4-wire details for new replacement dual fuel oven

Question

After excellent input in a previous question and chat over the past 2 days, I request information on new 4-wire and receptacle to install to support the installation of our new replacement oven.

We are installing a Wolf dual fuel stove to replace a Dacor.

• Breaker service is 30amp (C-H panel) and Wolf stove specifies 30amp.
• The distance for the new wire pull is <50'. Please advise the wire to pull?
• A convenient run is along the garage ceiling-wall corner 9' high then turning up through the ceiling and through the kitchen floor at the stove location.
• Is it required that the wire be pulled through conduit for the run in the garage?
• What NEMA designation is required for the receptacle to be used by the installer?

Answer 1

The NEMA designation will be 14-30 for a 30 amp breaker.

If you use cable, code wants cable to be protected below 8 feet, inside of a wall or conduit or something to prevent people pulling on it.

If using plain wires you need conduit all the way. Some people like to use conduit since it makes changing wires easier and adds protection to the wire from being damaged(mice, stuff laying on it).

The wire will need to be at least 10 gauge, but larger is allowed. The type will depend if using conduit(THHN/THWN) or just cable(NM-B)

Answer 2

Future-proof option: Install a 50A circuit

Since you are redoing the circuit in it's entirety anyway, I suggest installing a 50A circuit. You don't need to upsize the breaker to 50A, but I suggest to at least install 50A wire (#6 Cu or #4 Al -- see footnote regarding Al wire). My reasons are these:

• Future-proof: Like it or not, gas is on the way out. As the price of gas rises and the price of electricity falls, future owners (or even future you) might want to swap out the dual-fuel for an induction range. Those are at least 40A, and some require 50A.
• Anti-confusion: Dual-fuel is an odd duck since you'll have both a 240/120V big-kid receptacle and a gas cock behind the range. Traditional electric setups provide a NEMA 14-50 240/120V outlet (or NEMA 10-50, ugh), and traditional gas setups provide a standard NEMA 5-15 just for clock/control power. A future owner might see that big faceplate and decide they can plug in their trusty electric range, which would be worthless to them with only 30A wire in the wall.
• Compatibility: Your cord-whip is going to very likely be a 40A cord, which actually mates to a NEMA 14-50 (50A) receptacle. (This is an exception allowed by NEC since there isn't a class for a 40A receptacle) As you found, finding a 30A cord whip is easy, but convincing an installer to fit it is less so. If you run 50A-capable wire, your 50A receptacle is legal, your 40A cord is legal, and you can use a 40A breaker (due to the same NEC exception).

Of course, everything in my third bullet point is also totally kosher with 40A (#8 Cu or #6 Al) wire, but if you're running new wire anyway, it doesn't make sense to skimp. That way, future upgrade to 50A is only a breaker-swap away.

Note regarding Al wire - Aluminum wire is significantly less expensive than copper in comparable size, which makes it a no-brainer for feeders and a good option for large, dedicated branch circuits. Without straying into the weeds of chemistry and metallurgy, know that modern Aluminum wire is constructed of better alloys than the old stuff you've heard about. However, while the Aluminum wire manufactured today is not the same as your father's Aluminum that caused fires and panic in the 1970s/80s, some jurisdictions (and/or property insurers) have policies that disallow Aluminum wire in branch circuits. Check with your local authorities before choosing to make sure Aluminum is allowed.

Answer 3

Another answer covers receptacle type (14-30), wire/cable type, conduit, etc. However, I believe the answer to Which receptacle? is None.

Most ovens/ranges/etc., and in fact many other essentially permanently installed appliances such as dishwashers, disposals, HVAC equipment (except seasonal window air conditioners), water heaters, EVSE (a.k.a., "car chargers"), etc. can be hard-wired. The primary advantage of hardwiring an appliance are is that you remove a point of failure - no plug to get loose, no cheap receptacle to go bad. But interestingly enough, at least in an online search I am having trouble finding a proper 4-wire 10 AWG (for 30A) ready-to-use whip. Which means either I am looking in the wrong place (likely) or installers build their own (not so likely - lengths are pretty standard, typically in the 4 to 6 foot range, and trusting a regular installer (non-electrician) to get all the little details right is not a good idea). Actually, I have seen some appliances which come with a whip preinstalled, but typically on things such as wall ovens where hardwired installation is required rather than optional. I am pretty sure (but the experts can speak up if I'm wrong) that MC cable works for this - cut to length, use the right connectors/clamps to attach to the oven junction box and the wall junction box.

But, I hear you say, what about if I need to actually disconnect the oven for some reason? Guess what, removing one cover plate and 4 screw terminals will be the easy part. The harder part will be properly disconnecting and reconnecting your gas line! For anything else - e.g., move the oven away from the wall for in-place repairs or cleaning or painting the wall or whatever, a 4 or 6 foot whip permanently attached will work just fine.

Answer 4

Oddly enough the NEC has different rules for dedicated (called individual branch circuit in code terminology) and for multi-outlet circuits. For your dedicated circuit the receptacle only cannot be smaller than the breaker size. So you could use a 30A breaker as specified in the oven installation instructions, and use the minimum allowed size of NEMA 14-30, or you could use a 14-50.

210.21(B)(1) Single Receptacle on an Individual Branch Circuit. A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.

210.21(B)(3) Receptacle Ratings. Where connected to a branch circuit supplying two or more receptacles or outlets, receptacle ratings shall conform to the values listed in Table 210.21(B)(3), or, where rated higher than 50 amperes, the receptacle rating shall not be less than the branch-circuit rating.

The drawback of using a 14-50 on a 30A breaker is somebody could replace the range with a 50A model and he plug would fit, but the wire would not support a 50 amp load. I would recommend 50A wire so all that would be needed to support a 50A range is a simple inexpensive breaker swap.