Appendix D - Example D2(b)

Status
Not open for further replies.
Hopefully I am not asking a question already posted. I have seen some questions related to residential service sizes, but nothing to answer my questions. We are involved in a project that is installing 1 hp, 240v, 1ph sewer grinder pumps in residential neighbor hood. Each home owner is getting one. We instructed the electrician to provide a service calculation for each resident to determine if a service upgrade is needed. The calculation was based on Example D2(b) of the 2005 NEC. First question - if the calculation totals 85 amps (including new load) will the existing 100 amp service be adaquate per code? Where would an upgrade be required, over 100 amps? I would contend the countertop mounted microwave is not a fixed appliance and would be included in the small appliance load - yes/no? I have seen from some other posts that it is possible to have more than 2 small appliance circuits. Has anyone seen 4, 5 or 6 small aplliance circuits? Some of the residental calculations have that many. If a circuit is dedicated to the countertop is that what will label it as a SAC? Any insight would be appreciated.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
First question - if the calculation totals 85 amps (including new load) will the existing 100 amp service be adaquate per code?
Yes


Where would an upgrade be required, over 100 amps?
When the calculated load is over 100 amps


I would contend the countertop mounted microwave is not a fixed appliance and would be included in the small appliance load - yes/no?
I agree it is in the small appliance branch circuit allowance of 1500 watts.


I have seen from some other posts that it is possible to have more than 2 small appliance circuits. Has anyone seen 4, 5 or 6 small aplliance circuits? Some of the residental calculations have that many. If a circuit is dedicated to the countertop is that what will label it as a SAC? Any insight would be appreciated.
You can have as many small appliance branch circuit's as you wish however the load calculation is still 3000 watts (2 *1500) per dwelling
 
Dennis,

Thanks for the info. Mosly what I thought.

My last concern is the small appliance circuit. 210.11(C)(1) states the two or more are required. 220.52(A) states that 1500 watts per SAC required by 210.11 shall be used. In our case the electrician has up to 6 SAC's in the calculations. I see the code stating 2 or more also in 210.52(A).
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Dennis,

Thanks for the info. Mosly what I thought.

My last concern is the small appliance circuit. 210.11(C)(1) states the two or more are required. 220.52(A) states that 1500 watts per SAC required by 210.11 shall be used. In our case the electrician has up to 6 SAC's in the calculations. I see the code stating 2 or more also in 210.52(A).
The code states 2 or more minimum for install but we still only calculate for 2 small appliance branch circuit.

I agree the wording does not seem to support what you're saying but every calculation I have seen only uses 3000 watts. What does the number of circuits have to do with the load in a kitchen. I can have 2 circuits with 8 receptacles or I can have 8 circuits for each receptacle. The load is the same.
 
Last edited:
Because the electrician is including in excess of two SAC's in the service calculation (claiming that is what is installed) and using 1500 watts per each the load for the service comes close to or exceeds the service size. I don't see anything in the code limiting the calculation to two SAC's. I have also used two in my calculations for new design, however we are evaluting the existing service size in the context of adding another load (grinder pump). So if there are two or more circuits dedicated to the kitchen counter receptacles each would be 1500 watts or 6.25 amps each. If the calculation is 102 amps (or 98 amps) and there are four SAC's shown in the calculation, in my opinion there is 12.5 amps more than should be accounted for and a service upgrade is not warrented. The code does not clearly state two for calculations though.
 

Smart $

Esteemed Member
Location
Ohio
Because the electrician is including in excess of two SAC's in the service calculation (claiming that is what is installed) and using 1500 watts per each the load for the service comes close to or exceeds the service size. I don't see anything in the code limiting the calculation to two SAC's. I have also used two in my calculations for new design, however we are evaluting the existing service size in the context of adding another load (grinder pump). So if there are two or more circuits dedicated to the kitchen counter receptacles each would be 1500 watts or 6.25 amps each. If the calculation is 102 amps (or 98 amps) and there are four SAC's shown in the calculation, in my opinion there is 12.5 amps more than should be accounted for and a service upgrade is not warrented. The code does not clearly state two for calculations though.
I disagree with Dennis as to how to calculate more than two SABC's. 200.52(A) clearly states 1500W per 2-wire circuit... and SABC's have to cover more than just the kitchen countertop(s).

As to whether anyone includes more than two SABC's on their load calculations??? His experience in that department easily shadows mine... :happyyes:
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I disagree with Dennis as to how to calculate more than two SABC's. 200.52(A) clearly states 1500W per 2-wire circuit... and SABC's have to cover more than just the kitchen countertop(s).

As to whether anyone includes more than two SABC's on their load calculations??? His experience in that department easily shadows mine... :happyyes:

I read your post and I said that you were agreeing with me but I reread my post and realized I didn't type what I wanted to say. I wanted to say that the words do seem to state what "you're" saying, I wrote what "I am" saying. I will fix the typo. We actually agree
 

JoeStillman

Senior Member
Location
West Chester, PA
Bear in mind that the NEC calculated load for a residence is NOT continuous and doesn't have to be multiplied by 125%. I confirmed this with the NFPA.

I often put more than two SABC's in residential kitchens, but I never count the load as more than 3,000 VA, and I never use 20A circuits for more than two of them. I like to count a dishwasher as a fixed appliance in the calcs, but that's it, no microwaves or refrigerators.

3VA/ft2 is actually a lot of juice for a house.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Bear in mind that the NEC calculated load for a residence is NOT continuous and doesn't have to be multiplied by 125%. I confirmed this with the NFPA.

I often put more than two SABC's in residential kitchens, but I never count the load as more than 3,000 VA, and I never use 20A circuits for more than two of them. I like to count a dishwasher as a fixed appliance in the calcs, but that's it, no microwaves or refrigerators.

3VA/ft2 is actually a lot of juice for a house.

Correct a house is not considered to have continuous loads in the calc.

Interesting point is that most electric water heaters are considered continuous load however I have never seen it used for calculation purposes only for branch circuit.
 
Status
Not open for further replies.
Top