Go Back  DoItYourself.com Community Forums > Electrical, AC & DC. Electronic Equipment and Computers > Electrical - AC & DC
Reload this Page >

Is a 60A circuit sufficient for a cooktop and double oven?

Is a 60A circuit sufficient for a cooktop and double oven?

Reply

  #1  
Old 03-11-12, 09:01 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
Is a 60A circuit sufficient for a cooktop and double oven?

Hello all,

I bought a house that has a 4 smooth element cooktop and a Kenmore double oven. Both are connected to the same 60 AMP circuit. The wire that comes from the service panel goes behind the double oven in a junction box where it is split to go to the double oven and then cooktop. I do not see any writing on the wire that says what gauge it is but it looks slightly thicker than the 10/3 wire that goes to the cooktop from the junction box. The wiring has two hot, 1 neutral and 1 ground.

My first question is, is 60 AMPs sufficient for both appliances? The labels on the appliances say:

Cooktop - 240V 7.0KW 208V 5.3KW
Double oven - 240V 6.80 KW 208V 5.10 KW

By my calculations 60A can do 7.2KW so it seems like there should be two separate 60A wires going from the service panel, one to each device?

What do you guys think? It will not be an issue for me to have another line installed, I just need to know if it is best. Thanks in advance.
 
Sponsored Links
  #2  
Old 03-11-12, 09:47 PM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
So each oven is 3.4Kw? Seems to be fine, accept to say the breaker is oversized. The cooking appliance calculation is determined by NEC T.220.55—where the demand load is treated as one range. The tap is acceptable if installed per NEC 210.19 (A)3. What size and type [copper or Alum] cable they use from the panel to the junction.
 
  #3  
Old 03-11-12, 10:05 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
I would assume each oven is 3.4KW, they appear to be equally sized. All of the wiring is copper. The junction is behind the oven, there is a couple of feet of wire from the double oven to the junction box to allow the double oven to be removed. The cooktop is next to the double oven and the 10-3 wire from the junction box to the cooktop is probably 3-4 feet long. Does this all sound acceptable?


So are you suggesting that I should change the 60A breaker with a 50A breaker? Is it oversized because the wires aren't of sufficient gauge or because 60A is overkill for the application? If both ovens are turned on and all 4 cooktop burners, would the breaker trip with a 60A? How about a 50A? Thank you.
 
  #4  
Old 03-11-12, 10:46 PM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
The junction is behind the oven, there is a couple of feet of wire from the double oven to the junction box to allow the double oven to be removed. The cooktop is next to the double oven and the 10-3 wire from the junction box to the cooktop is probably 3-4 feet long. Does this all sound acceptable?
Sounds good, as it relates to the tap rule.

So are you suggesting that I should change the 60A breaker with a 50A breaker? Is it oversized because the wires aren't of sufficient gauge or because 60A is overkill for the application?
I’m saying, based on code you are allowed to calculate the cooking appliances as one load. This calculation per code gives us 8.8Kva. If we covert the calculated load to amps, we get 36.7 amps, or 40 amps required to serve the cooking appliances.. But, to apply the tap rule you should heed NEC 210.19(A) where it “ says: tap conductors from a 50A branch circuit". This section seems somewhat unclear. But it would seem to say the tap needs to be from a 50A branch circuit. So, in your case, you would need to install a 50A breaker. Note: My question needs to be answered: I need to know the size of the branch circuit conductors from the source to the cooking appliances junction box. It seems your conductors from the junction to the appliances are code compliant.
 
  #5  
Old 03-11-12, 11:08 PM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
If both ovens are turned on and all 4 cooktop burners, would the breaker trip with a 60A? How about a 50A? Thank you.
Please note that the NEC calculation has figured-in the demand for the loads being calculated. In fact, for your situation (Cooking Appliance Branch circuit), we are permitted to compute the branch circuit load for one range in accordance to NEC Table 220.55. Normally, this is permitted for feeder, and service load calculations. So, in a nut shell, your breaker should not trip--unless the conductors are undersized. In your case, you should have at least a #6 copper per NEC T310.16.
 
  #6  
Old 03-11-12, 11:14 PM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
By my calculations 60A can do 7.2KW so it seems like there should be two separate 60A wires going from the service panel, one to each device?
60 amps can supply up to 14.4Kva<<<In some situations
In your case, we aren’t talking a high number—as we are allowed a lower demand.
Example:
1. Oven 3.4kva
2. Oven 3.4kva
3. Cooktop 7.0kva
-Total nameplate= 13.8kv (For simplicity lets round this up to 14Kva)
-Per NEC T220.55 note 4. we can determine the Kva by treating the combined cooking units as one range. One range under column C=8Kva. So, the total nameplate of 14kva will be: 14-12=2(5%)=10%. Then 10%(8kva)=800va. Then: 800va+8kva=8.8kva/240v=36.7A
The above is how we get our number. Note: I didn’t go into detail on the reason for the percentages. Sorry, maybe someone else will.
 
  #7  
Old 03-12-12, 05:00 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
There was writing on the wiring that comes from the service panel to the junction box but it did not mention the gauge of the wiring. Is there some other way for me to identify the size of the conductor?
 
  #8  
Old 03-12-12, 08:30 PM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
Sometimes the lettering is hard to see. I think you should try looking again. How old is the install?
 
  #9  
Old 03-12-12, 09:41 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
The house is 40 years old so probably 40 years old. I read online that you can use the holes/labels on a wire cutter to see what gauge the wire is. I will try that.
 
  #10  
Old 03-13-12, 07:18 AM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
That want work for your gauge. Yet, I guess it will tell you if it’s undersized. The largest you will get on a typical wire stripper is 10AWG. A caliber with a couple calculations is an option. If you have access to at least 4 feet of the cable, in most cases—even a 40 year old cable—you will see the writing.
 
  #11  
Old 03-13-12, 11:18 AM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,053
My usual suggestion is to go to a hardware store and buy a foot of #8, and #6 THWN. Take it home strip off a couple of inches of insulation and compare to a stripped potion of the cable you have. I say hardware store, because they may have a couple of scraps they will just give you. Or just buy a wire gauge but that could cost $20+.
 
  #12  
Old 03-13-12, 04:43 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
I took another look at it and finally figured out that its 6-3 wire. It says 6 AL-3 on it, which confused me because I never saw letters in the gauge. It turns out the wire is aluminum, I was wrong before. The wires are much thicker than the 10-3 copper.

This is what it said:
KAISER ALUMINUM-B TYPE XHHW CDRS 6 AL-3 300 VOLTS TO GROUND (UL)

All the other wiring I've seen in the house is copper. Is this wire sufficient?
 
  #13  
Old 03-13-12, 04:54 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,053
#6Al is equivalent to #8Cu so it is only good for 40 amps if you use the 60° column so no.
 
  #14  
Old 03-13-12, 05:01 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
Should I replace with 6-3 Copper? Should I also change the breaker from 60A to 50A?
 
  #15  
Old 03-13-12, 05:13 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,053
Yes. #6 copper should be fine and a 50a breaker.
 
  #16  
Old 03-13-12, 05:27 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
I need roughly 45 feet of cable. Does this look acceptable?

50 ft. 6/3 NM-B Wire-147-4203B at The Home Depot

I cannot believe how expensive it is. Only two or three years ago I bought 6-3 wire for my mom's stove and it was much cheaper. Thanks!
 
  #17  
Old 03-13-12, 07:46 PM
Justin Smith's Avatar
Member
Join Date: Dec 2010
Location: Cressona, Pa, USA
Posts: 2,546
That's about what I pay at the supply house for 50'.
 
  #18  
Old 03-13-12, 08:33 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
One additional question. When my double oven dies I may replace it with an oven/microwave combo. Would my 50A 6-3 wire setup be sufficient for a cooktop and oven/microwave combo or do I need to beef it up? I would rather not have to redo the wiring twice. Thank you.
 
  #19  
Old 03-13-12, 09:58 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
Also, since I have to run a wire anyway now and replace a breaker... would it be better to run an 8-3 wire and 40A circuit for the cooktop and a 10-3 wire and 30A circuit for the double oven? I looked through a lot of cooktop/double oven specs and they are all rated for 40A/30A respectively.
 
  #20  
Old 03-13-12, 11:41 PM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
This is what it said:
KAISER ALUMINUM-B TYPE XHHW CDRS 6 AL-3 300 VOLTS TO GROUND (UL)
I knew it was on there some where

It would be best to buy a full roll (125 feet) of #8-3NM-B and use it to run two circuits. The price should be cheaper over buying a 50ft roll of 10-3 with a roll of 8-3. Plus you get extra—just in case you need more. I’m not a fan of alum for appliances, and never will be!!! So, the above option is best in my opinion.
 
  #21  
Old 03-14-12, 05:51 AM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
Thanks for the advise! Should I use a 40A and 30A breaker or two 40A?
 
  #22  
Old 03-14-12, 09:21 AM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
it seems you need two 30A circuits, but send your appliance Manufacture names and model numbers so we can be sure.
 
  #23  
Old 03-14-12, 09:41 AM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
One additional question. When my double oven dies I may replace it with an oven/microwave combo. Would my 50A 6-3 wire setup be sufficient for a cooktop and oven/microwave combo or do I need to beef it up? I would rather not have to redo the wiring twice. Thank you.
I believe most appliances have become complicated. I’ve seen single cooktops requiring 50 amps. It depends. But, I believe you should be covered, as most micro-oven combinations may require up to 40 amps. Just think about your future needs, and adjust now.
 
  #24  
Old 03-14-12, 03:44 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
Magic Chef 8670R Cooktop (White) - http://www.youserguide.com/wiki/Magic_Chef_8670R
Kenmore Double Oven (White) 790.47732404

All of the electric cooktops I looked up in 30" (my size) and even 36" (larger size) call for 40AMPs in their manuals

All of the double ovens and oven/microwaves calls for 30AMPs in their manuals

As long as 40A and 30A is sufficient for my appliances (listed at top of post) I think it would be a good idea to get 40A and 30A breakers for my new 8-3 circuits. Do you agree, or is there reason to get two 40A breakers?
 
  #25  
Old 03-14-12, 05:36 PM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
Base it on the manufacture specifications.Based on your numbers 3.4kva (x2) and 7kva, The 8-3 will cover you either way.

Side note: Cooktops come in 20/30/40/and 50A
 
  #26  
Old 03-14-12, 09:03 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
Sorry but I'm still not sure about the breakers. Do I use 40A each, 30A each or 40A/30A? Will it hurt anything if I get two 40A and the appliances only need 30A?
 
  #27  
Old 03-14-12, 10:16 PM
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,399
If the instruction manuals for your new equipment have requirements listing the maximum circuit breaker or fuse (may state maximum OCPD) then that is what size circuit breaker you should use. If no maximum is listed for the appliance then you may use 40 ampere circuit breakers in each circuit as long as you use #8 copper wire or larger.
 
  #28  
Old 03-15-12, 04:30 PM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
Consult your manufacture specs. I tried to see them, but wasn’t able to (No comment on Sears). So, if you have the manual, then you will need to get your electrical requirements from them. Note my last post as well.
 
  #29  
Old 03-15-12, 06:51 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
I ended up getting 6-3 wire, it was $44 more for 125 feet than 8-3 wire so I figured I would future proof it now in case I get a 50A product in the future. I got two 40A breakers as well. I looked at the 30A breakers but it did not look like the 6-3 wire would fit inside of them. I just got the house and the appliances came with them so unfortunately I do not have the original paperwork.
 
  #30  
Old 03-15-12, 07:47 PM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
I ended up getting 6-3 wire, it was $44 more for 125 feet than 8-3 wire so I figured I would future proof it now in case I get a 50A product in the future. I got two 40A breakers as well. I looked at the 30A breakers but it did not look like the 6-3 wire would fit inside of them. I just got the house and the appliances came with them so unfortunately I do not have the original paperwork.
:NO NO NO:
Seeing that you do not have the Manufacture specs, You will be violating code if you install any breaker over the calculated load. Name Plate—as specified by you=single unit-7kva and Double unit-6.8Kva.
SO:
-Double oven will need a 30A breaker using a #10AWG or larger
-Single cooktop will need a 30A breaker using a #10AWG or larger.
Do not oversize the breaker. The conductors can be pigtailed down, to work with the 30A breakers.
Per my post #22
 
  #31  
Old 03-15-12, 08:09 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
Got it. I will get 2 30A breakers and use the 6-3 wire. Thanks.
 
  #32  
Old 03-16-12, 03:34 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
I noticed something else today. I have a 10-2 aluminum core wire with copper on the outside of the wire. The circuit is 20A and the outlet it is connected to is 20A. This circuit is used by the dishwasher. Is there any issue with this? Thank you.
 
  #33  
Old 03-16-12, 06:38 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 9,391
I noticed something else today. I have a 10-2 aluminum core wire with copper on the outside of the wire. The circuit is 20A and the outlet it is connected to is 20A. This circuit is used by the dishwasher. Is there any issue with this? Thank you.
In my opinion, yes, it should be replaced if possible. What you have is copper clad aluminum wire which is just slightly better than aluminum wire. Neither are allowed under today's code for good reasons.
 
  #34  
Old 03-17-12, 08:02 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
Ok I will replace it and check all the other wiring for aluminum wiring but so for I've only seen it in the 10 gauge or lower wiring which is great because most of the other wiring in the house is hopefully 12/14 gauge copper.

Is it ok to reuse the nuts that were attached to the aluminum wiring? I just want to make sure they didn't use any special kind of nuts back when they installed it that could cause me an issue if I reuse with copper wiring. The reason I can't just chuck them is because they got mixed up with my other stuff. Thanks!
 
  #35  
Old 03-19-12, 10:41 PM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
I would install new wire-nuts per manufacture specs.
 
  #36  
Old 03-20-12, 05:01 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 9,391
Is it ok to reuse the nuts that were attached to the aluminum wiring? I just want to make sure they didn't use any special kind of nuts back when they installed it that could cause me an issue if I reuse with copper wiring.
Wire nuts that were used back then for aluminum to aluminum or aluminum to copper wiring may have been approved for that application back then, but those approvals have long since been removed. Be sure that what ever connector you use is new and is listed for the application, that cuts your wire nut choice down to one. Personally, I'd try to substitute the AlumiConn connectors for wire nuts where ever possible.
 
  #37  
Old 03-23-12, 09:58 AM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
Thanks I will toss all of the old wire nuts and only use new ones.
 
  #38  
Old 03-23-12, 06:04 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
Ok I took off the service panel cover and checked every single wire. There were 4 aluminum circuits. Luckily most of the house is copper. I am in the process of replacing the cooktop/oven and dishwasher circuits already. The other two circuits go to wall mounted air conditioners. Those two wires are going to be a pain to replace because I'll need to demo some drywall to get the wires through. One air conditioner is on the second floor and one is on the first floor. I am planning to replace all of the outlets so I will double check those ends to ensure its all copper. Thanks everyone for your help.
 
  #39  
Old 03-23-12, 07:04 PM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 351
Sounds good!
 
  #40  
Old 03-25-12, 04:45 PM
Member
Thread Starter
Join Date: Mar 2012
Location: USA
Posts: 305
Surgery went well, all aluminum disconnected from main panel and capped off on both ends. I placed a label on the wires in the air conditioner outlet boxes which say something like: DO NOT USE, ALUMINUM WIRE. I will put blank covers on those outlet boxes. I was able to rip out the dishwasher and range/oven aluminum wires. I installed the 6 gauge wires for the oven and range and two 30A circuit breakers. I also installed a 12 gauge copper wire for the 20A dishwasher circuit breaker.

Two circuit breakers are now not in use. I set them to the off position and labeled them as NOT IN USE at the breaker, but I'm not sure if I am supposed to pull the breakers out and somehow cap those two empty spaces. What is the recommended method for dealing with disconnected breakers?

Thanks for all of your help.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes