Capacitor to bypass GFI outlet?

The official word from X10 Customer Support is that one way to get the X-10 signals to hop from one phase to another is by "installing a 0.1 microfarad,

600VDC capacitor across the two phases in the panel, i.e. by connecting the capacitor across any 220V breaker."

Can a similar trick be used to get the signal across a GFI outlet? That is, what would happen if I attached a 0.1 uF 600V cap from the line to the load? Would the X-10 signal get through? Would it affect the ability of the GFI outlet to detect ground faults?

Thanks! Chris

Reply to
Chris Shearer Cooper
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The reactance of the cap is 1 / (2 * Pi * f * C), or roughly 1 / (400 * C) at 60 Hz, so it has a reactance of approximately 25K ohms. If you assume the current sense circuit in the GFCI drops one volt (I have no idea how good an assumption this is, but you could measure it), the cap would put 40 microamps of unbalanced current into the load circuit (or looked at another way, it would "steal" 40 uA from the hot-side current sensor). Dunno if that's enought to trip the interrupter, but it's a pretty easy experiment to try.

I haven't really looked at GFCIs, but isn't it a four-terminal device? I would guess so, since it needs to monitor current on the neutral as well as the hot side. If that's the case, put an identical cap across the neutral side as well, and things will be back in balance.

- Dennis Brothers

Reply to
Dennis Brothers

Yes, the GFCI is a 4-terminal device, so I can give it a shot!

Thanks.

Reply to
Chris Shearer Cooper

But, what if you use 2 capacitors, one on hot side (hot in to hot out) and one on the neutral side, that should keep the balance. More guessing here.

Reply to
Art Todesco

One question is, do you really need to? Normal GFI outlets usually don't present a problem with X10 signals. (The newer types designed to additionally detect arcing may be a different matter.)

Reply to
Charles Sullivan

I'm pretty sure the GFI is the problem (need to do some additional testing to verify). I have a CM11A in my office, and I can control X-10 modules in the office and the nearby bedrooms, and also in the kitchen (on a different level) but modules in the living room ignore the CM11A completely. I tried the trick of turning on the oven (hoping to bridge the two phases) and that didn't help.

I'm go>

Reply to
Chris Shearer Cooper

It's possible you have some noise generators or signal suckers in that room or on the same branch of the power line. Try unplugging any and all electronic gear (TV, VCR, DVD, Stereo, CF lamps, etc) from their AC sockets and see if that makes a difference. (If so, you'll need to put filters on the offending appliances.)

You might also want to map out which rooms/receptacles are > I'm pretty sure the GFI is the problem (need to do some additional testing

Reply to
Charles Sullivan

Reply to
w_tom

"Chris Shearer Cooper" wrote in

[/sermon on]

Sorry to feel compelled to butt in here. Even the slightest chance that such a mod could compromise your GFI's ability to protect you makes your proposed mod a very bad idea. As Tom noted, the wrong capacitor choice could have serious consequences.

It seems that some GFI's are X-10 friendly, and some aren't. Therefore, I respectfully submit that the better course of action is to find a GFI that presents no problem to X-10 and switch yours out. It would also be helpful to the whole X-10 user universe to identify the make and model of the GFI so that brand can be avoided by others.

[/sermon ended]

I don't recall if you ever fully explained your X-10 problem in detail in the OP, so it may be that your proposed fix won't do anything at all. The GFI may be a signal sink. It may even be functioning perfectly and the X-10 interference/attenuation is coming from something other device(s) along the circuit path.

Personally, I'd do a little more investigation into the nature of the problem before assuming the GFI is not passing signals. That's doubly true when the modification has the potential to cripple the life-saving function of the unit. The capacitor fix is designed to couple opposing phases at the breaker box or at a 220V outlet. I've never read or heard of it being applied to a GFI.

Your local electrical inspector would probably have a canary or two if you started adding external components to a GFI. Could you live with yourself if someone in your house died as a result of a GFI failure because of the mod? You're going to be working in the electrical box anyway, how much does a new GFI cost? $10? You'll probably expend the same amount of effort locating just the right value and type of capacitor!

-- Bobby G.

Reply to
Robert Green

If there's a reasonably-priced X-10 friendly GFI outlet, that sounds like a better plan ... but I have no idea how to find out which ones are friendly and which ones ain't ...

Reply to
Chris Shearer Cooper

Put the capacitors across, perform the tests, then remove those capacitors. Robert Green's warnings carry much merit.

BTW, those capacitors are well below what should trip any GFCI. Two high voltage, 0.001 uf caps should be sufficient to test. There may be someth> If there's a reasonably-priced X-10 friendly GFI outlet, that

Reply to
w_tom

Regarding appropriate capacitors, the reactances are linear in both frequency and capacitance; i.e., any given capacitance will have 60/120K lower reactance at X10 frequencies than at line frequency, so the 0.1 uF caps that have 25K ohms reactance at 60Hz will have (60/120K)*25K or 12.5 ohms reactance at 120 KHz (doing this in my head - don't beat me up if I slipped a decimal place). That seems negligible. Moving to .001 uF (a factor of 100 lower than the originally proposed 0.1 uF) moves the 60 Hz current-stealing into the too small to bother with domain, but raises the X10 reactance to 1,250 ohms (times two, given the same cap in both legs), which might be significant, depending on the impedance of the X10 receiver.

Just being anally analytical - - Dennis Brothers

Reply to
Dennis Brothers

The simplest, cheapest thing to try is to temporarily replace the GFCI outlet with a regular (non-GFI) outlet - around $0.60 at Loews. Test to see if it makes any difference. If not, put back the original GFCI and look elsewhere for the problem.

As it happens I've > If there's a reasonably-priced X-10 friendly GFI outlet, that sounds like a

Reply to
Charles Sullivan

That's an even better way to determine if the GFCI is the problem!

Unfortunately, manufacturers often change their design in midstream. I have virtually identical APS UPS's but one's a signal sink, the other's not. Same with CFL bulbs. But at least it's a good start knowing which equipment has worked for other people.

-- Bobby G.

Reply to
Robert Green

I don't know of any listing of X-10 friendly equipment so all I can suggest is to buy a different one than what you have. Or, you can simply replace it, as Charles suggested, with a non-GFCI outlet just to see if that really is the problem point and go from there. One thing I would suggest is searching Google in this newsgroup for GFCI or GFI problems and avoid buying any brand that's listed in those messages.

-- Bobby G.

-- Bobby G.

Reply to
Robert Green

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