Power requirement Appliance (watts)
Attic fan 400 Central air conditioning 6,000 Clothes dryer 4,500 Dishwasher 1,500 Forced-air furnace (electric heat) 28,000 Freezer 575 Garbage disposal 900 Hand iron 1,000 Instant hot water dispenser 1,000 Lamp (each bulb) 25 –150 Microwave oven 500 Range, electric 8,000 Portable room heater 1,600 Room air conditioner 1,100 Sauna 8,000 Steam bath generator 7,500 Television (color) 150 – 450 Water heater 2,500 – 4,500
The capacity of the electrical service should be great enough to satisfy the power requirements of the various electrical appliances to be used. Table 12-2 shows some typical electrical appliances and their associated power requirements.
Considering the many electrical appliances that are available to the homeowner, the minimum electrical service is 100 amps at 110/220 volts. However, if the house is small and the intention is not to use many electrical appliances, 60 amps at 110/220 volts will probably suffice. When a house is equipped with an electric water heater, electric range, electric clothes dryer, and a central air-conditioning system, it should have at least 150-amp service. If electric heat is used in addition to the above appliances, the house should have 200-amp service.
Fuses and circuit breakers
The panel box contains either circuit breakers or fuses to protect individual branch circuits from an overload. Overloaded circuits are one of the chief causes of home electrical fires, and proper protection of branch circuits is essential. Figure 12-4 shows a circuit-breaker panel box, and FIG. 12-5 shows a fuse panel box. Circuit breakers are more convenient than fuses. Once they have been tripped, they can be reset like a switch, whereas once a fuse has blown, it must be replaced. On the other hand, circuit breakers are somewhat less reliable than fuses. Circuit breakers have been known to “freeze” in the on position and should be manually tripped periodically to ensure operational integrity.
Is the panel box a Federal Pacific Electric (FPE) service panel? There have been numerous reports questioning the safety of this panel box and its Stab Lok circuit breakers. Some of the breakers have failed to shut off, or “trip,” in response to an overload and arcing has occurred in the panel box. As a safety precaution, replacing the panel box is recommended.
It is important that the capacity of a fuse be matched with the current-carrying capacity of a branch circuit. When a fuse has been blown, it must be replaced by a new fuse with the same current-carrying capacity. Too often, a homeowner replaces a 15-amp fuse with a 20or 30-amp fuse, not realizing that all three are physically but not electrically interchangeable. In this case, if there is an overload on that branch circuit, the fuse will not blow, but the wires will become excessively hot and possibly cause a fire. This type of problem can be circumvented by replacing the fuse with a Fustat. (See FIG. 12-6.) A Fustat is basically a fuse with an adapter that fits into the fuse holder in the panel box. Once the adapter is inserted, it usually cannot be removed. The adapters are sized so that they accept only fuses of a specific current capacity and are not interchangeable.