Jump to content

40 amp vs 50 amp


Parsnip Totin Jack

Recommended Posts

What do the forum engineers say? @Thaddeus Kosciuszko We are looking at getting a new range installed in the kitchen. We need to pull a new circuit from the breaker, almost directly under the location where the range will go. The new range says 40 amps at 240v. Our electrician wants to know if he should put in a 40 amp outlet or a 50 amp. He says the cord they use for wiring the range has this stamped on it somewhere. Does the amp of the outlet matter if the appliance is only drawing 40 amp? 

Link to comment
Share on other sites

No but....As rated the range SHOULD never draw more than 40A at 240V.  UL or CSA has them rated and tested at max amperage.  If that thing ever draws more than 40 amps there is an issue - SHORT...  If he installs a 50A circuit you are good to go but you will pay more for the breaker and more for the copper (larger gauge wire).  Why do that?  Based on my days of sending to stuff to UL for testing, the 40A rating would be with every burner and every feature energized plus  17% safety factor.  

TK can shoot me down but I'd probably do 40A.

  • Heart 3
Link to comment
Share on other sites

The breaker box has open 40 and 50 amp circuits. The electrician wants to know what kind of outlet to install for the range. The salesman said that the installers will bring a three prong and a four prong wire (rated at 40amp) to match the outlet the electrician is putting in. So to me, it doesn’t matter but the electrician wants to know what the NEMA receptacle configuration is that’s stamped on the cord. Seems like overthinking to me.

Link to comment
Share on other sites

8 minutes ago, Old No. 7 said:

Seems like overthinking to me.

I bet he has made a lot of trips back to the supply house cause the male & female weren't compatible. I know I have. I think I remember a 40 amp outlet that was pretty standard for ranges. Code now require 4 wire.

Link to comment
Share on other sites

1 minute ago, jsharrwick said:

I would use a old sollid copper penny and an old screw in fuse and a really heavy extension cord and 3M electrical tape, not the cheap stuff.  SAFETY FIRST!!!

So... that explains a lot.   No wonder the power went off last year in TX.  

  • Haha 3
Link to comment
Share on other sites

35 minutes ago, Bikeguy said:

The way it looks to me...  I'd wire the circuit for 50 amps, but install a 40 amp breaker, and use a 50 amp outlet and cord to the range.   Match the breaker to the what the oven needs. 

https://diy.stackexchange.com/questions/103120/40-amp-range-into-50-amp-plug

From your link...
 

Using a 50A plug and receptacle is allowed on a 40A circuit because of an exception in the Electrical Code. The exception is because 40A receptacles do not exist, (I didn't know this - so the NEMA recept. is really rated for 50A - Huh) or rather, are not part of the NEMA standards. (There are enough varieties of receptacle already!)

The circuit breaker must be no larger than the wiring is fit for  (THIS IS THE IMPORTANT PART)- if the wiring is 8 AWG, the breaker must be 40A (or smaller). If the wire is 6 AWG, the breaker may be 40 or 50 amps (or any value up to 50A). With large circuits like this, there is only one appliance per circuit. I am not sure whether it is legal to plug a 40A rated appliance into a circuit breakered for 50A. I would downgrade the breaker to 40A for an extra bit of safety.  <--- This too

  • Thank You 1
Link to comment
Share on other sites

There's a sticker on the stove that tells you what to do. The service needs to meet the demands of the stove.  The only important information is what is the wiring of the stove capable of. Don't put a 40A stove on a 50A breaker. The plug and service wires can be rated for 50A, though. 

Link to comment
Share on other sites

You guys!  You've given out all the good advice, and there's none left! :angry:  I'm going to show this thread to the owners at my company and see if they want to hire any of you.

;)

My suggestions:

First check the oven installation manual.  Many will allow either a three prong plug or a four prong installation.  However, some only allow a four prong.

It sounds like you're running a new installation for the new stove. I would suggest running a four wire circuit, installing a four prong receptacle (outlet) and wiring the stove with a four prong cord. 

Kzoo is correct; you will have to use a 50 amp plug because there's no standard 40 amp plug.

Unless you're planning to upgrade the stove, I'd suggest using the 40 amp breaker and using 40 amp wire.  If you think you'll upgrade soon, then run the 50 amp wire.  If you decide to run the 50 amp wire anyway, that's allowable by the Code.  Just connect the 50 amp wire to the 40 amp breaker.

So, let's start at the panel.

You've got the 40 amp two pole breaker already, but just to be sure it should look similar to this:

image.png.66c17abfd42da3efc64a9a0347b980df.png

There will be variations in shape and color between manufacturers.  Note the handles are factory-tied together with a bar.  Don't use two single 40 amp breakers with the handles tied together with a bolt or nail. 

 

For the branch circuit wire between the panel and the stove you will need one with a total of four conductors: black, red white, and bare ground.  Typically this is called 8/3 Romex or 8/3 NM (non-metallic)  It should look like this:

image.png.b23cd4b88f3d73109959f9e520294ff6.png

The outer jacket can be any color; doesn't matter.  Don't let the "8/3" description throw you - it's industry terminology for counting the insulated conductors and not counting the ground.  When connecting to the breaker, it doesn't matter how the red and black wires connect to the breaker as long as you have the black on one terminal and the red on the other.

 

The receptacle that goes on the wall should look similar to this:

image.png.ab35cbcbc9d3555922dfceb5fdee2a78.png

The outer body shape doesn't matter, it's the 'hole' arrangement that does.  It should say  "NEMA 14-50R" on the face.  It doesn't matter to the electrons if the receptacle is installed upright as shown, or if you install it on its side.  If you get the receptacle type that mounts in a box, install the ground pin down or to one side or the other.  If you install that type with the ground pin up, you may not be able to plug the cord in because the cord will bind on the floor,

 

You'll need a #8AWG 4 conductor range cord that looks similar to this:

image.png.ddf0febd0b65c1c6cce167f7332d5027.png 

I'd suggest a 6 foot cord, as a 4 foot cord may be too short and you may have trouble getting from out behind the stove after you've plugged it in, not to mention the hassle if you have to unplug it later on.  Note how the pin arrangement on the wall receptacle matches the plug, and there are four wires in the cord.  The plug should say 'NEMA 14-50P'. 

 

To connect the end of the cord to the stove, check the installation manual (if you haven't already thrown it out).   In most cases on a new stove there will be a copper 'strap' between the neutral/white and ground/green (dotted line in picture below).  This should be removed for a 4 wire installation.  You can file it in the circular file with the installation manual.  Then connect the range cord as shown.  Unless otherwise directed in the installation manual, the black and red wires can go as shown in the picture or they can be swapped between themselves - but only those two.  Do not swap the white with green, or any other wires or wire positions.

image.png.f8e78d186d24fdceb9fb8422fe0d66e3.png

 

I started at the panel because that was the easiest way to explain it.  In reality, the panel is where you want to finish up. I'd highly recommend shutting off the main breaker and covering the bare incoming terminals at the top of the main breaker.  You'll also want to wear protective gear.  Connect the white and the ground to the neutral bar inside the panel, with the last step being where you connect the branch circuit wires (black and red) to the breaker. 

 

And happy cooking!  :)

 

 

  • Heart 1
  • Thank You 1
Link to comment
Share on other sites

12 hours ago, Thaddeus Kosciuszko said:

The receptacle that goes on the wall should look similar to this:

image.png.ab35cbcbc9d3555922dfceb5fdee2a78.png

The outer body shape doesn't matter, it's the 'hole' arrangement that does.  It should say  "NEMA 14-50R" on the face.  It doesn't matter to the electrons if the receptacle is installed upright as shown, or if you install it on its side.  If you get the receptacle type that mounts in a box, install the ground pin down or to one side or the other.  If you install that type with the ground pin up, you may not be able to plug the cord in because the cord will bind on the floor,

Me.... I'd go with the outlet that is in a box that is recessed into the wall.   @Thaddeus Kosciuszko  posted a picture of a surface mounted receptacle that is installed ON the wall.   He is correct you need to figure out how the plug is configured (which way the cord leaves the plug) to be sure you won't have issues with the routing of the cord.

Also... one more thing..  You need to find WHERE the stove manufacture recommends to outlet should be installed.    You probably want your stove to slide up to the wall.  Some stoves have specific areas where the stove is recessed in (away from the wall) to allow room for the outlet and power cord.  (In my case the gas line needed to be installed in a specific location too.) Some stoves may even recommend the outlet to be on the floor. (which I've never seen)

The last thing you need is to plug in the stove and slide it back to the wall, and find out the plug (or cord) hits the back of the stove and it won't side back all the way to the wall. 

 

 

 

  • Heart 1
Link to comment
Share on other sites

@Thaddeus Kosciuszko thank you for the detailed and informative response to my question. Having the NEMA 14-50P information was exactly what I needed. Our electrician now knows exactly what is needed for the project and we are scheduling the work date sometime soon. I now have to learn how the propane stove is hooked up and secured to prevent tipping so I can get that ready for removal and disposal. My initial thought is to turn off the propane supply first.

  • Haha 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...