We recently bought a new stove for our house. I was trying to hook it up and I was unsure how to proceed. The problem is this: the old stove is attached to a cable carrying 3 wires (2 hot and 1 neutral/ground) while the new stove has a plug with 4 wires (2 hot, 1 neutral and 1 ground). How can I make this work?
Possibilities:
Attach the hot wires to their respective terminals and split the neutral wire to attach it to both the neutral and ground terminals.
Attach the hot wires to their respective terminals, attach the neutral wire to its terminal, and run a new wire from the ground terminal to a nearby water pipe.
Any suggestions Opal?
Anybody with some knowledge about such things care to offer some advice? I would greatly appreciate any input. Thanks,
Hire an electrician. You obviously don’t understand the diff. between 240V and 120V lines and that is just plain dangerous. Do not try to do this mod yourself (esp. since every one you list is just flat out wrong).
ftg, thanks for checking in. I do realize that this circuit is 240V. I am considering getting an electrician to do this for me, but friends have suggested that is not necessary. They have also suggested doing the first option. Since you seem knowledgeable about these matters could you explain why the old stove has only 3 wires going in but the new requires 4? And why the 2 strategies outlined would be dangerous? I really don’t want to create a hazardous situation so I will likely get professional help, but I also want to learn what is going on (fighting ingnorance and all that).
-Do not “split” the neutral to connect to the ground. The neutral is not always at ground potential. The ground connects to the range’s chassis & could present a shock hazard if the neutral is connected to it & there is an unbalanced load in the house (pretty common for the two legs to be at least a little unbalanced).
-Do not connect the ground to a convenient water pipe. Your water pipes may have discontinuities, such as dielectric unions or sections of plastic pipe. This will result not only in an ungrounded electric appliance, but spreading potential shock hazards to every sink & shower.
If you are going to wire this yourself, run a new ground wire back to the panel & connect to the ground bus.
The stove’s plug has two hots, one neutral, and one earth ground.
So what to do?
Well I can tell you what not to do: Do not connect the neutral (in the stove’s power cord) to the earth ground connection in the receptacle. Doing so would violate code.
I would first find out why the stove has a neutral:
Some stoves have a 120 VAC “convenience” receptacle on the front panel. If this is the only reason the stove has a neutral wire in its power cable, then simply don’t hook up the neutral and stick a plastic thingy in the 120 VAC so no one tries to use it. (It won’t work anyway.) Check the owner’s manual or schematic to see if this is the case.
The stove might need 120 VAC to power its control circuitry. If that’s the case, you’re going to have to run a neutral line to your stove - there’s no way around it. Sorry.
Hmm… I’m NOT an electrician, but could someone (ScoobyTX?) tell me why neutral isn’t always at ground? In my circuit breaker box (and I realize this is my circuit breaker box), the neutral is wired directly to the ground rod outside. Hence they’re electrically equal. Or not? There are no 220VAC circuits in the house, if that makes a difference.
Okay, I just checked the air conditioner (today’s a voting holiday for some reason - took all of 5 minutes), and it is 220VAC, wired directly to the meter. Its outside neutral is wired to a different ground rod.
Neither am I an electrician but as I understand it;
Using the simple case of 120V circuits, both the HOT and NEUTRAL wires have current flowing through them, and the GROUND does not, so at the point where the load/appliance is plugged in the NEUTRAL wire will have built up some voltage differential with respect to the GROUND. (There is voltage build-up in any current-carrier due to “Ohm-ic” loss, which would go away if we rewired our homes with superconductors, I guess.)
In a 220/240V appliance most of the load flows between the two HOT leads. However, if a 240V device has some additional load or circuitry (electronic controls and displays, or perhaps a lower-voltage secondary motor, ) from only one of the HOT leads to NEUTRAL, it will result in the same scenario as in 120V above.
There may be cases where the 240V load actually consists of two separate HOT-to-NEUTRAL loads, and if those aren’t exactly matched you will have a net current in the NEUTRAL again resulting in a voltage differential with respect to GROUND.
I don’t know of any specific 220/240 devices that operate that way, but I do know that many “Y-Connected” three phase systems do operate like that (typically these are 208V, I believe) . Three-phase “Delta-Connected” systems have all HOT-to-HOT loads, and do not do that. (Delta typically used for 480V, IIRC)
In all the above I’m describing US-based wiring only. European wiring/voltages are a bit different, I believe.
Of course, the above could be full of holes, but its what I remember rightly or wrongly from technical High School.
The new four prong plug is due to a code change. In the past, you were allowed to ground the appliance to the neutral. This is no longer allowed and you have to use a separate ground.
To summarize, you have two choices. The code change is not retroactive, so you can refit your stove with a three prong plug. (This is the less safe but cheapest option.) Or you can rewire the stove outlet. This is mildly painful to do, but because the kitchen is usually right above the basement, running the new wire isn’t that tough. (There’s a small chance that you might get lucky and have an unused ground wire in the current wiring scheme.)
The safety issues occur if something happens to disrupt the connection of the grounding wire (neutral) to ground (oxidation or mechanical disconnection). If you are using the grounding wire as a ground wire as well, then it will be attached to the outer skin of your appliance. So if the grounding wire becomes detached at the circuit box, for example, the stove will be hot in more ways than one. Very bad news.
IANAElectrician (but I have a bit of understanding in power circuit design as a consequence of my job as a mechanical engineer).
The neutral is grounded at the panel, but it is also the path of the current from circuits on one leg (hot A-neutral) to those on the other (hot B- neutral). Since, most of the time, the loads on each leg are not perfectly balanced, there is a bit of current carried by the neutral. This current might flow to your neighbors house (on the same transformer) to balance out an imbalance over there, or it might flow to ground (or usually a bit of both). Also, the neutral will normally be at some potential above ground, due to losses in the pathway to ground. If you become a reasonably good path to ground (i.e. standing in a puddle, holding onto your sink faucet, etc.) part of the current will flow through you.
The ground wire/ground bus is wired directly to ground, and does not normally carry any current or have any potential to ground. The abnormal case is that there is a fault in some grounded appliance in your house- in this case there will be current in the ground wire and a potential to ground, and a risk of shock if you are a decent path to ground.