"was installed since" is correct and usable in written English.
You can use it when talking about something that was installed or set up at a point in time in the past, and is still in place. For example: "The security cameras were installed since last summer and have been providing a sense of safety for the neighborhood ever since."
Thousands of the so-called culvert denial systems were supposed to have been installed since 2009.
Some 1,300 systems have been installed since the Long Island Power Authority instituted its rebate program in 2000.
Thus Akihito becomes the first Emperor to be installed since Japan was transformed into a constitutional democracy under the American Occupation at the end of World War II.
And even if the monuments were delivered, they could not be installed, since there is no one to pour the concrete foundations to support them.
Ramsey was not fined for its water violations, for example, though a Ramsey official said that filtration systems have been installed since then.
Above workers' heads, powerful fans circulated the air, fans that Nike officials said had been installed since Mr. O'Rourke's visit.
All have been installed since around 1990, when America's other 48 states, not unreasonably, asked themselves why Las Vegas in Nevada and Atlantic City in New Jersey should have the lucrative field of legal gambling all to themselves.
It is one of almost 30,000 that have been installed since 2006, many of them in the same Walmart stores that together represent the single most important retail outlet for film discs.
Safeguards have been installed since the Depression, but if a drop in unemployment can make the market skittish, what happens if the price of oil collapses, if Mexico defaults on its loans, if any of a dozen other things happen.
Speculation over the election date has swirled around since the summer, adding to a lengthy period of political instability in which six prime ministers have been installed since Junichiro Koizumi's resignation in September 2006.
