack when the screwdriver blade touches both terminals. It can certainly make you jump and may even erode away a bit of the capacitor terminal (and your screwdriver). It is the easiest way though.

Many homes do have a low value resistor that is capable of discharging very high currents - the heating element in an electric tea kettle (with the switch on).

One other point if you are checking with a voltmeter to see if a capacitor is charged :
Although in use the capacitor is on an ac supply, once you disconnect the supply you will need to set the voltmeter to read dc voltage to check for any remaining charge.

Like others say lay a screw driver on it. There are capacitors made in America that I suggest over china maypops. They are Titan HD capacitors. China capacitors are garbage.
Attached a photo of a nice capacitor blowout for your entertainment.

Thanks for the info. I THINK the repair guy checked the voltage with his meter and the used a screw driver to discharge what power was left.

Since I don't need the heat pump until it gets hot again, I have some time to look at the problem myself. The capacitor is cheap enough to buy a new one, and after the first on died I meant to buy a new one to keep as a spare. I will look at the Titan brand.

Thanks,
Dan

 

[5030]

We used to charge up an electrolytic capacitor and tuck it under a seat cushion in some unsuspecting place...like a library and let some unsuspecting person sit on it. Makes for some excitement.

 

[kenmac]

Do you know the amount of emergency/back up heat that is in the unit ?...You say the house didn't heat up very quick..I just wonder if you only 5 or 10 KW heat strip installed..If you had 15 or even 20 kw ,the house should have headed fairly quickly..Of course, I don't know the size of your home either..+1 on the American made caps..they seem to last longer....Most HVAC companies around here won't install them due to less call backs

 

[kenmac]

Like others say lay a screw driver on it. There are capacitors made in America that I suggest over china maypops. They are Titan HD capacitors. China capacitors are garbage.
Attached a photo of a nice capacitor blowout for your entertainment.

The smoke got out of that 1...Funny how long parts last until the smoke gets out..Once that smoke gets out, that's it !

 

[CobyRupert]

A 500 Watt lamp is around 29 Ohms.

 

[Ken45101]

the wood stove could not keep up with the cold. That meant the living room was at 72 instead of 80 and the Wifey was not happy.

Buy your wife a couple of warm sweaters, that will cost a LOT less. Even in more mild weather, think of all the extra wood you are using. If she wants 80 degrees, she should be helping cut, split and stack the firewood ;-)

 

[Eric Salop]

I was going to say that I'd just toss it to my partner and yell catch.

I got that treatment regularly as part of the initiation when I first started working in an electric motor factory. The guys would use the "flash testing" gear on 500V dc to make sure they were fully charged.
Took more than once before I learned to keep my hands still and let the caps drop to the floor.

 

[Loadstar]

The smoke got out of that 1...Funny how long parts last until the smoke gets out..Once that smoke gets out, that's it !

Would have been nice if it was just smoke but it had to violently puke its guts out all over the rest of the components. Once I fixed it you can hardly notice lol

 

[kenmac]

Would have been nice if it was just smoke but it had to violently puke its guts out all over the rest of the components. Once I fixed it you can hardly notice lol

Yes, I saw the puke.
can't say I've ever seen 1 do that !

 

[Industrial Toys]

If you have a friend with a pierced tonge, well, that may be the only usefull thing they ever do. That, or just grab a crappy screwdriver and short the terminals.