**Originally Posted By: dvalley**

**This post was automatically imported from our archived forum.**

Here ya go…

Load Calculations

General Lighting

Take the square footage of the house times 3va (volt-amperes)= __________ then add that number to 4500, which would be 2 small appliances and 1 laundry load.

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Take this subtotal and determine the *total general lighting load & small appliance as follows:

Take the first 3000 at 100% 3000

Take the remainder at 35% _____

(Total general lighting load

and small appliance minus 3000)

Then add those two together to

obtain the *total general

lighting load & small appliance _____

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Now determine the following and add them to the *general lighting load & small appliance:

Dishwasher 1200 va

Disposal 1200 va

Dryer 5500 va

Oven 8000-12000

(On the oven check the breaker size. If it is a 40 amp breaker it is 8000. If it is a 50 amp breaker it is 12000.)

Air Conditioner 5500-12000

(On the air conditioner, 700 sq ft requires 1 ton of air conditioning. A house of 2800 sq ft would require 12000 va whereas a house of 700 sq ft would only require 5500 va.)

Swimming pool 1500

Hot Tub 9000

(On the hot tub if the breaker is a 50 amp it would require 9000. If it is a 30 amp, it would require 6000.)

Electric Heaters, well pumps, and compressors would be figured out by taking the breaker size times the voltage required to use the breaker, and then times 35%. ( A single pole 20 amp breaker would result in 840 va [120 x 20 x .35=840]. A 20 amp two pole would be 1680 va [240 x 20 x .35=1680].)

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Take the total of the above and divide it by 240 volts. The result will be the total amount of amperes needed by the house.

A house at 80 amperes or less is good for a 100 amp panel and service.

A house at 81 amperes to 90 amperes is marginal for 100 amp panel and service.

Anything over 90 amperes should be upgraded to at least a 150 amp panel and service.

A house at 160 amperes or less is good for a 200 amp panel and service.

A house at 161 amperes to 180 amperes is marginal for a 200 amp panel and service.

Anything over 180 amperes should be upgraded to a higher than 200 amp service and panel.

Here is an example of a load calculation:

The house is 2000 sq ft, therefore 2000 x 3va =6000

6000 + 4500= 10500

The 1st 3000 is at 100% 3000

The remainder of 7500 is at 35% 2625

The sum of these two is: 5625

This number is the general lighting load and small appliance.

The house has a disposal 1200

A dishwasher 1200

A electric dryer 5500

A electric oven at 50 amps 12000

A air conditioner 10000

The sum of all these appliances plus the general lighting load and small appliance is: 35525

Take 35525 and divide it by 240 volts = 148 amps

This house would require a panel and service upgrade to at least 200 amps.

--

David Valley

MAB Member

Massachusetts Certified Home Inspections

http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."