The D.C. police department is installing a new infrared security system outside Mayor Marion Barry's Southeast Washington home after finding that the existing system using three television cameras breaks down too often and does not pick up some blind spots around the house.

The new installation, which is costing $1,500, will make it easier for the police officer in the guard house adjacent to the major's home to readily detect any intrusion on the property on Suitland Road SE.

Although police refused to reveal details about the system, officials at area security firms said that with infrared detection, small temperature changes and body motion can be measured, setting off an alarm to alert the officer monitoring the master control of any intrusion.

Police officials said it was necessary to put in the new system because the old one kept breaking down. Capt. Richard Pennington, head of the police department's budget office, said his office has spent $3,800 on repairs to the three television camera security in the last year.

He said the lenses on the television cameras were replaced several times after being damaged by rain. The cameras and the monitor also needed repairs on several occasions.

The three television cameras and the guard house for the police officer were installed two years ago at a cost of $11,711.l6 to city taxpayers.

They were installed to provide maximum security for the mayor, police officials have said. There have been no major intrusions at the mayor's home, although occasionally the police officer on guard has had to stop uninvited guests from knocking on the mayor's door, officials said.

Barry has a much more elaborate security system than his predecessor, Mayor Walter E. Washington, who had an around-the-clock police guard at his home, but no television cameras. Instead of a guard house, police officers took shelter in a cruiser parked out front.