Greetings...I just purchased a Harman PB105 pellet boiler to "add on" to my existing oil boiler. I am trying to determine what the pros/cons would be for doing an in-series install versus an in-parallel. The in-parallel is a bit more expensive since it requires cutting into the oil boiler's in and out pipes and adding a balancing valve on the oil boiler's out connection. The in-series is more simple as it only ties into the oil boiler's return (in). Is it worth paying more money for an in-parallel setup? I only plan on using the pellet boiler during the late fall through early spring timeframe, and then the oil boiler during the warmer months for domestic hot water only. In the in-parallel set-up, I can shut off the flow to the pellet boiler when it's not in use, versus the in-series where the oil heated water would flow through the dormant pellet boiler. Would be interested to hear other's experiences and thought on this. Thanks!