Testing Residential Electrical Load Calculator - Need Help Testing

[jar546]

This is a work in progress. Can someone run a load or two and check for accuracy? I'm burned out right now and can't be looking at the same thing again.

Residential Load Calculation

 

[wwhitney]

From a quick once-over, a few comments:

- The title says standard load calc (Article 220 Part II), but the part about HVAC references 220.83, which is the optional load calc (Article 220 Part III)
- No Table 220.45 demand factor for the lighting/general receptacles load is implemented.
- Missing option for 75% factor for appliances if 4 or more (220.53)
- The calculation for the cooking appliances does not follow 220.55. If I enter a single cooking appliance, the output should be 80% of the rating if 1.75 kW to 8.75 kW; a flat 8 kW if between 8.75 kW and 12 kW; and 8 kW * (1 + ceiling(kW - 12)*.05) for 12 kW to 27 kW.
- No extra 25% for the largest motor
- 2023 NEC 220.57 specifies a minimum 7200 VA for any EVSE.
- For the HVAC, maybe have spots for both heating and cooling loads, and a check box to specify they are non-coincident, in which case you can use the larger. Although properly implementing 220.60 is a little tricky (the code language there has been a bit garbled the last few cycles).
- And the optional load calc is probably more useful, as it is generally lower, and I think also simpler to implement.

Cheers, Wayne

 

[jar546]

From a quick once-over, a few comments:

- The title says standard load calc (Article 220 Part II), but the part about HVAC references 220.83, which is the optional load calc (Article 220 Part III)
- No Table 220.45 demand factor for the lighting/general receptacles load is implemented.
- Missing option for 75% factor for appliances if 4 or more (220.53)
- The calculation for the cooking appliances does not follow 220.55. If I enter a single cooking appliance, the output should be 80% of the rating if 1.75 kW to 8.75 kW; a flat 8 kW if between 8.75 kW and 12 kW; and 8 kW * (1 + ceiling(kW - 12)*.05) for 12 kW to 27 kW.
- No extra 25% for the largest motor
- 2023 NEC 220.57 specifies a minimum 7200 VA for any EVSE.
- For the HVAC, maybe have spots for both heating and cooling loads, and a check box to specify they are non-coincident, in which case you can use the larger. Although properly implementing 220.60 is a little tricky (the code language there has been a bit garbled the last few cycles).
- And the optional load calc is probably more useful, as it is generally lower, and I think also simpler to implement.

Working on it. Thank you!!!

 

[jar546]

OK, a bunch of changes made. I am now more interested in checking the math right now and cleaning up the verbiage later. Folks, try it out again, please.

 

[wwhitney]

OK, a bunch of changes made. I am now more interested in checking the math right now and cleaning up the verbiage later. Folks, try it out again, please.

At the moment, the web page does not respond to pressing Calculate, nothing happens.

Cheers, Wayne

 

[jar546]

At the moment, the web page does not respond to pressing Calculate, nothing happens.

Cheers, Wayne

OK, let's give that another try. Works for me now offline and online. Sorry about that.

 

[wwhitney]

OK, let's give that another try. Works for me now offline and online. Sorry about that.

You've left the 1500 VA SABCs and laundry circuits out of the 220.42 demand calculation, but 220.52(A) and (B) specify that the 220.42 demand factors apply to them.

While unlikely, it's possible that of the Microwave, Dishwasher, Disposal and Water Heater, there are only 2, and that there are 2 appliances combined under "Other Appliances". So perhaps it would be better to label these as "Appliance 1 (e.g. Microwave), "Appliance 2 (e.g. Dishwasher)", etc, still leaving the fifth field for all other appliances combined. Along with checking that none of the first four entries are zero if the fifth entry is non-zero.

On the cooking equipment, it's not actually possible to do the 220.55 calculation without knowing the number of appliances. If I have an 8 kW cooktop and a 4 kW oven, that's 12 kW * 65% = 7.8 kW (column B row 2), while a single 12 kW range is 8 kW (column C row 1).

Possibly more later, have to go now.

Cheers, Wayne

 

[jar546]

You've left the 1500 VA SABCs and laundry circuits out of the 220.42 demand calculation, but 220.52(A) and (B) specify that the 220.42 demand factors apply to them.

While unlikely, it's possible that of the Microwave, Dishwasher, Disposal and Water Heater, there are only 2, and that there are 2 appliances combined under "Other Appliances". So perhaps it would be better to label these as "Appliance 1 (e.g. Microwave), "Appliance 2 (e.g. Dishwasher)", etc, still leaving the fifth field for all other appliances combined. Along with checking that none of the first four entries are zero if the fifth entry is non-zero.

On the cooking equipment, it's not actually possible to do the 220.55 calculation without knowing the number of appliances. If I have an 8 kW cooktop and a 4 kW oven, that's 12 kW * 65% = 7.8 kW (column B row 2), while a single 12 kW range is 8 kW (column C row 1).

Possibly more later, have to go now.

Cheers, Wayne

Thanks for the feedback. I’ve been struggling with this and spent a few hours on it. If I don’t get this straightened out within a reasonable amount of time spent on it, I’m going to probably abandon it. I even looked at some Excel spreadsheets, but I’ve noticed that some of those are actually incorrect also. Honestly, most of the time what we get are the panel schedules with the wattages and then it gets calculated per panel and then we add up all the panels, especially for commercial. It’s not often that we’re seeing the actual calculation sheet like I’m trying to provide anymore.