exhaust smell

Hi, I am homeowner trying to troubleshoot a problem with my heater. I have Navien NCB-240E installed 1 1/2 yrs ago (manufactured 2016) on propane. I have 500gl outside propane tank with 2 regulators (on the tank and on the house). A month ago after refill my Navien started to make short (1-3sec)...

I have a TriangleTube Prestige 110 natural gas boiler that was installed in 2012. There is an intermittent gas smell that we (myself, my HVAC guy and PSEG gas company) believe to be an exhaust smell meaning the gas exhaust is coming back into the house from the boiler itself. It happens when...