Multi family dwelling unit calculations
- Thread starter rp9ball
- Start date
- Status
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
I did not review the calcs, but the optional method, 220.84, is almost always going to be smaller.
As to which is better, that is subjective and a matter of personal opinion IMO.
As to which is better, that is subjective and a matter of personal opinion IMO.
Service Load
Service Load
If you read 220.84C, you have to recalculate the load per apartment without the discounts prior to using the .38 multiplier. That means you give up your discount for over 3000VA - you use 3VA/sq ft for the whole apartment. You also must have an electric stove and either air conditioner or heater in the calculation, which you do. So, this loses your 40% reduction that you got on the panelboard sizing. It also loses you any discounts you have for multiple ranges, heaters or other things.
So, for the service size, you take the undiscounted values, sum them up and multiply THAT by 38%. Then you add your discounted house panel loads. Please read the intoductory paragraph of 220.82 B and 220.84 C and see the differences.
You need a bigger service.
Service Load
If you read 220.84C, you have to recalculate the load per apartment without the discounts prior to using the .38 multiplier. That means you give up your discount for over 3000VA - you use 3VA/sq ft for the whole apartment. You also must have an electric stove and either air conditioner or heater in the calculation, which you do. So, this loses your 40% reduction that you got on the panelboard sizing. It also loses you any discounts you have for multiple ranges, heaters or other things.
So, for the service size, you take the undiscounted values, sum them up and multiply THAT by 38%. Then you add your discounted house panel loads. Please read the intoductory paragraph of 220.82 B and 220.84 C and see the differences.
You need a bigger service.
- Location
- Connecticut
- Occupation
- Engineer
Your standard calculation should be a little lower, and your optional calculation should be a little higher...the optional will be about 30% lower rather than the 45% lower that your calc shows.
In your standard calc, your dryer load should be 68,250va, not 105,000va. 14x2=28...28 dryers have a demand of 45,500va, which equals 22,750 per phase, which equal 68,250va 3ph equivalent.
The oven demand load should be 64,500va 3ph equivalent.
When you added the standard loads, you included the full appliance load (186,880) rather than the demand load (140,160.)
On the optional method calc, you need to use the nameplate rating of the range rather than 8kw.
Also, for your House Panel calc, you can't use the dwelling unit lighting demand.
- Status