2 hots, ground, NO neutral. How to wire to 4 wire 240V/120V appliance?

Thread Starter

Bfarmed

Joined Jan 27, 2019
4
In a house, I have 2 hots, a ground, but NO neutral ran where I would like to hook up a 240V/120V gas/electric range. I am aware that one could connect the appliance neutral to the ground and it would work, however that could be potentially dangerous/deadly. In my situation it would be extremely difficult and expensive to run a neutral back to the circuit breaker, so I was wondering if it would be OK to wire the appliance neutral to the ground if one was to add an additional ground wire that connects the appliance ground to a new grounding rod outside? Thank you.
 

MaxHeadRoom

Joined Jul 18, 2013
21,198
AFAIK according to the latest NEC & CEC it is not permitted, as it was at one time, to use the GND as a neutral.
Personally I would not do it.
Max.
 
Last edited:

MaxHeadRoom

Joined Jul 18, 2013
21,198
What might be cheaper is to use a 240v/120v transformer and re-reference one side of the secondary to earth ground conductor and then take a neutral from there, the 120v demand is not usually that high.
Max.
 

sghioto

Joined Dec 31, 2017
1,326
When you say "ground" do you mean a bare wire? What are the colors of the "hots"?
Maybe not as efficient but what about wiring the range on 120 vac.
SG
 

Thread Starter

Bfarmed

Joined Jan 27, 2019
4
Thank you very much for the response Max. If you don't mind, could you elaborate with more detail how one would go about the installation of a '240v/120v transformer and re-reference one side of the secondary to earth ground conductor and then take a neutral from there'.

sghioto - The ground is a bare wire ground. The 'hots' are black and white (I tested with multimeter to be 240V together and 120V each). I marked the white with red tape since the electrician that ran it did not indicate the white was hot. Your suggestion would then be to make the white wire neutral again and run the electric oven on only 120V?
 

jpanhalt

Joined Jan 18, 2008
10,079
The 'hots' are black and white (I tested with multimeter to be 240V together and 120V each). I marked the white with red tape since the electrician that ran it did not indicate the white was hot. Your suggestion would then be to make the white wire neutral again and run the electric oven on only 120V?
The "hots" for 240V in the US should be any color except white or green. If one of the hots is white, how will you tell that from the grounded wire (common) that is also white?
 

Reloadron

Joined Jan 15, 2015
5,605
I would like to hook up a 240V/120V gas/electric range.
Make and model of the range would help. Our range is natural gas and the only electrical requirement is 120 VAC for the convection blower, ignition, clock and lighter powered electronics. All of the heating is natural gas. I have not seen a range in the US or Canada which was gas fired and used 240 VAC.

If your range uses electric for any of the heating you may want to check out the nameplate data as to the actual wattage requirements at 240 VAC to allow for a sufficient gauge of wire.

I would not use a ground line as a neutral. I don't know your location but here in the US the only bond between Neutral and Ground is at the service entry panel. While the NEC does not get specific or require color coding there are common industry standards applied normally. When using 240 volt service L1 Hot is normally Black, L2 Hot is normally Red, Neutral is normally White and Ground is normally Green.

3-Prong vs. 4-Prong
Ranges and clothes dryers have a similar story. Prior to 1996 (it was actually closer to 2000 when the new rules were widely adopted), electric ranges and dryers were wired with three conductors: two “hots” and one neutral. The appliance body, or case, was grounded through the neutral so that the dryer cord and receptacle did not have a separate ground. After the change, appliances began to be sold with the case ground separated from the neutral. This configuration calls for a 4-conductor power cord that has a separate ground wire that connects to the ground screw on the appliance. The old system worked just fine, but the new system is safer.
The link covers things well and again, this applies to an electric range or stove where electric is used for creating the heat.

Ron
 

MaxHeadRoom

Joined Jul 18, 2013
21,198
Thank you very much for the response Max. If you don't mind, could you elaborate with more detail how one would go about the installation of a '240v/120v transformer and re-reference one side of the secondary to earth ground conductor and then take a neutral from there'.
It would help to have a copy of the stove schematic, mostly a stoves LV (120v) circuits work from N and L1.
So I believe you would need to wire the 240v/120v up in a buck/boost arrangement.
The attached NFPA79 DWG shows how a 120v transformer is configured for a neutral, although it is a 3ph supply, the principle is the same. (see X1 X2).
If connecting up in a buck/boost then one side of the 120v secondary would be connected to the earth ground conductor as a neutral, the other 12v secondary to the L1 terminal in a Buck arrangement, before connecting the secondary to the stove, you would need to confirm that you have 120v from the now established neutral to each of the L1 L2 conductors.
Max.
 

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MaxHeadRoom

Joined Jul 18, 2013
21,198
Actually after reviewing and seeing it is a Gas range, where and what is the 240v used for?, there certainly would not be a high wattage demand for the typical gas stove.
Max.
 

Thread Starter

Bfarmed

Joined Jan 27, 2019
4
Yes, "Dual fuel" as jpanhalt stated. It's a electric oven and gas cooktop burners. It's a Thor Kitchen TKD3001U.

Attached is the range info and wiring diagram. Thanks for all the help.
RangeWiring.jpg
ThorInfo.jpg
 

MaxHeadRoom

Joined Jul 18, 2013
21,198
It would appear that the 240v L1, L2 and the 120v L2 & N, are quite separate, so you should be a able to use L1 L2 to feed a 240v/120v secondary transformer, the 120v demand does not seem that high.
Max.
 

MaxHeadRoom

Joined Jul 18, 2013
21,198
The 120v is fairly low current so it will not require #12 on the 120v side.
One side of the secondary should be taken to the earth GND conductor at one of the secondary terminals, as per the NFPA sheet.
@Bfarmed if you go this route, disconnect the L2 and N shown as small Gauge conductors, that require to be fed by the secondary and first check if there is continuity between them and the L1/L2 supply terminals. There should be an O/C or close.
Max.
 

Thread Starter

Bfarmed

Joined Jan 27, 2019
4
Wire looks to be 10 gauge.

Ok, so I would need a 240V to 120V transformer. One like this, and wired as described at 1'23" to 2'30"
Best place to buy would be just a local electric supply store?

Thank you all very much for your help.
 
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