I replaced an old 240v line voltage thermostat with a new Lux LV2. I've discovered that a very little amount of electricity is getting through to the load lines when it's turned off. The voltmeter fluctuates between 1 and 2 volts and my non-contact tester picks up the current on these lines as well. Considering none of the old ones that still work have this issue, I'm thinking I ordered a couple of defective thermostats. I tried the one I was going to install in the kitchen as well. Same result. 2 volts isn't much, but it's enough to make me worry. Should this be happening?

There should be Zero volts leaving the stat. This is suppose to be a mechanical device,and both contacts of the double pole switch should be open when the stat is off.

Lux - Mechanical Thermostats: LV2-1042

I, personally, never heard of this brand, so I have no opinion or experience of the quality.

Perhaps a call into their office may be in order.

Lux Products Corporation: Contact

Some of those line voltage tstats have a resistor inside across the load leads. Probably some kind of heater, or "anticipator". I have seen them installed backwards (load exchanged with line pigtails, professional electricians too!) and because of that there was always some current flowing, but that was on the line side. Possibly the unit you have is doing something like that.

The other thing I can think of is capacitive coupling from line to load that will cause a NCV tester to give a false positive. Also depending on the grade of meter you are using a 1V reading could be instrument noise. However since you said the old ones don't give those readings I will assume that your reading is OK.

I am not familiar with Lux line voltage units, so I can't speak authoritatively on them. Double check the line and load connections for correctness.

EPM

Capacitive coupling sounds less likely than say inductive coupling from a nearby circuit. All it would take is the heater wire to run parallel to an existing circuit and bingo. Phantom voltages.

Kill everything in that room except the heater power at the breaker and try doing the test again.

Interested, for curiosity's sake.

Quote:

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Originally Posted by KeepItSimpleStupid

Capacitive coupling sounds less likely than say inductive coupling <snip>

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You're right. I got the wrong term for what I had in mind.

EPM

Well, I had ordered 6 more of these through Amazon for about half the price I paid at prothermostats.com. The first thing I noticed was that the ones ordered through Amazon came in a retail package with a Lux label on the cover. The ones from prothermostats came in a plain white box and the labels had been sanded off. It makes me wonder what went on with these thermostats.

Anyway, I installed one and sure enough, no voltage registers on my voltmeter across the load lines when it's turned off. For some reason the non contact tester is still picking something up, but I'll trust the voltmeter.