I have a customer who is having their kitchen remodeled. They will be using a wall mounted oven, and a counter top range - two seperate appliances.
I'm not sure exactly which range the customer is buying, but I do know that four out of ten they are more than likely considering are above 8.75kW (9.6kW, 8.8kW, 9.6kW, 9.6kW).
The oven the customer is buying is a GE Profile JT955 - 7.2kW
The house is not currently wired for electrical cooking appliances in the kitchen. The panel only has room for one 2-pole breaker, however, I may be able to put in a quad. I'll have to look and check. If not, I want to use Table 220.19 and only use one circuit for both appliances. Actually, even if I could use a quad, I think 220.19 would be best for the customer (cheaper).
I'll do two calculations utilizing Table 220.19, one with an 8.75kW range, and one with a 9.6kW range.
I think you could get away with putting both on a single 50 but I would put in 2 circuits, just so I don't get a call on Thanksgiving wanting to know why the breaker tripped. Just about the time I really start believing nobody would be using all the burners and the oven at the same time, I walk in the kitchen and see my mother in law doing it. I believe the installation instructions limit you to 50a. That is dictated by the internal wiring.
Re: Table 220.19#89132 09/04/0403:02 AM09/04/0403:02 AM
Calculation looks ok, but yeah, expect a call on turkey day and X-mas!
Also, why not do them a favor by up-grading the service. Two spots left you're going to fill.... They're gonna have to do it sooner than later. Don't know the service size, but X-mas could be a main trip. Both units and every light, plus some, on in the house. Who knows what else... Not to mention they may whan to add a 120v 15A, "Well sorry, you need a new panel for that..." Do the new panel now, and save the hassle of pulling out your own work for this stuff, to do it later.
Or, if the service is beefy enough, do it on a sub.....
Mark Heller "Well - I oughta....." -Jackie Gleason
Re: Table 220.19#89133 09/04/0409:38 AM09/04/0409:38 AM
Correct calculation is as follows: 9.6kW + 7.2kW = 16.8kW 16.8kW - 12kW = 4.8kW = 5kW (Note 1 says to round up, right?) 5% X 5kW = 25% .25 X 8kW (from Row 1, Column C) = 2kW 8kW + 2kW = 10kW 10kW / 240V = 41.7kW
What's happening, is that I'm getting confused by the example on p.109 of the '02 NEC Handbook. It lists the three appliances' kW ratings: 8kW, 7kW, and 6kW. Because the equation uses 8kW and the highest individual appliance is also rated at 8kW, I incorrectly used the highest rated appliance (9.6kW) for my math. The Handbook example would make more sense if the highest rated appliance was 10kW.
Re: Table 220.19#89134 09/04/0411:38 AM09/04/0411:38 AM
These 220 calcs are good for computing the average load on the service since we assume diversity but when these all end up on a single branch you are looking at the instant load at any particular time. What you *can* do may not translate to what you *should* do.