We had a peerless purefire installed in the spring. Ever since the heat was put on we have enormous amounts of dust which seems to bother our breathing. Was it installed wrong by the plummer?

Your Peerless boiler heats an moves water through water lines. If they replaced a forced air system with a water coil at the time its possible you may have some air leaks on the return. If it was just the boiler replaced your dust may be due to a leaky house--(doors,windows,plumbing penetrations, electrical penetrations, and so on) it all adds up.