If we are performing the calculations for a residential service, what allowance should we use if the job requires more than two small appliances circuits. In other words for two circuits we allow 1500va for each circuit. Now we have a kitchen that has five small appliances circuits for the kitchen counter top receptacles.
That seems to be the issue here, the homeowner will overload the "two required" circuits due to how he/she uses the kitchen. That being the case, they want additional circuits to prevent nuisance tripping. I've been an inspector for 20 years and deal with mostly high end housing and this is a problem. I agree with your comments per 210.52(3) but I think you can see my issue. My thoughts are, if you are adding circuits to handle the coincidental load, this should and would impact on the Service or feeder. As the attorneys say- "What say you"
Ryan, I have only been able to justify extra load when they install dedicated circuits for appliances such as Micro, coffee brewer, warming drawer or other cord and plug connected appliances. Had a homeowner ask me why I didn't inspect to code when the conuter top micro asked for a separate circuit. So now we have 3000va for counter top receptacles and another circuit for (1100va) for micro plus 1000va for coffee brewer.
Are these appliances fixed in place? I take it not, which I’m sure is the source of the confusion.
I’m a little frustrated too with trying to figure the BEST way to do these calc.’s verses the minimum by code. And yes, the code will dictate what is minimum and you could easily say “It wouldn’t hurt to just bump up to the next” – which I agree with. Or “It’s not worth splitting hairs” – which I also agree with.
But what if another group of people had spent a lot of time looking at data, graphing and wearing out their slide rule and came to the conclusion that the NEC leaned more toward requiring more capacity than they think vs. not requiring enough. (Again, look at POCO) Wouldn’t that have some effect on how we interpret the gray areas. There is a lot of room for interpretation and I would like to know which side I should favor. For liability reasons you could always argue “just sell them more. The owner gets the ego boost and it will never come back to me as a problem in the future.” Which in most cases would be the best way go.
But what if for competitive reasons, or maybe just sensible reasons I want to confidently jam my calcs right up to that line, why not?
Does anyone have a source besides the NEC that could offer some insight into the best way to figure these residential load calcs.? Maybe some sort of engineering approach? Or UL? Or AIC or another code authority?
Not just crunching the numbers (thanks Sparkly for the links in a different post) but how to treat different spaces and different loads. How to define different spaces. Different ways to figure demand?
What about garages? As far as I can tell, if I have a four car garage with (8) fluorescents, (4) door openers, (6) coach lights, and 600 watts worth of flood lighting, I don’t have to figure anything for it according to NEC.
What about detached garages?
Sorry George, not trying to take over your thread here.
As previously stated, if only one Kitchen then the NEC's MINIMUM Volt-Amps for Small Appliance circuits will be 3 KVA.
Nothing says the Service Load Calcs MUST ONLY be figured with 3 KVA for the Small Appliance branch circuits - only that it shall not be <3KVA. If the Designer/EE/EC wishes to add 1500 VA per additional Small Appliance circuit to the Service Load Calc, this is Okee-Dokee.
There are several other circuits which fit the same criteria - such as Laundry room circuits, Lighting circuits; and Dedicated circuits not required for minimum compliance - such as Refrigerator circuits, Microwave Oven circuits, etc.
For the required circuits above, minimum VA load values may be "bumped up" per how many additional circuits are installed. On Lighting, the normal VA/Ft² value for General Lighting and Recepts could be beefed up by including the value of each additional circuit.
The clincher: How much is too much? Where does one draw the line, when including more circuit load values to a Service Load Calculation.
I see many Houses with 400 Amp services, and these Houses are <3,500 Ft².They use gas appliances, water heaters and FAUs. Swimming Pool water heaters also gas powered.
Having this large of a Service is not a bad idea - it's just kind of a strange consept. (could anyone possibly draw that much power in a House!)
If I was "Let Loose" to perform EE and installations, then I could easily list and compile enough load values for those Houses, and make a Service Load Calculation appear almost as if the resultant demand load comes within 70% of the 320 LCL Amp rating for those 400 Amp 1Ø Panels.
Nevertheless, PoCo is going to feed the service with conductors that meet the Calculated Load. These Service Feeders will not be sized per NEC Article 310-16 or 310-17, but will follow the NESC guidelines. So if the Load Calcs show 250 Amp demand load, PoCo will not install 350 Kcmil (MCM) aluminum feeders - but more likely to install two 3/0 al + one #1 al feeders to the service.
The PoCo's Transformer, which is also feeding six other Houses - several of which have 400 Amp services too, is a mere 25 to 37.5 KVA rating.
In these common cases, the Service Equipment has ample capacity for future growth, but nothing on the Service Entrance side does. The PoCo's stuff still is limited to 25-37.5 KVA.
Once again, I am not saying anything is bad with additional values + circuits and service capacity - only that when it comes to load calcs, and especially load calcs for 1 family dwellings, there is a point at which including too many load values will be of no benefit.
Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!
Thanks guys, I have read your post and last week had E-mail communication with NFPA personnel who agrees with the concept of adding circuits @ 1500va per if the load is justified and while his was not a formal interpertation, I think this is the way to go or at least recommend to the homeowner/contractor to prevent an inefficient system. As to enforcing the added circuits I guess I can't do it. There's usually no way of knowing what "portable" appliances will be used concurrently and unless it's called out on the print I can only recommend- if asked
George is the problem that if they add the extra circuits they will change the required service and thus be in violation.If so then they must have went to the absolute minimum.I mean around here there`s not that much difference in 150a and 200 amp equipment for a regular residence.I`m not the expert but I`ve wired my share of houses and I can`t think of one that if I added extra circuits it throw my service feeder out line.But seems as if its a catch 22 for electrical contractor.He puts in the nessesary additional circuits and knowing this won`t have a great impact on the service you now fail job.based on cal. but would it actually.I guess we`d have to have a example of a house to actually know the loads.And effect extra circuits would have.
What got me going on this was I made the statment that we should count each Small Kitchen Appliance circuits @ 1500va. I made this statment from the podium in front of about 125 Inspectors and they almost tared and featherred me on the spot. Any of us who do public speaking should expect controversy and most of the time you'll get it. I would only say that if I could afford a house that would need more than two small appliance circuits, I would certianly build my service to handle my kitchen circuits. :-)