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Author Topic: 2-Wire Appliance On/Off Switch or Outlet?  (Read 10606 times)

Offline DrHitch

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Re: 2-Wire Appliance On/Off Switch or Outlet?
« Reply #15 on: June 19, 2012, 06:01:32 pm »
Hi stylekyle,
Having done a lot of electrical work on older homes, I think i can help here.

1)  Your knob & tube wiring as well as the two-conductor Romex does not have an separate earth ground.  It is a two-wire system.  That said, one of those two leads back at your fuse box or breaker panel is indeed hooked to earth ground.

2)  In the attic, you can't really tell which is the "hot" wire and which is the neutral/ground wire.  You could "guess" that someone hooked the Romex up properly and therefore the black Romex is the "hot" wire.

3)  If there is any metal pipe in the attic, you could put a voltmeter on the two knob & tube leads (individually).  The "hot" wire will have 120 volts, the neutral/ground will not.  If there is nothing in the attic that can act as earth ground, proceed with step 5

4)  In order for a z-wave outlet to work, you may need to use the neutral wire at the outlet to be both neutral and ground.  So, in your fan switchbox, replace that switch with a normal duplex plug and tie the (white) neutral wire to both the silver lug of the outlet as well as the green ground lug.  Attach the "hot" (black) wire to the brass lug on the outlet.  Now, plug into that outlet your three-prong z-wave controller.  Create a plug pigtail from the fan motor and plug into the z-wave.  It doesn't matter which lead from the fan motor as an AC motor will always go the same direction; there is no right/wrong polarity.

5)  If you can't determine from your knob & tube which is hot and which is neutral, I'd look at the color of the inner copper wire itself.  Sometimes they're silver and brass.  If there is a color difference in the knob & tube wire itself, the silver is 99.9% likely to be your neutral (longer blade/silver screw on a new duplex outlet)

If you're still not certain, get an electrician.....

Offline stylekyle

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Re: 2-Wire Appliance On/Off Switch or Outlet?
« Reply #16 on: July 06, 2012, 03:50:08 pm »
Hi stylekyle,
Having done a lot of electrical work on older homes, I think i can help here.

1)  Your knob & tube wiring as well as the two-conductor Romex does not have an separate earth ground.  It is a two-wire system.  That said, one of those two leads back at your fuse box or breaker panel is indeed hooked to earth ground.

2)  In the attic, you can't really tell which is the "hot" wire and which is the neutral/ground wire.  You could "guess" that someone hooked the Romex up properly and therefore the black Romex is the "hot" wire.

3)  If there is any metal pipe in the attic, you could put a voltmeter on the two knob & tube leads (individually).  The "hot" wire will have 120 volts, the neutral/ground will not.  If there is nothing in the attic that can act as earth ground, proceed with step 5

4)  In order for a z-wave outlet to work, you may need to use the neutral wire at the outlet to be both neutral and ground.  So, in your fan switchbox, replace that switch with a normal duplex plug and tie the (white) neutral wire to both the silver lug of the outlet as well as the green ground lug.  Attach the "hot" (black) wire to the brass lug on the outlet.  Now, plug into that outlet your three-prong z-wave controller.  Create a plug pigtail from the fan motor and plug into the z-wave.  It doesn't matter which lead from the fan motor as an AC motor will always go the same direction; there is no right/wrong polarity.

5)  If you can't determine from your knob & tube which is hot and which is neutral, I'd look at the color of the inner copper wire itself.  Sometimes they're silver and brass.  If there is a color difference in the knob & tube wire itself, the silver is 99.9% likely to be your neutral (longer blade/silver screw on a new duplex outlet)

If you're still not certain, get an electrician.....

Dr. Hitch... thanks for your reply.  I will give this a go.  I'm going to turn off everything on that circuit, and then use a non-contact ac sensor to see if i can determine which is one is hot that way.  Hopefully I'll get to this, this weekend.  I'll report back on my results.

Thanks for the help.

Offline hsmaier

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Vera 2 U14, Vera 2 U15, Two Trane TZEMT400AB32 Thermostats. Insteon Light Switches, Insteon Outlets, Power Linc Modem.

Offline stylekyle

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Re: 2-Wire Appliance On/Off Switch or Outlet?
« Reply #18 on: July 15, 2012, 10:57:51 pm »
thanks for the help everyone... i used a non-contact ac sensor to identify the positive and the neutral.  wired in an appliance on/off outlet, and wired a plug onto the end of the fan.  Took all of 20 minutes, and now my whole house fan is on z-wave.

 ;D