Phase bridging capacitor blew up

[rjniles]

About 3 weeks ago I installed a x10 phase bridging capacitor in my circuit breaker panel. I used 2 single pole 20 amp breakers that were side by side and serve the 2 bathrooms. Last night the power was off in one of the baths. Checked panel CB and one of the bath breakers was tripped. Reset and heard a loud pop from inside the panel. The other breaker was now tripped. Reset the second breaker and another loud pop. Open panel to find the bridging capacitor was gone (vaporized with a short piece of the wire leads left).

I know the capacitor was installed correctly and was bridged across the 2 legs of the single phase service. My concern is: was this a freak occurence and should about a reoccurence? Has this ever happened to any of you?

[Brian H]

Was it rated for across an AC power line or just a common capacitor?
Do you know the rating of the capacitor?
I guess reading it maybe a problam as it blew up.
Some capacitors not rated for across an AC power line can short out even if the DC rating was high enough to cover the AC equivalent.

Next time get a 0.1uf 275 VAC type with an X2 specification. X2 is across power line filtering.
Some of the online vendors will indicate their capacitors are rated for AC power line use. While others just sell capacitors. That may or may not work with out a bang. 

[Dan Lawrence]

Do you have an electric stove?  All are 220 volts, so you can put a 0.1uf 275 VAC type with an X2 specification across the contacts in the stove outlet. It bridges the phases and the stove never knows its there.

[steven r]

...I know the capacitor was installed correctly and was bridged across the 2 legs of the single phase service...

If you had anything installed in your breaker box other than a breaker, it was incorrect as that violates the the electrical building code. Installing in the breaker box can void your home owners insurance. The capacitor needs to be installed outside the breaker box. Even inside a 220 stove or drier outlet may be a code violation but at least it's safer.

[Dan Lawrence]

Sorry, but unless the inspector is Superman, there is NO way a proper capacitor in a stove outlet can be detected if it is not visible by the eye.

[steven r]

...there is NO way a proper capacitor in a stove outlet can be detected if it is not visible by the eye.

Unless the fire starts there.

[Dan Lawrence]

...there is NO way a proper capacitor in a stove outlet can be detected if it is not visible by the eye.

Unless the fire starts there.

Between slim and none.   A capacitor draws no power.   All the capacitor does is pass X10 signals between the phases. 

[JeffVolp]

...there is NO way a proper capacitor in a stove outlet can be detected if it is not visible by the eye.

Unless the fire starts there.

Between slim and none.   A capacitor draws no power.   All the capacitor does is pass X10 signals between the phases. 

And as recommended above, a 275VAC X2 capacitor is rated for direct across-powerline installation.  They are available from electronic distributors, such as Mouser and Digikey.

Of course, a better choice is a tuned passive coupler, such as the X10 XPCP.  It offers significantly lower impedance than a simple capacitor.

Jeff

[dave w]

A capacitor draws no power.   All the capacitor does is pass X10 signals between the phases. 

Unless it shorts, and then hopefully it explodes, rather than go incendiary.

[Brian H]

Since the current and voltage are not in phase with a capacitor. I am not sure how much actual power it uses.
I measured 3.84 ma AC current through a .1uf 275VAC cap on a 120 volt power connection. With my Radio Shack 22-813 DVM.
So it probably does use a small amount of power.

[Noam]

Of course, a better choice is a tuned passive coupler, such as the X10 XPCP. 

Or, Jeff's XTB-IIR ;-)