Column Design Calculations

Calculating Electrical Load Capacity a home

Understanding the load and capacity becomes essential if you plan the electrical system for a new residence or thinking about an upgrade in your electrical service to an older house.

Knowing what the load requirements are will help you select the electrical service that has an adequate capacity. In older homes, it's typical for the current service to be inadequately sized to accommodate the demands of modern appliances and features currently being used.

The electrical power that an electrical system can provide is measured by amps (amps). For homes built in the past that have knob-and-tube wiring as well as screw-in fuse connections, you could discover that the original electrical service is 30 amps.

A few homes (built prior to 1960) might have 60 amp service. In many houses constructed after 1960 (or modernized older homes) 100 amps will be the typical size of service. In larger, more modern houses, 200-amp service is now a minimum.

With some newer homes, you could have 400-amp electrical services installed. On the other hand, in the top portion of the market, with homes that are more than 10,000 sq feet it's not uncommon to find 800 amp service.

How can you determine whether your current electrical system is sufficient, or what are you planning to do with an upgrade to electrical service? Calculating this will require math to measure the available capacity with the expected demand that will be put on the capacity.

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These are used to Loading Calculation in the following manner:

1. volume/time x amount/volume x time = amount.
2. feet3/second x mg/L x days x conversion factor = metric tons.
3. liters/feet3 x sec/day x metric tons/mg = conversion factor.
4. 28.32 x 86,400 x 1 x 10-9.
5. = 0.0024468.
6. liters/feet3 x seconds/day x metric tons/mg.

Understanding Electrical Capacity

Knowing the amount of power your home requires is as simple as finding the amperage load for each of the appliances and fixtures, and then building with a safety margin. In general, it is recommended that the load not over 80 percent of an power service's capacity.

To make use of maths, you must be aware of the relation between volts, watts and amps. The three terms commonly used in electrical terminology are mathematically related and can be expressed in a variety variations:

Volts + Amps = Watts

Amps = Watts/Volts

These formulas can be used to determine the capacity and load of specific circuits and for the whole electrical service. For instance, a 20-amp 120-volt branch circuit can have an overall power of 2400 watts (20 amps divided by 120 Volts). The standard recommendation is that the load should be no more than 80 percent of its capacity, this means the circuit that is 20 amps can be used at a capacity of 1920 watts. 

It's relatively easy to check the wattage ratings of TV sets, lightbulbs, and other equipment that are connected to the circuit in order to determine the likelihood of a circuit to be overloaded. For instance, if, for example, you regularly plug in 1500-watt space heaters into the circuit, and then run numerous lighting fixtures or lamps that have 100-watt bulbs that are connected to that same circuit you've already exhausted most of the safe capacity of 1920-watts.

The same formula is used to calculate the power capacity of the entire electrical service. Since the primary service of a home is at 240 volts, the calculation is as follows:

100 amps = 240 volts. = 24,000 watts

20% of the 24,000-watt electricity equals 19,200 Watts

That is an electrical service of 100 amps can be expected to deliver not more than 19200 watts of power at any time.

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