I had a lennox gas hot water boiler installed and when the burner fires on the boiler bangs shortly after my heating contracter tells me its the way the house is piped or the honywell zone valves close to fast but the banging comes when they are open also this never happened with the old boiler please help
To determine if it the piping, have the technician run the circulator without the burner running. If the bang is from the pipe arrangement the bang should occur.
Sometimes castings can have small pockets where steam is produced and then the water bangs in the casting when the steam bubble collapses in cooler water as the bubble expands out of the space. Your technician may change or stop the bang by raising the boiler water pressure to see if the bubble can be forced to stay in the cavity.
Changing the speed of the flow of water within the boiler may eliminate the bang.
One of these culprits is the cause, so you need an experienced boiler plumber to check this for you. It is not a do-it-yourself problem.