# Another fun practice Load Calc

#### Konen

##### Member
Single Family Dwelling
Use standard method of calculation
120/240v
Looking for minimum size THWN Aluminum conductors
Service Size?

30' x 60' dwelling space
Garbage disposal- 864va
Dishwasher- 1100va
Trash compactor- 1188va
Water heater- 4500va
Attic Fan- 750va
Swim pool pump- 1250va
Dryer- 4500va
Range- 12kw
Heat- 10kw @240v
A/C- 32A @240v

150A Service
2/0 Aluminum for Line
#2 for the Neutral.

#### NAjxBUEEdA7PoKoX7vD2

##### Member
 full demand VA amps square feet 1800 5400 small appliance 2 3000 laundry 1 1500 Total lighting 9900 22.56 dishwasher 1100 disposal 846 compactor 1188 water heat 4500 fan 750 other 3 Total app 8384 26.20 C cooking 12000 33.33 dryer 4500 20.83 FESH 1 10000 pump 1563 Total FESH 28063 48.18 Total 151.11 *0.83 125.42 2 / 0 AL 135 amps

#### david luchini

##### Moderator
Staff member
 Total 151.11 *0.83 125.42 2 / 0 AL 135 amps
A 151A dwelling load would require a minimum 3/0 Al conductor size.

#### Dennis Alwon

##### Moderator
Staff member
 Total 151.11 *0.83 125.42 2 / 0 AL 135 amps

The code states that the 83% is of the service rating not the load. So if you have a load of 151 amps the service could be 175 amps minimum

83% of 175 = 145 amp conductor which would be 3/0 as David stated

#### david luchini

##### Moderator
Staff member
30' x 60' dwelling space
Garbage disposal- 864va
Dishwasher- 1100va
Trash compactor- 1188va
Water heater- 4500va
Attic Fan- 750va
Swim pool pump- 1250va
Dryer- 4500va
Range- 12kw
Heat- 10kw @240v
A/C- 32A @240v
What did you consider to be "appliance load" and what did you consider to be "motor load"?

#### lauraj

##### Senior Member
Would it be wrong to include the swimming pool pump with the appliance load and if so, why?

#### Dennis Alwon

##### Moderator
Staff member
Would it be wrong to include the swimming pool pump with the appliance load and if so, why?

Although the definitions of appliance is weak I don't see a pool pump as an appliance.

Appliance. Utilization equipment, generally other than industrial,
that is normally built in standardized sizes or types and is
installed or connected as a unit to perform one or more functions
such as clothes washing, air-conditioning, food mixing,
deep frying, and so forth.

#### lauraj

##### Senior Member
Although the definitions of appliance is weak I don't see a pool pump as an appliance.
But we don't have a problem including the attic fan, I just don't see the difference between the two.

#### david luchini

##### Moderator
Staff member
But we don't have a problem including the attic fan, I just don't see the difference between the two.
I'm not sure I would include the attic fan with the appliance load either.

#### NAjxBUEEdA7PoKoX7vD2

##### Member
I would exclude from appliances the attic fan, the water heater, and the pool pump.

The 2020 NEC now requires a minimum of ¼ hp or 500 VA for appliances. Too many 25 VA bath fans.

The water heater is clearly an appliance in articles 220 and 422.

How about instantaneous water heaters and car chargers?

#### Konen

##### Member
What did you consider to be "appliance load" and what did you consider to be "motor load"?
I calculated the pool pump as appliance, along with 25% of that load.

#### Konen

##### Member
The code states that the 83% is of the service rating not the load. So if you have a load of 151 amps the service could be 175 amps minimum

83% of 175 = 145 amp conductor which would be 3

The code states that the 83% is of the service rating not the load. So if you have a load of 151 amps the service could be 175 amps minimum

83% of 175 = 145 amp conductor which would be 3/0 as David stated
Good catch, I applies the 83% demand factor to both the service and conductors. I Calculated 154A which make it a 175A service.

#### NAjxBUEEdA7PoKoX7vD2

##### Member
Here is the commentary from the 2017 Handbook:

The main service or feeder to a dwelling unit is permitted to be sized at
83 percent of the disconnect rating. The calculation is not based on the
rating of the overcurrent device protecting the main feeder. The minimum
disconnect rating for a dwelling unit is 100 amperes according to
225.39 and 230.79. This calculation applies only to conductors carrying
100 percent of the dwelling unit’s diversified load.

If a 120/240-volt single-phase service supplies a one-family dwelling,
or an individual unit of two-family or multifamily dwelling, then the
reduced conductor size is applicable to the service-entrance conductors
or feeder conductors that supply a dwelling unit. The feeder conductors
to a dwelling unit are not required to be larger than its service-entrance
conductors.

Exhibit 310.5 illustrates where 310.15(B)(7) could be applied. The
reduced conductor size permitted is applicable only to the service entrance
conductors run to each apartment from the meters. The
reduced conductor size permitted is also applicable to the feeder conductors
run to Apartment 3 from the service disconnecting means,
because this feeder carries the entire load.

#### Konen

##### Member
Got my Major load calculation test today @ 5pm

#### NAjxBUEEdA7PoKoX7vD2

##### Member
Good luck.
Spreadsheets should be a large part of Article 220. Unfortunately, Article 220 was written before they were available and has not been revised to incorporate their usefulness.

#### Konen

##### Member
Can't you bring in ANY copyrighted material into the test?

PASSSS!!!