3 wire versus 4 wire system

[drdad100]

the new kitchen range has a warning stating that the range is equipped for use with an electrical system which uses a separate grounding conductor (4 wire system). if the range is connected to a system which uses a single conductor for a ground and neutral (3 wire system) a grounding jumper must be connected. so i put in a nema 14-50R receptacle to accept the the 4 pronged plug of the range. from the receptacle i ran 10 gauge romex (4 wire). at the subpanel i connected the 10 gauge wire (black and red) to a 30amp double pole breaker. the white neutral was connected to the neutral bar, and the ground was connected to a separate grounding bar. the subpanel is on a 40 amp breaker. from the subpanel 8 gauge romex ( 4wire - black red white and ground) runs back to the main breaker. here is the question. at the main panel i noticed that there are no separate neutral and grounding bars as in the subpanel. the neutral whites and the grounds are comingled together in a long bar. does this configuration at the main panel make the system a 3 wire system, do i have to connect the grounding jumper. thank you

[Wgoodrich]

The main service rated panel is required to join the neutral and grounding together as one entity electrically. However once you leave that main service rated panel you are not allowed to touch the neutral to the grounding again except a couple of exceptions. In you case you changed the branch circuit wiring connections correctly using four wire other than that new branch circuit is too small for the range you are serving. An electric range requires minimum amp size of the branch circuit to be 8 awg copper to a 40 amp breaker. You need to install the proper branch circuit size being either a 40 or a 50 amp branch circuit not a 30 amp branch circuit. You wire is too small.

Your house has a four wire system. YOu main panel is the only place the neutrals and grounding is required to join together all others require four wire system once you have left within that main service rated panel. This includes sub panels and branch circuit wring requiring the 4 wire system.

Good Luck

Wg

[drdad100]

thank you for the information. in terms of the branch circuit i followed the maunfacturers specifications. its a ge monogram range the 30" model. the installation instructions actually call for a 25amp breaker for the 30" model. so i put in a 30amp breaker. interestingly the 36" models call for a 30amp breaker and the 48" models call for a 50amp breaker. it is a code requirement to have a 40amp breaker with 8gauge wire

[suemarkp]

I this a range, an oven, or a cooktop -- makes a big difference (a range is a combined oven and cooktop)? The code mandated minimum circuit for a range is 40A, as most ranges require over 30 amps to run. What is the KW rating of your appliance? And what else is on your subpanel -- with the 40A subpanel run everything connected to it?

[drdad100]

my mistake in identifying it as a range. it is a dual fuel item, gas for the range and electrical for the oven. where would i find the kw rating for the appliance. i cant seem to locate it. what is on the subpanel is mostly lighting and a microwave. the refigerator i put on another separate 40amp subpanel in the basement. in addition that other subpanel carries the kitchen receptacles so other kitchen appliances, such as toaster, blender etc. run off of that subpanel as does the washer and dryer. if i am still not up to code or in a dangerous situation let me know. i just thought that if the manufacturer called for 25 amps, i didnt want to have 40amps flowing into the appliance thanks

[suemarkp]

You're probably fine for just an oven. The nameplate can be hidden in various places. I've found in most recently on the front of the frame behind where the bottom drawer slides in and out (usually on the right side).

The only remaining issue is whether you can put it on a 30A circuit when the manufacturer says a 25 amp circuit. The 25A double pole breakers are hard to find a home centers. Generally, unless there is a marking on the nameplate that says max breaker 25A, you are allowed to upsize 50% over the nameplate amps (or calculate those amps by dividing the KW by 240V) and rounding up to the next standard size .