Residential duplex calculation

[JustWork]

Hello all I am in need of some assistance. We just took over in the middle of an existing project which is an existing two story residential duplex the size of the building is 25' x 30' = 750 sq ft per floor. This dwelling currently has a 200A OH service (seu) to a wp wireway from there it is split to two 100A Pans then to the main panels one in lower apartment (no renovations and all gas appliances) and the other to upper apartment (renovations in progress all electric appliances). The upper dwelling has been wired by another contractor with the exception of heat pump, electric dryer, and water heater. According to the permit information which was originally submitted by others which I didn't pick up on :slaphead: they had put down retaining existing 100A panel in lower apartment and installing new 200A panel in upper apartment. My issue is that I retained both existing 100A panels in the upper and lower apartments and was told I have to upgrade the upper apartment to a 150 or 200A because the 100A is undersized. I figured it as follows 750sq ft @ 3va =2250 two appliance @ 3000 laundry @ 1500 range @ 12K Water heater @ 4500 Dryer @ 5000 Dish washer @ 1200 Heat pump @ 6000 Airconditioning @ 5000 for a total of 40,450 the first 10k @100% = remainder of 30,450 @ 40% = 12,180 divided that by 240= 50.75A did I not figure this out properly?:ashamed1: We are maxed out in breaker space requirements within the panel.

 

[normbac]

Try mike holt free stuff resi load calc

 

[curt swartz]

There are a number of things you are doing wrong. You didn't add the first 10KVA back into your calculation. Its 12,180 + 10,000 = 22,180.

You can't apply the 40% demand to the heating and cooling equipment. A heat pump and A/C unit is generally the same piece of equipment. What are the 6KVA and 5KVA loads for? Are the loads of the fans included these figures? Would all of this equipment run at the same time? You normally only use the largest load of either the heating or A/C equipment since they will not run at the same time.

 

[Buck Parrish]

A correct calculation may come in around a 100 amps. Did you add the heat strips ? Physically most electricians would definetly use more then a 100 amp service.
For example as per code if a correct calculation it came in at 90 amps. Although code compliant. It's pushing a 100 amp breaker to it's limit and will likely overheat in a year or 8 years. ( speaking from expierience)


That said many electrical companies would do it any way. As long as it is code compliant it's allowed.

 

[infinity]

I figured it as follows 750sq ft @ 3va =2250 two appliance @ 3000 laundry @ 1500 range @ 12K Water heater @ 4500 Dryer @ 5000 Dish washer @ 1200 Heat pump @ 6000 Airconditioning @ 5000 for a total of 40,450 the first 10k @100% = remainder of 30,450 @ 40% = 12,180 divided that by 240= 50.75A did I not figure this out properly?:ashamed1: We are maxed out in breaker space requirements within the panel.

For the non-coincidental loads (heat and A/C) you would only use the larger of the two. {220.60} The 12KW range would use the demand factor in T220.55 which for a single range would be 8KW. The clothes dryer would use the minimum of 5KW not 4.5KW. {220.54}

 

[david luchini]

I figured it as follows 750sq ft @ 3va =2250 two appliance @ 3000 laundry @ 1500 range @ 12K Water heater @ 4500 Dryer @ 5000 Dish washer @ 1200 Heat pump @ 6000 Airconditioning @ 5000 for a total of 40,450 the first 10k @100% = remainder of 30,450 @ 40% = 12,180 divided that by 240= 50.75A did I not figure this out properly?

For the non-coincidental loads (heat and A/C) you would only use the larger of the two. {220.60} The 12KW range would use the demand factor in T220.55 which for a single range would be 8KW. The clothes dryer would use the minimum of 5KW not 4.5KW. {220.54}

He appears to be using the optional calculation in 220.82, so he would need to use the nameplate rating of the range rather than the 8kW demand. (He does figure the dryer at 5000, the water heater is 4500.)

I come up with 99.1 Amps at 240V

 

[JustWork]

I do see where I didnt add the 10k back. yes the heat strips were figured in my information I have the heat pump with air handler at 6k and the 5k that was listed as air condition was the heat strip in the airhandler. The clothes dryer is listed at 5k