With warmer weather coming, homeowners planning to install a window air conditioner or fans should check their electrical service before they plug in.

Homes built 50 or 100 years ago required much less electrical capacity than modern homes. Their service was often just 60 amps. Houses 20 or 30 years old were built with 100-amp service, but now, 200-amp service is the norm. A large air-conditioner may require as much power as an entire home did 60 years ago.

Mark Burrows, Warrior Run Area Fire Department chief, said overloaded electrical circuits are the major cause of electrical fires in homes, and he said air conditioners and fans are major culprits in such fires.

Burrows recommends having an electrician rate your electrical service before buying a unit. If you're already using an air conditioner, watch the lights in the house. If they flicker when the unit cycles, the circuit may be overloaded. If the unit blows fuses or trips the circuit breaker, the circuit definitely is overloaded. Stop using the unit immediately, Burrows said, and move it to a circuit that can handle the load.

Mike Rhoads, property maintenance officer in Sunbury's code office, said homeowners should inspect wiring and electrical service panels annually, in addition to looking over electrical cords to lamps and appliances.

"Look at the condition of the insulation," he said. "If it's cracked or brittle, get it replaced."

Rhoads said owners of older homes must be especially careful. Old-fashioned knob and tube wiring, with cotton, rubber or even paper insulation, easily is damaged. Original switches and outlets also may overheat and eventually ignite nearby wooden studs or insulating materials.

Old-style screw-in fuses should never be replaced by higher-capacity fuses if they keep blowing, and never put a penny behind a fuse or wrap it in aluminum foil. Instead, the reason for the blow should be found and corrected. Over time, the contact between the fuse base and the buss bar oxidizes or charcoals from poor contact. This generates heat that eventually could cause a fire. In fact, some insurance companies will not renew homeowners' policies in homes with the old-style fuse boxes.

Ken Nunamaker, of K&N Electric, Sunbury, said first-time homebuyers sometimes are shocked to learn they must spend $1500 or more to upgrade their electrical service before they can get insurance.

He said people don't think about the condition of the wiring in their homes as long as it works.

"The lifespan of wiring in houses built 40 or 50 years ago is about over," he said. "It's starting to deteriorate now."

There are thousands of houses in the region that should have their wiring inspected and renewed, he said.

When his electricians go out to upgrade electrical service, they make a visual inspection of the wiring. The current day standards call for a 200-amp service, and circuit breakers are sized to protect the wiring. Most domestic circuits are 15 amps, he said.