ESolar
Senior Member
- Location
- Eureka, CA Humboldt County
- Occupation
- Electrician/Contractor
In 220.55 I can combine loads of a cooktop and oven if they are connected to a single branch circuit:
"The branch-circuit load for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same room, shall be calculated by adding the nameplate rating of the individual appliances and treating this total as equivalent to one range".
Assume one 30A and one 20A appliance. This allows one to use the one appliance row and column C to reduce the computed demand from near 45A to 33A. Further assume that I only have 44A to work with on a 50A panel.
To meet the requirement for one appliance, however, I have to run one 40A minimum circuit from the panel and tap it using 210.19(A)(3). But now the taps by definition are rated for less than 40A (obviously not optimal, but to code).
Now I ask: Would it not be better to run separate, properly sized circuits off of that subpanel to each appliance? Of course it would. But as I read the code it does not allow for that, and at the same time to use the reduced demand of one combined appliance in column C of 220.55. As a result, the available ampacity of the panel feeder would be surpassed, despite have the exact same equipment, and in the same room.
A modification of the code would allow for the combined demand calculation in col C if the appliances are serving the same room, regardless of the circuits supplying them. And that makes sense to me. And it would allow for safer installs, No?
Or I am reading it wrong? For example, the 50A feeder is one circuit (although branched), and it is serving both appliances, so maybe that is an subtle exception for use in 220.55?
Another way to put this is that the requirement of a single circuit to reduce demand appears to make no sense, and reduces safety.
"The branch-circuit load for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same room, shall be calculated by adding the nameplate rating of the individual appliances and treating this total as equivalent to one range".
Assume one 30A and one 20A appliance. This allows one to use the one appliance row and column C to reduce the computed demand from near 45A to 33A. Further assume that I only have 44A to work with on a 50A panel.
To meet the requirement for one appliance, however, I have to run one 40A minimum circuit from the panel and tap it using 210.19(A)(3). But now the taps by definition are rated for less than 40A (obviously not optimal, but to code).
Now I ask: Would it not be better to run separate, properly sized circuits off of that subpanel to each appliance? Of course it would. But as I read the code it does not allow for that, and at the same time to use the reduced demand of one combined appliance in column C of 220.55. As a result, the available ampacity of the panel feeder would be surpassed, despite have the exact same equipment, and in the same room.
A modification of the code would allow for the combined demand calculation in col C if the appliances are serving the same room, regardless of the circuits supplying them. And that makes sense to me. And it would allow for safer installs, No?
Or I am reading it wrong? For example, the 50A feeder is one circuit (although branched), and it is serving both appliances, so maybe that is an subtle exception for use in 220.55?
Another way to put this is that the requirement of a single circuit to reduce demand appears to make no sense, and reduces safety.
Last edited: