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[The Keeper]

Hello all,

I've been using X10 since the BSR days, so I know all about coupling (using an XPCR) and filtering (have XPPF's everywhere that a computer plugs in, and an XPF for the server gear in the basement). I'm also good with electrical wiring as well (I've had my work inspected previously). 

I have no idea how many X10 modules (and some Z-Wave as well) I have deployed at this point, but it's probably approaching 100 between my house and my wife's store.

But this XPS3 problem has me stumped. It's not http://kbase.x10.com/wiki/Switch_Turns_On_But_Not_Off#Questions because right now I'm not even concerned right now about the X10 signals.

Cut to the chase, if I connect the line and neutral wires to the XPS3 but not the load wire, I can tap the XPS3's button and locally control it. LED on the XPS3 turns on with the "click" and turns off with the "click".

When I connect the load wire to the XPS3... Tap the button, and that's it. The XPS3 turns on, but the XPS3's LED doesn't illuminate, and no further taps of the button have any effect.

The load in question is a chandelier with three incandescent light bulbs.

I tried another out-of-the-box XPS3, and the same symptoms were exhibited. An XPDI3 does work, but this is only a temporary workaround because I intend to switch to CFLs.

There's something more insidious going on here than simply a failure of an XPS3. The circuit I'm working with is the original knob-and-tube (one of the few remaining circuits of that sort; the rest have been replaced with romex) in a 100-year-old Victorian house. It's a ceiling fixture, so I'm stuck with this wiring unless I go and pull the plaster and lath down, which isn't on my list of fun things to do. Or even can do, for that matter -- the store is open 6 days a week, so I can't go demoing a ceiling just because a light switch isn't behaving.

Any thoughts?

Thanks,
Chris

[JeffVolp]

It sounds to me like the switch loses its own power source once the load is powered.  Have you verified you have a solid neutral connection?  (Is there 120V across the hot and neutral wires when the load is powered?)

Jeff

[The Keeper]

Thanks for the reply. Yes, the neutral is good -- I had to fish a 14-ga neutral line up from the basement, tied into a new work box with a romex feed.

Any idea what sorts of load conditions could cause an XPS3 to misbehave like that? I have installed a couple dozen XPS3's over the years, and this is the first time I've encountered this behavior.

Chris

[JeffVolp]

Any idea what sorts of load conditions could cause an XPS3 to misbehave like that? I have installed a couple dozen XPS3's over the years, and this is the first time I've encountered this behavior.

While I don't use the XPS3 here (all Leviton), I believe it is essentially a different form-factor X10 appliance module.  And I have used them with all sorts of loads with no problems.

Jeff

[Brian H]

Did you have a chance to measure the actual voltage on the Line and Neutral Connections when the XPS3 was ON?

[The Keeper]

The thought hadn't occurred to me to ring out the hot to neutral with the module "on". So, what would be your recommended remediation if it reads a bit low? I can't see it reading any higher than 120 -- the fished neutral is tied to the bus bar in the breaker panel, so I know it's not going to be hot itself.

[Noam]

Did you swap the Line and Load wires by accident, maybe?

[The Keeper]

An XPS3 doesn't do anything at all if you reverse the two, actually...

[The Keeper]

Ok, so, the general consensus seems to be that nobody really knows for sure how these modules work, and what their anomalous behavior modes are?

Chris

[Brian H]

You never answered the question. What is the measured voltage from Line to Neutral terminals of the XPS3 when it is On?

The reason we are asking. You had to pull a Neutral into the switch box. That would indicate the old switch was in a switch loop. It is possible neither of the original wires in the switch box is a true Line Voltage and you maybe reading through the load when you measured it.

[The Keeper]

I guess I could similarly state that you didn't answer my counter-question, but since you asked first, then I guess the onus is on me to find out. With that said, there were only two wires in the box when I started, and I properly identified the supply wire (which presented 120V relative to the fished neutral which is tied to the bus bar in the breaker panel) and the load wire (which did not present 120V), so the problem is not that I'm reading the wrong wire.

It would have been good to know the reason why the XPS3 is exhibiting this behavior, but if there's no visibility into the XPS3's design, then it appears that my only options for remediation are either stick with the XPDI3 (which appears to work "fine") or to tear down the plaster and lath in the 9' high living room ceiling to replace the wiring.

Take care,
Chris

[JeffVolp]

there were only two wires in the box when I started, and I properly identified the supply wire (which presented 120V relative to the fished neutral which is tied to the bus bar in the breaker panel) and the load wire (which did not present 120V), so the problem is not that I'm reading the wrong wire.

If you made those measurements with the lightbulb connected and the switch open circuit, then you really didn't confirm what was asked.  The light could be fed directly from the hot line, with the switch in the return path.  If that is the case, the switch would lose its power source when turned on.

Jeff

[Brian H]

Jeff and The keeper.
On my test stand I wired a switch loop as Jeff described.
Line to the light bulb and then the other bulb wire to the Line Terminal of the XPS3.
Neutral wire to the Neutral terminal of the XPS3.
With a 100 watt bulb and the XPS3 Load not connected. It went On and Off along with the RED Indicator.

In the switch loop Jeff described the switch actually went back to Neutral.
When the Load Terminal of the XPS3 was tied to Neutral. The XPS3 went On. No LED but light bulb was On and you could not turn it Off. Until the load terminal was again removed.

Measure the voltage with your lamp removed and see if you still have 120 volts to your XPS3.
My guess is the XPDI can steal enough current to work even though you are in a switch loop.

[Brian H]

Switch Loop we think you may have.

Line in fixture--------------{Bulb}------------{Switch}-------Neutral in fixture.

[Noam]

Depending on how the wiring is at the fixture, you still may be able to get this working.

If Brian's diagram is correct, you are switching the Neutral, not the Hot (which I think is against the NEC, but I don't know for sure).

If you re-wired like this:

Line in fixture--------------{Switch}------------{Bulb}-------Neutral in fixture, and then tied the extra neutrla you fished to the neutral wire on the switch, I think it would work.

You'll need to open up the wiring at the fixture, to be sure.
Hopefully, you'll see a Hot (black) and Neutral (white) entering the box, that should have 110V between them with nothing else connected to them. If that's correct, then you would tie the Hot to one of the wires heading down to the switch, one side of the fixture (black) to the wire coming back from the switch, and the other side of the fixture (white) to the Neutral in the box.
If you do this, it is important to know which wire goes TO the switch (the one connected to the black wire in the ceiling box), and which comes BACK from the switch (the one connected to the black wire of the fixture in the ceiling box). Usually, a black/white pair is used, with the white being marked with black paint, or a strip of tape, to indicate it is really a "Hot" wire. when I've done wiring like this in my house, I've spent the extra money for #12/3 or #14/3 wire, which has a third, red wire (not counting the ground). I use the Black wire for the "Line" going to the switch, and the Red for the "Load" going back to the fixture. I cap off the white at both ends. That way, there is no confusion later on if someone has to open the box up later to trace wires.

At the switch box, the "TO" wire would go to "Line," and the "FROM" wire would go to the "Load." You would attach the neutral from the switch to the new neutral you fished.

I found a diagram, that (hopefully) shows this more clearly:
http://www.buildmyowncabin.com/electrical/wiring-switch-power-into-light.html

In your case, there would be an extra Neutral wire, that you fished right to the switch box.

I hope that makes sense. Let me know if you have any questions.