I just had my old gas boiler replaced with a new Peerless unit. The installer told me that my programmable thermostat from the previous boiler won't work because it won't open the automatic chimney damper on the new boiler. He installed an older type dial thermostat and the boiler works just fine. Is there a programmable thermostat that will work with a boiler that has an automatic chimney damper?

Sorry... maybe a bit more info would help. The system is a gas boiler / steam heat, and the previous boiler was a Weil-McClain that lasted 30+ years before finally quitting. I installed the programmable thermostat several years ago and it worked just fine. I thought all 24 volt thermostats were the same, and since it's only a 2-wire setup, I thought it acted only as a simple switch. I'm having trouble understanding why the programmable one won't work with the new boiler, but the older dial type does work. Is it possible the installer is mistaken when he said the 24 volt programmable won't work? Does the auto / manual switch on the chimney damper have anything to do with it? I'm really confused.