Updating old 2 wire circuits


Old 08-25-07, 01:30 PM
Thread Starter
Join Date: Oct 2004
Location: USA
Posts: 114
Updating old 2 wire circuits

I am working on a 1920 era home. Most of the old knob and tube wiring has been replaced and updated.

My current question concerns a 240 volt 2-wire circuit that was added some time in the relatively recent history of the house.

The circuit powers an electric heater and the connection goes from the breakers in the basement into the attic then down to a heater in the second floor. The wire is two conductor romex type cable and the connections are two hots. The heater has no connections for either a neutral or for a ground.

My question concerns adding a ground. I cannot practicly run a new three wire conductor from the panel to the heater. I do however have access in the attic to two 110 volt grounded circuits (14 gauge conductors). I also have access from the attic to the heater connection.

Is it permissible to install a junction box in the attic then run 3 conductors from the junction box to the heater. Power the two hot legs of the circuit with the original hot feeds coming into the attic from the panel (12 gauge conduits) and ground the junction box and the third conductor to the heater from one or both of the grounded circuits accessible from the attic (14 gauge conductors)?

Thanks for your help.

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Old 08-25-07, 02:50 PM
Join Date: Aug 2007
Posts: 4
Ungrounded Heater on Second Floor

Unless you have been ordered to upgrade this heater to a grounded unit by the AHJ, the NEC does not require you to do anything. The solution you proposed is not an easy one and is technically unsound. By the way, I did not see in your post what AWG size the heater feeder was.

If the heater is in the bathroom on the second floor, you might ground the existing case to a nearby galvanized or copper water pipe using an approved pipe clamp and a green ground wire the same size as the heater feeder conductors. The ground wire must be protected from damage. Wiremold makes suitable surface raceways which can be used to protect the ground wire. Check with HD and Lowes.

The green insulated ground wire can be launched from the heater metal case using a "green pigtail" which is an approved green hex headed screw and 6 inches of green insulated #12 copper wire, routed to a Wiremold surface box butted against the heater shell with the balance of the grounding circuit attached by a wire nut. The whole can be inspected easily by an inspector by removing the blank box cover. I prefer the plastic Wiremold, but if you use metal, be sure to include a bond to the metal Wiremold as well. The heater shell must remain cool to use the plastic version. Drill smaller hole and use a 10-32 tap for the green hex head screw.

Be certain no one has cut out portions of the galvanized or copper water pipe between the second floor and the basement and replaced with plastic. If so, you need to jumper (bond) around the plastic using approved clamps and bare or green insulated wire. Always get a permit and inspection. Protect your fire insurance policy. Check with the inspector first. Not all inspectors will permit you to use this method. Ask them to make a suggestion and then you can follow it. Good luck.
Old 08-25-07, 07:17 PM
Join Date: Dec 2006
Location: orange county
Posts: 285

I am a novice but I am pretty certain you cannot ground to the "nearest galvanzed or copper pipe". I forgot the exact details but I believe you can only ground (bond) to a pipe that is within 5 ft. of the main panel.
Old 08-26-07, 11:08 AM
Thread Starter
Join Date: Oct 2004
Location: USA
Posts: 114
2 Wire Circuit - Update

Thanks for the replies.

To follow up on some of vayidaho's comments and questions

I have not been ordered to upgrade the unit. I just discovered this situation and would prefer, if able and safe, to eliminate the possibility that I could have a live hot touching the case without blowing a breaker.

The wire size to the 220V heater is 12 gauge. I have two 110V circuits going to the attic with 14 gauge wire so I have two ground conductors that run from the attic to the panel.

Old 08-26-07, 07:48 PM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
You cannot get a proper ground for a 20 amp circuit from 15 amp circuits.

Your only solution for a proper ground is a a 12 gage wire run all the way back to the panel, or all the way to a 20 amp circuit that has a 12 gage ground wire.

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